JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION Vol. 51, No. 2 AMERICAN WATER RESOURCES ASSOCIATION April 2015 CAN RAPID ASSESSMENT PROTOCOLS BE USED TO JUDGE SEDIMENT IMPAIRMENT IN GRAVEL-BED STREAMS? A COMMENTARY1 Thomas E. Lisle, John M. Buffington, Peter R. Wilcock, and Kristin Bunte2 ABSTRACT: Land management agencies commonly use rapid assessments to evaluate the impairment of gravel-bed streams by sediment inputs from anthropogenic sources. We question whether rapid assessment can be used to reliably judge sediment impairment at a site or in a region. Beyond the challenges of repeatable and accurate sampling, we argue that a single metric or protocol is unlikely to reveal causative relations because channel condition can result from multiple pathways, processes, and background controls. To address these concerns, a contextual analysis is needed to link affected resources, causal factors, and site history to reliably identify human influences. Contextual analysis is equivalent in principle to cumulative effects and watershed analyses and has a rich history, but has gradually been replaced by rapid assessment methods. Although the approaches differ, rapid assessment and contextual analysis are complementary and can be implemented in a two-tiered approach in which rapid assessment provides a coarse (first-tier) analysis to identify sites that deserve deeper contextual assessment (second-tier). Contextual analysis is particularly appropriate for site-specific studies that should be tailored to local conditions. A balance between rapid assessment and contextual analysis is needed to provide the most effective information for management decisions. (KEY TERMS: rapid assessment; sediment impairment; contextual analysis; gravel-bed channels.) Lisle, Thomas E., John M. Buffington, Peter R. Wilcock, and Kristin Bunte, 2015. Can Rapid Assessment Protocols Be Used to Judge Sediment Impairment in Gravel-Bed Streams? A Commentary. Journal of the American Water Resources Association (JAWRA) 51(2): 373-387. DOI: 10.1111/jawr.12255 ment impairment is difficult to assess because sediment is an intrinsic part of river systems and is controlled by both natural and human factors. An assessment of impairment requires not only identification of excess instream sediment storage, but evidence that the condition is due to human disturbance rather than natural conditions and their variability. It also requires one or more metrics that reliably indicate change, which may then be compared to suitable standards or historical conditions to evaluate impact. INTRODUCTION Sediment impairment is the degradation of channel conditions by human activities that alter the volume and/or the particle size of sediment in the channel. A stream impairment of broad concern, for example, is the accumulation of fine-sediment (commonly sand and finer material) in coarse-grained river beds, which can degrade instream habitat. Sedi- 1 Paper No. JAWRA-13-0174-P of the Journal of the American Water Resources Association (JAWRA). Received August 19, 2013; accepted July 30, 2014. © 2014 American Water Resources Association. This article is a U.S. Government work and is in the public domain in the USA. Discussions are open until six months from print publication. 2 Research Hydrologist (Lisle), Pacific Southwest Research Station, U.S. Forest Service, 1700 Bayview Drive, Arcata, California 95521; Research Geomorphologist (Buffington), Rocky Mountain Research Station, U.S. Forest Service, Boise, Idaho 83702; Professor (Wilcock), Department of Watershed Sciences, Utah State University, Logan, Utah 84322; and Research Scientist (Bunte), Department of Civil and Environmental Engineering, Colorado State University, Fort Collins, Colorado 80523 (E-Mail/Lisle: thomas.lisle@gmail.com). JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION 373 JAWRA LISLE, BUFFINGTON, WILCOCK, BUNTE ments). Similarly, Bunte et al. (2009, 2012) demonstrate that the percentage of fine material (<5.6 mm) determined from rapid protocols can differ by a factor of 2 relative to detailed sampling. Uncertainty in rapidly measured values can work against the basic goal of change detection and may preclude the detection of all but the most extreme conditions (i.e., least vs. most disturbed; e.g., figures 7 and 8 of Kaufmann et al., 2008). Moreover, rapid assessment protocols frequently employ random sampling of sites (e.g., Stevens and Olsen, 2002, 2004) that may not capture the underlying spatial variability of physical conditions, human disturbances, and channel responses, nor is such sampling amenable to elucidating pathways of disturbance and response. An important challenge facing rapid assessment programs is an essential tension that lies at the heart of many environmental monitoring and assessment programs: to sample extensively at a few locations or to sample rapidly at many. There is no general resolution to this dilemma because the tradeoff between intensive and extensive monitoring protocols depends on the objective of the monitoring and the variability of the quantities measured. However, the standard that must always be addressed — one that supersedes logistic and cost considerations — is that the information collected must be sufficient to answer the questions asked. The question addressed in this study is, can we judge sediment impairment accurately and meaningfully with rapid assessments? Although we recognize the compelling reasons that motivate a rapid assessment approach, we question whether the approach is sufficient to the task. We contend that rapid assessments have limited value due to their demonstrated uncertainty and to the fact that they do not directly link cause and effect in a way that allows land managers to develop defensible sediment mitigation or remediation plans. We argue that rapid assessment may be effective if used in combination with analyses that accommodate watershed and historical context. In this study, we examine the metrics available for judging sediment impairment and discuss the available standards and references used for comparison and evaluation. We then evaluate the ability of rapid assessments to judge sediment impairment at two different spatial scales: Federal programs in the United States (U.S.), such as the Environmental Protection Agency’s Environmental Monitoring and Assessment Program (EMAP) (Kaufmann et al., 1999; USEPA, 2004; Stoddard et al., 2005; Peck et al., 2006), the Forest Service’s Aquatic and Riparian Effectiveness Monitoring Program (AREMP) (Reeves et al., 2004; Lanigan et al., 2014), and the PACFISH INFISH Biological Opinion monitoring program (PIBO) (Kershner et al., 2004; E.K. Archer, R.A. Scully, R. Henderson, B.B. Roper, and J.D. Heitke, “2012 Sampling Protocol for Stream Channel Attributes”, unpublished manual. PIBO-EMP, PACFISH/INFISH Biological Opinion Effectiveness Monitoring Program for Streams and Riparian Areas, Logan, Utah, http://www.fs.fed.us/ biology/resources/pubs/feu/pibo/pibo_stream_sampling_ protocol_2012.pdf, accessed March 2014), evaluate physical conditions and their temporal trends in stream channels in first- to third-order basins at regional and national scales. An important element of these programs is assessing sediment-related impacts on channel stability and on instream and riparian habitat. Regulatory and administrative requirements compel the evaluation of many streams as well as a regional assessment of stream health. The large number of sites to be monitored inevitably strains the resources available for monitoring, such that each of these programs has developed rapid assessment protocols that are designed to be efficient, repeatable, and widely applicable. Rapid assessments devote a day or less at each site to provide a snapshot of particular stream conditions at each site which, taken together, can be used to develop an assessment for an entire region. Changes over time are assessed with a resampling plan in which a few sites are visited annually and others are revisited over longer intervals. Another part of the strategy is to base the assessment on a small number of parameters measured at each site. Given limited agency time and personnel, the rapid assessment strategy is to trade precision, accuracy, and detail at any site for a large number of sample sites to overcome the statistical demands of variability in a large geographic area. By their nature, rapid methods may be expected to provide a coarse assessment that is less precise and accurate relative to more detailed monitoring (Roper et al., 2002, 2008, 2010; Whitacre et al., 2007; Bunte et al., 2009, 2012). For example, Roper et al. (2010) report substantial uncertainty in rapidly measured sediment metrics (coefficients of variation ranging from about 30 to 70% within monitoring groups for measurements of median grain size and percent fines) and widely varying levels of accuracy (coefficients of determination ranging from 0.07 to 0.92 for correlating rapidly measured sediment metrics with those determined from more intensive measureJAWRA AND 1. Can rapid assessment be used to accurately judge sediment impairment in a region? Are the origins and manifestations of sediment impacts in a variety of watersheds so similar that a single metric or protocol can diagnose human influences on a variety of channel resources in all of them? If so, can meaningful deviations be detected given precision, accuracy, and sample size? 374 JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION CAN RAPID ASSESSMENT PROTOCOLS BE USED TO JUDGE SEDIMENT IMPAIRMENT We focus on gravel-bed rivers because of their habitat value for many threatened and endangered aquatic and riparian species (the management of which frequently drives sediment monitoring programs) and because most sediment metrics have been developed for this channel type. Critiques of rapid assessment protocols and evaluations of their accuracy and precision are reported elsewhere (e.g., Roper et al., 2002, 2008, 2010; Whitacre et al., 2007; Bunte et