Geomorphology 139–140 (2012) 384–402
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Geomorphology
journal homepage: www.elsevier.com/locate/geomorph
Structural organization of process zones in upland watersheds of central Nevada and
its influence on basin connectivity, dynamics, and wet meadow complexes
Jerry R. Miller a,⁎, Mark L. Lord a, Lionel F. Villarroel a, Dru Germanoski b, Jeanne C. Chambers c
a
b
c
Department of Geosciences & Natural Resources, Western Carolina University, Cullowhee, NC 28723, United States
Department of Geology and Environmental Geosciences, Lafayette College, Easton, PA 18042, United States
Rocky Mountain Research Station, USDA Forest Service, 920 Valley Road, Reno, NV 89512, United States
a r t i c l e
i n f o
Article history:
Received 24 June 2011
Received in revised form 4 November 2011
Accepted 6 November 2011
Available online 12 November 2011
Keywords:
Fluvial geomorphology
Sensitivity
Connectivity
Groundwater recharge
Great Basin
a b s t r a c t
The drainage network within upland watersheds in central Nevada can be subdivided into distinct zones each
dominated by a unique set of processes on the basis of valley form, the geological materials that comprise the
valley floor, and the presence or absence of surficial channels. On hillslopes, the type and structure (frequency, length, and spatial arrangement) of these process zones is related to the lithology and weathering characteristics of the underlying bedrock. Process zones dominated by sediment accumulation, storage, and
groundwater recharge are associated with less resistant rocks that weather into abundant but relatively
small particles. Sediment transport and runoff-dominated zones are associated with resistant, sparsely fractured rocks that produce limited but larger clasts. The type and structure of process zones along axial valleys
depend on the characteristics of the process zones on the hillslopes. Numerous sediment storage-dominated
reaches leads to a relatively high number of unincised fans located at the mouth of tributaries along the axial
valleys and to frequent and lengthy unincised valley segments, both of which disconnect large sections of the
drainage basin from channelized flows. In contrast, a relatively high density of transport-dominated process
zones leads downstream to the incision of side-valley fans and axial valley deposits as well as a high degree of
basin connectivity (defined by the integration of surficial channels). Connectivity also is related to the lithology of the underlying bedrock, with higher degrees of connectivity being associated with volcanic rocks that
presumably yield high rates of runoff. Lower levels of connectivity are associated most frequently with extensively fractured, locally permeable sedimentary and metamorphic rock assemblages. Thus, basins underlain
by volcanic rocks appear to be more sensitive to incision and produce more dynamic channels in terms of
the rate of channel/valley modification than those underlain by other lithologies.
Considerable attention has been devoted in recent years to the management of wet meadow ecosystems that
serve as important riparian habitats within upland basins of central Nevada. The data presented here show
that, within basins characterized by a high degree of connectivity, areas of wet meadow are minimal.
Where they do exist in these basins, they tend to be severely degraded by incision or gully erosion and
will be difficult to manage given the dynamic nature of the axial channel processes. Wet meadows within basins that exhibit a low degree of connectivity and high sediment storage-to-transport ratios on hillslopes will
likely be more responsive to management activities because of the reduced threats of channel incision and,
presumably, a larger supply of groundwater flow to the meadows created by an extensive network of recharge sites. Importantly, human activities that lead to an increase in basin connectivity can negatively impact downstream meadows through a decrease in groundwater recharge and an increase in stream
dynamics, in spite of the fact that these activities may be physically separated from the wet meadow areas.
© 2011 Elsevier B.V. All rights reserved.
1. Introduction
The Great Basin forms the largest section of the Basin and Range
Physiographic Province and is composed of a series of north–northwest-trending mountain ranges separated by alluviated,
⁎ Corresponding author. Tel.: +1 828 227 2269.
E-mail address: jmiller@wcu.edu (J.R. Miller).
0169-555X/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.geomorph.2011.11.004
intermountain basins formed by high angle extensional faulting. The
ranges within the central Great Basin comprise >40% of the landscape and reach elevations 1500 to 2000 m above the surrounding
valley floors. Precipitation varies significantly with elevation but
may reach 55 cm at upper elevations and decreases to as little as
20 cm within the intermountain valleys (Chambers and Miller,
2004). As a result of the limited precipitation, particularly at lower elevations, riparian areas within the Great Basin encompass b1% of the
total landscape and are found mostly within small (b100 km 2)
J.R. Miller et al. / Geomorphology 139–140 (2012) 384–402
upland watersheds. Despite their limited size, riparian areas support
most of the region's native biodiversity including the Lahontan cutthroat trout (Oncorhynchus clarki henshawi), which is listed as threatened under the U.S. Endangered Species Act (Dunham et al., 1997).
Unfortunately, an estimated 50% of the riparian areas in the Great
Basin, as in many semi-arid regions, are in poor ecological condition
(Jenson and Platts, 1990). One of the highest priority ecosystems for
management and restoration are riparian meadow complexes.
These meadow ecosystems are hydrogeomorphic features characterized by elevated water tables and riparian grasses and broad-leafed
plants (i.e., riparian obligate graminoids and forbs). Emphasis on
their management and restoration results from the fact that they
represent unique habitats that in many cases are being degraded by
385
ongoing stream incision and its associated impacts on shallow
groundwater flow.
Numerous geomorphic, hydrologic, and ecologic studies have
been conducted in the region during the past decade with the intent
of providing the information necessary to develop sound management practices for riparian areas (Chambers et al., 1998, 1999;
Castelli et al., 2000; Chambers and Linnerooth, 2001; Germanoski et
al., 2001; Martin and Chambers, 2001a,b, 2002; Chambers and
Miller, 2004,2011). These studies have shown that many wet meadow complexes are located upstream of alluvial fans formed at the
mouth of tributaries (referred to here as side-valley fans) and other
forms of valley constriction (Fig. 1). The valley, then, is characterized
by a distinct segmented pattern with regards to valley form,
Side-valley
fan
A
B
C
Fig. 1. (A) Side-valley fan located at mouth of tributary. During the Holocene, fan prograded across valley and inhibited downstream flow of water and sediment; (B) Aerial view of
wet meadow complex located upstream of side-valley fan; and (C) Channel incised into wet meadow complex. Photograph is looking downvalley toward side-valley fan show in
(A) and (B). Reach is classified as an incised alluvial valley.
386
J.R. Miller et al. / Geomorphology 139–140 (2012) 384–402
Table 1
Summary of basin sensitivity types identified by Germanoski and Miller (2004); table modified from Chambers et al. (2004).
Category
Geology
Geomorphic characteristics
Watershed sensitivity
Group 1
Flood-dominated
Tertiary volcanic rock
Very high
Group 2
Deeply incised channels
Tertiary volcanic rock
Group 3
Fan-dominated
Sedimentary and
meta-sedimentary rock
Group 4
Pseudo-stable channels
Intrusive igneous, and
sedimentary rock
•
•
•
•
•
•
•
•
•
•
•
•
•
•
High relief basins
Narrow bedrock controlled
Minimal sediment storage
Multiple, discontinuous terraces
Large, high relief basins
Incised channels/trenched fans
Multiple, semi-continuous terraces
Lower relief basins
Large side-valley fans
Metastable channels with low incision values, but active downcutting
Moderate/minor incision
Potential for catastrophic incision via groundwater sapping
Cobbles or smaller bed material
Multiple, discontinuous terraces where incised
processes, and deposits where wet meadows are present. Along the
constricted reach, the channel typically exhibits a steep gradient
and is bound by bedrock and coarse-grained alluvium and/or colluvium often associated with side-valley fans. This high gradient reach
typically links higher and lower elevation stream segments creating
a “stepped” longitudinal channel profile. Stratigraphic studies in nearly 30 basins revealed that fan deposition primarily occurred during an
intensive period of hillslope erosion extending from ~2580 ± 70 to
1980 ± 60 YBP (Miller et al., 2001). During this period many sidevalley fans temporarily blocked the downvalley movement of water
and sediment producing upstream zones of sediment accumulation
and low valley gradients. Downstream of the fans, reworked fan and
other alluvial sediments were deposited along the valley floor creating an episode of channel/valley aggradation marked by a distinct alluvial unit that is often several meters in thickness. Since about
1980 YBP, stream systems throughout the region have exhibited periods of stability that were separated by episodes of channel incision
often by the headward migration of knickpoints (Miller et al., 2001,
2004, 2011).
Detailed hydrologic studies that involved sediment coring, seismic
and ground penetrating radar surveys, and the installation of numerous piezometers (more than 90 at one site) have been carried out
within five wet meadow complexes (Lord et al., 2011). These analyses
have shown that wet meadow formation requires (i) a significant upstream supply of water, (ii) some form of valley constriction that
leads to reduced downvalley flow rates and upward flow patterns,
and (iii) fine-grained valley fill deposits that retard groundwater
flow to create shallow water tables. Thus the integrity of meadow
complexes is strongly dependent on the magnitude of groundwater
recharge and the flow of groundwater along the drainage network
as well as the magnitude of channel incision that has the potential
to lower water table levels within the meadow complexes.
Germanoski and Miller (2004) found that the rates, magnitude,
and nature of channel incision vary spatially between basins and
along the axial valley of any given basin. Such differences in response
are often explained in terms of landform sensitivity, which is defined
by Brunsden and Thornes (1979) as “the likelihood that a given
change in the controls of the system will produce a sensible, recognizable, and persistent response [in the landform of interest].” This
definition of sensitivity includes two distinct components of change:
(i) the likelihood for a geomorphic feature such as a stream reach to
change as governed by a set of resisting and driving forces, and
(ii) the ability of a stream to remain in an equilibrium state
(Schumm, 1991; Downs and Gregory, 1995). The rate of change also
is important because, while a stream may be in a state of disequilibrium,
it may exhibit little change if the driving and resisting forces are such
that adjustments occur at an exceedingly slow rate.
