1. HYDROMODIFICATION: AN INTRODUCTION AND OVERVIEW Presented by Jeffrey Haltiner, Ph.D., P.E. Philip Williams & Associates, Ltd. San Francisco, CA May2006

2. Hydromodification: An Integrated Element of Stormwater Management DISCUSSION TOPICS HISTORICAL PERSPECTIVE HYDROMOD PROCESSES MANAGEMENT STRATEGIES CONCLUSIONS

3. HISTORICAL CHANGES IN CALIFORNIA STREAMS: subtitled: “whither goest Willow Creek “How did we get here and whose fault is it anyway?”

5. Native American Life in California

6. An “adaptive” lifestyle Dry Season Wet Season

8. Arrival of the Spanish… and their cows

9. All of this occurred before the invention of the modern “low impact” cow

11. California in the 20 th Century

12. California in the 20 th Century: Urban and suburban growth

13. Development sequence: 1. Develop the watershed 2. Build near the river 3. River floods 4. Call for help: “somebody do something!”

14. A hero arose… In the hour of need…

15. Our tools… and the scale of our projects rapidly expanded

16. But along the way, our vision of rivers and streams

17. Began to get lost

18. As did our natural connection with streams

19. We began to get some bad press

20. And our image changed for the worse

22. The era of multi- objective watershed mgmt In response to these problems, the regulatory climate has changed dramatically, and we have entered

23. Regulatory Framework Flood management – FEMA – Local Flood Control Districts Habitat protection – US Fish & Wildlife Service (Section 7) – CA Department of Fish & Game (Section 1601) Water Quality – Federal Clean Water Act (US EPA) – Regional Water Quality Control Boards (RWQCBs)

24. In response to the regulatory requirements, we developed methods to address: 1. Flood hazard management 2. Wildlife habitat 3. Urban Runoff Water Quality

25. Despite our flood control and water quality efforts, channel problems continued…. Channel incision Downstream deposition

26. DISCUSSION TOPICS HISTORICAL PERSPECTIVE HYDROMOD PROCESSES MANAGEMENT STRATEGIES CONCLUSIONS

27. Urbanization Direct Hydrologic Impacts Increased runoff volume Increased peak flow rates Reduced time lag to peak flow Increased duration of high flow Increased frequency of flow events

28. runoff infiltration precipitation Runoff Processes

29. Hydrograph Modification Impacts Runoff Time Pre-Development Urbanization tends to increase stormwater runoff: peak flows volume frequency Post-Development

30. While we understand the basic effects of urbanization, the detailed processes are v. complex We use simple tools to characterize these impacts.

31. Scientific/modeling overview: Rainfall-runoff processes/modeling Rainfall-runoff: spatial and vertical complexity

32. Scientific/modeling overview: Stream channel processes Basic concept is that altered hydrology results in channel erosion Very difficult to predict the “threshold” for channel response

33. Urbanization Indirect Hydrologic Impacts Increased Channel network complexity Increased channel “efficiency”

34. Historical Channel Modification associated with development Stevens Creek, ca 1870 and 1899 ca 1870 1899

35. Expansion of channel incision: creation of new first order channels

36. Urbanization Hydrologic Impacts: Variability (all watersheds and streams are not created equal) Soil characteristics Cover (vegetation, duff layer etc) Channel characteristics (bed material, slope etc) Sensitivity to hydromod varies greatly

37. Watershed sensitivity to flow: Central coast example

38. Stream Channel sensitivity to flow changes: Stream response depends on morphology

39. DISCUSSION TOPICS HISTORICAL PERSPECTIVE HYDROMOD PROCESSES MANAGEMENT STRATEGIES CONCLUSIONS

40. Management Strategies Regulatory compliance/Implementation Integrating hydromod with other hydrologic project elements Development location/footprint Managing site runoff Channel management

41. Regulatory Framework Flood management Habitat protection Water Quality Hydrograph Modification Management – New NPDES permit requirements (RWQCBs) – How should it be regulated? Who should lead the regulatory side? – Which agency should manage this?

42. In developing hydrologic strategies in urbanizing areas, we now need to integrate four key elements: 1. Flood hazard management 2. Wildlife habitat 3. Urban Runoff Water Quality 4. Downstream impacts from increased runoff (hydro- modification)

43. Management Strategies Regulatory compliance Integrating hydromod with other hydrologic project elements Development location/footprint Managing site runoff Channel management

44. Much of the urbanization in the state has already occurred Much of the new permitting will be on small infill projects and small to medium developments at the urban fringe.

45. Site design and layout has a major effect on the stormwater runoff effects. Mass site grading and extensive, connected paving lead to large increases in runoff rate and volume. -Maintain open space -Maintain pervious soils -Disconnect impervious areas -Create pervious zones/buffers

46. Management Strategies Integrating hydromod with other hydrologic project elements Regulatory compliance Development location/footprint Managing site runoff Channel management

47. Designing a ‘storage’ vs. ‘conveyance’ approach to runoff management

48. On-site/individual unit mgmt: Planter Box

49. IMP Gallery Infiltration trench/ basin Vegetated swale

50. Detention facilities can be modified to include hydromod Park/permanent pond Wetland/wildlife Habitat Expanding our flood detention facilities to include hydromod: -they will have to be considerably larger -outlet structures will be more complex -allows regional mgmt

51. Water Quality Management Wetland treatment ponds

52. Management Strategies Integrating hydromod with other hydrologic project elements Regulatory compliance/Implementation Development location/footprint Managing site runoff Channel management

53. DOUGHERTY VALLEY: ALAMO CREEK RESTORATION

54. EXCAVATION OF A NEW FLOODPLAIN TERRACE

55. ALAMO CREEK AND RESTORED FLOODPLAIN: POST CONTSTRUCTION

56. DISCUSSION TOPICS HISTORICAL PERSPECTIVE HYDROMOD PROCESSES MANAGEMENT STRATEGIES CONCLUSIONS

57. Concluding thoughts We are inheriting watersheds and streams with extensive impacts Hydromod management must be integrated with other management elements Hydromod management must be applicable to different watershed locations The regulatory process is ahead of technology; no long- term experience The regulatory process is ahead of administration Long-term Performance/Maintenance?

58. In Response: Monitoring is important Flexibility in technology, regulation, administration Expect rapid evolution in the field: “Adaptive Management”

59. You learn about natural systems by field observation and data collection (NOT just sitting behind a computer screen or a book) Field Data Collection

60. Ignore the discomforts Bring the kids Be thorough The importance of field work: We learn more from observation than from computer models

61. You learn how to build projects by trying things out and learning from your mistakes and successes Project Design and Implementation It is easier to criticize than to do! Be humble; there is a lot to learn

62. Hydro mod means urban: Get involved in the community

63. Build Education into your projects

64. Share what you’ve learned

65. Teach the next generation too… (they’ll be paying for your social security)

66. Hydromod management is poised at the crossroads of Technology and Innovation