Geomorphic methods for TMDLs:Data collection

� Purpose of data collection� Basics of surveying� Components of channel survey� Regional traits� Historic assessment

Need for channel survey data in TMDLs� In WARSSS, need channel type to

assess risk of channel evolution –downcutting, widening

� In CEM, channel evolution stages are strongly linked to sediment yield (Simon Stages III-IV have highest load)

Figure 4Figure 4--23. Risk rating for potential introduced 23. Risk rating for potential introduced sediment and channel instability by stream type sediment and channel instability by stream type based on percentage of channel length affected by based on percentage of channel length affected by vegetation change.vegetation change.

Relationship to WARSSS stages

� RLA: eliminate stable watersheds from list

(problem in MRB they’re all unstable: must rank highest sediment sources)

� RRISSC: collect more detailed geomorphic and hydrologic data to assess risk of high sediment yield

� PLA: predict how much sediment is coming from stream erosion using BANCS, RIVERMORPH

Categories of RRISSC assessment

� Hillslope processes� Mass-wasting� Road impacts� Surface erosion

� Hydrologic processes� Factors altering streamflow (+ or -)

� Channel processes (subject of this presentation - data collection methods)

WARSSSWARSSS, Page 4, Page 4--33

RRISSCRRISSCProcedural Procedural

Steps: Steps:

Chapter 4Chapter 4

((RosgenRosgen))

Data collection - desktop

� Level 1 Rosgen and RLA�Use topos and aerials

�Can get rough estimates of width, slope, entrenchment, valley type

�Planview – sinuosity, radius of curvature�Need field survey for bed and bank materials;

bank height and bankfull height

Channel surveys

� In general: characterize channel as source or sink of sediment; departure from reference state� slope� channel materials (bed and bank), � cross section� Plan-view pattern (sinuosity, curvature, etc.)

Survey Basics

� Types of equipment �Manual (optical) level

�Laser level�Total Station

�Differential GPS�LIDAR

Survey Concepts

� Elevation and benchmarks� relative vs. reference to sea level

� Two vs. three dimensional� Information from hand survey data vs.

GIS, USGS topos and aerial photos

Steps to doing a survey

� Setting up level � Must be above all survey points)

� Laying out tapes for horizontal distance� Holding the rod� Working in teams of 2 or 3� Plot data

90 + 93 Wolverton Creek, Riffle

892

893

894895

896

897

898

899

900901

902903

0 20 40 60 80 100 120 140

Width

Ele

vatio

n

Reading numbers on stadia rod

� Distance, point or station� Height of instrument� Backsite� Foresight� Elevation

Note taking

Survey notesdata + map + notes.

Data is meaningless without notes

Quality over quantity

� Breaks in slope, steep changes in elevation are important

� Bankfull and terraces are critical especially to entrenchment

� Notes are critical, especially if others must interpret your data

� Example: too much data without bankfullmeasurements

Sources of error

� Rod not vertical (sway back and forth to get lowest number)

� Unstable bottom surface (stream bed)� Reading #s wrong� Non-sensical numbers ?? Subtracting

backsite wrong

Common surveying problems

� Vegetation blocks view� Rod too short (12 or 16’ rod)� Avoiding turning points (backsites) they

are confusing and time-consuming (can bring two levels)

� Translating data into usable format

Plants blocking downstream view

Check list of equipment

� Stadia rod� Laser level� Tripod� Notebook� Extra pencils for dropping in water� Backpack� Waders, water gear, bug spray

Components of survey

� Longitudinal profile� Horizontal measurements using tape

measure or GPS� Data taken at:

�Bed�Water surface

�Bankfull elevation

Channel Features in long. Profile

� Riffle� Run� Pool

Water surface vs. bed surface

� Water surface slope key for energy/force� Bed surface key for habitat features / biota

Components of x-section

Cross sectional data

� Blue = bankfull elevation, red = floodprone

90 + 93 Wolverton Creek, Riffle

892

893

894

895

896

897

898

899

900

901

902

903

0 20 40 60 80 100 120 140

Width

Ele

vatio

n

Valley vs. channel x-section

� Entrenchment� Valley type� Bluff vs. bank

erosion

Survey of bed materials

Methods� Pebble count� Sediment sampling

Importance :Erodibility of bed, mobilityAggradation or degradation ?

Depth of fine sediment in stream

� Modified Lisle method� Use metal probe ¼ - ½ inch diameter� Indicator of deposition, sediment balance� Burial of stream habitat features� Legacy sediment?

Riffle Surface Pebble Count, WEC 159 - Elm Creek at Highway 159

silt/clay sand gravel cobble boulder

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.01 0.1 1 10 100 1000 10000

particle size (mm)

perc

ent

finer

tha

n

0

2

4

6

8

10

12

number of particles

cumulative % # of particles

Channel stability indices

� Semi-quantitative � Techniques

�BEHI (Rosgen)�Pfankuch

�Rapid Geomorphic Assessment (Simon)

Problems: Finding bankfull

� How is bankfulldefined?

� It’s not always top of bank. Is channel-forming flow; approx. 1.5 year recurrence flow

WEC 159 - Elm Creek at Highway 159, Riffle

84

86

88

90

92

94

96

98

0 20 40 60 80 100 120 140 160

Width

Ele

vatio

n

Which elevation is bankfull?

Verifying bankfull with stream flow data

� For streams with USGS gauges, obtain annual peak flow series

� Bankfull flow is approximately = 1.5 year flood

� Calculate recurrence intervals to obtain 1.5 year flood

� Relate calculation to height in field

Compare to regional data

� Regional curves: bankfull vs. drainage area

� Provides check on field data

Bankfull area vs. drainage area in Elm Creek

y = 0.3253x + 24.632R2 = 0.9287

0

50

100

150

200

250

300

350

0 200 400 600 800

Drainage area (km 2)

ban

kfu

ll ar

ea (

squ

are

feet

)

Measuring change over time: Historic stream data� Historic aerial photos� GLO maps � Relict channels; sedimentology� Plant indicators (age of trees)� Historic channel survey data

History provides context

� What is a high bank erosion rate� When was sediment deposited in ditches,

lakes, channels, etc?� Are restoration and management options

possible given landscape and infrastructure constraints?

Data entry

� Mcklenburg spreadsheet speeds process � Need at minimum

�Slope�Cross section

�Bankfull estimate�Pebble count

Analyzing data: what does it mean?

� Quantifying instability� Connecting the dots: how do channel

measures relate to impairment�Turbidity�Biota

Turbidity

� Where is sediment coming from� Is it getting to the channel?� If so, is it suspended ?

(use particle size data)� What about organic matter?

Biota

� Sedimentation of gravel/cobble riffles; pools

� W:D ratio can effect temperature, oxygen� Low flow conditions effect biota� Historic alterations to headwaters – loss of

spawning areas etc.

Further analysis

� Quantification of sediment load from channels; modeling

� Rosgen�BANCS model using BEHI and NBS�RIVERMORPH – modeling of sediment

transport

� Simon�BSTEM and CONCEPTS

Future issues

� What is connection between geomorphology and impaired biota?

� Do these techniques provide the answer?