The analysis by Germanoski and Miller (2004) showed that the
examined watersheds (nearly 20 in total) could be subdivided into
Low to moderate
Low to moderate
Moderate to high
four distinct groups characterized by different degrees of landscape
sensitivity and channel dynamics (Table 1). The observed differences
in sensitivity represent a powerful management tool as they provide
insights into (i) the likelihood that a given river or meadow will respond to future disturbances, (ii) the timing, duration, rate, and nature of the response, and ultimately (iii) the potential for a given
system to be stabilized or restored (Chambers et al., 2004;
Germanoski and Miller, 2004). However, three short-comings of the
sensitivity analysis were noted. First, differences in basin dynamics
could not be entirely explained using commonly applied methods of
basin morphometric analysis. Second, it was apparent that channel,
valley floor, and meadow ecosystem sensitivity varied along the riparian corridor of a given basin. Classifying the sensitivity of an entire
watershed did not adequately describe the spatial variations in geomorphic response that occurred within a basin or the controls on
channel/valley sensitivity within a given reach of the drainage system. Third, the analysis did not directly attempt to integrate groundwater flow patterns and processes into the study. An improved
understanding of recharge mechanisms, local water table elevations,
and their relationships to streams permits a more holistic approach
to sensitivity.
Since the early 1990s, the classical continuum view of river systems has been questioned and often replaced by a hierarchical perspective of a drainage network (Frissell et al., 1986; Kishi et al.,
1987; Grant et al., 1990; Montgomery and Buffington, 1993; Grant
and Swanson, 1995; Brierley and Fryirs, 2001, 2005). This conceptual
shift is related to the realization that hierachical classifications are extremely useful in understanding the interactions between processes
functioning over differing temporal and spatial scales and for capturing abrupt spatial variations in channel and valley form, processes,
and behavior that are not adequately described by the classical continuum approach. While these classification systems differ in their
specifics, the unifying theme is that drainage networks consist of
channel and valley floor environments that can be subdivided into
progressively smaller units, each of which are morphologically homogeneous with respect to landforms, processes, and the controlling
factors of geology, vegetation, substrate, and hillslope influences
(Grant and Swanson, 1995). Commonly included categories range
from localized channel-scale units (defined on the basis of various
channel-bed features such as pools, riffles, bars, etc.), reach-scale
units (defined according to the nature of both the channel and valley
floor), and larger scale units ranging up to and beyond the entire
drainage basin.
Application of the hierarchical approach has been found to be particularly well suited to the investigation and management of mountainous streams where factors external to the channel play a more
significant role in controlling channel and valley form than is the
case for lowland watersheds (Montgomery and Buffington, 1993;
Grant and Swanson, 1995; Montgomery and Buffington, 1997).
J.R. Miller et al. / Geomorphology 139–140 (2012) 384–402
These external (nonfluvial) constraints include passive factors such as
bedrock outcrops as well as mass wasting and other hillslope processes that produce localized accumulations of colluvial and alluvial materials (Grant and Swanson, 1995). The significance of these
external constraints is that semicontinous downstream changes in
channel/valley form and process observed along many lowland rivers
are replaced by a segmented drainage net where individual segments
terminate abruptly along the network and may be repeated multiple
times throughout the drainage system. Often referred to as process
zones, these reach-scale units include segments of the stream channel
and adjacent valley floor with homogenous landforms and processes.
The objective of this study is to determine if the hierarchical approach can more effectively explain spatial variations in geomorphic
response to late Holocene perturbations and the present distribution
of wet meadow complexes. We examine the linkages between channel dynamics, wet meadow complexes and the spatial structure and
connectivity of process zones at reach and basin scales. Variations in
the spatial structure (type, length, and spatial arrangement) of delineated process zones on basin- and reach-scale sensitivity and the
factors that control these variations are also examined. Connectivity,
as used here, refers to the degree to which water and sediment can
be transferred from one zone to the next downstream zone on the
surface through a distinct channel. Thus the adopted definition of
connectivity does not include groundwater flow.
2. Methods
2.1. Basin selection
Germanoski and Miller (2004) conducted an extensive study of
landscape sensitivity within 18 watersheds in central Nevada. They
found that the watersheds could be subdivided into four groups
with respect to the style of geomorphic adjustment and the sensitivity of the axial channel to change during the late Holocene (Table 1).
The current study utilizes eight watersheds that are considered to be
representative of these four groups. The studied basins are Barley
Creek, Birch Creek, Cottonwood Creek, the north and south branch
of Corcoran Canyon, Kingston Canyon, Pine Creek, San Juan Creek,
387
Table 2
Basin characteristics of studied watersheds.
Kingston C.
Birch Cr.
San Juan Cr.
Cottonwood Cr.
N. Corcoran C.
S. Corcoran C.
Barley Cr.
Pine Cr.
South Twin R.
Basin area
(km2)
Basin relief
(m)
Divide
elevation
(range, m)
Drainage
density
(km/km2)
Drainage
frequency
(#/km2)
60.46
46.09
27.34
20.54
8.06
7.03
89.22
31.66
49.90
1546
1400
1044
1268
508
555
1005
1309
1674
3497–2597
3290–2067
3117–2228
3341–2292
2757–2292
2805–2292
3212–2457
3601–2737
3588–2701
3.21
4.11
3.37
3.53
3.59
4.42
2.97
3.31
4.42
11.5
17.5
11.7
11.1
14.3
18.4
9.10
11.8
18.4
and the South Twin River (Fig. 2). The north and south branches of
Corcoran Canyon were examined separately because the two subbasins
exhibit differences in the number and area of contained wet meadow
complexes. General topographic and morphologic characteristics of
the studied basins are provided in Table 2.
2.2. Delineation, characterization, and mapping of process zones
Elements of the hierarchical classification systems presented by
Frissell et al. (1986), Montgomery and Buffington (1993), and Grant
and Swanson (1995) were modified, combined and fit to the characteristics of the watersheds in central Nevada for this study. In general,
the watersheds were subdivided into hillslope, low-order valley, axial
valley, and side-valley fan components (Fig. 3). Each component was
then subdivided further into process zones on the basis of the composition of the valley fill or underlying geological materials (bedrock,
colluvium, alluvium), and the presence or absence of a distinct channel throughout the length of the reach (Fig. 3). The classification
resulted in 13 process zones (Fig. 3).
Delineation and mapping of process zones involved a multistepped approach beginning with the classification and mapping of
distinct reaches of the drainage network on mylar overlays using
B
4
1
3
A
2
7
6
8
5
25 km
Fig. 2. (A) Distribution of the Basin and Range Physiographic Province in the U.S.; (B) map showing the location of the study basins in central Nevada. 1 — Kingston Canyon; 2 —
Cottonwood Creek; 3 — San Juan Creek; 4 — Birch Creek; 5 — Barley Creek; 6 — Corcoran Creek; 7 — Pine Creek; and 8 — South Twin River; aerial imagery for part B from Google
Earth™.
388
J.R. Miller et al. / Geomorphology 139–140 (2012) 384–402
Fig. 3. Classification system used to categorize process zones within the study basins.
2006, 1:12,000-scale, georectified aerial photographs. Where an accurate designation could not be determined on the georectified photos
(in two-dimensions), 1993 photographs allowing stereo viewing
were consulted. Google Earth™ images also were used to gain
insights into the nature of the valley system. Once mapped, paper
copies of the mylar overlays were used to check the accuracy of the
mapped process zones in the field. The maps were then edited to reflect map revisions made during field inspections (see Fig. 4 as an
example).
The number and length of each process zone type was subsequently determined from the constructed maps and combined with
basin morphometric data to assess frequency (#/km 2) and density
(total length in km/km 2) of the process zones within the individual
study basins. All length–area measurements were made with a Planix
digital planimeter. Downstream patterns in process zone types were
determined by examining the frequency with which specific zones
were linked to one another. The process zone maps also were
compared to existing maps of bedrock geology to assess geological
controls on the nature and structure of the process zones.
Field characterization of the process zones involved the random
selection of ~10 characterization points for the predominant types
of process zones within each of the study basins. Some process
zones, such as incised alluvial valleys that comprise large sections of
the axial channel network, were more intensively characterized in
order to capture downstream differences in channel morphology.
Other process zones were either too dangerous to access (e.g., steep
bedrock valleys), or rarely occurred in the basins (e.g., bedrock
hollows) and were not quantitatively characterized in the field. Data
were collected at a total of 389 sites; the number of reaches characterized within an individual basin ranged from 20 to 108. The parameters collected at each characterization point included descriptors of
hollow/valley/channel form, bed material lithology, hydrologic features, and grain size distribution of the bed material (Table 3). Cross
section/valley measurements were made using the tape/stadia
rod method, whereas gradients were measured using a laser level.
Particle size distribution of the bed material was determined using
an Excel-based grain size analysis algorithm developed by the U.S.
Forest Service Stream Technology Center (http://www.stream.fs.fed.
us/publications/software.html) on 50 randomly selected clasts measured with a gravelometer. Approximately 9700 clasts were examined within the seven basins (field data were not collected from the
South Twin River because of access and other problems). The long, intermediate, and short axes of the ten largest clasts also were
measured at each site. Hydrologic features, such as flow conditions
(water depth) and springs, were recorded where present.
2.3. Characterizing process zone connectivity
The geomorphic and hydrologic connectivity of the system are
highly dependent on the time scale under consideration, particularly
in semiarid environments such as that in central Nevada. Our previous work in the region, for example, demonstrates that an integrated
drainage system may be hydrologically connected only during the
seasonal snowmelt period, but disconnected during the late summer
months when the channel possesses both perennial and ephemeral
reaches (Lord et al., 2011). Over longer timescales (years to decades),
sections of the drainage network may become incised, thereby increasing connectivity between the zones, or become filled, creating
a discontinuous drainage system with decreased connectivity between process zones. For this analysis, the focus is on channel connectivity of the system over a period of years, and connectivity is
operationally defined as the existence of a recognizable, physically integrated channel (Hooke, 2003). Thus, process zones that do not have
a channel (e.g., unincised colluvial or alluvial valleys, or unincised
side-valley fans) represent zones that disconnect upstream portions
of the drainage network from those farther downstream. While
some surface water connection may occur during extreme hydrological events where channelized systems are lacking, the ability of unincised reaches to transfer water, sediment, and other constituents
downstream is significantly less than along channelized reaches of
the drainage network. Connectivity of the system was quantified by
mapping and measuring the amount of connected basin area immediately up- and downstream of selected tributaries to the axial drainage
in terms of both an absolute value and percentage of the total upstream basin area.
We had originally intended to determine the relationships between such parameters as process zone length, slope, abundance, particle size, contributing basin area, etc. using multivariate statistical
methods. However, the inability to safely access steep, bedrock hollows
and valleys locally covered by a thin veneer of loose sediment prevented
collection of the necessary data. Nonetheless, basic statistical/empirical
data (e.g., data means, ranges, and standard deviations) combined with
field observations and the available cartographic information provide insights into the relationships between geology, process zone type and
structure, and drainage net connectivity. All statistical analyses were
conducted using SYSTAT 9.
