1. 8-1

2. 8-2

3. 8-3

4. 8-4

5. 8-5

6. 8-6 Alluvial Fan

7. 8-7 Delta

8. 8-8 Which stream is more likely to be “Seasonal”?

9. 8-9

10. 8-10

11. 8-11

12. 8-12

13. 8-13

14. 8-14

15. 8-15

16. 8-16

17. 8-17

18. 8-18  Insurance Companies & Homeowners  Study historical “Peak Discharge”  Discharge determines area to be flooded  Use Recurrence Interval Equation  Allows you to “predict” flooding  Why is it getting worse?

19. 8-19  Recurrence Interval (RI) = (N+1)/M  N= number of years of data  M=magnitude of the event  This equation allows you to predict frequency of flooding events

20. 8-20

21. 8-21

22. 8-22

23. 8-23  Type of Precipitation event  Ground Conditions  Vegetation Cover

24. 8-24  Removal of Vegetation  Destruction of Wetlands  Construction Activity  Urbanization

25. 8-25  Flash Floods (Upstream Floods)  Smaller Streams  Steeper Slopes  Shorter “Lag Time”  Little or No Warning

26. 8-26

27. 8-27  Downstream Floods  Wider valley and larger floodplain  Regional water from higher in drainage basin  Significant “Lag Time”  Time for Warning  Covers larger area

28. 8-28

29. 8-29 Build Dams

30. 8-30

31. 8-31 Channelization

32. 8-32 Retention Basins

33. 8-33 Erosion Control

34. 8-34 Floodplain Management & Wetlands Restoration

35. 8-35

36. 8-36