Dam Breach Analysis for Urbanizing Basins
Absher, Charles D.
McWhorter, John K.
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Development downstream of old and in many cases deficient, dams is responsible for a growing concern within communities that are transitioning from a rural to suburban environment. There are instances of permitted development being constructed in the shadow of a dam embankment without regard to the potential consequences from a dam failure. Loss of life is a real and sobering risk if a home is built in a potential dam breach zone. In Georgia, many of the dams in formerly rural areas do not fall under the regulatory oversight of the Georgia Safe Dams Program simply because they are smaller than the minimum size necessary by law to bring them into the Program. This does not diminish their potential for causing damage in the event of a breach. It is therefore imperative for development to account for the potential breach zone of even the smallest dams if they present a potential threat to downstream lives and structures. However, many breach zone delineation models are cumbersome and difficult to use, even for the most experienced modelers. It is therefore expensive to contract for that work, and as a result, modeling is often omitted. If a breach zone is delineated by a rough approximation, there is the potential to remove from development projects a substantial, and probably overestimated, portion of the usable land, thereby unnecessarily reducing the investment return for the developer. GIS and HEC-RAS offer a cost-effective and quick method to delineate a reasonable and effective potential dam breach zone. Through the use of a set of simple, but effective techniques, a breach zone can be defined for a reasonable cost that will protect lives and property, but not unduly impact the investment return potential for the development.