J.R. Miller et al. / Geomorphology 139–140 (2012) 384–402
389
Fig. 4. Map of process zones produced for Kingston Canyon.
3. Results
3.1. Process zone characteristics
3.1.1. Hillslope hollows
Hillslopes within the upland watersheds possess three types of
U-shaped depressions that are commonly referred to in studies of
Table 3
Summary of collected parameters.
• Basin/subbasin
• Latitude/longitude (GPS)
• Grain size distribution of bed material
(D50, D84, size of 10 largest);
bedrock exposures
• Clast lithology
(for 50 clasts and 10 largest)
• Valley and channel slope
• Valley width (where applicable)
• Water width and depth (if present)
• Channel or hollow cross profile
• Bank material composition;
stratification
• Bank failure mechanisms
• Groundwater seepage; springs
• Channel bed features
(pools, riffles, etc.)
• Maximum hillslope gradients
• Landforms present on valley floor
• Underlying bedrock geology
basin morphometry as zero-order channels (Tsuboyama et al., 2000;
Sheridan and Spies, 2005). These hillslope features are referred to
here as ‘unincised hollows’, ‘incised hollows’, and ‘bedrock hollows.’
The morphologic and sedimentologic characteristics of each are described in Table 4 and below.
3.1.1.1. Unincised hollows (UH). The most frequently observed type of
process zone on hillslopes is called ‘unincised hollows’. These features
represent the first recognizable, upslope segment of the drainage network. They are devoid of an integrated surface channel with welldefined banks (Fig. 5A). Rather, the floor of the depression is characterized by angular, well-sorted, highly porous gravels of relatively
small size (D50 of ~ 17 mm, Fig. 6). Sagebrush (Artemisia tridentata
spp), wild rose (Rosa woodsii), and other upland species partially
cover axial deposits that typically exhibit thicknesses on the order
of 0.5 to >1 m. Bedrock outcrops within the floor of the unincised
hollows are rare, although they may occur along the margins. Slope
of the unincised hollows is variable, but on average is relatively
high in comparison to the other types of process zones as a result of
their position within the drainage network (Fig. 6).
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J.R. Miller et al. / Geomorphology 139–140 (2012) 384–402
Table 4
Summary of geomorphic and hydrologic process zone characteristics.
Process zones
on hillslopes
Process zones
within low-order
valleys
Process zone
Morphology
Sediment storage
Dominant process(es)
Unincised
hollow (UH)
U-shaped depression oriented roughly
parallel to slope
Incised hollow
(IH)
U-shaped depression oriented roughly
parallel to slope; channel incised in
center of depression
U-shaped depression oriented roughly
parallel to slope
V-shaped valley oriented roughly parallel
to slope; channel does not possess welldefined banks; channel often floored by
bedrock with local knickpoints present
Broad, rectangular shaped channel
formed in resistant, scarcely
fractured bedrock
Rectangular to asymmetrical channel
formed in thick alluvial deposits;
channel often characterized by pools,
riffles, and point bars
Well-sorted, angular sediment of limited
lithologic variation; sediment typically
b1–2 m thick
Well-sorted, angular sediment of limited
lithologic variation along margins of
bedrock-floored channel
No continuous layer of sediment present;
occasional large clasts present
Very little sediment found within
the valley
Deposition of sediment from
adjacent hillslopes; significant recharge
with limited runoff
Rapid transport of water and sediment
derived from adjacent hillslope; incision
associated with single, catastrophic event
Rapid transport of water and sediment
derived from adjacent hillslope
Transport of water and sediment delivered
to the channel and valley from upstream
channel reaches and adjacent hillslopes
No continuous layer of sediment present;
occasional large boulders located along
depression
Thick alluvial sediments (often thicker
than 5 m) within channel bed and
adjacent floodplains; sediments exhibit
wide range of lithologies, moderately
sorted, and moderately rounded
Transport of water and sediment delivered
to the channel and valley from upstream
channel reaches and adjacent hillslopes
Transport of surface water and sediment
delivered to the channel from upstream
reaches. Significant groundwater recharge
through channel bed where coarse grained
and a deep water table; sediment is
periodically deposited within channel and
floodplain, and moved during large events
Deposition of sediment delivered
to the valley floor during flood events;
significant zone of recharge
Transport of sediment through
continuous channel; recharge into
bed sediment locally important
Bedrock hollow
(BH)
Unfilled valley
(UV)
Bedrock
valley (BV)
Process zones
within axial
valleys
Process zones
within axial
valleys
Process zones
associated with
side-valley fans
Incised alluvial
valley (IAV)
Unincised
alluvial valley
(UAV)
Incised colluvial
valley (ICV)
Low-relief valley floor surface with
no continuous channel
Rectangular to asymmetric channel
with variable bank heights formed in
colluvial and side-valley fan sediments
Incised alluvial/
colluvial
valley (IACV)
Rectangular to asymmetric channel
with variable bank heights formed in
colluvial and side-valley fan sediments
Anabranching
valley (ANBV)
Multi-channel system in which
channels are separated by vegetated
islands; numerous debris dams present
Fan-shaped accumulations of sediment
at mouth of tributaries; no continuous
channel present
Fan-shaped accumulations of sediment
at mouth of tributaries; channel
extends from fan apex to toe
Unincised
side-valley
fan (UF)
Incised
side-valley
fan (IF)
The highest density (km/km 2) and frequency (#/km2) of the unincised hollows (measured as total length/number of the hollows divided
by basin area) are found in Kingston Canyon, Cottonwood Creek, San
Juan Creek, Birch Creek, and the South Twin River (Fig. 7). In constrast,
Barley Creek and Corcoran Canyon exhibit a low density and frequency
of unincised hollows.
3.1.1.2. Incised hollows (IH). These features exhibit a well-defined
channel that typically exceeds 1 to 2 m in depth and several meters
in width and that is floored by bedrock. In every other way, incised
hollows are morphologically similar to unincised hollows. In comparison to unincised hollows, incised hollows are scarce (b0.4/km 2);
they are most common, and exhibit the highest densities, within the
Pine Creek basin and to a lesser degree the South Twin River basins
(Fig. 7).
3.1.1.3. Bedrock hollows (BH). Bedrock floored, U-shaped depressions,
shown in Fig. 5C, are called ‘bedrock hollows’. Although they are morphologically similar to the sediment-filled, unincised hollows, bedrock hollows lack continuous accumulations of unconsolidated
debris. Detailed measurements of their form (cross-sectional morphology and gradient) were not collected in the field because of the
dangers of traversing slick bedrock on steep slopes. Nonetheless,
field observations suggest that they exhibit similar dimensions,
form, and gradients as the other types of hollows. Bedrock hollows
Surface underlain by alluvial deposits
often >5 m thick; significant zone of
sediment accumulation
Channel bed sediment overlying colluvial
material of considerable thickness;
colluvial valley fill associated with past
episodes of hillslope erosion and deposition
Channel bed sediment overlying colluvial
material of considerable thickness; often
characterized by colluvial and alluvial
sediments on opposite sides of channel
Thin (b2.5 m thick) deposits consisting
of cobble-sized sediment with occasional
boulders overlying bedrock
Thick (> 10 m) accumulations of alluvial
and colluvial sediments
Thick (> 10 m) accumulations of alluvial
and colluvial sediments
Transport of sediment through
continuous channel; some deposition
on alluvial floodplain; recharge into bed
sediment locally important
Spatially and temporally variable
episodes of deposition and erosion;
highly dynamic valley floors
Deposition of sediment; significant zone
of groundwater recharge
Represent long-term zone of deposition;
currently, zone of sediment and water
transport
occur most frequently and exhibit the highest densities within the
Barley, Pine, Corcoran, and South Twin River basins (Fig. 7).
3.1.2. Low-order valleys
Two types of process zones, referred to here as ‘bedrock valleys’
and ‘unfilled valleys’, receive water and sediment from hillslopes
and hillslope hollows. Both are found at relatively high elevations
within the watersheds and are considered low-order channels by
the classical Horton (1945) and Strahler (1952) drainage net classification systems.
3.1.2.1. Unfilled valleys (UV). Process zones that exhibit a V-shaped
cross-sectional valley form and are characterized by hillslopes that
grade directly into a bedrock-dominated channel are referred to as
‘unfilled valleys’ (Fig. 5B). Alluvial and colluvial deposits within the
valley bottom are limited. Locally, small knickpoints are present in
the bedrock, indicating channel bed incision. The unconsolidated sediment that is present tends to possess a larger median grain size and
is more poorly sorted than sediment found in hillslope hollows
(Fig. 6). The average gradient of unfilled valleys is approximately
half of that observed for the upslope hollows. These features are relatively common, typically occurring at higher frequencies and densities than the bedrock valleys described below (Fig. 7).
3.1.2.2. Bedrock valleys (BV). In contrast to unfilled valleys, bedrock
valleys exhibit relatively wide valley floors that often reach widths
J.R. Miller et al. / Geomorphology 139–140 (2012) 384–402
A
B
C
D
E
F
391
Fig. 5. Photographs showing typical morphology and composition of the major process zones mapped within the study basins. (A) unincised hollow; (B) unfilled valley; (C) bedrock
hollow (U-shaped feature) draining into bedrock valley); (D) rugged nature of bedrock outcrop associated with bedrock valleys; (E) incised alluvial valley; and (F) incised colluvial
valley.
of 5 to >10 m (Fig. 5C). Unconsolidated sediment, typically eroded
from the underlying bedrock, tends to be larger and more poorly
sorted than is found in the other types of process zones (Fig. 6). Bedrock valleys occur most frequently and exhibit the highest densities in
the Barley, Corcoran, and the South Twin River basins (Fig. 7). They
are also common in the Kingston Canyon watershed where they are
predominately located on carbonate rocks (as will be discussed in
more detail below).
3.1.3. Axial valleys
Higher-order, lower elevation segments of the drainage network
are characterized by relatively wide valleys (measured in 10s of
meters) that have been partially filled with alluvial and colluvial sediments (Figs. 1C and 5E). These process zones are collectively referred
to as ‘axial valleys’. It is important to note, however, that they not only
occur along the predominant (main) channel within the watershed,
but often extended into the lower reaches of a tributary basin
where they serve as the axial drainage route within that subbasin.
