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Stream ordering• Quantitative way of studying
streams. Developed by Horton and then modified by Strahler.
• Each headwater stream is designated as first order stream
• When two first order stream combine, they produce second order stream
• Only when two streams of the same order combine, the stream order increases by one
• When a lower order stream combines with a higher order stream, the higher order is retained in the combined stream
Routing a hillslope hydrograph through the network
Rainfall
Hillslope Flow
Channel Output
Time
Intensity
Time
Intensity
Time
Intensity
Channel Hydrograph
Hillslope Hydrograph
Rainfall
Time
Intensity
A
B C
ABC
Combination of hillslope hydrographsfrom points A, B and C.
1: Rainfall is transformed by the hillslopes into a hydrograph which is delivered throughout the network .
2: Hydrographs from A take longer to travel to the outlet than those from B, and those from C arrive sooner still.
3. When these are combined, the outlet hydrograph is more drawn out, and the peaks from A, B, C do not coincide
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Jan Feb Mar Avr MaiJun Jul Aug Sep Oct Nov Dec
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Débits Qd , m3 j-1 Précipitations, mm j-1
Répartition des volumes à écouler pendant l´année
