1. Strategies Addressing Hydromodification in Channels Through Unstable Terrains John Gartner Barry Hecht Shawn Chartrand Edward Ballman, P.E. BALANCE HYDROLOGICS, INC.

2. Field Problem Incision by streams draining urbanized areas

3. Channel dredging, Mowry Slough, Fremont, California Field Problem

4. (Leopold, 1968)  Semi-permanent hydrologic change to which the channel must adjust  Decreased lag time  Increased peak  Increased volume  More frequent erosive flows Erosion threshold?? Understanding Hydromodification LOGARITHMIC AXIS!

5. Regulatory context Downstream impacts are becoming unacceptable CEQA and NEPA Endangered Species Act County permits per Bay Area RWQCB

6. Role of geomorphologist Recognize disturbed landscapes and importance as sediment sources Understand channel form, function Comprehend channel adjustments to environmental change

7. Outline Site Assessment Solutions Summary

8. Case study: Coyote Gulch

9. 560 acres Site Ridgetop Downstream Steep Disturbed

10. “Orinda” Formation –Tightly folded –Mass movements –Beds with varying resistance Geology

11. Clay Soils Low Infiltration Millsholm Soils

12. Larger watershed context Downstream Hydromod Biota Network Barbed

13. Flow monitoring and baseline Host of info Lag time Calibrate model Seasonal effect saturation – baseflow steps Date Discharge (cfs) WY 2004

14. Sediment monitoring, baseline Mostly suspended Regional context Baseline Assess success

15. Stream walks Channel Stability

16. Presentation is continued in: Gartner GSA talk hydromodification 5-1-05 part 2.pdf