Axial valleys are subdivided into distinct process zones on the basis
of (i) the composition of the valley fill, and (ii) the presence or absence of a continuous channel (Fig. 3). The four recognized types
are described below.
3.1.3.1. Incised alluvial valley (IAV). In most basins, the majority of
axial valley floors consist of incised alluvial valleys (Fig. 5E). Incised
alluvial valleys are characterized by a continuous (integrated) channel cut into alluvial sediments that comprise the majority of the valley fill. Core data collected from five basins in the area demonstrate
that the thickness of the valley fill is often measured in a few tens
of meters. Sedimentologically, the fill is highly variable, ranging
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J.R. Miller et al. / Geomorphology 139–140 (2012) 384–402
Fig. 6. Slope and grain size characteristics of channel or valley materials for predominant types of process zones. Values based on data from all seven study sites for which field data
are available. Largest clast values based on intermediate diameter of 10 largest clasts found at characterization site. Filled rectangle — mean; box — standard deviation; line across
box — median intermediate diameter; whiskers — 10 and 90% exceedence values. UH — unincised hollow; IH — incised hollow; BH — bedrock hollow; UV — unfilled valley; BV —
bedrock valley; ICV — incised colluvial valley; IACV — Incised alluvial/colluvial valley; IAV — Incised alluvial valley; and UAV — Unincised alluvial valley.
from coarse gravel-sized material to fine-grained silt- and claydominated units (Lord et al., 2011). Bed material within the channels
exhibits a wide range of particle sizes, but is typically larger than
clasts found in unincised hollows and smaller than those found in
bedrock hollows and valleys (Fig. 6). Lithologically, the clasts are
more diverse than the particles found in higher elevation process
zones reflecting a wider range of source rocks. The average slope of
incised alluvial valleys is variable, but is relatively low (b0.1) in comparison to other types of process zones found along the axial valley
(Fig. 6).
The frequency of incised alluvial valleys is similar across the study
basins with the exception of Corcoran Canyon (Fig. 8). The high frequency within the north and south Corcoran Canyon basins reflects
(i) the relatively small area of the basin (Table 2), and (ii) incised
alluvial valley segments that are frequently disrupted by colluvial
landforms. The density of incised alluvial valleys is more variable
between basins than other types of axial valley zones, with larger
densities found in the Birch Creek, Barley Creek, and Corcoran Canyon
basins (Fig. 8).
The depth of channel incision below the valley floor is highly
variable, among basins and along the riparian corridor of a given
basin, ranging from a few tens of centimeters to more than 5 m.
Downstream variations within Kingston Canyon, Cottonwood Creek,
San Juan Creek, and Birch Creek tend to alternate between deeply incised reaches and reaches with limited entrenchment, until reaching
the basin mouth where incision tends to increase to a maximum.
As an example, observed downstream variations in incision along
Kingston Canyon are shown in Fig. 9.
3.1.3.2. Incised colluvial valleys (ICV). These features, shown in Fig. 5F,
represent the second most abundant type of axial valley (Fig. 8).
They are characterized by a continuous channel cut into colluvial valley fill or fan deposits that slope from the hillslope toward the valley
axis. Incised colluvial valleys are located in two primary locations:
(i) within tributaries well upstream of the tributary basin's mouth,
and (ii) along the main channel at the toe of side-valley fans. These
process zones, on average, are slightly steeper and possess slightly
larger material than is found within the incised alluvial valleys
(Fig. 6).
A few reaches within the Kingston Canyon, Birch Creek, San Juan
Creek, and Cottonwood Creek basins consist of incised alluvial/colluvial
valleys. As the name implies, these process zones are transitional in
character between incised alluvial and incised colluvial valleys in that
the channel is cut into both alluvial and colluvial valley fill deposits.
They tend to possess higher channel gradients and coarser bed
material than is found along the other types of axial valley process
zones (Fig. 6).
3.1.3.3. Unincised alluvial and colluvial valleys (UAV/UACV). In contrast
to incised alluvial and colluvial process zones, unincised alluvial and
unincised alluvial and colluvial valleys lack an integrated channel network. Although the valley floor deposits may locally possess shallow
(b1 m deep) gully systems, they are typically characterized by a low
relief valley floor covered in sagebrush and other vegetation. The surface sediments in most instances are composed of fine-grained (siltdominated) deposits. In a few locations, however, upstream axial
channels transport sediment onto the valley floor on a semiannual
J.R. Miller et al. / Geomorphology 139–140 (2012) 384–402
393
Fig. 7. Density and frequency of selected hillslope and low-order channel process zones stratified by studied basin. UH — unincised hollow; IH — incised hollow; BH — bedrock
hollow; UV — unfilled valley; and BV — bedrock valley.
basis, allowing for localized valley floor aggradation. These reaches
tend to exhibit, on average, the lowest channel/valley floor gradients
and the smallest particle sizes of any process zone type (Fig. 6).
3.1.3.4. Anabranching channels (ANBV). Downstream segments of the
axial channel in Pine Creek and the South Twin River exhibit an anabranching pattern that was not observed in the other study basins.
Fig. 8. Density and frequency of axial valley process zones stratified by studied basin. ICV — incised colluvial valley; IAV — incised alluvial valley; IACV — incised alluvial/colluvial
valley; IABV — anabranching valley; UAV — unincised alluvial valley; and UACV — unincised alluvial/colluvial valley.
394
J.R. Miller et al. / Geomorphology 139–140 (2012) 384–402
Incision depth (m)
4
system (called ‘incised side-valley fans’), and (ii) fans that are devoid
of a defined channel or that possess a channel only in apex or medial
areas of the fan before flowing onto the fan surface (referred to as
‘unincised side-valley fans’) (Table 4).
With the exception of Birch Creek, the number of side-valley fans
per unit basin area is consistent across the study basins, ranging from
~0.7 to 1.5/km 2. Birch Creek possesses a high number of side-valley
fans (Table 5), many of which are located within wide tributary basins (in comparison to the other studied watersheds). In contrast to
the density of fans within the basins, significant differences exist in
the proportion of incised to unincised fans between the basins
(Table 5). A higher percentage of unincised fans occur in the Kingston
Canyon, Cottonwood, San Juan, and Birch Creek basins than is found
within the other studied watersheds.
3
2
1
0
% Distance downstream
Fig. 9. Downstream variation in maximum depth of incision below valley floor in
Kingston Canyon. Data points represent location of measured cross sections. Trend,
which exhibits considerable variability in the depth of incision along the axial valley,
is typical of basins with high storage-to-transport ratios for hillslope process zones
and lower degrees of connectivity including Birch Creek, Cottonwood Creek, and San
Juan Creek.
3.1.5. Downstream patterns
The sequence of process zones that occurs within the studied
basins was quantified by recording the frequency at which selected
process zone types are linked to one another at the downstream
end. The data reveal that the downstream pattern of process zone
types is similar between the basins. The most commonly observed
sequence is characterized by the flow of unincised and incised
hollows into unfilled valleys that are linked to either side-valley fans
or incised alluvial valleys. Further downbasin, incised alluvial valleys
commonly alternate with incised colluvial valleys associated with
large side-valley fans that extend across the valley floor (Fig. 10).
The pattern is characterized by the splitting and rejoining of the channel around vegetated islands forming a multichannel system. Formation of individual anabranches is typically related to channel
aggradation and filling upstream of woody debris dams, followed by
overbank flooding, floodplain erosion, and channel avulsion. The net
product is a highly dynamic valley floor characterized by localized
cutting and filling that creates multiple, discontinuous terraces with
terrace scarps on the order of 1 to 2 m or less in height
(Germanoski and Miller, 2004). This process zone type is characterized by minimal sediment storage in floodplains or terraces within
the valley as the channel bed is frequently composed of bedrock,
and floodplains and terraces consist of thin (b2.5 m) cobble-sized alluvium that can apparently be mobilized by floods having a recurrence interval measured in years (Germanoski and Miller, 2004).
3.1.6. Geological controls on process zones
In order to quantify bedrock–process zone relations, the rock type
underlying each of the delineated process zones within the Kingston
Canyon, Birch Creek, Cottonwood Creek, and San Juan Creek basins
was determined using existing geologic maps (the other basins are
underlain exclusively by volcanic rocks and thus were not included
in this analysis; Fig. 11). The collected data are presented in Fig. 12
in terms of the percent to which a given process zone is associated
with a specific rock type. However, the basins differ in the degree to
which they are underlain by a given geological unit. Thus, the normalized percentage for which a specific process zone is associated with a
given lithology is also provided. The normalized values are based on
the percent of the basin that the rock type underlies. Fig. 12A demonstrates that there is a preference for bedrock hollows, bedrock valleys,
and unfilled valleys in Kingston Canyon to form on carbonate rocks
and, to a lesser degree, siliciclastic sedimentary rocks. There also appears to be a preference for unincised hollows to form on siliciclastic
3.1.4. Side-valley fans
Accumulations of alluvial and colluvial sediments at the mouth of
tributary channels are common within the upland watersheds of central Nevada (Fig. 1). The size (length, area), gradient, and composition
of these side-valley fans is highly variable and, as shown by
Germanoski and Miller (2004), is dependent on basin size and
shape as well as tributary size, relief, and gradient. These side-valley
fans can be subdivided into two types: (i) those in which the tributary
channel traverses the length of the fan and joins the axial channel
Table 5
Summary of meadow, process zone and connectivity characteristics of studied basins; groupings are modified from Germanoski and Miller (2004).
Unincised-toincised ratio
# and area of
meadows (km2)
% Meadowto-basin area
Character of
lower-most reacha
90
0
2/0.02
0.06
66
86
0.06
2/0.02
0.04
98
61
85
0.02
1/0.06
0.07
0.21
0.13
0.82
100
74
81
14
9
234
100
89
55
0
0
0.15
2/0.05
5/0.07
5/0.1
0.62
1.00
0.22
ANBV in bedrock
controlled canyon
ANBV in bedrock
controlled canyon
IAV; >4 m incision
at mouth
IAV
IAV
IAV in narrow
bedrock canyon
1.06
88
32
28
0.10
1/0.02
0.10
0.76
75
49
35
0.07
5/0.18
0.30
1.02
87
42
60
0.18
2/0.09
0.33
Category
Basins
Dominant
bedrock
Storage-totrans. ratio
Group 1
Flood-dominated
Pine Cr.
