Diversion of Flooding Rivers to Residual Mining Open Pits

Abstract

Massive flooding in East Germany in the summer of 2002 was first alleviated, and then exacerbated, by diversion of the river flood waters into residual open pits, the legacy of lignite mining. The pits at first contained the flood waters but, once filled to capacity, leaked precipitously, causing massive flooding in the flat lands around the pits. This paper examines the problem of constructing quantitative models for assessments of fill, bypass and leakage from such floodwater containing pits. Emergency management teams can then generate quickly not only many different scenarios to help with immediate flood control options and fall-back positions, but can also investigate long term planning that can then be undertaken to estimate better the consequences of permitting such diversion. While the models developed are simple, and are numerically implemented in easy to use spreadsheet format, they have the advantage of guiding directions of flood assessment control and consequent results. The illustrative numerical examples show how one can quickly use such quantitative models to obtain patterns of flooding relevant to situations of sustained, torrential rainfall and subsequent river overflow.