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RAINFALL-RUNOFF MODELING EXERCISE USING THE SOIL CONSERVATION SERVICE CURVE NUMBER METHOD

MODEL

( )( )

numbercurveCNCN

S

parameterretentionSinchesionprecipitatstormP

inchesrunoffstormQwhere

SPSPQ

=

−⎟⎠

⎞⎜⎝

⎛=

=

=

=

+

−=

101000

)()(

:8.02.0 2

ASSIGNMENT

1. Use the SCS Curve Number method to estimate approximate runoff response to the 100-yr 6-hour rainfall for three locations in Mānoa Valley: (1) near the Ko‘olau crest; (2) in the middle of the valley floor; and (3) in the lower part of the valley floor near the UH athletic facilities. Determine runoff for each of four hydrological soil groups and for each of three antecedent moisture conditions. Do one set of estimates for assumed natural land cover and one for the current land cover. Use the attached sheet to organize your results (see last page of packet).

2. By comparing your results, speculate as to what were the most important factors

producing the flood of 31 October 2004 that did extensive damage to parts of the UH campus. For information about the Mānoa flood of October 2004, see: http://www.prh.noaa.gov/hnl/pages/events/ManoaFlood20041030/

3. Your 100-yr runoff estimates are valid as point values. How would an estimate of areal average runoff from the basin differ from these point values? (see pages 68-69 and Figure 2-23 of the Dunne and Leopold text)

4. Give a step-by-step procedure for estimating the volume of runoff from the 2004

flood using the SCS Curve Number method and storm rainfall measurements.

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Source: Giambelluca, T.W., Lau, L.S., Fok, Y.S., and Schroeder, T.A. 1984. Rainfall frequency study for O`ahu. Division of Water and Land Development, Department of Land and Natural Resources, State of Hawaii. 232 p.

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Source: Dunne, T. and Leopold, L. 1978. Water in Environmental Planning. W.H. Freeman & Co., Inc

4

Source: Dunne, T. and Leopold, L. 1978. Water in Environmental Planning. W.H. Freeman & Co., Inc

5

Source: Dunne, T. and Leopold, L. 1978. Water in Environmental Planning. W.H. Freeman & Co., Inc

6

Source: Dunne, T. and Leopold, L. 1978. Water in Environmental Planning. W.H. Freeman & Co., Inc

7

Source: Dunne, T. and Leopold, L. 1978. Water in Environmental Planning. W.H. Freeman & Co., Inc

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Name: GEOG 405

6-hr 100-yr RF

Natural LC Current LC Natural LC Current LC Natural LC Current LC

Hydrologic Soil Group A

AMC I CN

Q

AMC II CN

Q

AMC III CN

Q

Hydrologic Soil Group B

AMC I CN

Q

AMC II CN

Q

AMC III CN

Q

Hydrologic Soil Group C

AMC I CN

Q

AMC II CN

Q

AMC III CN

Q

Hydrologic Soil Group D

AMC I CN

Q

AMC II CN

Q

AMC III CN

Q

Crest Mid-Valley Lower Campus