Biological Objectives Tied to
Physical Processes
Dr. William Trush
Scott McBain
Arcata, CA
Outline

Geomorphic-Hydrology work with Biologist

Geomorphic-Biotic linkages

Attributes of alluvial river integrity

Analytical techniques which include:
Hydrograph component analysis, bar morphology, integration

Reconsideration of standard techniques on
assessing impacts of dams
Historical Perspective

Need to have a good understanding of
how the system historically functioned,
both physical components and biotic
components
–Evaporation
–Precipitation
–Different Species
–Variety of hydrologic regimen
–Variable geology
Conceptual Framework
Supply /Control
Process
Form
Habitat
Biota
Watershed Inputs
Water, sediment
Fluvial Geomorphic Processes
Transport, deposition
Geomorphic Attributes
Channel morphology (size, shape,
slope)
Habitat Structure, Complexity
In stream aquatic habitat, woodlands
Biotic Response
Abundance and distribution of
native/exotic species
For
all take note of: Human land use and flow regulation, natural disturbance
Bottom-Up vs. Top-Down

Bottom-Up- Biologist
– Start under water, without understanding the
history and geomorphic processes. They
never challenge the base line of the river.

Top-Down- Geologist
– Start above water need to consider a
biological stand point.

Have to approach both ways- integration
is the key
Processes You Need To Go
Through…

Data

Spend time getting historical condition,
land and species

Conceptual model

Objectives
Priority Hypothesis

Geomorphic
– Dam has eliminated upstream sediment
supply, decreasing in-channel coarse
sediment storage

Salmonid
1) Spawning gravel supply has been decreased
2) Spawning habitat is limiting salmonid
production
Attributes of Alluvial Rivers

Historical Model of “Trinity River”
– Look at conceptual models to identify key
process and formation that maintained the
ecosystem
– The process of developing the attributes is
most important and different for every river
Attributes of Alluvial Rivers cont.
1)
2)
3)
4)
5)
6)
Spatially complex channel morphology
(migrate, meander, side channels)
Flows and water quality are predictably
variable (Trends in river that are consistent per
year during certain times)
Bed moves frequently (1-2 year)
Bed scour and fill (5-10 year)
Balance fine and coarse sediment
Channel migrates/avulsion
Attributes of Alluvial Rivers cont.
1)
2)
3)
4)
Floodplains (oxbows, fine sediment dep.)
Channel Resettling floods (20-50 yrs.
Large scale geomorphic change)
Plant communities
Fluctuating ground water table (wetlands
and animals)
Channel Complexity

Very Complex

Point bars (plants), scours, oxbows, sheer
zones/pools (fish), side channels, variable
particle size
Create and Maintain Channel
Morphology

Hydrograph
– Print our every hydrograph for the periods of
record, develop hypothesis
– Conduct water year analysis to evaluate interannual flow variability (wet year vs. dry year)
– Intra-annual flow variability with in water
year, evaluate changes relate geomorphic
processes and life history of key biota
– Link biota to hydrology
Different water years = Different ecological
functions
Condition
Hydrologic
Geomorphic
Ecological
Extremely
Wet
Large winter floods,
large snowmelt runoff
peak- melting occurs
through June
Channel avulsion,
migration, bed load
transport, bed scour,
lots of fine sediment,
floodplain scour and
dep.
Vegetation removal,
woody debris, greater
migration up stream,
high juvenile salmon
growth rates, low
salmon out migration
mortality
Normal
Moderate winter floods,
moderate
snowmelt/runoff,
moderate base flows
Moderate: Channel
migration, bed load
transport, floodplain,
fine sediment
Minor veg. removal,
mod salmon migration
access up stream, low
salmon out migration
mortality
Critically
Dry
Small winter floods,
miner snowmelt, short
duration of runoff,
higher water temp
No channel
migration, no gravel
transport
Veg. lower in channel,
no scour, low
migration up stream,
mod. Water tempstress mortality to
salmon, moderate
salmon out migration
mortality
Other Biological Hotspots
Sediment deposition
 Channel complexity (bars, side channels)
 Riparian vegetation
 Spawning areas
 Amphibian egg laying locations
 Large wood accumulation

Suggestions
Historical perspective to understand how the
system naturally worked
 Hypotheses on how project changes the
components of the system (Geomorphic-Biotic)
 Use top/down and bottom/up approach with lots
of coordination between physical scientist and
biologist
 No river is the same, nor does every dam have
the same impacts

Case Study 1
Overview of hydrology, geomorphology,
and channel morphology of the Clavey
River
 Develop hypotheses
 Illustrate some conceptual models and
analytical tools useful for access damrelated impacts to steep bedrock rivers

Summary of Changes
Substantial loss of flow volume
 Substantial reduction on flood magnitude
and frequency
 Constant year found base flows
 Loss of coarse sediment supply
 Reduction or loss of fine sediment
 Downstream tributaries and valley walls
still contribute fine and coarse sediment to
channel

Potential Impacts
Accumulation of fine sediment and gravels
in channel
 Riparian and upland vegetation intrusion
 Abandoned side channels and ponded
areas
 Reduction of residual pool volume by
gravel-boulder filling
 And…

Potential Impacts
Reduced magnitude, duration, and
frequency of bed mobility of alluvial
features
 Reduced coarse sediment storage
immediately downstream of the dam
