Module # 6 Field Methods to Determine/ Verify Bankfull Elevation, XS Area & Discharge Iowa s River Restoration Toolbox Level 1 / Base Training
Overview of Basic Field Data Collection Site Map Cross Sections Longitudinal Profile Sediment Samples Reach Ave Pebble Count Riffle Armor Pebble Count Bar Sample Stream Assessment Harrelson, C.C., Rawlins, C.L., and Potyondy, J.P. Stream Channel Reference Sites: An Illustrated Guide to Field Technique: General Technical Report RM-245, Fort Collins, CO: U.S. Department of Agriculture - Forest Service, Rocky Mountain Forest and Range Experiment Station, 1994.
Site Map General Info Legend Photo Points Terraces Features Pool/Riffle Sequences Gravel & Sand Bars Abandoned Channels Measurements
Bankfull Discharge Controls Average, Long- Term Channel Form Corresponds to the Discharge that Channel Maintenance is Most Effective over the Long- Term Low Recurrence Interval Lower Recurrence Interval in Urban Watersheds flow bkf Buffalo Run, KY courtesy Stantec time
Bankfull Indicators Flat, Depositional Surface Adjacent to Active Channel Height of Depositional Features (Point Bars) Change in Vegetation Slope or Topographic Breaks or Changes Along the Bank Check Versus Water Level
Survey Equipment
Cross Section Measurements Source: DL Rosgen
Cross Section Measurements
Cross Section Measurements Bankfull Call/Elevation Inner Berm Features Floodprone Width Bankfull Area Bankfull Width and Depth
Profile Survey Thalweg Water Surface Define Facets Bankfull Indicators Lowest Bank Terraces, Etc.
Measuring Water Depths Height of Rod @ Thalweg Location Hold Rod at Water Surface Move to River s Edge
Profile Survey Bankfull Slope Facet Slopes Always Measure Water Surface Pool to Pool Spacing Pool Lengths Facet Maximum Depths Channel Bottom to Bankfull Elevation Low Bank Height or Valley Bottom
Particle Size Distributions Field Measurements of Channel Materials Reach Average (classification) Riffle Bed (armor layer) Depositional (bedload transport) Estimate Distributions Used to Estimate Bed Roughness
Pebble Counts & Bar Samples 1. Obtain a 100-particle pebble count on 10 transects from bankfull to bankfull throughout the reach (Classification) 3. Obtain Sieve Analysis at the location of the largest particle on lower 1/3 of point bar or other depositional feature 2. Obtain a 100-particle pebble count in the riffle bed (Sediment Transport)
Wolman Pebble Counts
Wolman Pebble Counts
Wolman Pebble Counts
Particle Size Distributions
Planform Geometry Measurements Wbkf = Bankfull Width Wblt = Belt Width Am = Amplitude Lm = Meander Wavelength Rc = Radius of Curvature
Sinuosity Channel Length/Valley Length -or- Valley Slope/Channel Slope
Design Reach Data Collection Dependant Upon Purpose of Project Impacted Reach (Minimum Data per Stream Type) Planform Measurements Riffle Cross Section Reach Average Pebble Count Riffle Bed Material Pebble Count Bar Sample Sieve Analysis Longitudinal Profile
Additional Design Reach Data Collection Site Constraints Upstream and Downstream Tie-In Tributaries Valley Type and Slope Available Material Onsite Potential Restoration Methods
Reference Reach Criteria Stable Reference Stream in Same Hydro-Physiographic Region Same Stream Type as Intended Design Stable for Two Meander Wavelengths (20 Bankfull Widths) Best if Similar Valley Slope and Sediment Regime as Impacted/Design Reach
Reference Reach Data Collection Planform Measurements Facet Cross Sections (Riffle, Run, Pool & Glide) Longitudinal Profile through 2 Meander Wavelengths (Minimum) or 20 to 30 Bankfull Widths Reach Average Pebble Count Riffle Bed Material Pebble Count Bar Sample Sieve Analysis Pfankuch Channel Stability Assessment Site Controls (Bedrock, Wood)
Module # 6 Field Methods to Determine/ Verify Bankfull Elevation, XS Area & Discharge Iowa s River Restoration Toolbox Level 1 / Base Training