al., 2009, 2012). Here, we focus on the ability of rapid assessments to provide adequate information to identify sediment impairment and link it to its causes and possible remediation. We recognize that not all impairments of stream condition are influenced by sediment, but we suggest that some of our commentary is relevant to assessments of those impairments as well. SEDIMENT IMPAIRMENT: DEFINITION AND CONTROLS Because a stream’s sediment composition can depend on both natural and anthropogenic factors, it is important to begin by carefully defining the terms of the problem. Sediment impairment can be defined simply as harm to stream resources as a result of anthropogenic changes in the sediment transport regime. Any definition of harm requires standards and references with which to judge important deviations from the norm as specified by laws and regulations. For example, the Clean Water Act defines impairment as (1) “A classification of poor water quality for a surface water body,” or (2) “Detrimental effect on the biological or physical integrity of a water body caused by an impact that prevents attainment of the designated use” (USC, 1972). To implement these broad definitions, specific metrics are needed to indicate and quantify impairment. Furthermore, taken together, these definitions highlight the fact that the severity of impairment depends not only on the magnitude of change in sediment (as judged by one or more reliable metrics) but also on the sensitivity of the resource affected. OF THE AMERICAN WATER RESOURCES ASSOCIATION GRAVEL-BED STREAMS? A COMMENTARY Because sediment is a natural part of stream systems, identification of sediment sources, pathways, and sinks is particularly important to distinguish between natural and anthropogenic influence. Sediment delivery to channels is complex, often localized, and episodic. Changes in sediment composition may be triggered by pulses in sediment supply produced by a range of geomorphic events, including floods (De Jong, 1992; Nolan and Janda, 1995), debris flows (Benda and Dunne, 1987; Benda, 1990; Berger et al., 2010), landslides (Perkins, 1989; Sutherland et al., 2002), and wildfire (Klock and Helvey, 1976; Megahan, 1983; Robichaud and Brown, 1999; Legleiter et al., 2003; Eaton et al., 2010; Goode et al., 2012). The factors controlling the magnitude, frequency, and location of these events may be natural, anthropogenic, or both. Identification of sediment sources and supply rates is insufficient, however, because the downstream influence of sediment pulses can be strongly mediated by in-channel and near-channel storage (Benda and Dunne, 1997; Lisle, 2008). Evaluation of any stream reach requires an understanding of the routing of sediment from its sources. The range of aquatic resources that may be impacted by sediment, as well as the complex mix of natural and human factors that influence sediment supply and storage, indicates that a judgment of sediment impairment must consider a wide range of interactions. For example, different aquatic resources (e.g., fisheries, water supply, and recreation) may be impacted by sediment. The condition and vulnerability of these resources, in turn, can depend on a variety of factors (e.g., stream temperature, channel morphology, and riparian vegetation) which themselves depend on both sediment and nonsediment controls (e.g., the magnitude and frequency of floods and drought, the availability of large woody debris). Furthermore, a range of human activities can either directly (e.g., channelization, water storage) or indirectly (e.g., roads, dams, grazing) change the supply, transport capacity, and storage of sediment. Consequently, an assessment of sediment impairment requires an understanding of the full suite of these linkages. The lag time between sediment inputs and stream response can vary from days to centuries, depending on the quantity, grain size, and location of the sediment input. Channel change at any one location may well reflect the combined influence of multiple watershed disturbances. Spatial variability, process interactions, and variable lag times all conspire to make it difficult to link current stream conditions to a particular cause or causes. Although stream monitoring (whether rapid or detailed) can tell the current state of the local system, it cannot explain its cause. This link between cause and effect is crucial because 2. Can rapid assessment be used to accurately judge sediment impairment at a particular site? Given that site-specific projects (e.g., watershed and channel restoration) are commonly evaluated and monitored using some of the same metrics as rapid assessments, can we sacrifice some precision and accuracy and use rapid assessment protocols to adequately judge impairment at individual sites with different resources, causal pathways, and environmental issues? JOURNAL IN 375 JAWRA LISLE, BUFFINGTON, WILCOCK, AND BUNTE difficulty of measuring sediment load, most sediment metrics do not measure load directly but use measures of channel condition that might register variations in load. These include channel dimensions (width, depth, or width:depth ratio), channel planform (e.g., meandering, braided), and bed texture (bed-surface particle size and concentration of fine sediment). it is necessary for any explanation of degradation and for developing plans for remediation. In practice, a determination of sediment impairment is based on deviation of an indicator from a desired condition or reference value (Stoddard et al., 2006) and evidence that links such a deviation to human causes (e.g., Reeves et al., 2004). Metrics of sediment impairment have been correlated with watershed disturbances that are believed to cause increased sediment loading, such as road density or absence of riparian trees (e.g., Kaufmann et al., 2009; Al-Chokhachy et al., 2010). Correlation is not causation, of course, and the wide range of potential interactions and lags linking stream channels to their watersheds suggests that assessment of sediment impairment must depend additionally on context. This context includes intrinsic watershed features such as geology, relief, and climate, the pattern, intensity, location, and timing of human disturbance, and recent changes in process variables such as streamflow, water temperature, and pollution. As much as problems associated with accuracy and uncertainty in rapid assessments, it is the challenge of connecting cause and effect that causes us to have concerns about using rapid assessment for judging sediment impairment. Without explanation accounting for context, it is not possible to reliably demonstrate sediment impairment, describe its cause, and develop defensible remediation plans that address the root causes of impairment. We suggest that rapid assessment protocols can be combined with contextual analysis to provide the necessary confirmation and guidance for the task. Channel Geometry Increases in channel width or width:depth ratio are commonly associated with increases in bed-material load (Lyons and Beschta, 1983; Schumm, 1985), but sediment load cannot be interpreted from width by itself because other factors (depth, slope, grain size, bank strength, vegetation) mutually adjust to the imposed flow and sediment load (Dietrich et al., 1989; Eaton et al., 2004; Buffington, 2012). Without a generally applicable reference for channel width, and by extension, channel planform, assessing sediment impacts using channel width or width:depth ratio is inconclusive. Moreover, decreases in width or width: depth ratio can signal either an increase or decrease in sediment supply. For example, both narrowing and widening of stream channels has been observed below dams (Williams and Wolman, 1984). In addition, channel incision by gullying, debris-flow scour, or erosion of debris-jam deposits can increase downstream sediment load, triggering local channel response that is not indicative of general channel condition. Bed-Material Texture and Bed Mobility Adjustments among sediment supply, bed-material texture, and the boundary shear stress exerted by flow in gravel-bed channels provide a basis for evaluating sediment influences, while avoiding some of the factors complicating variations in channel morphology. Gravel-bed streams usually contain a wide range of bed-material sizes, including a fraction of fine sediment (mostly sand). Increases in sediment supply can affect the grain-size distribution and mobility of the bed surface in various ways, depending on the volume (rate) and texture of the input sediment. For example, flume, numerical experiments, and field studies suggest that an increase in the rate of sediment supply can fine the bed surface, rendering it more mobile (Dietrich et al., 1989; Buffington and Montgomery, 1999b; Lisle et al., 2000; Pitlick et al., 2008). However, supplied sediment may also be finer than the river bed. Large inputs of sand not only directly increase transport rates of sand but also mobilize the gravel fraction (Iseya and Ikeda, 1987; Wilcock et al., 2001; Curran and Wilcock, 2005; Venditti et al., SEDIMENT METRICS Sediment load (the volume and particle size of sediment transported by a channel) is a primary influence on channel condition, but it is difficult to measure (Bunte and MacDonald, 1999). Sediment transport measurements are impractical for rapid assessments, and quantification of stored sediment available for transport (an element of sediment supply) is complicated by the fact that alluvial channels are formed in the sediment that they transport and store. Changes in the supply of sediment can be expected to alter the channel as it adjusts to transport the imposed sediment load, although the magnitude and pace of channel adjustments can be difficult to judge (Schumm, 1985; Dietrich et al., 1989; Lisle et al., 1993; Buffington and Montgomery, 1999b; Wilcock and DeTemple, 2005; Eaton and Church, 2009; Pryor et al., 2011; Buffington, 2012). Because of the JAWRA 376 JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION CAN RAPID ASSESSMENT PROTOCOLS BE USED TO JUDGE SEDIMENT IMPAIRMENT 2010). Changes in bed grain size depend on a balance among the existing bed-material size, the sediment supply rate and texture, the flow, and the transport capacity of the stream channel (Wilcock, 2001) such that different sediment metrics may be needed to monitor the effects of different sediment supply scenarios. Several metrics have been proposed for gravel-bed rivers that relate the volume (or rate) of sediment supply to the degree of textural fining relative to a reference grain size. Each of these metrics is an index of bed mobility and transport rate, which, in turn, is a measure of bed-load supply, if one assumes a quasiequilibrium state in which the channel has adjusted to its supply. For example, Dietrich et al. (1989) propose that the degree of bed surface armoring and consequent bed mobility is related to the upstream supply of bed material. They parameterize bed mobility in a dimensionless term q*, which is the bed-load transport rate of the surface material normalized by that of the load, and relate q* to equilibrium transport rates from flume studies. Values of q* range from 0 to 1 (high to low bed-material supplies, respectively), with the reference grain size defined as the median grain size (D50) of the load, which can be approximated by that of the subsurface material when bed-load transport observations are not available. Another family of metrics that relate bed-material size to sediment load is based on the concept of a threshold channel in which the channel is assumed to have a near-bankfull threshold for bed-material entrainment. The reference grain size is typically defined as the D50 of the bed surface and is predicted by rearranging the Shields (1936) equation to solve for the D50 that can be mobilized by the bankfull flow (Dietrich et al., 1996; Olsen et al., 1997; Power et al., 1998; Buffington and Montgomery, 1999a, b; Kappesser, 2002; Kaufmann et al., 2008, 2009). The difference between the predicted and observed D50 is a measure of bed mobility at bankfull flow and can be related to equilibrium transport rates (and thus bedmaterial supply) if boundary shear stress is corrected for channel roughness (Buffington and Montgomery, 1999a). Similarly, Kaufmann et al. (2008) use the ratio of observed to predicted grain size as an index of sediment load, assuming a bankfull threshold channel. The threshold channel approach is limited to a certain class of rivers. It is a useful approximation of mobility in gravel- and cobble-bed rivers (typically plane-bed and pool-riffle channels), which have been OF THE AMERICAN WATER RESOURCES ASSOCIATION GRAVEL-BED STREAMS? A COMMENTARY shown to have, on average, a near-bankfull threshold for motion (Leopold et al., 1964; Li et al., 1976; Parker, 1978; Andrews, 1984; Buffington and Montgomery, 1999a; Buffington, 2012), although bed mobility is only loosely associated with channel type (Bunte et al., 2010, 2013). However, the approach is inappropriate for both sand- and boulder-bed rivers (dune-ripple, step-pool, and cascade morphologies), because bed mobility in those channels generally does not exhibit a bankfull threshold (Buffington and Montgomery, 1999a; Bunte et al., 2010, 2013; Buffington, 2012). For example, the bankfull shear stress in sand-bed channels can be more than 100 times the critical shear stress (Dade and Friend, 1998; Parker et al., 2003; Church, 2006; Buffington, 2012), indicating a high degree of transport at bankfull stage. Similarly, at bankfull stage, the mobility of the median grain size systematically increases with channel slope in coarse-grained rivers and outpaces slope-dependent increases in the critical Shields stress (Buffington, 2012), suggesting mobility at stages less than bankfull in steeper channels or the need to correct boundary shear stress for systematic increases in roughness with greater slope (i.e., smaller values of both the width-to-depth ratio and relative submergence) (Buffington and Montgomery, 2001; Buffington, 2012). Consequently, bankfull threshold grain sizes predicted for sand- and boulder-bed rivers will provide inappropriate references and metrics for assessing sediment impairment. Furthermore, it should be recognized that the notion of a bankfull threshold channel is a simplifying construct based on the central tendency among many rivers. Natural, unimpacted gravel, and cobble rivers may have an entrainment threshold at flows smaller or larger than bankfull, depending on a range of variables including the rate and size of supplied sediment, the flow regime, and the valley slope and confinement (Mueller et al., 2005). Although the threshold channel approach is limited in terms of basin-wide application, it may be particularly relevant for assessing sediment impacts in salmon-bearing streams because anadromous salmonids generally prefer gravel- and cobble-bed rivers in which they can excavate redds (Montgomery et al., 1999). In contrast, the q* approach may be more robust in terms of application; it was developed for gravel-bed rivers, but is not limited to threshold channels. There is a correlation between grain size and channel roughness (e.g., energy dissipation due to banks, bars, wood, downstream changes in channel geometry; Buffington and Montgomery, 1999a), such that it is important that the above metrics use boundary shear stress corrected for roughness to avoid a false indication of sediment loading (Buffington and Mont- Textural Metrics Related to the Volume of BedMaterial Supply JOURNAL IN 377 JAWRA LISLE, BUFFINGTON, WILCOCK, BUNTE 1992; Paola and Seal, 1995; Lisle and Hilton, 1999; Dietrich et al., 2005). Inferring watershed sediment supply from the concentration of fine sediment on streambeds is problematic. First, the abundance of fine material in streambeds may not be sensitive to sediment inputs if the inputs contain low concentrations of sand (Lisle and Hilton, 1999; Montgomery and MacDonald, 2002), such that the fines are transported predominately in suspension over an armored bed. Second, form roughness (e.g., large woody debris, boulders, bars) can force variations in sand abundance independent of sediment load by creating wakes, eddies, and pools where sand can deposit (Buffington and Montgomery, 1999a) and zones of high shear stress (e.g., riffles) where sand is winnowed. More intensive sampling can help overcome problems of heterogeneity within a given channel reach, but variations in channel structure between sites complicate the establishment of a standard reference for sand concentration. Spatial variation in fine-sediment concentrations in gravel beds poses challenges to the precision and repeatability of measurements and the comparison to a meaningful reference. High variation in channel texture requires intensive, unbiased sampling to obtain reach-mean values of adequate precision, even if surface sampling is restricted to certain areas of the channel such as pool tails (Bunte et al., 2012). The rapid assessment protocols used by EMAP, AREMP, and PIBO all measure the percent of fine sediment on the easily identifiable, but laterally variable wetted part of the bed surface, neglecting deposits of fines along the dry portions of the banks. EMAP uses a visual estimate of particle-size class at five points along 21 transects spanning the reach; AREMP and PIBO protocols use grid counts on the tails of the first 10 pools in a reach. Temporal trends are best evaluated by repeating the same field protocols (e.g., surface grid counts, surface pebble counts, and volumetric samples) at a particular site during every visit. However, measuring at precisely the same point, transect, or area can introduce false variability if morphological changes cause shifts in the depositional environment. For example, a location that is a pool tail one year may become a riffle crest the next. This can be partially offset by sampling pool tails wherever they exist in a reach from year to year, but the definition of a pool tail or other morphological unit can be uncertain and influenced by the presence or absence of fines, thereby introducing bias. Even if bias and spurious variation can be reduced by careful selection of sampling sites, channel heterogeneity (e.g., due to sharp bends or large wood debris) can force variations in fine-sediment abundance between reaches independent of sediment load. For example, the bed surfaces of simple gomery, 1999b; Kaufmann et al., 2008; Rickenmann and Recking, 2011). Precise estimates of boundary shear stress and characteristic grain size are necessary because small differences in these values can correspond to large differences in particle entrainment, transport rate, and associated estimates of sediment loading (Buffington and Montgomery, 1999b). These requirements may preclude determination of the above metrics from rapid assessment protocols because rapidly measured channel characteristics can have large uncertainty due to the limited number of samples, observer bias, and methodological differences between assessment protocols (Roper et al., 2002, 2008, 2010; Whitacre et al., 2007; Bunte et al., 2009, 2012). Sediment metrics based on bed mobility relate sediment supply to transport capacity. Consequently, these metrics are sensitive to changes in both bedmaterial supply and shear stress (Buffington and Montgomery, 1999b), which may confound interpretation of sediment impairment from streambed texture. Furthermore, the above metrics describe textural response to altered rates (or volume) of bed-material supply, but do not specifically address the supply of fine sediment, which may be particularly detrimental to aquatic habitats and characteristic of certain types of anthropogenic disturbance (e.g., roads, grazing). Textural Metrics Related to Fine-Sediment Loading The abundance of fine sediment on the bed surface is commonly the basis for metrics of sediment impairment. Fine sediment is often transported and locally deposited at moderate