1. Update to the 1992 Dry Creek Watershed Flood Control Plan
FEMA CTP HYDROLOGY
Update to the 1992 Dry Creek Watershed Flood Control Plan
CESI/RBF
RR/KM

2. Purpose of the Plan Update
To develop updated hydrologic model that can adequately evaluate the flood damage reduction potential of achievable projects,
Asses the impact of the development that has occurred with realistic consideration of the effectiveness of local developer installed detention basins,
Identify plausible multiple objective regional flood reduction and/or mitigation measures that could be expected to be met with broad support,
Provide a list of local, cost effective, flood damage reduction projects, and
Prepare a funding plan consistent with Plan Update project recommendations and current development projections
Update to the 1992 Dry Creek Watershed Flood Control Plan

3. New Modeling Major Revisions to the Previous (1992) Plan Model
Watershed Boundary Changes
Finding Mitigation in the Urbanized Dry Creek Watershed

4. New Modeling Major Revisions to the Previous (1992) Plan Model
Watershed Detail Substantially Increased watersheds became 1,250+ watersheds.
Finding Mitigation in the Urbanized Dry Creek Watershed

5. New Modeling Major Revisions to the Previous (1992) Plan Model
HEC-HMS replaces HEC-1 for individual hydrograph development portion of modeling.
Integrated GIS functionality
Adds greater Flexibility in Future
DRY CREEK TOOLBOX
Update to the 1992 Dry Creek Watershed Flood Control Plan

6. 1992 Estimated Imperviousness of the Watershed = 17.8%.
Baseline Comparison
1992 Estimated Imperviousness of the Watershed = 17.8%.
Dry Creek Watershed Imperviousness
1992
Finding Mitigation in the Urbanized Dry Creek Watershed

7. Current Estimated Imperviousness of the Watershed = 22.0%.
Baseline Comparison
Current Estimated Imperviousness of the Watershed = 22.0%.
Dry Creek Watershed Imperviousness
Current
Finding Mitigation in the Urbanized Dry Creek Watershed

8. Future General Plan Build-out Estimated Imperviousness = 27.0%.
Baseline Comparison
Future General Plan Build-out Estimated Imperviousness = 27.0%.
Dry Creek Watershed Imperviousness
Future GP Build-out
Finding Mitigation in the Urbanized Dry Creek Watershed

9. Acreage of Development (acres) Rural Residential Portion (acres)
Baseline Comparison
The development area of the watershed has increased from 35,900 acres to 44,400 acres, and will increase to 58,700 acres at General Plan build-out.
Timeline Condition
Acreage of Development (acres)
Rural Residential Portion (acres)
1992
35,900
9,000
Current
44,400
12,300
General Plan
Build-out
58,700
17,200
Finding Mitigation in the Urbanized Dry Creek Watershed

10. Historical Flooding in the Watershed
Documented Recent Major Floods:
Feb 1986 ( yr)
Jan 1995 (200-yr)
Dec 1995 (2-yr)
Jan 1997 (10-yr)
Feb 1998 (10-yr)
Dec (10-yr)
Finding Mitigation in the Urbanized Dry Creek Watershed

11. Historical Flooding in the Watershed
JAN 1995
2-day event – 358 Structures Flooded within Roseville.
Rainfall Matched 200-year intensities for a 6-hour and 24-hour storm event.
Between 3.9 inches and 7.6 inches of rain in Dry Creek Watershed
End of strong (5-year) El Nino/beginning of weak La Nina event
Finding Mitigation in the Urbanized Dry Creek Watershed

12. Historical Flooding in the Watershed
What to Avoid!
Update to the 1992 Dry Creek Watershed Flood Control Plan

13. Historical Flooding in the Watershed
1986
JAN
1997
1995
DEC
2005
2010
Comparison of Pacific Pressure (El Nino effect)
Update to the 1992 Dry Creek Watershed Flood Control Plan

14. New Modeling Major Revisions to the Previous (1992) Plan Model
Hydraulic Routing Model as a Hydrologic Component (HEC-RAS)
Update to the 1992 Dry Creek Watershed Flood Control Plan

15. Dry Creek Watershed Study Update Calibration

16. Dry Creek Watershed Study Update Calibration

17. Dry Creek Watershed Study Update Technical Analysis Status
Raw Precipitation Values published in SWMM

18. Dry Creek Watershed Study Update Technical Analysis Status
Raw Precipitation Values published in SWMM

19. Dry Creek Watershed Study Update Calibration

20. Dry Creek Watershed Study Update Calibration

21. Dry Creek Watershed Study Update Calibration

22. Dry Creek Watershed Study Update Calibration

23. Dry Creek Watershed Study Update Calibration

24. Dry Creek Watershed Study Update Calibration

25. Dry Creek Watershed Study Update Calibration

26. Dry Creek Watershed Study Update Calibration

27. Dry Creek Watershed Study Update Calibration

28. New Modeling Major Revisions to the Previous (1992) Plan Model
Storm Centering: Analysis of all storm centers and 4 different potential storm angles at each storm centering location, yielded 7 storm combinations that can control peak flows for the various locations in the watershed.
DRY CREEK TOOLBOX

29. Dry Creek Watershed Study Update Technical Analysis Status
Raw Precipitation Values published in SWMM

30. Dry Creek Watershed Study Update Technical Analysis Status
Raw Precipitation Values published in SWMM