CE 372 Engineering Hydrology and Hydraulics
Fall 2006
Comments on homework 8
30. I promised that you will have a storm sewer design problem on the final exam. Make
sure you understand where all of the numbers come from. . .About half the groups had
problems with the duration calculation. The duration in the last section of pipe in a
network must be large enough that the entire catchment will contribute. Therefore
the duration for two pipes in series with each other can never decrease. Most groups
used the inlet time plus the sewer flow time when they should have used the duration
plus the sewer flow time. Many groups commented on pipe 2.2-3.1 not meeting the
minimum velocity requirement of 0.6 m/s or 2 ft/s. You could increase the slope of
the pipe by lowering manhole 3.1 (and others). You could also use a pipe made of a
different material, or you could argue that since the pipe is not flowing full the velocity
will actually be larger.
31. The main trouble here was in accounting for the minor losses (which are not really
minor).