flows that are unable to transport gravel (Jackson and Beschta, 1982; Bathurst, 1987; Beschta, 1987; Carling, 1988; Ashworth and Ferguson, 1989; Wilcock, 1998; Hassan and Church, 2001; Wilcock et al., 2001). Because fine sediment is commonly abundant in eroded soil mantles and its residence time in streambeds is shorter than that of the gravel framework, it can be a sensitive indicator of sediment impact from watershed disturbances. Moreover, fine material has a strong influence on stream biota (Bjornn et al., 1977; Chapman, 1988; Suttle et al., 2004; Cover et al., 2008). Fine sediment is distributed nonuniformly over the surface and in the subsurface of natural gravel-bed channels. Local hydraulic conditions winnow fine sediment from some areas of the bed and deposit it in others, commonly forming patches of fine sediment in pools and eddies, among large woody debris, and on the downstream end of bars. Large supplies of fine sediment also create sandy patches on the bed surface and result in reach-averaged bed-material size distributions having distinct modes of sand and gravel (Lisle and Madej, JAWRA AND 378 JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION CAN RAPID ASSESSMENT PROTOCOLS BE USED TO JUDGE SEDIMENT IMPAIRMENT STANDARDS AND REFERENCES Judging sediment impairment involves comparing values of one or more sediment metrics against a standard or reference, which can take one of several forms (Stoddard et al., 2006). All types of reference have strengths and weaknesses, and the use of more than one may improve the quality of site assessment (Lisle et al., 2007). An ecological threshold is a standard marking the onset of harm to a resource that is measured or indexed by the metric. Ecological thresholds can provide precise standards for harm. There are some thresholds for sediment [e.g., the concentration of fine sediment in salmonid egg pockets (e.g., Milan et al., 2000)], but their values differ between affected resources. In contrast to chemical pollutants, for example, the mere presence of sediment is neither indicative nor necessarily harmful, but rather influences factors that are important to aquatic ecosystems, such as hyporheic flow, dissolved oxygen, turbidity, water temperature, and riparian vegetation. OF THE AMERICAN WATER RESOURCES ASSOCIATION GRAVEL-BED STREAMS? A COMMENTARY A pristine reference is the central tendency or range of natural variability of sites that have experienced little human disturbance. Although local human influence may be slight, the history of natural disturbances (Reeves et al., 1995) and the influence of background conditions (Lisle et al., 2007) can cause the range of pristine conditions to overlap with those where human impacts are significant (Lisle, 2002; Diehl and Wolfe, 2010) and to exceed ecological thresholds (Diehl and Wolfe, 2010). A regional central tendency is the mean, median, range, or some part of the frequency distribution of values of an assessed metric. Regional central tendencies provide straightforward comparisons between a value at a given site and those from a sample of sites in the same domain and can motivate a deeper analysis to explain significant deviations. Comparisons outside the domain are seldom valid, so variations in regional conditions can only be evaluated for the same region over time. The regional approach offers a sliding scale that accounts for differences between regions and avoids imposing unrealistic goals based on absolute standards. However, if conditions are generally degraded within a region, references and standards drawn from the observed population of values may be poor targets, and care should be taken to distinguish “least disturbed” vs. “best attainable” conditions when evaluating sediment impairment (Stoddard et al., 2006). Valid comparisons between measured sites and regional central tendencies or pristine references require comparing channels of the same general type and using sediment metrics appropriate for that channel type. This enhances the sensitivity of the metric to environmental influences while reducing spurious variations between channels due to differences in channel type and applicability of the metric (use in a channel type for which the metric was intended). Stratification of sites according to the background factors that influence values of the metric can also strengthen interpretations of regional variation. A temporal benchmark compares observations at the same site over time and is the basis for trend monitoring. This well-proven referencing gives unambiguous trends in conditions, provided sampling is adequate. Although an ecological threshold may be lacking, time trends can establish whether conditions are becoming more or less favorable. Temporal benchmarks are applicable to both site and regional assessments. However, lag times between sedimentgenerating disturbance (e.g., wildfire, road construction) and increased sediment loads in channels vary widely between systems and can be as long as decades (Madej and Ozaki, 1996) or centuries. This can make it difficult to establish background conditions channels tend to maintain less fine sediment than those of complex channels (Buffington and Montgomery, 1999a). These problems exist whether finesediment concentration is measured on the bed surface or subsurface. A fine-sediment parameter that can overcome the problem of spatial variation of fine-sediment concentration in a reach (due to heterogeneity of surface textures, hydraulic conditions, and channel structure) is the fraction of pool volume filled with fine sediment, or V* (Lisle and Hilton, 1992, 1999). A flow-dependent scouring mechanism simultaneously controls the volume of fines and the residual pool volume (that below the riffle crest) in each pool. Thus, the ratio V* appears to be independent of pool size, as well as local hydraulic conditions, e.g., gradient (Lisle and Hilton, 1999). Variation in a reach can be further minimized by selecting pools without large wood or other complex roughness elements that tend to trap fines. The remainder of the influences on V* are sand supply rates and factors that characterize background watershed conditions (e.g., geology, flow regime), which can confound interpretations of variations in V* across geologic provinces (Sable and Wohl, 2006). The time required to measure V*, whose standard error can be computed on-site, typically exceeds the time limitations of rapid assessments (a day or less), depending on acceptable error (Hilton and Lisle, 1993). JOURNAL IN 379 JAWRA LISLE, BUFFINGTON, WILCOCK, BUNTE Such complexities and uncertainties can be addressed through contextual analysis, which examines site history, physiography, and process linkages to elucidate causes for the current channel condition. Regarding sediment impairment, a contextual analysis would aim to explicitly link human activity to a sediment-related condition of a channel. Common examples of contextual analyses are cumulative effects analyses (Reid and Dunne, 1996; Reid, 1998) and watershed analyses (Montgomery et al., 1995; USDA, 1995; Shilling et al., 2005), although these are not limited to sediment-related issues. By evaluating both cause and effect, a contextual analysis can ask “How did it get this way” and can identify the origins of sediment impairment, potentially guiding management to improved outcomes. As a watershed approach, it focuses on hillslopes and channel networks, as well as channel condition, and can be adapted for a number of resources. The approach does not rely on a formal or fixed protocol, but rather employs a bottom-up inquiry into factors leading to conditions at a site and/or a top-down inquiry into the propagation of apparent watershed disturbances downslope and downstream to affected sites. The goal is to use the weight of the evidence to identify the most important, site-specific cause-and-effect mechanisms. Some rapid assessments provide contextual analysis, but they are typically limited. The relative bed stability index (RBS; Kaufmann et al., 1999, 2008, 2009), which is defined as the ratio of the geometric mean surface particle size (Dgm) to the median grain size predicted to be mobile at bankfull flow (D*cbf) in a threshold channel, is an example of an analytical reference approach that is correlated with basin disturbance. RBS was developed for regional assessments as an element within EMAP, but may be applicable to site evaluations of sediment impairment if more precise parameter measurements are conducted (Kaufmann et al., 2008). In regional applications, anthropogenic disturbance is quantified by a combination of a riparian condition index, which is evaluated at the stream measurement site using a variety of visual scores and road density, which is calculated from road coverage provided by the U.S. Census Bureau (Kaufmann et al., 1999; USEPA, 2004; Peck et al., 2006; Kaufmann et al., 2008, 2009). Disturbance category correlates weakly with values of RBS and varies with basin lithology (Kaufmann et al., 2008, 2009). However, evaluation of sources of variation in RBS is reduced to categories of disturbance, rather than evaluation of watershed-specific types of disturbance and process pathways. Furthermore, cause and effect are not directly established, but only linked through correlation. Hence, the approach provides limited contextual analysis and is (Grant and Wolffe, 1991) or to detect a disturbance in the watershed in time to remedy the problem before it impacts the stream, unless monitoring extends beyond the channel to the watershed (L.M. Reid and M.J. Furniss, “On the Use of Regional Channel-Based Indicators for Monitoring,” unpublished report, USDA Forest Service, Redwood Sciences Laboratory, Arcata, California, 1998). An analytical reference is a theoretical value determined from relatively simple physical models that is based on first principles of watershed and channel processes (Dietrich et al., 1996; Power et al., 1998). Deviations from predicted values can be used to explore influences of