Watershed Assessment of River Stability and Sediment Supply: Advancing the Science of Watershed Analysis

Transcription

1 Watershed Assessment of River Stability and Sediment Supply: Advancing the Science of Watershed Analysis 2009 MWEA Annual Conference Rob Myllyoja, CET

2 Watershed Assessment of River Stability and Sediment Supply Overview Pros and Cons Upland vs. In-stream sources Key components Case Study Need for further info (where to go from here)

3 Watershed Assessment of River Stability and Sediment Supply Stability thresholds (causes & consequences) Clean sediment TMDLs Stream restoration planning and design (correction & communication) Permitting and grants Section 319 WMP updates

4 EPA Sec. 319 Minimum Elements 1. Sources and causes load reductions 2. Estimate expected load reductions 3. Describe management measures needed 4. Estimate technical and financial assistance 5. Public education and participation 6. Implementation schedule 7. Describe measurable milestones 8. Criteria to determine load reductions 9. Effectiveness monitoring - implementation

5 TSS from Streambank Erosion Old Woman Cr., OH 63% of TSS came from the banks during high flows (Whiting, 2006) Weeks Bay, AL 64% of TSS from banks Winchester Creek, OR 45% TSS from banks Soda Butte Cr., MT 50-89% TSS from banks Madison R. - >90% of TSS during Qbkf was associated with instability (Rosgen, 1973) E.F.San Juan R. - 46% of annual sediment yield from unstable 3 miles (Rosgen, 2001)

6 Land Use River Processes Channel instability/adjustments Upland surface erosion Mass erosion Channel enlargement Channel degradation/incision Channel aggradation/excess deposition Lateral channel confinement Accelerated meander migration

7 Pros and Cons of WARSSS Evaluates Problems with: Bedload, Fine Sediment, Phosphorus, In-Stream Habitat Not a substitute for a comprehensive water quality monitoring program Provides empirical data to validate models Level III training in River Assessment and Sediment Supply by Dave Rosgen PH PhD Wildland Hydrology

8 Watershed Assessment of River Stability and Sediment Supply Due to the nature of this methodology, it is essential that assessments be conducted by individuals with training and experience in geomorphology, hydrology, engineering, geology, soil science, plant science, and other related scientific disciplines. Individuals should be specifically trained and experienced in hillslope, hydrologic and channel processes. (WARSSS, Rosgen, 2007)

9 Pollutant Removal Mechanisms of Natural Streams Connectivity of Hydrologic Floodplain Deposition, nutrient capture adsorption, transformation, de-nitrification Variable Bed Aeration, off-gassing Low W/d Ratio Aerobic hyporheic zone Riparian Plants Nutrient uptake Hydrology Bank storage, flood pulse

10 Is treating upland NPS pollutant sources alone going to restore water quality?

11 3-Phase Assessment Process I. Reconnaissance II. Screening III. Prediction IV. Validation

12 Stability of alluvial streams is achieved by allowing the river to develop a stable dimension, pattern, and profile such that, over time, channel features are maintained and the stream system neither aggrades nor degrades (Rosgen, 1996).

13 Stream classification is not the answer

14 Regional Curves Stratified by Stream Type

15 Hillslope Processes

16 Ecohydrology Source: MDNR, R. Haas

17 Comparison of Flow Duration Curves of the Black R. and Clinton R.

18 Vertical Stability Bankfull

19 Convert measurements to numeric ratings to narrative descriptions. For Example: What is the Bank Height Ratio?

20 Converting BEHI/NBS to Sediment Load

21 Sediment Transport Analysis Empirical vs. Modeled Data

22 Sediment Sampling

23 Colorado Case Study: Ohio Creek Excessive sediment deposition Accelerated streambank erosion Wide, shallow channel

24 The Approach Departure analysis - Is the river stable? Allows us to address root causes. Band-Aids The data is also used in restoration design.

25 MEANDER PATTERNS (M3, M5, M7)

26 DEPOSITIONAL PATTERNS (B1, B3, B4, B5)

27 Conclusions Conversion from moderately meandering to braided channel due to cattle & diversions Insufficient sediment transport capacity Entrainment not competent Inappropriate patterns, dimensions and slope Bankfull shear stress too low Pool filling >>> poor habitat, increased temps.

28 Ohio Creek Restored

29 Michigan Case Study: Randolph Street ICD Incision, channelization Slope reversals Altered riparian vegetation No floodplain connectivity

30 Reference Reach for Departure Analysis

31 SLOPE REVERSALS Steep Pools Flat Riffles

32 Solutions Stream types Channel pattern Dimensions Profile

33 WHERE DO WE GO FROM HERE?

34 Dimensionless SDR Curves (Rosgen, 2001)

35 USGS Gauging Stations