Volcanic
0.52
99
29
South Twin R.
Volcanic
0.56
95
Barley Cr.
Volcanic
0.43
N. Corcoran
S. Corcoran
Birch Cr.
Volcanic
Volcanic
Siliciclastics
Carbonates
Intrusives
Other
Metamorphic
Siliciclastics
Carbonates
Volcanic
Group 2
Deeply incised
channels
Group 3
Fan-dominated
Cottonwood Cr.
Kingston C.
San Juan Cr.
a
IAV — Incised alluvial valley; ANBV — anabranching valley.
% basin
connected
# of
fans
% fans
incised
IAV; incised several
meters at mouth
IAV in narrow
bedrock canyon
IAV; incised several
meters at mouth
J.R. Miller et al. / Geomorphology 139–140 (2012) 384–402
Unincised
hollow
Bedrock
valley
Unfilled
valley
Incised
Unincised colluvial
alluvial
valley
valley
Unincised
fan
Unincised
hollow
Unincised
hollow
Unincised
hollow
Incised
fan
Bedrock
hollow
Wet
Meadow
Incised alluvial valley
395
Incised
alluvial
valley
Incised
colluvial
valley
Unfilled
valley
Incised alluvial
valley
Incised alluvial valley
Unincised
fan
Unfilled valley
Unfilled valley
Fig. 10. Schematic diagram of the most common downstream patterns in process zones observed within the studied basins. Diagram based on statistical analysis of downstream
linkages.
rocks. In contrast, a relatively high number of unincised hollows and
unfilled valleys are located on volcanic rocks within the Birch Creek
basin in spite of the fact that volcanic assemblages underlie less
than about 1% of its area. Comparison of the actual to normalized
data (Fig. 12D) suggests that these process zones are preferentially located on volcanic rocks within the San Juan Creek basin as well.
Geology also can influence basin dynamics by controlling the size
of the alluvial/colluvial sediment found within the basin. An examination of more than 9700 clasts in seven of the basins (all but the South
Twin River) reveals that clasts from highly fractured metamorphic
(metasedimentary) and siliciclastic rocks are generally finer when
all process zones are considered, whereas clasts from quartzite and
intrusive rocks tend to be larger (Fig. 13). The size of carbonate clasts
varies between basins but tends to be relatively large in Kingston
Canyon and Birch Creek, where carbonate rocks are relatively abundant, and fine-grained where carbonate rocks are rare. The size of
volcanic particles also varies widely between the basins, but tend to
be of relatively moderate size.
Fan-dominated
basins
Deeply-incised
basins
3.2. Connectivity
Geomorphic connectivity was operationally defined by the existence of a continuous channel within a given process zone that allows
for the channelized transport of water and sediment through the
reach. Fig. 14A was produced by measuring the relative proportion of
the drainage area that was connected (and disconnected) upstream of
all major tributary confluences within the basin. The figure illustrates
that (i) the degree of connectivity measured at the basin mouth varies
significantly (from ~74 to 100%) between the eight studied watersheds
and (ii) the way in which connectivity changes downvalley varies between the basins. The Pine Creek, South Twin River, Barley Creek, and
North Corcoran Creek basins, which are underlain by volcanic rocks, exhibit the highest degree of connectivity (exceeding 95% throughout the
basin). Cottonwood Creek possesses a fully connected drainage network in the upstream areas of the basin, but significant areas are not integrated with the axial channel downstream. As a result, about 15% of
the basin is disconnected with the axial channel at the basin mouth.
Flood-dominated
basins
Fig. 11. Bedrock composition of studied basins (modified and updated from Germanoski and Miller, 2004).
396
J.R. Miller et al. / Geomorphology 139–140 (2012) 384–402
Fig. 12. Proportion of process zones underlain by a given rock type in Kingston Canyon (A), Birch Creek (B) Cottonwood Creek (C), and San Juan Creek (D). Graphs on right show
relative frequency of zone type normalized according to percent of basin area underlain by given lithology and illustrates tendency of process zone type to be associated with specific rock type.
The loss of connectivity begins in the upstream-most areas of the
Kingston Canyon, Birch Creek, San Juan Creek, and South Corcoran
Creek basins and semisystematically declines before acquiring a variable but moderate (~10–20%) or high (20–30%) degree of disconnectivity throughout the middle and lower portions of the basins. At the basin
mouth, about 15 to 25% of the upstream basin area in these watersheds
does not contribute water or sediment to the axial drainage via a channel. Inspection of the process zone maps (e.g., Fig. 4) reveals that connectivity of the drainage network is primarily disrupted by two types
of process zones: unincised side-valley fans and unincised valley floors.
J.R. Miller et al. / Geomorphology 139–140 (2012) 384–402
Kingston Canyon
(n= 2500)
Cottonwood Creek
397
Birch Creek
(n= 1550)
San Juan Creek
(n= 1400)
(n= 1700)
Other Basins
Total Clasts
(n= 9700)
(n= 1350)
(n= 750)
(n= 850)
Fig. 13. Basic statistics for intermediate particle diameter measured within all process zones within the 7 basins for which data are available. Data stratified by clast lithology where
multiple lithologies exist (i.e., within Kingston Canyon, Birch Creek, Cottonwood Creek, and San Juan Creek). Graph for total clasts represent statistics stratified by lithology for all
clasts examined within the studied basins. Filled rectangle — mean; box — standard deviation; line across box — median intermediate diameter; whiskers — 10 and 90% exceedence
values; and n represents number of clasts used in statistical analysis.
4. Discussion
4.1. Basin sensitivity and dynamics
An objective of this investigation was to expand on the work of
Germanoski and Miller (2004) to gain a more detailed understanding
of landform sensitivity and dynamics in upland watersheds in central
Nevada. The hierarchical approach used here was particularly aimed
at quantifying spatial variations in channel/valley form and process
observed in the earlier analysis. Upstream reaches of Kingston
Canyon, for example, are clearly affected by side-valley fans; whereas
side-valley fans are truncated by a deeply incised channel near the
basin mouth. As a result, classification of the entire watershed into a
single sensitivity type proved problematic, prompting Germanoski
and Miller (2004) to subdivide Kingston Canyon into two distinct
sensitivity types (fan-dominated and deeply incised, respectively).
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J.R. Miller et al. / Geomorphology 139–140 (2012) 384–402
A
B
% Connected
120
100
80
60
40
y = -133.85x + 97.59
R² = 0.47
20
0
0
0.05
0.1
0.15
0.2
Area of meadows (km2)
Fig. 14. (A) Downstream changes in percent of drainage connected by surface channels.
Symbols represent individual meadows within the studied watersheds; (B) relation
between basin connectivity and total meadow area (sum of all meadow areas) within
the 9 studied basins. Relationship is statistically significant.
They hypothesized that a hierarchical approach would largely eliminate the problems of classifying basin sensitivity imposed by spatial
variations in process and form.
At the watershed scale, the hierarchical approach allowed the
eight investigated basins (counting north and south Corcoran Canyon
as a single catchment) to be subdivided into three broad groups in
terms of landscape sensitivity to change and basin dynamics. These
groups are consistent with the groups described by Germanoski and
Miller (2004) as flood-dominated channels (group 1), deeply incised
channels (group 2), and fan-dominated channels (group 3) (Table 5).
Two basins, San Juan Creek and Birch Creek, categorized by
Germanoski and Miller (2004) as deeply incised and pseudostable
channels, respectively (Table 1), are categorized as fan-dominated
channels using the hierarchical approach in this analysis. Reclassification of the two basins reflects (i) a focus by Germanoski and Miller
(2004) on downstream segments of the riparian corridor where a
majority of meadow complexes are found and (ii) a more detailed
analysis of reach-scale processes during this study and the spatial variations in valley/channel form and process throughout the entire watershed. We believe that the hierarchical approach used here is more
effective from a management perspective because it not only considers the general (average) form and process rates of the riparian
corridor, but classifies basins according to the type and structural arrangement (frequency, density, spatial pattern) of process zones that
are present within any given part of the basin. Understanding of the
process zone types and structure subsequently allows for a more effective prediction of such processes as channel incision, avulsion,
and the preservation of wet meadow ecosystems along any given segment of the riparian corridor. Moreover, the process zone approach
provides important insights into the spatial and temporal variability
of runoff and recharge processes along the drainage network, as will
be described in more detail elsewhere. It is important to note, however,
that the work conducted by Germanoski and Miller (2004) showed that
clear differences in channel incision and watershed-scale parameters
exist between the studied drainages that can be related to ecological
processes (Chambers et al., 2004) and that these differences are recognized in the analysis performed here.
The most dynamic basins studied in central Nevada, referred to as
‘flood-dominated’ basins (Table 5), include Pine Creek and the South
Twin River. Both basins possess an anabranching channel pattern
within the lower reaches of the watershed. The pattern is characterized by high rates of sediment transport that allows for localized
zones of deposition and erosion behind debris dams and for the
rapid change of the valley floor through the production and erosion
of low-relief, discontinuous terraces. The alluvial sediments are transported over a shallow bedrock surface and through a bedrock canyon
that forms the local hillslopes. Meadow complexes are absent within
the anabranching channel reach and are extremely limited within
other parts of the basin (Table 5). The basins are underlain exclusively
by volcanic rocks (Fig. 11) that generate abundant, relatively large
clasts (mean intermediate diameter is >50 mm) (Fig. 13). On hillslopes, these sediments are primarily stored within unincised hollows, which occur with moderate frequencies and densities (Fig. 7).
At the base of the hillslopes, side-valley fans occur with a frequency
similar to that within the other watersheds (with the exception of
Birch Creek); however, nearly all of these are located in headwater
areas and are incised (Table 5).
Within reaches characterized by anabranching channels, incision
is limited by shallow bedrock. Upstream in more headwater areas
valleys are filled with alluvial and colluvial deposits. Nearly all of
these valleys have been incised creating incised alluvial and incised
colluvial valley reaches that on a basin scale are present at relatively
low densities and frequencies (Fig. 8). Unincised valleys, which
limit the connectivity between hillslope and axial channel areas, are
limited in number and length. Upstream of the anabranching
channels, then, the riparian corridor is prone to rapid and pervasive
incision associated with a dynamic channel.