factors not included in the model. For example, observed values of surface D50 that are finer than those predicted by the threshold channel model (an analytical reference) could reveal influences of sediment supply or channel roughness (Buffington and Montgomery, 1999a, b), whereas values of D50 coarser than predicted could reveal the presence of lag material from landslides or rock falls. Analytical references must be limited to the channel type for which the theory applies. In general, the simplification involved in an analytical reference is so severe that it is most appropriately used as a starting point (e.g., a hypothesis to be tested) from which comparisons with field observations might motivate further study. Comparison with an analytical reference alone is not sufficient to judge impairment. CONTEXTUAL ANALYSIS None of the reference types outlined above point to the specific cause for a deviation from the reference, so comparison between observation and reference alone cannot be used to conclusively identify impairment or its cause. An observed channel condition can result from multiple pathways and processes that may be human-caused or natural (Table 1). For example, a streambed can become finer by channel widening caused by trampled banks, by decreased peak flows and reduced transport capacity downstream of a diversion, or by increased sediment supply from debris flows. An observation of finer bed material does not point to a specific cause, nor does it necessarily indicate impairment because either human or natural causes may be involved. Moreover, a particular channel reach may be fine grained due to a direct local disturbance (e.g., suction dredging, bank trampling, and logging slash) rather than cumulative effects of basin-scale disturbance, and therefore not representative of watershed condition. JAWRA AND 380 JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION CAN RAPID ASSESSMENT PROTOCOLS BE USED TO JUDGE SEDIMENT IMPAIRMENT IN GRAVEL-BED STREAMS? A COMMENTARY TABLE 1. Causal Linkages between Human or Natural Disturbance, Geomorphic Response, and Channel Change. Human Cause Natural Cause Geomorphic Response Logging, roads, urban development, vegetation conversion, grazing, off-road vehicles (ORVs) dam removal, climate change Water diversion, climate change Grazing, ORV traffic Gravel mining, ORV traffic, suction dredging, grazing Impoundments, grade control structures Habitat structures, logging slash Wildfire, landslides, debris flows, large floods, channel migration Forest growth, stream capture Meander migration Intensive salmon spawning Increased total sediment input Increased fine sediment input Decreased flow Channel widening Armor layer disturbance Log jams, tributary deltas, landslide deposits Woody debris Deposition from backwater effects Increased form roughness Dams, watershed rehabilitation, gravel mining Gravel injections, hillslope disturbance Decreased sediment input Transbasin diversion, flow releases Stream cleaning, channelization Watershed recovery, debris flows, log jams Debris flows, landslides, tributary inputs Large runoff events Scour by large floods Causes for increased sediment input (see above) Grazing, dewatering of riparian vegetation Logging, development, roads, channelization, climate change Causes for increased sediment input (see above) Succession from sod to forest, increased meandering Wildfire, large floods, change in flow regime Increased sediment input Causes for decreased sediment input (see above), stream cleaning Disturbance of fine-grained soils and bedrock Peak flow reduction below dams, finesediment inputs (see cause above) Grazing, impacts leading to increased runoff, removal of large wood from channels Causes for decreased sediment input (see above), scour of wood Volcanic ash eruptions Channel incision from decreased sediment input or roughness Increased suspended sediment to build banks Riparian encroachment Channelization, stream cleaning Causes for increased sediment input (see above) Grazing, removal of woody riparian vegetation, desiccation of riparian vegetation by water withdrawals Debris flows and floods Causes for increased sediment input (see above) Bank erosion by floods, natural loss of riparian vegetation Loss of scour elements Increased sediment input Habitat structures, logging debris, blowdown of riparian buffers Causes for decreased sediment input (see above) Suction dredging Wood inputs, debris flows and landslides Causes for decreased sediment input (see above) Gain in scour elements Fine-sediment inputs (see cause above), reduced peak flows Steep landscapes with fine-grained, cohesive sediments OF THE AMERICAN WATER RESOURCES ASSOCIATION Finer surface grain size Coarser surface grain size Inputs of coarse sediment Increased flow Decreased form roughness Channel widening Weakening banks Increased peak flow Channel narrowing Gullying Decreased pool frequency and/or volume Channel widening Decreased sediment input Increased pool frequency and/or volume Direct effects best viewed a first-order estimate of the causal linkages for measured sediment impairment, as recognized by Kaufmann et al. (2008). Moreover, the riparian and watershed indices may not be independent of channel type. For example, absence of large-diameter riparian trees (an indicator of human disturbance in the EMAP approach) is a common phenomenon for streams passing through fields and meadows, and may have little to do with recent watershed disturbances. JOURNAL Channel Change JUDGING SEDIMENT IMPAIRMENT Regional Assessments Whether or not to incorporate contextual analysis in a regional assessment of sediment impairment has a strong influence on sampling strategy, interpretation of results, and the degree of uncertainty of judgments. The absence of a contextual analysis in a 381 JAWRA LISLE, BUFFINGTON, WILCOCK, BUNTE establish baselines from which to design site-specific monitoring of recognized stressors and sensitive channel metrics, without the need to revisit the analysis in detail later. Moreover, lengthening the schedule may hold little risk for trend monitoring, since significant changes from one year to the next are unlikely given long lag times of sediment routing in drainage basins and long recurrence intervals between geomorphic events that can trigger large sediment inputs (e.g., flooding or post-fire debris flows). According to this strategy, sites in AREMP and PIBO are revisited on a rotating schedule spanning five years (Henderson et al., 2004; Gallo et al., 2005). An impediment to using a contextual analysis can be an access to information and observations of basin conditions, particularly in locations with mixed public/private ownership. Although rapid assessment and contextual analysis differ in approach, they can be combined in a complementary, two-tiered strategy for assessing sediment impairment. For example, rapid assessments can be used as a coarse (first-tier) analysis to identify sites that deserve a deeper contextual assessment (secondtier analysis), provided that uncertainties of the rapid protocol are such that change and degree of impairment can actually be detected. This strategy would streamline contextual analyses by targeting their use in specific locations, thereby optimizing the utility of a large sample of sites (rapid assessments) and strengthening regional interpretations of trends through contextual analysis. Some land management agencies implement such multilevel approaches, in which rapid assessments may be followed by detailed studies (e.g., Peck et al., 2006; Csiki, 2010). regional assessment of sediment impairment imposes a weak link between human disturbance and resource impairment and reflects a shift in management strategy from watershed analyses advocated in the 1990s to status-and-trend monitoring that is currently in use by management agencies in the U.S. Some compensation can be gained by screening or stratifying regional values by characteristics of channels and valleys (classification, drainage area or order, confinement) and basins (climate, geology, physiography). Screening for some human influences such as dams can be used to avoid competing effects on channel response variables (Table 1), and sampling can be designed to target sensitive resources (e.g., fish habitat) to reduce the number of linkages between human activities and impacts. These selection criteria can help constrain the possible pathways between human impacts and channel response. The time that would otherwise be devoted to a contextual analysis can be spent on measuring more sites and conducting replication. However, the necessary assumption that human activity is responsible for variations in channel condition is difficult to test without the explanatory information provided by contextual analyses. Regional sediment metrics can be used to assess status (good vs. poor) and trend (increasing, decreasing, no change) of the associated resource. However, because causal pathways of disturbance are not established, land managers and policy makers cannot defensibly use this information to prescribe specific treatments or level of effort. Hence, rapid assessments and their resultant status-and-trend values provide an initial assessment, akin to a canary in a coal mine, but provide little or no causeand-effect understanding needed for remediation. The purpose of contextual analysis is specifically to identify causes and pathways for sediment impairment, such that appropriate remedies can be developed. Site- and basin-specific courses of action could then be integrated to inform regional programs and policies for addressing the identified sediment conditions. Inclusion of contextual analysis in an assessment of sediment impairment establishes the linkages between human disturbance and channel condition and between channel condition and resource viability, and thereby allows judgment of sediment impairment at each site independently of others, but requires more detailed measurements and a deeper analysis at each site than is afforded by rapid assessments. Assuming fixed resources for monitoring, the cost of more time devoted to each site is fewer sites visited in a region or a longer time between successive visits. However, contextual analyses can JAWRA AND Assessments at Individual Study Sites At the site scale, there are even greater needs and opportunities to use a contextual analysis to design a monitoring program and interpret its results. Contextual analysis is particularly useful for selecting monitoring parameters and protocols appropriate to local conditions, providing increased flexibility compared to the fixed metrics used in rapid regional assessments. Although consistent monitoring, over time, can demonstrate change at a site, contextual analysis is needed to identify causal relations and the most appropriate monitoring metrics. Monitoring with a contextual analysis at any scale can go beyond judging sediment impairment by providing constructive answers to essential management questions: (1) How did it get this way? (2) What is the trajectory of change? (3) How can management affect the trajectory? 