The City of Ames Water and Pollution Control staff operate a
flood prediction system based on HEC-1, a software program
developed
by the U. S. Army Corps of Engineers Hydrologic
Engineering Center
(HEC).
The above graph shows the series of peaks in both the Skunk River and Squaw Creek
in October of 2007. The rapid response to rainfall of both basins classifies them as "flash flood" basins.
Two separate models are used: one for the Skunk River
basin and another for Squaw Creek basin. Each
model subdivides the basin into sub-basins according to
the natural topography. Rainfall, initial stream
levels, and soil moisture conditions are input into the
models; and a predicted runoff amount is calculated for
each sub-basin. The model combines the outlet
flows from each of the sub-basins to estimate the time
and magnitude of a flood peak.
The models are run in real-time.
Rainfall data are collected by several rain gauges
scattered around the basins. These gages are
connected to a data receiving computer, allowing
real-time rainfall data to be entered into the
predictive models
The rainfall gauges were installed in 1997 to provide
actual rainfall data. Prior to 1997, the models used radio reports of rainfall
location and intensity. The City also has stream gauges providing flow depth data
for comparison of the predictions with real river data.
