Flood frequency analysis for downstream gauging sites.

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For flood frequency analysis, we need to analyze the flows at all the available gauging sites. But the problem arises when there is a gauging site downstream of a storage structure. In such cases, the flows are no longer monitored and modelling them could be erroneous. How to cater such uncontrolled flows while carrying out flood frequency analysis?

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3 Answers

  1. Reservoirs will influence the flood flow magnitude, however one can still study the downstream gauge, while introducing a reservoir routing component in the model. Of course it would be better to place a gauge upstream of the reservoir as well, in order to have greater certainty.

  2. A dam is a better gauging site. Every dam has a gauge to measure the depth of water in the dam and a gauge storage curve is also available. The reservoir gauge is recorded at even intervals of time. Thus you know correctly how what quantity of water reached the dam in a particular time interval. By dividing the quantity of water received by time interval , you may may find the discharge received. This is also the function of the river gauge. You may like to explain what information you will not get / derive if there is a dam upstream?