382 JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION CAN RAPID ASSESSMENT PROTOCOLS BE USED TO JUDGE SEDIMENT IMPAIRMENT Extensive stream monitoring in the western U.S. is undertaken to establish status and trends for threatened and endangered salmonids and their ecosystems. The methodology uses rapid assessment protocols to monitor a large number of sites. Although there are compelling reasons to use a repeatable, efficient, and quick monitoring protocol, we question whether the approach is sufficient. The question we address in this study is: can we judge sediment impairment accurately and meaningfully with rapid assessments? We contend that rapid assessments, on their own, have limited value due to their demonstrated uncertainty and to the fact that they do not directly link cause and effect in a way that allows land managers to develop defensible sediment mitigation or remediation plans. (1) Can rapid assessment be used to accurately judge sediment impairment in a region? Rapid assessments allow a large number of sites to be sampled across a region. If conducted for a sufficient length of time, consistent monitoring of this type can indicate change. However, such monitoring cannot conclusively indicate sediment impairment because the variability in natural stream conditions is large and the same stream condition may be caused by different drivers. More important, an indication of channel condition cannot provide information on the cause of that condition, providing little defensible basis for taking corrective action. An analysis of cause and effect, termed here contextual analysis, is needed to interpret monitoring results and guide future action. Broad correlations between, for example, land use and stream sediment grain size are too weak to provide explanation or guidance. Rapid assessment monitoring and contextual analysis are different approaches, but complement each other well. Rapid assessment can indicate change (if repeat samples are collected) and can be used to find sites that deviate from expected conditions. These sites can then become a focus for closer analysis. Contextual analysis can provide a basis for evaluating monitoring results and guiding the selection of monitoring variables. But the main purpose of contextual analysis is to link cause and effect such that the reasons for impairment can be determined and appropriate remedial actions taken. Contextual analysis may compete for resources with rapid assessment monitoring. A balance between the two is needed to provide information that is reliable, empirical, understood, and actionable. Rapid assessment and contextual analysis can be combined in a two-tiered effort that capitalizes on the strengths OF THE AMERICAN WATER RESOURCES ASSOCIATION GRAVEL-BED STREAMS? A COMMENTARY of each approach (large sample size vs. in-depth analysis of cause and effect). (2) Can rapid assessment be used to accurately judge sediment impairment at a particular site? Assessment and remediation for projects at individual sites often provide sufficient resources and time such that monitoring can be more detailed and tailored to local conditions. The strong constraints of a regionally fixed protocol are appropriately relaxed to make observations most appropriate to the problem at hand. Contextual analysis plays a key role in determining how human influences on the watershed scale may influence local channel processes. Such an approach will be much more valuable to a manager than a rapid judgment of whether or not the resource is impaired. Due to their large uncertainty, rapid assessment protocols are rarely appropriate at the site scale for judging sediment impairment, requiring refinement of techniques for site analysis (Kaufmann et al., 2009). Much more valuable information can be gained by designing an assessment that suits the targeted watershed and can expand the scope beyond sediment impairment. CONCLUSIONS JOURNAL IN ACKNOWLEDGMENTS John Potyondy encouraged the authors to write this manuscript and provided constructive comments for an earlier draft. Additional comments from three anonymous reviewers further improved the manuscript. Funding comes, in part, from the U.S. Forest Service Stream Systems Technology Center. LITERATURE CITED Al-Chokhachy, R., B.B. Roper, and E.K. Archer, 2010. Evaluating the Status and Trends of Physical Stream Habitat in Headwater Streams within the Interior Columbia River and Upper Missouri River Basins Using an Index Approach. Transactions of the American Fisheries Society 139:1041-1059. Andrews, E.D., 1984. Bed-Material Entrainment and Hydraulic Geometry of Gravel-Bed Rivers in Colorado. Geological Society of American Bulletin 95:371-378. Ashworth, P.J. and R.I. Ferguson, 1989. Size-Selective Entrainment of Bed Load in Gravel Bed Streams. Water Resources Research 25(4):627-634. Bathurst, J.C., 1987. Measuring and Modelling Bedload Transport in Channels with Coarse Bed Material. In: River Channels. Environment and Process, K.S. Richards (Editor). The Institute of British Geographer Special Publication Series, Basil Blackwell, Oxford, United Kingdom, pp. 272-294. Benda, L., 1990. The Influence of Debris Flows on Channels and Valley Floors in the Oregon Coast Range, USA. Earth Surface Processes and Landforms 15:457-466. Benda, L. and T. Dunne, 1987. Sediment Routing by Debris Flows. In: Erosion and Sedimentation in the Pacific Rim, T.R.H. Davies and A. Pearce (Editors). International Association of Hydrologic Sciences Publ. no. 165, pp. 213-223. 383 JAWRA LISLE, BUFFINGTON, WILCOCK, BUNTE Cover, M.R., C.L. May, W.E. Dietrich, and V.H. Resh, 2008. Quantitative Linkages among Sediment Supply, Streambed Fine Sediment, and Benthic Macroinvertebrates in Northern California Streams. Journal of the North American Benthological Society 27(1):135-149. Csiki, S., 2010. Geomorphic Assessments of New Hampshire’s Rivers. Presentation to Water Quality Standards Advisory Committee. http://des.nh.gov/organization/divisions/water/wmb/wqs/ meetings/documents/geomorph_pwrpnt.pdf, accessed December 2012. Curran, J.C. and P.R. Wilcock, 2005. The Effect of Sand Supply on Transport Rates in a Gravel-Bed Channel. Journal of Hydraulic Engineering 131(11):961. Dade, W.B. and P.F. Friend, 1998. Grain-Size, Sediment-Transport Regime, and Channel Slope in Alluvial Rivers. The Journal of Geology 106:661-675. De Jong, C., 1992. A Catastrophic Flood/Multiple Debris Flow in a Confined Mountain Stream: An Example from the Schmiedlaine, Southern Germany. In: Erosion, Debris Flows and Environment in Mountain Regions, D.E. Walling, T.R. Davies, and B. Hasholt (Editors). International Association of Hydrologic Sciences Publ. no. 209, pp. 237-245. Diehl, T.H. and W.J. Wolfe, 2010. Suspended-Sediment Concentration Regimes for Two Biological Reference Streams in Middle Tennessee. Journal of the American Water Resources Association 46(4):837. Dietrich, W.E., J.W. Kirchner, H. Ikeda, and F. Iseya, 1989. Sediment Supply and the Development of the Coarse Surface Layer in Gravel-Bedded Rivers. Nature 340:215-217. Dietrich, W.E., P.A. Nelson, E. Yager, J.G. Venditti, M.P. Lamb, and L. Collins, 2005. Sediment Patches, Sediment Supply, and Channel Morphology. In: 4th Conference on River, Estuarine, and Coastal Morphodynamics, G. Parker and M. Garcia (Editors), July 12-16, 2005. A. A. Balkema Publishers, Rotterdam, the Netherlands. Dietrich, W.E., M.E. Power, K.O. Sullivan, and D.R. Montgomery, 1996. The Use of an Analytical Reference State in Watershed Analysis. In: Abstracts with Programs, Geological Society of America Annual Meeting, Boulder, Colorado 28(5):27906A. (Abstr.) Eaton, B., M. Church, and R.G. Millar, 2004. Rational Regime Model of Alluvial Channel Morphology and Response. Earth Surface Processes & Landforms 29(4):511-530. Eaton, B.C., C.A.E. Andrews, T.R. Giles, and J.C. Phillips, 2010. Wildfire, Morphologic Change and Bed Material Transport at Fishtrap Creek, British Columbia. Geomorphology 118:409424. Eaton, B.C. and M. Church, 2009. Channel Stability in Bed Load Dominated Streams with Nonerodible Banks: Inferences from Experiments in a Sinuous Flume. Journal of Geophysical Research – Earth Surface 114:F01024, doi: 10.1029/2007JF 000902. Gallo, K., S.H. Lanigan, P. Eldred, S.N. Gordon, and C. Moyer, 2005. Northwest Forest Plan — The First 10 Years (1994-2003): Preliminary Assessment of the Condition of Watersheds. Gen. Tech. Rep. PNW-GTR-647. U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station, Portland, Oregon, 133 pp. http://www.fs.fed.us/pnw/publications/pnw_gtr 647/pnw-gtr647a.pdf, accessed October 2012. Goode, J.R., C.H. Luce, and J.M. Buffington, 2012. Enhanced Sediment Delivery in a Changing Climate in Semi-Arid Mountain Basins: Implications for Water Resource Management and Aquatic Habitat in the Northern Rocky Mountains. Geomorphology 139-140:1-15. Grant, G.E. and A.L. Wolffe, 1991. Long-Term Patterns of