The inner rectangle represents DCIA, consisting of rooftops, streets, sidewalks, driveways, and so on. The dimensions of the inner rectangle are 1000 ft wide by 2500 ft tall, life pervious area behaves like "lawns, sandy soil, average slope." The DCIA has characteristics of streets and roofs. "High-end" values of runoff coefficients should be used.
The inlet time for flow from the far upper end of the catchment (e.g., an upper corner of the pervious area) is 2 hrs. The inlet time just for the DCIA is 20 min.
a) What is the 25-yr outflow, by the rational method? Remember to compute runoff for both the total area and just for the DCIA.
b) Use the USGS regression equations for Tallahassee to compute the 10-yr peak flow. Observe that this value is close to the rational method estimate for DCIA, from part a.
c) A corrugated steel pipe (CSP) culvert (n = 0.024) will receive the 25-yr flow from
the catchment, using the rational method of part a. If the pipe slope is 1%, what standard U.S. diameter (see problem 6.9) should be used?