A New Methodology Developed to Assess the Impacts of Floods on Environment

Flood is one of the most serious natural disasters, which has significant and negative impacts on economy and society. In addition, floods also have potential adverse consequences on environment when floods polluted by flood-exposed pollutant sources go into clean waterbody or other protected areas. Generally, the effects of floods on environment are qualitatively described, which is hard to compare the relative impacts of different flood events on environment. In this paper, we develop a methodology which can half-quantitatively evaluate the effects of floods on environment. Firstly, we identify the potential pollutant sources and protected areas, and then make the corresponding distribution maps. For the potential pollutant sources, the hazard of typical pollutants is also determined. Second, we set rating standards (5 levels) of two indexes, i.e., the hazard level of potential pollutant sources and the protection level of protected areas. Third, we superimpose flood extent map, potential pollutant source distribution map and protected area distribution map to analyze the levels of the two indexes according to the aforementioned rating standards, respectively. In the last, we use matrix method to comprehensively combine two indexes and divide the severities of environmental consequences into 5 levels. We apply this method to a part of the South-to-North Water Diversion Middle Route Project and evaluate the environmental impacts under 12 different levee break flood scenarios. The results show that only one flood scenario has small adverse impact (level 2) on local environment. The other flood scenarios have minimum impacts (level 1) on local environment.