Sediment Transport after Timber Harvest, Western Cascade Mountains, Oregon, USA. In: Sediment and Stream Water Quality in a Changing Environment: Trends and Explanation, Benda, L. and T. Dunne, 1997. Stochastic Forcing of Sediment Routing and Storage in Channel Networks. Water Resources Research 33(12):2865-2880. Berger, C., B.W. McArdell, and F. Schlunegger, 2010. Sediment Transfer Patterns at the Illgraben Catchment, Switzerland: Implications for the Time Scales of Debris Flow Activities. Geomorphology 125:421-432. Beschta, R.L., 1987. Conceptual Models of Sediment Transport in Streams. In: Sediment Transport in Gravel-Bed Rivers, C.R. Thorne, J.C. Bathurst, and R.D. Hey (Editors). John Wiley, Chichester, United Kingdom, pp. 387-419. Bjornn, T.C., M.A. Brusven, M.P. Molnau, J.H. Milligan, R.A. Klamt, E. Chaco, and C. Shaye, 1977. Transport of Granitic Sediment in Streams and Its Effects on Insects and Fish. Bulletin 17, College of Forestry, Wildlife and Range Sciences. University of Idaho, Moscow, Idaho, 43 pp. Buffington, J.M., 2012. Changes in Channel Morphology over Human Time Scales. In: Gravel-Bed Rivers: Processes, Tools, Environments, M. Church, P.M. Biron, and A.G. Roy (Editors). John Wiley, Chichester, United Kingdom, pp. 435-463. Buffington, J.M. and D.R. Montgomery, 1999a. Effects of Hydraulic Roughness on Surface Textures of Gravel-Bed Rivers. Water Resources Research 35(11):3507-3521. Buffington, J.M. and D.R. Montgomery, 1999b. Effects of Sediment Supply on Surface Textures of Gravel-Bed Rivers. Water Resources Research 35(11):3523-3530. Buffington, J.M. and D.R. Montgomery, 2001. Reply to Comments on “Effects of Hydraulic Roughness on Surface Textures of Gravel-Bed Rivers” and “Effects of Sediment Supply on Surface Textures of Gravel-Bed Rivers” by John M. Buffington and David R. Montgomery. Water Resources Research 37:1529-1533. Bunte, K., S.R. Abt, K.W. Swingle, D.A. Cenderelli, and J.M. Schneider, 2013. Critical Shields Values in Coarse-Bedded Steep Streams. Water Resources Research 49(11):7427-7447, doi: 10. 1002/2012WR012672. Bunte, K., S.R. Abt, K.W. Swingle, and J.P. Potyondy, 2009. Comparison of Three Pebble Count Protocols (EMAP, PIBO, and SFT) in Two Mountain Gravel-Bed Streams. Journal of the American Water Resources Association 45(5):1209-1227, doi: 10.1111⁄j.1752-1688.2009.00355.x. Bunte, K., S.R. Abt, K.W. Swingle, and J.P. Potyondy, 2010. Bankfull Mobile Particle Size and Its Prediction from a Shields-Type Approach. In: Proceedings of the 2nd Joint Federal Interagency Conference (9th Federal Interagency Sedimentation Conference, 4th Federal Interagency Hydrologic Modeling Conference), CD-ROM, 27 June-1 July, Las Vegas, Nevada. http://acwi.gov/sos/ pubs/2ndJFIC/Contents/4B_Bunte_03_01_10_paper.pdf, accessed December 2012. Bunte, K. and L.H. MacDonald, 1999. Scale Considerations and the Detectability of Sedimentary Cumulative Watershed Effects. National Council of the Paper Industry for Air and Stream Improvement (NCASI), Research Triangle Park, North Carolina, Technical Bulletin No. 776, 327 pp. Bunte, K., J.P. Potyondy, K.W. Swingle, and S.R. Abt, 2012. Spatial Variability of Pool-Tail Fines in Mountain Gravel-Bed Stream Affects Grid-Count Results. Journal of the American Water Resources Association 48(3):530-545, doi: 10.1111⁄j.17521688.2011.00629.x. Carling, P.A., 1988. The Concept of Dominant Discharge Applied to Two Gravel-Bed Streams in Relation to Channel Stability Thresholds. Earth Surface Processes and Landforms 13:355-367. Chapman, D.W., 1988. Critical Review of Variables Used to Define Effects of Fines in Redds of Large Salmonids. Transactions of the American Fisheries Society 117:1-21. Church, M., 2006. Bed Material Transport and the Morphology of Alluvial Rivers. Annual Review of Earth and Planetary Sciences 34:325-354. JAWRA AND 384 JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION CAN RAPID ASSESSMENT PROTOCOLS BE USED TO JUDGE SEDIMENT IMPAIRMENT OF THE AMERICAN WATER RESOURCES ASSOCIATION GRAVEL-BED STREAMS? A COMMENTARY Lisle, T.E., 2002. How Much Dead Wood in Channels Is Enough? In: Proceedings of the Symposium on the Ecology and Management of Dead Wood in Western Forests, W.F. Laudenslayer, Jr., P.J. Shea, B.E. Valentive, C.P. Weatherspoon, and T.E. Lisle (Editors). General Technical Report PSW-GTR-181. USDA Forest Service, Pacific Southwest Research Station, Albany, California, pp. 85-93. Lisle, T.E., 2008. The Evolution of Sediment Waves Influenced by Varying Transport Capacity in Heterogeneous Rivers. In: Gravel Bed Rivers VI: From Process Understanding to River Restoration, H. Habersack, H. Piegay, and M. Rinaldi (Editors). Elsevier, Amsterdam, the Netherlands, pp. 443-472. Lisle, T.E., K. Cummins, and M.A. Madej, 2007. An Examination of References for Ecosystems in a Watershed Context: Results of a Scientific Pulse in Redwood National and State Parks, California. In: Advancing the Fundamental Sciences: Proceedings of the Forest Service National Earth Sciences Conference, M. Furniss, C.F. Clifton, and K.L. Ronnenberg (Editors). PNW GTR-689. USDA Forest Service, San Diego, California, pp. 118-130. Lisle, T.E. and S. Hilton, 1992. The Volume of Fine Sediment in Pools: An Index of the Supply of Mobile Sediment in Stream Channels. Water Resources Bulletin 28(2):371-383. Lisle, T.E. and S. Hilton, 1999. Fine Bed Material in Pools of Natural Gravel-Bed Channels. Water Resources Research 35(4): 1291-1304. Lisle, T.E., F. Iseya, and H. Ikeda, 1993. Response of a Channel with Alternate Bars to a Decrease in Supply of Mixed-Size Bed Load: A Flume Experiment. Water Resources Research 29(11): 3623-3629. Lisle, T.E. and M.A. Madej, 1992. Spatial Variation in Armouring in a Channel with High Sediment Supply. In: Dynamics of Gravel Bed Rivers, P. Billi, R.D. Hey, C.R. Thorne, and P. Tacconi (Editors). John Wiley and Sons, Chichester, United Kingdom, pp. 277-293. Lisle, T.E., J.M. Nelson, J. Pitlick, M.A. Madej, and B.L. Barkett, 2000. Variability of Bed Mobility in Natural Gravel-Bed Channels and Adjustments to Sediment Load at the Local and Reach Scales. Water Resources Research 36(12):3743-3756. Lyons, J.K. and R.L. Beschta, 1983. Land Use, Floods, and Channel Changes: Upper Middle Fork Willamette River, Oregon (1936-1980). Water Resources Research 19:463-471. Madej, M.A. and V. Ozaki, 1996. Channel Response to Sediment Wave Propagation and Movement, Redwood Creek, California, USA. Earth Surface Processes and Landforms 21:911-927. Megahan, W.F., 1983. Hydrologic Effects of Clearcutting and Wildfire on Steep Granitic Slopes in Idaho. Water Resources Research 19(3):811-819. Milan, D.J., G.E. Petts, and H. Sambrook, 2000. Regional Variations in the Sediment Structure of Trout Streams in Southern England: Benchmark Data for Siltation Assessment and Restoration. Aquatic Conservation: Marine and Freshwater Ecosystems 10:407-420. Montgomery, D.R., E.M. Beamer, G.R. Pess, and T.P. Quinn, 1999. Channel Type and Salmonid Spawning Distribution and Abundance. Canadian Journal of Fisheries and Aquatic Sciences 56:377-387. Montgomery, D.R., G.E. Grant, and K. Sullivan, 1995. Watershed Analysis as a Framework for Implementing Ecosystem Management. Journal of the American Water Resources Association 31(3):369-386, doi: 10.1111/j.1752-1688.1995.tb04026. Montgomery, D.R. and L.H. MacDonald, 2002. Diagnostic Approach to Stream Channel Assessment and Monitoring. Journal of the American Water Resources Association 38(1):1-16. Mueller, E.R., J. Pitlick, and J.M. Nelson, 2005. Variation in the Reference Shields Stress for Bed Load Transport in Gravel-Bed Streams and Rivers. Water Resources Bulletin 41:W4006, doi: 10.1029/2004WR003692. D.E. Walling and N. Peters (Editors). International Association of Hydrologic Sciences Publ. no. 203, pp. 31-40. Hassan, M.A. and M. Church, 2001. Sensitivity of Bedload Transport in Harris Creek: Seasonal and Spatial Variation over a Cobble-Gravel Bar. Water Resources Research 37(3):813-825. Henderson, R.C., E.K. Archer, and J.L. Kershner, 2004. Effectiveness Monitoring for Streams and Riparian Areas within the Upper Columbia River Basin: Sampling Protocols for Integrator Reaches Stream Channel Parameters — 2001. In: Guide to Effective Monitoring of Aquatic and Riparian Resources, J.L. Kershner, E.K. Archer, M. Coles-Ritchie, E.R. Cowley, R.C. Henderson, K. Kratz, C.M. Quimby, D.L. Turner, L.C. Ulmer, and M.R. Vinson (Editors). Gen. Tech. Rep., RMRS-GTR-121. U.S. Department of Agriculture, Rocky Mountain Research Station, Fort Collins, Colorado, 57 pp. http://www.fs.fed.us/biology/ resources/pubs/feu/rmrs_gtr_121.pdf, accessed October 2012. Hilton, S. and T.E. Lisle, 1993. Measuring the Fraction of Pool Volume Filled with Fine Sediment. PSW Research Note PSW-RN-414. USDA Forest Service, Pacific Southwest Research Station, Albany, California, 11 pp. Iseya, F. and H. Ikeda, 1987. Pulsations in Bedload Transport Rates Induced by a Longitudinal Sediment Sorting: A Flume Study Using Sand and Gravel Mixtures. Geografiska Annaler 69A:15-27. Jackson, W.L. and R.L. Beschta, 1982. A Model of Two-Phase Bedload Transport in an Oregon Coast Range Stream. Earth Surface Processes and Landforms 7:517-527. Kappesser, G.B., 2002. A Riffle Stability Index to Evaluate Sediment Loading to Streams. Journal of the American Water Resources Association 38(4):1069-1081. Kaufmann, P.R., J.M. Faustini, D.P. Larsen, and M.A. Shirazi, 2008. A Roughness-Corrected Index of Relative Bed Stability for Regional Stream Surveys. Geomorphology 99(1-4):170. Kaufmann, P.R., D.P. Larsen, and J.M. Faustini, 2009. Bed Stability and Sedimentation Associated with Human Disturbances in Pacific Northwest Streams. Journal of the American Water Resources Association 45(2):434-459. Kaufmann, P.R., P. Levine, E.G. Robison, C. Seeliger, and D.V. Peck, 1999. Quantifying Physical Habitat in Wadeable Streams. EPA/620/R-99/003. US Environmental Protection Agency, Washington, D.C. Kershner, J.L., E.K. Archer, M. Coles-Ritchie, E.R. Cowley, R.C. Henderson, K. Kratz, C.M. Quimby, D.L. Turner, L.C. Ulmer, and