From a process perspective, hillslope process zones can be
grouped into reaches that (i) have a tendency to store sediment and
allow for infiltration and groundwater recharge (unincised hollows),
and (ii) lack extensive unconsolidated deposits, but can effectively
transport water and sediment through the reach to downslope areas
(including incised hollows, bedrock hollows, unfilled valleys, and
bedrock valleys). Fig. 15A shows that the ratio of zone storage-totransport (per unit basin area) is below 1 for Pine Creek and the
South Twin River and moderately low in comparison to the other
studied basins. Thus, the nature of the upper drainage network is
structurally organized to transport relatively large amounts of sediment temporarily stored in unincised hollows downstream, across incised alluvial fans, to the axial channel. It is then transported through
the incised alluvial and colluvial channel segments to the downstream anabranching channel reaches. These anabranching reaches
occur within relatively steep, narrow bedrock influenced valleys
that prevent the storage of large volumes of sediment. Thus, the dynamic nature of the anabranching channels in the lower reaches of
the watershed appears to be related to (i) an abundance of sediment
that can be effectively transported off the hillslopes by significant
runoff and (ii) a high degree of connectivity in the basin (>95%,
Fig. 14A) that allows for its continued movement toward the basin
mouth. The high degree of connectivity may also enhance the discharge of channelized flows that promote incision of the side-valley
fans and valleys filled with alluvial and colluvial sediments. The net
result of the basins' architecture is a highly dynamic channel system
in downstream basin areas and upstream valley segments that respond relatively quickly to changing environmental conditions by
means of channel incision.
As is the case for Pine Creek and the South Twin River, the Barley
Creek and Corcoran Canyon basins have deeply incised channels
(Table 5) and are underlain exclusively by volcanic rocks (Fig. 11).
However, the volcanic units found in Pine Creek and the South Twin
River basin differ from those found in Barley Creek and Corcoran
J.R. Miller et al. / Geomorphology 139–140 (2012) 384–402
A
B
Fan-dominated
basins
Deeply-incised Flood-dominated
basins
basins
Fig. 15. (A) Ratio of density of storage versus transport-dominated process zones located
on hillslopes. Lower ratios indicate tendency to transport sediment and water off
hillslopes; (B) ratio of the total length of unincised-to-incised (incised) process zones
within the studied basins. Lower ratios associated with highly connected drainage
network and higher proportion of incised channels.
Canyon in that they generate smaller clasts (mean intermediate diameter is b50 mm) (Fig. 13). The rocks also produce large quantities of
sand/grus-sized sediment (Barley Creek) and finer material from poorly
welded tuffs (Corcoran Canyon) as evidenced from thick alluvial deposits exposed along the incised alluvial valleys. Both the frequency
and density of unincised hollows are relatively low (Fig. 7), suggesting
that the amount of sediment stored on the hillslopes is limited. However,
the frequency and density of process zones that are conducive to water
and sediment transport are relatively high in comparison to the other
watersheds. As a result, the sediment storage-to-transport ratio is
lower than for the other basin types (Fig. 15A), suggesting that sediment
can be effectively transported off the hillslopes.
In contrast to Pine Creek and the South Twin River, the Barley
Creek basin is characterized by the highest density of incised alluvial
valleys (Fig. 8). Anabranching channels do not occur. Not only are incised alluvial valleys common, but the depth of incision is (at least locally) high, exceeding 5 m at the basin mouth within Barley Creek.
The incised alluvial valleys within the north and south Corcoran basins are less entrenched, although the axial valleys are frequently
characterized by large, upstream-migrating headcuts exceeding a
few meters in height.
Meadow complexes occur along the riparian corridor within
Barley Creek and Corcoran Canyon, but they have been severely
degraded by channel/gully incision. In the case of Barley Creek, the
meadow near the basin mouth is preserved only along the valley margins and represents a local zone of groundwater discharge distant
from the deeply incised axial channel. Five meadows exist in south
Corcoran (Table 5), but each is being dissected by numerous gullies
with migrating headcuts that began on narrower and steeper parts
399
of the valley floor (Miller et al., 2011). The fine-grained sediments underlying the meadows prevented a pervasive drop in the water table
caused by incision, permitting persistence of meadows (Lord et al.,
2011). In Barley Creek and Corcoran Canyon, the dissection has
resulted in relatively small meadows (generally b0.02 km 2).
Connectivity within these basins is high, exceeding 95% (Table 5).
Thus, once reaching the base of the hillslopes, sediment can be transported through the side-valley fans (nearly all of which are incised,
Table 5) and through the incised alluvial and colluvial valleys before
exiting the basin. It is not entirely clear why these basins lack anabranching channel reaches, but it may be related to the more deeply
buried bedrock near the basin mouth, lower valley side relief along the
axial drainage, and lower availability of stored sediment on the hillslopes. Given the similarities in the underlying bedrock and process
zone type and structure on the hillslopes, the degree of incision along
the lower valleys in Corcoran Canyon might be expected to be significantly greater, approaching that observed along Barley Creek. It appears,
however, that incision was limited within both the north and south
Corcoran basins by (i) their relatively small size (b10 km2), (ii) the relatively low elevation of the drainage divides that limits the accumulation
of snow and spring runoff and (iii) their relatively low relief (Table 2).
The remaining basins are fan-dominated (Table 5) and include
Kingston Canyon, Cottonwood Creek, San Juan Creek, and Birch
Creek. They exhibit a number of similarities at both the basin and
reach scale. These similarities include (i) a high frequency and density
of unincised hollows in comparison to the other studied basins
(Fig. 7); (ii) high hillslope storage-to-transport ratios (Fig. 15A);
(iii) a relatively high percentage of unincised fans (Table 5); (iv) a
relatively high frequency and density of unincised valleys leading to
a high unincised valley-to-incised valley length ratio (Fig. 15B); (v)
large areas of the basin that are disconnected from the axial drainage
(Fig. 14A); (vi) a loss of connectivity that typically begins in the
upstream-most areas of the basin, decreases to the middle of the
basin, and subsequently remains constant or decreases downstream;
(vii) an alternating pattern of incised alluvial valleys with incised colluvial valleys along the riparian corridor within the upper reaches of
the basin (e.g., shown on Fig. 4). The incised colluvial valleys are typically associated with large side-valley fans that project across the
valley floor and that create a ‘stepped’ longitudinal channel and valley
profile (as discussed in the introduction); (viii) channels that are incised into the valley floor within the lower reaches of the basin; (ix)
relatively large (>0.04 km 2) wet meadow complexes, often located
with the upper or middle segments of the basin (Table 5); and (x) a
variety of underlying bedrock types, including sedimentary, metamorphic, and intrusive rocks (Fig. 11). The nature of the incised alluvial and colluvial valleys within upstream basin areas indicates that
these parts of the basin have a high potential for axial channel incision and meadow degradation centered on the removal of the
‘steps’ that occur along the incised colluvial valleys. However, the
combined character of the hillslope process zones, the underlying
rock types, and the high degree of basin area that is disconnected
from the axial valley limits the rate and magnitude of incision that
can and has occurred. Immediately upstream of the basin mouth, an
increase in basin area and discharge has led to deeper channel incision (e.g., shown for Kingston Canyon, Fig. 9), and the steppedlongitudinal profile of the channel has largely been replaced by a
more continuously sloping channel bed. In addition, downstream
meadows have been replaced by drier plant communities and are significantly degraded. These downstream areas have a lower potential
for further incision, but are more dynamic in terms of the potential
rate of incision following an environmental disturbance.
4.2. Geological controls on process zone structure and connectivity
Data presented above suggest that the nature and behavior of the
drainage system along axial valleys depends in part on the type and
J.R. Miller et al. / Geomorphology 139–140 (2012) 384–402
spatial structure of the process zones on the hillslopes and the degree
of connectivity within the watershed. It is therefore important to understand the factors that control both connectivity and the nature of
the process zones on the hillslopes.
The formation of unincised/incised hollows appears to have two
requirements. First, the resistance of the underlying bedrock to erosion must be such that it allows for the development of U-shaped depressions oriented semiparallel to the hillslope. Second, erosion of
the bedrock must produce an abundant supply of relatively small
particles (a median clast diameter of ~20 mm) that accumulate within the depression. Fig. 12A shows that within Kingston Canyon these
two factors are met most often by siliciclastic rocks and, to a lesser
degree, carbonates. Within the Birch and San Juan Creek basins,
hillslope hollows have a distinct tendency to form on volcanic rocks
that weather into easily eroded, relatively small clasts. In contrast,
bedrock hollows and bedrock valleys are favored by resistant rock
units that produce limited, but larger clasts and steep (locally vertical), jagged outcrops (Fig. 5C,D). Fig. 12A shows that within Kingston
Canyon these characteristics are predominantly met by carbonate lithologies. The fact that unincised hollows and bedrock hollows and
valleys form on carbonate and volcanic rocks indicates that the lithology of the rock units may not be as important in controlling the type
of process zone that is present as the weathering characteristics of the
materials. In the case of carbonates, some units are highly fractured,
allowing them to be more easily eroded and to produce an abundance
of relatively small clasts. These clasts are frequently transported to
and deposited along downstream incised alluvial valleys where they
locally comprise as much as 70% of the >2.8 mm sediment fraction.
Other carbonate rocks are poorly fractured and break into large clasts
and boulders (Fig. 5C). Differences in weathering characteristics, and
their influence on the distribution and type of process zone present
on the hillslopes, are also apparent for metamorphic, intrusive, and
volcanic rocks. Bedrock hollows and valleys are present on these
rock types where they are locally more resistant to erosion (Fig. 12).
In most areas, however, these rock units are relatively easy to erode
and, as shown by the normalized data in Fig. 12, tend not to produce
bedrock hollows and valleys.
Unfilled valleys also form preferentially in easily eroded rock
types. In fact, unincised hollows are most often linked downstream
with unfilled valleys (Fig. 10), and both are rarely associated with
bedrock hollows and valleys. In other words, unincised/incised hollows and unfilled valleys commonly form a couplet that are most frequently found on easily eroded rock types. Where rocks are more
resistant, bedrock hollows and valleys occur. The net result, then, is
that there is a tendency at the basin scale for the density of unincised/incised hollows and unfilled valleys to be inversely related to
bedrock hollows and valleys (Fig. 7).
