1. FLOODS

2. RIVER FLOODS Stream overflows levees Stream overflows levees Most destructive of all geologic hazards Most destructive of all geologic hazards Causes Causes –Weather –Dams breaking

3. Floods of the 20 th century

5. Cincinnati, OH

6. Des Moines, Iowa 1993

9. Mississippi 2001

10. Artificial Levees To prevent river from flooding To prevent river from flooding Walls made of- Walls made of- –Dirt –Sandbags –Concrete

11. levees Dutch Dutch England England

12. US levees

14. floodplains Flat area around a river; floods Flat area around a river; floods Paving creates more run-off Paving creates more run-off Leaving natural, acts like “sponge” Leaving natural, acts like “sponge”

15. Flood plain use Best use? Leave it alone! Best use? Leave it alone! OK use? Golf course, park, farm OK use? Golf course, park, farm Worst use? Worst use?

16. How to recognize a floodplain?

17. Floodplain map

18. 100 year flood Misleading term Misleading term 1-in-a100 chance of river flooding every year! (1%) 1-in-a100 chance of river flooding every year! (1%) 10 year flood? 10 year flood?

19. 1 in 100 chance

20. How can flooding be good? When river floods, nutrients from bottom of the river are distributed onto land When river floods, nutrients from bottom of the river are distributed onto land Provides natural fertilizer Provides natural fertilizer Great farmland! Great farmland!

21. See any problems?

22. Marquette, MI 2003 tourist park

23. Flood uncovered glacier grooves

24. Flood insurance Most homeowners do not have Most homeowners do not have Government assistance Government assistance –Relief –relocation

25. Flash Floods Most deadly Most deadly Most vehicle related Most vehicle related Due to impermeable ground Due to impermeable ground Storm sewer back up Storm sewer back up

26. Vassar, MI 1986

27. Stream gauges measures stream height to calculate crest measures stream height to calculate crest

28. OR gauges measure stream discharge

29. hydrograph

30. Dams increase erosion downstream (white water) Increased deposition upstream Make river colder Make river colder

31. Glen Canyon Dam Purposes: Purposes: Flood control Flood control Electricity Electricity Drinking water Drinking water

32. Glen Canyon Dam

34. Hoover dam

36. Grand Canyon Flooding http://youtube.com/watch?v=EIXn_KNI5dQ http://youtube.com/watch?v=EIXn_KNI5dQ To simulate nature’s floods To simulate nature’s floods Replenish beaches Replenish beaches

37. Water cycle