SCS Curve Number

Runoff Using Unit Hydrograph

Develop and plot a unit hydrograph given the hydrograph below. Baseflow is $40cfs.$

Develop and plot the stream hydrograph resulted from the rainfall intensity, i$,$ and infiltration,

$f,$ given in the table below using the unit hydrograph developed in question $1.$

The United States National Park Service is considering building a larger lodge and visitor

center at Crater Lake. To determine how runoff will be affected by the development, calculate

the composite $CN$ before and after development. Cover conditions within the watershed are

shown in the following tables.

Before Development:

Find the runoff depth, Pe$,$ before and after development using the SCS method for a total

rainfall of $5\mathrm{.}8$ inches. Assume there have been no storms in the preceding weeks $($conditions are

dry$).$ Comment on how runoff will be affected by development.

a$)$ Develop the SCS triangular unit hydrograph for a $400-$acre watershed that has been

commercially developed. The flow length is $1500ft,$ the slope is $3\%,$ and the soil group is B$.$

b$)$ Using the curvilinear unit hydrograph, determine the runoff $(q$ in cfs$)$ when time is $0\mathrm{.}1hr$

since the rainfall started.