M.R. Vinson, 2004. Guide to Effective Monitoring of Aquatic and Riparian Resources. Gen. Tech. Rep. RMRS-GTR-121. U.S. Department of Agriculture, Rocky Mountain Research Station, Fort Collins, Colorado, 57 pp. Klock, G.O. and J.D. Helvey, 1976. Debris Flows Following Wildfire in North Central Washington. In: Proceedings of the Third Federal Inter-Agency Sedimentation Conference. Sedimentation Committee of the Water Resources Council, March 22-27, 1976, Denver, Colorado. pp. 91-97. Lanigan, S., S. Miller, H. Andersen, P. Eldred, R. Beloin, M. Raggon, S. Gordon, and S. Wilcox, 2014. Aquatic and Riparian Effectiveness Monitoring Program. Interagency Monitoring Program – Northwest Forest Plan Area, 2013 Annual Report. http://www.reo.gov/monitoring/reports/2013%20AREMP%20Tech %20Rpt%20140121%20.pdf, accessed March 2014. Legleiter, C.J., R.L. Lawrence, M.A. Fonstad, W.A. Marcus, and R. Aspinall, 2003. Fluvial Response a Decade after Wildfire in the Northern Yellowstone Ecosystem: A Spatially Explicit Analysis. Geomorphology 54:119-136. Leopold, L.B., M.G. Wolman, and J.P. Miller, 1964. Fluvial Processes in Geomorphology. Freeman, San Francisco, California. Li, R., D.B. Simons, and M.A. Stevens, 1976. Morphology of Cobble Streams in Small Watersheds. Journal of the Hydraulics Division, American Society of Civil Engineers 102:1101-1117. JOURNAL IN 385 JAWRA LISLE, BUFFINGTON, WILCOCK, BUNTE Water Resources Research 47:W07538, doi: 10.1029/2010WR 009793. Robichaud, P.R. and R.E. Brown, 1999. What Happened after the Smoke Cleared: Onsite Erosion Rates after a Wildfire in Eastern Oregon. In: Wildland Hydrology, D.S. Olsen and J.P. Potyondy (Editors). American Water Resources Association, Herndon, Virginia, TPS-99-3, pp. 419-426. Roper, B.B., J.M. Buffington, E. Archer, C. Moyer, and M. Ward, 2008. The Role of Observer Variation in Determining Rosgen Stream Types in Northeastern Oregon Mountain Streams. Journal of the American Water Resources Association 44:417427. Roper, B.B., J.M. Buffington, and S. Bennett, et al., 2010. A Comparison of the Performance and Compatibility of Protocols Used by Seven Monitoring Groups to Measure Stream Habitat in the Pacific Northwest. North American Journal of Fisheries Management 30:565-587. Roper, B.B., J.L. Kershner, E. Archer, R. Henderson, and N. Bouwes, 2002. An Evaluation of Physical Habitat Used to Monitor Streams. Journal of the American Water Resources Association 38:1637-1646. Sable, K.A. and E. Wohl, 2006. The Relationship of Lithology and Watershed Characteristics to Fine Sediment Deposition in Streams of the Oregon Coast Range. Environmental Management 37(5):659-670. Schumm, S.A., 1985. Patterns of Alluvial Rivers. Annual Review of Earth and Planetary Sciences 13:5-27. Shields, A., 1936. Anwendung der Aehnlichkeitsmechanik und der Turbulenzforschung auf die Geschiebebewegung, Berlin. Mitteilungen der Preußischen Versuchsanstalt f€ ur Wasserbau und Schiffbau 26:1-26. Shilling, F., S. Sommarstrom, R. Kattelmann, B. Washburn, J. Florsheim, and R. Henly, 2005. California Watershed Assessment Manual: Volume I. http://cwam.ucdavis.edu, accessed June 2012. Stevens, D.L. and A.R. Olsen, 2002. Variance Estimation for Spatially Balanced Samples of Environmental Resources. Environmetrics 14:593-610. Stevens, D.L. and A.R. Olsen, 2004. Spatially Balanced Sampling of Natural Resources. Journal of the American Statistical Association 99:262-278. Stoddard, J.L., D.P. Larsen, C.P. Hawkins, R.K. Johnson, and R.H. Norris, 2006. Setting Expectations for the Ecological Condition of Streams: The Concept of Reference Condition. Ecological Applications 16(4):1267-1276. Stoddard, J.L., D.V. Peck, S.G. Paulsen, J. Van Sickle, C.P. Hawkins, A.T. Herlihy, R.M. Hughes, P.R. Kaufmann, D.P. Larsen, G. Lomnicky, A.R. Olsen, S.A. Peterson, P.L. Ringold, and T.R. Whittier, 2005. An Ecological Assessment of Western Streams and Rivers. EPA 620/R-05/005. U.S. Environmental Protection Agency, Washington, D.C. http://www.epa.gov/emap2/west/html/ docs/wstriv.htm, accessed October 2012. Sutherland, D.G., M.E. Hansler, S. Hilton, and T.E. Lisle, 2002. Evolution of a Landslide-Induced Sediment Wave in the Navarro River, California. Geological Society of America Bulletin 114(8):1036-1048. Suttle, K.B., M.E. Power, J.M. Levine, and C. McNeely, 2004. How Fine Sediment in Riverbeds Impairs Growth and Survival of Juvenile Salmonids. Ecological Applications 14:969-974. US Congress, 1972. Water Pollution Prevention and Control. U.S. Code Title 33, Chapter 26, Section 1251. USDA Forest Service, 1995. Ecosystem Analysis at the Watershed Scale: Federal Guide for Watershed Analysis – Version 2.2. Regional Ecosystem Office, Portland, Oregon, 28 pp. http://www. reo.gov/library/reports/watershd.pdf, accessed June 2012. USEPA, 2004. Wadeable Stream Assessment: Field Operations Manual. EPA 841-B-04-004. U.S. Environmental Protection Nolan, K.M. and R.J. Janda, 1995. Impacts of Logging on StreamSediment Discharge in the Redwood Creek Basin, Northwestern California. In: Geomorphic Processes and Aquatic Habitat in the Redwood Creek Basin, Northwestern California, K.M. Nolan, H.M. Kelsey, and D.C. Marron (Editors). U.S. Geological Survey Professional Paper 1454, L1-L8. Olsen, D.S., A.C. Whitaker, and D.F. Potts, 1997. Assessing Stream Channel Stability Thresholds Using Flow Competence Estimates at Bankfull Stage. Journal of the American Water Resources Association 33(6):1197-1207. Paola, C. and R. Seal, 1995. Grain Size Patchiness as a Cause of Selective Deposition and Downstream Fining. Water Resources Research 31(5):1395-1407. Parker, G., 1978. Self-Formed Straight Rivers with Equilibrium Banks and Mobile Bed. Part 2. The Gravel River. Journal of Fluid Mechanics 89:127-146. Parker, G., C.M. Toro-Escobar, M. Ramey, and S. Beck, 2003. Effect of Floodwater Extraction on Mountain Stream Morphology. Journal of Hydraulic Engineering 129:885-895. Peck, D.V., A.T. Herlihy, B.H. Hill, R.M. Hughes, P.R. Kaufmann, D.J. Klemm, J.M. Lazorchak, F.H. McCormick, S.A. Peterson, P.L. Ringold, T. Magee, and M. Cappaert, 2006. Environmental Monitoring and Assessment Program-Surface Waters Western Pilot Study: Field Operations Manual for Wadeable Streams. EPA/620/R-06/003. U.S. Environmental Protection Agency, Office of Research and Development, Washington, D.C. Perkins, S.J., 1989. Landslide Deposits in Low-Order Streams – Their Erosion Rates and Effects on Channel Morphology. In: Proceedings of the Symposium on Headwaters Hydrology, W.W. Woessner and D.F. Potts (Editors). American Water Resources Association Technical Publication Series TPS-89-1, Missoula, Montana, pp. 173-182. Pitlick, J., E.R. Mueller, C. Segura, R. Cress, and M. Torizzo, 2008. Relation between Flow, Surface-Layer Armoring and Sediment Transport in Gravel-Bed Rivers. Earth Surface Processes and Landforms 33(8):1192-1209. Power, M.E., W.E. Dietrich, and K.O. Sullivan, 1998. Experimentation, Observation, and Inference in River and Watershed Investigations. In: Experimental Ecology, W.J. Resetarits, Jr. and J. Bernardo (Editors). Oxford University Press, New York City, New York, pp. 113-132. Pryor, B.S., T.E. Lisle, D.S. Montoya, and S. Hilton, 2011. Transport and Storage of Bed Material in a Gravel-Bed Channel during Episodes of Aggradation and Degradation: A Field and Flume Study. Earth Surface Processes & Landforms 36:20282041. Reeves, G.H., L.E. Benda, K.M. Burnett, P.A. Bisson, and J.R. Sedell, 1995. A Disturbance-Based Ecosystem Approach to Maintaining and Restoring Freshwater Habitats of Evolutionarily Significant Units of Anadromous Salmonids in the Pacific Northwest. American Fisheries Society Symposium 17:334-349. Reeves, G.H., D.B. Hohler, D.P. Larsen, D.E. Busch, K. Kratz, K. Reynolds, K.F. Stein, T. Atzet, P. Hays, and M. Tehan, 2004. Effectiveness Monitoring for the Aquatic and Riparian Component of the Northwest Forest Plan: Conceptual Framework and Options. Gen. Tech. Rep. PNW-GTR-577. U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station, Portland, Oregon, 71 pp. Reid, L.M., 1998. Cumulative Watershed Effects and Watershed Analysis. In: River Ecology and Management: Lessons from the Pacific Coastal Ecoregion, R.J. Naiman and R.E. Bilby (Editors). Springer-Verlag, New York City, New York, pp. 476-501. Reid, L.M. and T. Dunne, 1996. Rapid Evaluation of Sediment Budgets. Catena Verlag GMBH, Reiskirchen, Germany, 164 pp. Rickenmann, D. and A. Recking, 2011. Evaluation of Flow Resistance in Gravel-Bed Rivers through a Large Field Data Set. JAWRA AND 386 JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION CAN RAPID ASSESSMENT PROTOCOLS BE USED TO JUDGE SEDIMENT IMPAIRMENT IN GRAVEL-BED STREAMS? A COMMENTARY Agency, Office of Water and Office of Research and Development, Washington, D.C., 106 pp. Venditti, J.G., W.E. Dietrich, P.A. Nelson, M.A. Wydzga, J. Fadde, and L. Sklar, 2010. Mobilization of Coarse Surface Layers in Gravel-Bedded Rivers by Finer Gravel Bed Load. Water Resources Research 46(7). Whitacre, H.W., B.B. Roper, and J.L. Kershner, 2007. A Comparison of Protocols and Observer Precision for Measuring Physical Stream Attributes. Journal of the American Water Resources Association 43(4):923-937. Wilcock, P.R., 1998. Two-Fraction Model of Initial Sediment Motion in Gravel-Bed Rivers. Science 280:410-412. Wilcock, P.R., 2001. The Flow, the Bed, and the Transport: Interaction in Flume and Field. In: Gravel-Bed Rivers V, M.P. Mosley (Editor). New Zealand Hydrological Society, Wellington, New Zealand, pp. 183-219. Wilcock, P.R. and B.T. DeTemple, 2005. Persistence of Armor Layers in Gravel-Bed Streams. Geophysical Research Letters 32: L08402, doi: 10.1029/2004GL021772. Wilcock, P.R., S.T. Kenworthy, and J.C. Crowe, 2001. Experimental Study of the Transport of Mixed Sand and Gravel. Water Resources Research 37(12):3349-3358. Williams, G.P. and M.G. Wolman, 1984. Downstream Effect of Dams on Alluvial Rivers. USGS Prof. Paper 1286, 83 pp. JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION 387 JAWRA