A study of Alert Standard Rainfall for Urban Medium and Small Rivers

Abstract:

The flood forecast and warning system means the system which can analyze and predict flood disaster in advance and is one of the representing unstructured measures to mitigate flood disaster damage.

Especially, because the urban stream basins generally have the characteristics of high impermeability and short concentration time, the securing of forecast lead time is so important to prevent the flood disaster in urban stream.

This study suggested the analysis method and standard rainfall in order to secure the forecast lead time for flood warning in urban stream.

This method predicts the water level change in the stream when rainfall event is predicted and then upper- and down-stream water levels are considered to analysis the water level change according to the predicted rainfall depth.

Uper- and down-stream water levels are respectively the water level at warning point and the backwater level at joined stream point.

Then, the criteria table of rainfall depth for flood warning at the warning point is analyzed based on the scenario comprised of various rainfall duration and water level change considering the various backwater conditions. It is expected that the flood warning issuance criteria for small urban streams will assist in regard to the appropriate flood forecast and warnings and the establishment of related policies.

This study is suggested standard rainfall for flood warning in medium and small stream depending on variable backwater conditions. It can provide flood warning having high quality, and helps decide disaster prevention measures by this result.

This flood forecasting methodology would be useful for the decision making in disaster prevention field.