rivers and streams the hydrologic cycle. rivers and streams drainage basin or watershed
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Rivers and StreamsRivers and Streams
The Hydrologic Cycle
Rivers and StreamsRivers and Streams
Drainage basin or watershed
Mill Creek Drainage BasinA River Drainage BasinA River Drainage Basin
Mill Creek Drainage BasinWalla Walla River Drainage BasinWalla Walla River Drainage Basin
FlowFlow
FlowFlow
Equilibrium and the longitudinal Equilibrium and the longitudinal profileprofile
GradientGradient
VelocityVelocity
DischargeDischarge Q = V x A ftQ = V x A ft33/sec (cfs) or m/sec (cfs) or m33/sec (cms)/sec (cms)
V = velocity V = velocity
A = Cross-sectional area = Width x mean depthA = Cross-sectional area = Width x mean depth
Base levelBase level (ultimate and local) (ultimate and local)GradientGradient
Load Load
Velocity VariationVelocity Variation
Variations Variations with with
Discharge Discharge
LoadLoad
Load:Load: Bed loadBed load (rolling, saltation) (rolling, saltation) Suspended load:Suspended load: silt and clay carried in suspension silt and clay carried in suspension
Dissolved load:Dissolved load: ions in solution ions in solution
HCOHCO33-- SO SO44
2-2- Ca Ca2+2+ Na Na++ Mg Mg2+2+ typically typically 90% of 90% of
dissolveddissolved
Competence:Competence: the amount of load that a particular stream the amount of load that a particular stream can carrycan carry
Load: Suspended LoadLoad: Suspended Load
Load: Bed-loadLoad: Bed-load
200
400
600
800
1000
1200
1400
1600
1800
2000
Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep
Maximum
Mean
Hydrograph for Mill Creek at Walla WallaAverages for 1942-1990
Dis
char
ge (
cfs)
Dis
char
ge (
cfs)
The Graded StreamThe Graded StreamThe Longitudinal ProfileThe Longitudinal Profile
Braided/MeanderingBraided/Meandering
Braided/MeanderingBraided/Meandering
Velocity VariationVelocity Variation
Meandering and FloodplainsMeandering and Floodplains
Point Bar – Cut BankPoint Bar – Cut Bank
Point Bar – Cut BankPoint Bar – Cut Bank
Point Bar – Cut BankPoint Bar – Cut Bank
Point Bar – Cut BankPoint Bar – Cut Bank
Meandering Meandering and and
FloodplainsFloodplains
Meandering and FloodplainsMeandering and Floodplains
Meandering and FloodplainsMeandering and Floodplains
Meandering and FloodplainsMeandering and Floodplains
Meandering and FloodplainsMeandering and Floodplains
Meandering and FloodplainsMeandering and Floodplains
Meandering and FloodplainsMeandering and Floodplains
DeltasDeltas
DeltasDeltas
DeltasDeltas
DeltasDeltas
DeltasDeltas
Alluvial FansAlluvial Fans
Floodplain TerracesFloodplain Terraces
Floodplain TerracesFloodplain Terraces
Stream Piracy
FloodingFlooding is dependent upon is dependent upon precipitation in drainage basinprecipitation in drainage basin precipitation rate/infiltration rateprecipitation rate/infiltration rate topographytopography
Flood DischargeFlood Discharge = channel discharge when a = channel discharge when a river overflows its banksriver overflows its banks
Flood MagnitudeFlood Magnitude = discharge above flood = discharge above flood dischargedischarge
Flood StageFlood Stage = elevation of water surface for a = elevation of water surface for a high-water condition likely to high-water condition likely to damage damage
Thus depends on Thus depends on useuse of floodplain of floodplain
Mill Creek Flows
0
500
1000
1500
2000
2500
3000
3500
0 5 10 15
Day in Feb, 1996
Dis
char
ge
(cfs
)
Hydrograph for Mill Creek flood, Feb, 1996Hydrograph for Mill Creek flood, Feb, 1996Measured at KooskooskieMeasured at Kooskooskie
(max. was 6000 cfs at Walla Walla)(max. was 6000 cfs at Walla Walla)
Recurrence IntervalRecurrence Interval
as flood indicatoras flood indicator
Rec. Int. = (Y-1)/RRec. Int. = (Y-1)/R
Y = # of years for dataY = # of years for data
R = rank of floodR = rank of flood
Natural LeveeNatural Levee
Response to Flood Hazards Physical barriers
Levees Flood walls with huge steel gates around
towns Retention reservoirs Channelization to handle increase
discharge Storm channel system (LA)
Levees protect area behind until Levees protect area behind until flood becomes too greatflood becomes too great
failed leveefailed levee
working leveeworking levee
levee damming water levee damming water behindbehind it it
Floodwalls on Mississippi in St. Louis and New OrleansFloodwalls on Mississippi in St. Louis and New Orleans
Flood Hazard MappingFlood Hazard Mapping
Satellite images
Upper = normal flow 1988
Lower = 1993 flooding
Landscape Evolution