The downstream alteration of unincised hollows to unfilled valleys
is presumably driven by an increase in contributing drainage area to
the drainage net that leads to particle movement. More specifically, as
contributing area and presumably runoff increases, a threshold is
reached at which the generated particles can be entrained and transported downslope. The consistent ability to entrain and transport sediment leads to the development of V-shaped, sediment-limited valleys
in comparison to those found upslope.
Interestingly, the contributing area required to produce unfilled
valleys varies between rock types (Fig. 16A), indicating that bedrock
influences runoff. Volcanic rocks require the lowest contributing
area to produce an unfilled valley, whereas siliciclastic and carbonate
rocks tend to require the most (5 to 7 times more than for volcanic
rocks). The implication is that higher rates of runoff are associated
with volcanic lithologies. These data are consistent with three additional observations. First, unincised fans and unincised valleys are
most often associated with upstream contributing areas underlain
by carbonates and, to a lesser degree, siliciclastics. Thus, these rock
types tend to generate basins characterized by a large degree of
A
0.16
0.14
Contributing
area (km2)
400
0.12
0.10
0.08
0.06
0.04
0.02
0.00
B
Fig. 16. (A) Mean upstream area contributing flow to head of unfilled valley stratified
by rock type. Low values indicate that smaller areas are required to transport sediment
downslope, presumably as a result of higher runoff; (B) annual flood hydrograph
developed for Kingston Canyon and San Juan Creek by Amacher et al. (2004). Hydrographs indicate a tendency for higher peak flows and more rapid runoff (shorter
basin lag times) for basins underlain by volcanic rocks. Increased runoff from volcanic
basins is consistent with lower sediment storage to transport ratios, a higher percentage of incised side-valley fans, a lower unincised-to-incised valley ratio, and a higher
degree of basin connectivity.
disconnected drainage. Second, basins underlain by volcanic rocks
tend to exhibit more extensively incised fans and axial valley areas.
Finally, hydrographs presented by Germanoski and Miller (2004)
showed that annual peak discharges tend to be higher and peak
more rapidly in San Juan Creek, underlain predominately by volcanic
rocks, than in Kingston Creek, underlain by a large percentage of carbonates and highly fractured metasedimentary rocks (Fig. 16B).
While rock type appears to influence the nature of the process
zones on the hillslopes, the type and distribution of process zones
that are present may also influence connectivity. Unincised hollows
exhibited few signs of surface runoff within subbasins of Kingston
Canyon and Birch Creek hydrologically monitored during a threeyear period. This was not unexpected given the highly porous nature
of the unconsolidated sediment within the depressions. Thus, a high
density of unincised hollows would be expected to enhance groundwater recharge and reduce runoff and, therefore, downstream incision of alluvial and colluvial deposits. This suggestion is supported
by the relatively high frequencies and densities of unincised hollows
(Fig. 7) found in basins with a high percentage of unincised fans
(Table 5), unincised valleys (Fig. 8), and disconnected drainage
(Table 5, Fig. 14A).
4.3. Factors influencing meadow distribution
A total of 56 meadow complexes have been identified in upland
watersheds of central Nevada. The geomorphology, stratigraphy,
J.R. Miller et al. / Geomorphology 139–140 (2012) 384–402
and hydrology of many of these meadows have been extensively
studied using a variety of methods, ranging from the coring and description of the valley deposits, to the evaluation of groundwater
data collected from extensive arrays of monitoring wells and piezometers, to the application of ground penetrating radar and seismic surveys (Jewett et al., 2004; Lord et al., 2011). These analyses have
demonstrated that each meadow complex is a unique feature and
cannot be unequivocally described by any single model. Nonetheless,
nearly all of the meadows result from a combination of factors, including an adequate supply of water to the reach and a mechanism
that retards the downvalley movement of groundwater through the
valley fill and causes groundwater levels to rise to the valley surface.
A reduction in groundwater flow may be produced in several ways,
the most prominent of which are the vertical and/or lateral constriction of the valley fill by bedrock and a change in grain size of the
valley-fill deposits. Reductions in grain size and the low permeability
of the resulting deposits are commonly associated with deposition
upstream of side-valley fans and bedrock protrusions (Germanoski
et al., 2011). Thus, the majority of meadows are located upstream of
large side-valley fans that project across the valley floor (Fig. 1). In
addition, most of the meadows exhibit relatively impermeable finegrained sediment near the ground surface in comparison to deeper
deposits. These fine-grained surface materials (i) retard the ability
of water to rapidly discharge and drain the underlying aquifer and
(ii) create artesian flow conditions and springs that allow meadows
to remain saturated over long periods of time (Lord et al., 2011).
The above data show that the location of meadow development is
dependent in part on both watershed scale and local factors
(Germanoski et al., 2011). Meadows are unlikely, for example, to
form where rapidly evolving anabranching valleys occur as they possess neither the fine-grained sediment required for meadow formation nor the constrictions required to retard groundwater flow and
produce the necessary upward flow gradients. Meadows are scarce
in deeply incised alluvial valleys, such as is within the Barley Creek
basin, because the entrenched channel typically allows for direct hydrologic connection between the channel and permeable subsurface
units, rapid drainage of the shallow aquifer system, and lowering of
the groundwater table. Unlike flood-dominated basins with anabranching channels, some deeply incised alluvial valleys supported
meadow complexes prior to incision. With incision, the meadows
that existed became lost or highly degraded and typically occur as
small features along the valley margins fed by groundwater that is
poorly integrated with the entrenched channel (Lord et al., 2011).
Earlier we argued that the process zones that comprise the lower
axial valleys reflect the nature of the underlying bedrock and the
type and structure of the process zones on the hillslopes. It follows,
then, that meadow formation and distribution should also reflect
the type and structure of process zones within the basin. Such relations do exist. For example, 78% (18 of 23) of the meadows within
the studied basins are found along unincised valleys or incised alluvial valley floors characterized by shallow depths of incision, and which
possess upstream drainage areas exhibiting a relatively low degree of
connectivity (b90%). In fact, >20% of the upstream basin area is disconnected from the axial drainage network for a majority of the
meadows. At the basin scale, 47% of the variation in total meadow
area can be accounted for by the degree of basin connectivity within
the watershed (Fig. 14B), a high percentage given the local requirements for meadow formation.
The relationship between connectivity and meadow formation
and area is related to several factors. First, meadow development is
promoted by groundwater recharge and enhanced groundwater
flow. Clearly, groundwater recharge is promoted by the movement
of water from a tributary basin across the surface of an unincised
fan or unincised valley reach. In addition, basins with numerous unincised fans, unincised valleys, and a relatively high degree of disconnected basin area also exhibit a high frequency and density of
401
unincised hollows. The broad U-shaped nature of the hollows combined with their loose, highly permeable accumulations of sediment
are likely to increase the amount of upland recharge. In fact, we
argue that the relatively high magnitude of recharge that occurs within areas characterized by numerous unincised hollows reduces the
ability of surface flows to erode and incise downstream, side-valley
fan deposits. Second, channel incision, particularly across side-valley
fans, is less severe along axial valleys within basins characterized
by a relatively low degree of connectivity (e.g., Kingston Canyon,
Cottonwood Creek, Birch Creek, and San Juan Creek). Thus, incision
of the meadow deposits and degradation of the meadow complexes
are less likely. These observations are significant in that they suggest
that any activity within the upland areas that promotes an increase in
connectivity within the basin may negatively affect meadow complexes, in spite of the fact that the meadows are spatially separated
from the disturbance.
5. Summary and conclusions
The drainage network within the studied watersheds of central
Nevada was subdivided into distinct process zones on the basis of valley form, the inherent geological deposits, and the presence or absence of surficial channels. Each type of process zone is dominated
by a suite of geomorphic and hydrologic processes that produce the
morphologic characteristics upon which it is classified. U-shaped,
unincised hollows, for example, are characterized by sediment deposition and storage as well as groundwater recharge; whereas Vshaped, bedrock-floored unfilled valleys are dominated by sediment
transport and runoff. On hillslopes, the type and spatial structure of
the process zones are related to the lithology and weathering characteristics of the underlying bedrock. Unincised hollows and unfilled
valleys, to which the unincised hollows are frequently linked, are associated with less resistant rock types (including siliciclastic, volcanic,
and some carbonate formations) that weather into abundant but relatively small particles. Bedrock valleys and hollows are associated
with resistant, poorly fractured rocks that produce limited but larger
clasts. The type and spatial arrangement of process zones within
lower elevation (axial) valleys is dependent on the characteristics of
the process zones on the hillslopes. A high frequency and density of
unincised hollows are associated with numerous unincised sidevalley fans as well as frequent and lengthy unincised valley segments
that disconnect large sections of the drainage basin from channelized
surface flows. In contrast, a relatively high density of transportdominated process zones (including unfilled valleys, bedrock hollows,
and bedrock valleys) leads downstream to the incision of side-valley
fans and axial valley deposits. Connectivity is related to the lithology
of the underlying bedrock, with higher degrees of connectivity being
associated with volcanic rocks that presumably yield high rates of
runoff. Low levels of connectivity are associated most frequently with
sedimentary and metamorphic assemblages, particularly carbonates
that are locally permeable where they are extensively fractured.
At the basin scale, watersheds can be separated broadly into three
general groups (flood-dominated, deeply incised, and fandominated) on the basis of the underlying bedrock geology, the
ratio of sediment storage to transport-dominated process zones, the
degree of connectivity, and the severity of axial valley incision.
Meadow complexes are most extensive within basins characterized
by a high ratio of sediment storage to transport-dominated process
zones on hillslopes and by a relatively low degree of connectivity in
comparison to the other studied watersheds. The more extensive nature of meadows in these basins is thought to be related to (i) lower
runoff from sedimentary, intrusive, and metamorphic rocks in comparison to volcanic terrains that reduces the severity of incision
along the riparian corridor; (ii) enhanced groundwater recharge in
numerous and lengthy unfilled hollows on the hillslopes; and
402
J.R. Miller et al. / Geomorphology 139–140 (2012) 384–402
(iii) enhanced groundwater recharge upon unincised side-valley fans
and unincised valleys.
