Flash floods caused by localized thunderstorms are a natural hazard
of the semi -arid Southwest, and many communities have responded by
installing ALERT flood forecasting systems. This study explored a
rainfall- runoff modeling approach thought to be appropriate for
forecasting in such watersheds. The kinematic model KINEROS was
evaluated because it is a distributed model developed specifically for
desert regions, and can be applied to basins without historic data.
This study examined the accuracy of KINEROS under data constraints
that are typical of semi -arid ALERT watersheds. The model was validated
at the 150 km2, semi -arid Walnut Gulch experimental watershed. Under the
conditions examined, KINEROS provided poor simulations of runoff volume
and peak flow, but good simulations of time to peak. For peak flows, the
standard error of estimate was nearly 100% of the observed mean.
Surprisingly, when model parameters were based only on measurable
watershed properties, simulated peak flows were as accurate as when
parameters were calibrated on some historic data. The accuracy of
KINEROS was compared to that of the SCS model. When calibrated, a
distributed SCS model with a simple channel loss component was as
accurate as KINEROS.
Reasons for poor simulations were investigated by examining a)
rainfall sampling errors, b) model sensitivity and dynamics, and c)
trends in simulation accuracy. The cause of poor simulations was divided
between rainfall sampling errors and other problems. It was found that
when raingage densities are on the order of 1/20 km2, rainfall sampling errors preclude the consistent and reliable simulation of runoff from
localized thunderstorms. Even when rainfall errors were minimized,
accuracy of simulations were still poor. Good results, however, have
been obtained with KINEROS on small watersheds; the problem is not
KINEROS itself but its application at larger scales.
The study also examined the hydrology of thunderstorm -generated
floods at Walnut Gulch. The space -time dynamics of rainfall and runoff
were characterized and found to be of fundamental importance. Hillslope
infiltration was found to exert a dominant control on runoff, although
flow hydraulics, channel losses, and initial soil moisture are also
important. Watershed response was found to be nonlinear.
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/614156 |
| Date | 06 1900 |
| Creators | Michaud, Jene Diane |
| Contributors | Department of Hydrology & Water Resources, The University of Arizona |
| Publisher | Department of Hydrology and Water Resources, University of Arizona (Tucson, AZ) |
| Source Sets | University of Arizona |
| Language | en_US |
| Detected Language | English |
| Type | text, Technical Report |
| Source | Provided by the Department of Hydrology and Water Resources. |
| Rights | Copyright © Arizona Board of Regents |
| Relation | Technical Reports on Hydrology and Water Resources, No. 32-030 |
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