CWR 4101 Lab 5

Estimation of Rainfall Excess

PURPOSE:
  • To understand the use of a spreadsheet in Hydrology.
  • To effectively estimate rainfall excess.
  • 3 Points

 

 

EQUIPMENT:
  • Spreadsheet

 PROBLEMS:

 Section 5. 7.1 (4,15)

PROCEDURE:

Using the NRCS Curve Number Method, calculate the rainfall excess hydrograph for a residential watershed with 60% impervious area (2/3 NDCIA, 1/3 DCIA) and 40% pervious area. The pervious area has good grass cover with scattered trees. Use an NRCS Type II storm that has a return period of 25 years, a duration of 12 hours and occurs in Miami, Florida. Assume a hydrologic soil class of B.

Produce an AutoCAD drawing that represents the mass balance (P, F, Ia, R) for separate routing - refer to Figure 5.15 on page 166 of Hydrology for an example.

Use a spreadsheet to generate Rainfall Excess (R) using:

  • composite curve number method
  • separate routing method

 

 

OUTPUT:

Your output should include the following:

  • An AutoCAD drawing to represent the mass balance for separate routing (Appendix)
  • A spreadsheet with the solution to the CCN routing (Appendix)
  • A spreadsheet with the solution to the separate routing (Appendix)
  • A plot of cumulative rainfall excess vs. time for both CCN and separate routing on the same graph (Results)

CUMULATIVE PRECIPITATION (no dimensions)

0.000

0.002

0.005

0.008

0.011

0.014

0.017

0.020

0.023

0.026

0.029

0.032

0.035

0.038

0.041

0.044

0.048

0.052

0.056

0.060

0.064

0.068

0.072

0.076

0.080

0.085

0.090

0.095

0.100

0.105

0.110

0.115

0.120

0.126

0.133

0.140

0.147

0.155

0.163

0.172

0.181

0.191

0.203

0.218

0.236

0.257

0.283

0.387

0.663

0.707

0.735

0.758

0.776

0.791

0.804

0.815

0.825

0.834

0.842

0.849

0.856

0.863

0.869

0.875

0.881

0.887

0.893

0.898

0.903

0.908

0.913

0.918

0.922

0.926

0.930

0.934

0.938

0.942

0.946

0.950

0.953

0.956

0.959

0.962

0.965

0.968

0.971

0.974

0.977

0.980

0.983

0.986

0.989

0.992

0.995

0.998

1.000