1. Rivers and Streams The Hydrologic Cycle

2. Rivers and Streams Drainage basin or watershed

3. Mill Creek Drainage Basin A River Drainage Basin

4. Mill Creek Drainage Basin Walla Walla River Drainage Basin

7. Flow

8. Flow

9. Equilibrium and the longitudinal profile GradientVelocityDischarge Q = V x A ft 3 /sec (cfs) or m 3 /sec (cms) V = velocity A = Cross-sectional area = Width x mean depth Base level (ultimate and local)Gradient Load

10. Velocity Variation

11. Variations with Discharge

12. Load

13. Load: F Bed load (rolling, saltation) F Suspended load: silt and clay carried in suspension F Dissolved load: ions in solution HCO 3 - SO 4 2- Ca 2+ Na + Mg 2+ typically  90% of dissolved Competence: the amount of load that a particular stream can carry

14. Load: Suspended Load

15. Load: Bed-load

25. 200 400 600 800 1000 1200 1400 1600 1800 2000 OctNovDecJanFebMarAprMayJunJulAugSep Maximum Mean Hydrograph for Mill Creek at Walla Walla Averages for 1942-1990 Discharge (cfs)

26. The Graded Stream The Longitudinal Profile

31. Braided/Meandering

32. Braided/Meandering

33. Velocity Variation

34. Meandering and Floodplains

35. Point Bar – Cut Bank

40. Meandering and Floodplains

47. Deltas

48. Deltas

49. Deltas

50. Deltas

51. Deltas

52. Alluvial Fans

54. Floodplain Terraces

59. Stream Piracy

62. Flooding is dependent upon F precipitation in drainage basin F precipitation rate/infiltration rate F topography Flood Discharge = channel discharge when a river overflows its banks Flood Magnitude = discharge above flood discharge Flood Stage = elevation of water surface for a high-water condition likely to  damage Thus depends on use of floodplain

63. Mill Creek Flows 0 500 1000 1500 2000 2500 3000 3500 051015 Day in Feb, 1996 Discharge (cfs) Hydrograph for Mill Creek flood, Feb, 1996 Measured at Kooskooskie (max. was 6000 cfs at Walla Walla)

64. Recurrence Interval as flood indicator as flood indicator Rec. Int. = (Y-1)/R Y = # of years for data R = rank of flood

65. Natural Levee

67. Response to Flood Hazards F F Physical barriers   Levees   Flood walls with huge steel gates around towns   Retention reservoirs   Channelization to handle increase discharge   Storm channel system (LA)

68. Levees protect area behind until flood becomes too great failed levee working levee levee damming water behind it

69. Floodwalls on Mississippi in St. Louis and New Orleans

70. Flood Hazard Mapping Satellite images Upper = normal flow 1988 Lower = 1993 flooding

72. Landscape Evolution