From a management perspective, basins underlain by volcanic
rocks appear to be more sensitive to incision and produce more dynamic channels in terms of the rate of channel/valley modification
than those underlain by other lithologies. Where meadow complexes
exist in these basins, they are likely to be severely degraded and will
be difficult to manage given the dynamic nature of the axial channel
processes. Meadows within basins that exhibit a low degree of connectivity and high sediment storage-to-transport ratios on hillslopes
will likely be more responsive to management activities because of
the reduced susceptibility to channel incision and because of a large
supply of groundwater flow to the meadow through an extensive network of recharge sites. However, we should recognize that activities
that lead to an increase in basin connectivity may negatively impact
downstream meadows, in spite of the fact that these activities may
be located far upstream.
Acknowledgments
The authors want to thank a number of students from Western
Carolina University who were instrumental in collection of field and
laboratory data, including Harrison Carter, Rachael Tury, and Danvey
Walsh. We are also indebted to Blake Engelhardt and several other
students from the University of Nevada, Reno, for the collection of
field data along the axial drainage systems in three basins. The manuscript benefited greatly from the comments provided by Dr. Jordan
Clayton and three anonymous reviewers. Funding for the project
was provided by the U.S. Forest Service, Rocky Mountain Research
Station, without which the analysis could not have been conducted.
References
Amacher, M.C., Kotuby-Amacher, J., Grossl, P.R., 2004. Effects of natural and anthropogenic disturbances on water quality. In: Chambers, J.C., Miller, J.R. (Eds.), Great
Basin Riparian Ecosystems: Ecology, Management, and Restoration. Island Press,
Washington, DC, pp. 162–195.
Brierley, G.J., Fryirs, K., 2001. Variability in sediment delivery and storage along river
courses in Bega catchment, NSW, Australia: implications for geomorphic river recovery. Geomorphology 38, 237–265.
Brierley, G.J., Fryirs, K.A., 2005. Geomorphology and River Management: Applications
of the River Styles Framework. Blackwell Publishers, Oxford, UK.
Brunsden, D., Thornes, J.B., 1979. Landscape sensitivity and change. Transactions of the
Institute of British Geographers, NS 4, 463–484.
Castelli, R.M., Chambers, J.C., Tausch, R.J., 2000. Soil–plant relations along a soil–water
gradient in Great Basin riparian meadows. Wetlands 20, 251–266.
Chambers, J.C., Linnerooth, A.R., 2001. Restoring riparian meadows currently dominated by Artemisia using alternative state concepts — the establishment component.
Applied Vegetation Science 4, 157–166.
Chambers, J.C., Miller, J.R. (Eds.), 2004. Great Basin Riparian Ecosystems: Ecology,
Management, and Restoration. Island Press, Washington, DC.
Chambers, J.C., Miller, J.R. (Eds.), 2011. Geomorphology, Hydrology and Ecology of Great
Basin Meadow Complexes—Implications for Management and Restoration. General
Technical Report RMRS-GTR, U.S. Department of Agriculture, Forest Service, Rocky
Mountain Research Station, Fort Collins, CO, U.S. Department of Agriculture, Forest
Service, Rocky Mountain Research Station, 125 pp.
Chambers, J.C., Farleigh, K., Tausch, R.J., Miller, J.R., Germanoski, D., Martin, D., Nowak, C.,
1998. Understanding long- and short-term changes in vegetation and geomorphic
processes: the key to riparian restoration. In: Potts, D.F. (Ed.), Rangeland Management
and Water Resources. American Water Resources Association and Society for Range
Management, Herndon, VA, pp. 101–110.
Chambers, J.C., Blank, R.R., Zamudio, D.C., Tausch, R.J., 1999. Central Nevada riparian areas:
physical and chemical properties of meadow soils. Journal of Range Management 52,
92–99.
Chambers, J.C., Miller, J.R., Germanoski, D., Weixelman, D.A., 2004. Process-based approaches for managing and restoring riparian ecosystems. In: Chambers, J., Miller,
J.R. (Eds.), Great Basin Riparian Ecosystems: Ecology, Management, and Restoration. Society of Ecological Restoration International Island Press, Washington, DC,
pp. 261–292.
Downs, P.W., Gregory, K.J., 1995. The sensitivity of river channels to adjustment. The
Professional Geographer 47, 168–175.
Dunham, J.B., Vinyard, G.L., Rieman, B.E., 1997. Habitat fragmentation and extinction
risk of Lahontan cutthroat trout (Oncorhynchus clarki henshawi). North American
Journal of Fisheries Management 17, 910–917.
Frissell, C.A., Liss, W.J., Warren, C.E., Hurley, M.D., 1986. A hierarchical framework for
stream habitat classification: viewing streams in a watershed context. Environmental Management 10, 199–214.
Germanoski, D., Miller, J.R., 2004. Basin sensitivity to natural and anthropogenic disturbance. In: Chambers, J.C., Miller, J.R. (Eds.), Great Basin Riparian Ecosystems: Ecology,
Management, and Restoration. Island Press, Washington, DC, pp. 88–123.
Germanoski, D., Ryder, C.H., Miller, J.R., 2001. Spatial variation of incision and deposition within a rapidly incised upland watershed, central Nevada. Proceedings of
the 7th Federal Interagency Sedimentation Conference, Reno, Nevada.
Germanoski, D., Miller, J.R., Lord, M., Jewett, D., Chambers, J.C., 2011. Controls on meadow
distribution and characteristics. In: Chambers, J.C., Miller, J.R. (Eds.), Geomorphology,
Hydrology and Ecology of Great Basin Meadow Complexes—Implications for Management and Restoration. : General Technical Report RmRS-GTR. U.S. Department of
Agriculture, Forest Service, Rocky Mountain Research Station, Fort Collins, CO.
Grant, G.E., Swanson, F.J., 1995. Morphology and processes of valley floors in mountain
streams, western Cascades, Oregon. In: Costa, J.E., Miller, A.J., Potter, K.W., Wilcock,
P.R. (Eds.), Natural and Anthropogenic Influences in Fluvial Geomorphology:
American Geophysical Union Monograph, 89, pp. 83–102. Washington, DC.
Grant, G.E., Swanson, F.J., Wolman, M.G., 1990. Pattern and origin of stepped-bed morphology in high-gradient streams, western Cascades, Oregon. Geological Society of
America Bulletin 102, 340–352.
Hooke, J., 2003. Coarse sediment connectivity in river channel systems: a conceptual
framework and methodology. Geomorphology 56, 79–94.
Horton, R.E., 1945. Erosional development of streams and their drainage basins. Hydrophysical approach to quantitative morphology. Geological Society of America
Bulletin 56, 446–460.
Jenson, S.E., Platts, W.S., 1990. Restoration of degraded riverine/riparian habitat in the
Great Basin and Snake River regions. In: Kusler, J.A., Kentula, M.E. (Eds.), Wetland
Creation and Restoration: The Status of the Science. Island Press, Covelo, CA, pp.
367–398.
Jewett, D.G., Lord, M., Miller, J.R., Chambers, J.C., 2004. Geomorphic and climatic controls on flow regimes and groundwater systems. In: Chambers, J.C., Miller, J.R.
(Eds.), Great Basin Riparian Ecosystems: Ecology, Management, and Restoration.
Island Press, Washington, DC, pp. 124–162.
Kishi, T., Mori, A., Hasegawa, K., Kuroki, M., 1987. Bed configurations and sediment
transports in mountainous rivers. Comparative Hydrology of Rivers of Japan.
Final Report. Japanese Research Group of Comparative Hydrology, Hokkaido
University, Sapporo, Japan, pp. 165–176.
Lord, M., Jewett, D., Miller, J.R., Germanoski, D., Chambers, J.C., 2011. Hydrologic processes influencing meadow ecosystems. In: Chambers, J.C., Miller, J.R. (Eds.),
Great Basin Riparian Ecosystems: Ecology, Management, and Restoration. Island
Press. Gen. Tech. Rep. RMRS-GTR. U.S. Department of Agriculture, Forest Service,
Rocky Mountain Research Station, Fort Collins, CO.
Martin, D.W., Chambers, J.C., 2001a. Restoring degraded riparian meadows: biomass
and species responses. Journal of Range Management 54, 284–291.
Martin, D.W., Chambers, J.C., 2001b. Effects of water table, clipping, and species interactions on Carex nebrascensis and Poa pratenis in riparian meadows. Wetlands 21,
422–430.
Martin, D.W., Chambers, J.C., 2002. Restoration of riparian meadows degraded by livestock
grazing: above- and below-ground responses. Plant Ecology 163, 77–91.
Miller, J., Germanoski, D., Waltman, K., Tausch, R., Chambers, J., 2001. Influence of hillslope
processes and landforms on modern channel dynamics in upland watersheds of central Nevada. Geomorphology 38, 373–391.
Miller, J.R., House, K., Germanoski, G., Chambers, J.C., 2004. Responses to Holocene climatic variations and anthropogenic disturbances. In: Chambers, J.C., Miller, J.R.
(Eds.), Great Basin Riparian Ecosystems: Ecology, Management, and Restoration.
Island Press, Washington, DC, pp. 49–87.
Miller, J.R., Germanoski, D., Lord, M., Chambers, J.C., 2011. Geomorphic processes
effecting meadow ecosystems. In: Chambers, J.C., Miller, J.R. (Eds.), Great Basin
Riparian Ecosystems: Ecology, Management, and Restoration. : Island Press, Gen.
Tech. Rep. RMRS-GTR. U.S. Department of Agriculture, Forest Service, Rocky Mountain
Research Station, Fort Collins, CO.
Montgomery, D.R., Buffington, J.M., 1993. Channel classification, prediction of channel response, and assessment of channel conditions. Report TFW-SH10-93-002. Washington
State Timber, Fish, and Wildlife, Pullman, WA.
Montgomery, D.R., Buffington, J.M., 1997. Channel-reach morphology in mountain
drainage basins. Geological Society of America Bulletin 109, 596–611.
Schumm, S.A., 1991. To Interpret the Earth: Ten Ways to be Wrong. Cambridge University
Press, Cambridge, UK.
Sheridan, C.D., Spies, T.A., 2005. Vegetation–environment relationships in zero-order
basins in coastal Oregon. Canadian Journal of Forest Research 35, 340–355.
Strahler, A.N., 1952. Hypsometric (area–altitude) analysis of erosional topography.
Geological Society of America Bulletin 63, 1117–1142.
Tsuboyama, Y., Sidle, R.C., Noguchi, S., Murakami, S., Shimizu, T., 2000. A zero-order
basin: its contribution to catchment hydrology and internal hydrological processes.
Hydrological Processes 14, 387–401.