Flood disasters frequently occur in the flat river network region of eastern China. The current flood risk management concentrates only on the analysis of water quantity, and lacks in water quality investigations. In this study, the MIKE11 NAM module was used for the simulation of the rainfall-runoff processes, the MIKE11 HD module was used to simulate the hydrodynamic processes, and then the MIKE11 AD module was used to simulate the water quality processes. The coupled model was adequately calibrated using observed data, and then applied to simulate the processes of flood and water quality under four different rainfall conditions. The results indicate that rainfall has a significant influence on flood and water quality in a flat tidal river network, which can provide some assistance for flood and water quality management.
Flood disasters frequently occur in the flat river network area of eastern China. Abundant rainfall, flat terrain and fertile soil bring about a lot of agglomeration of cultivated land, large population and a lot of industries in this region (Xu, 2012). In combination with global climate change and rapid economic development in recent years, rainstorm and flood have caused complicated and changing hydrological characteristics in the flat river network areas (Han, 2014). Meanwhile, the problem of water environment is increasingly serious. In response to these concerns, new demands for flood forecasting and water resources management should be taken into consideration.
Nowadays, hydrodynamic and water quality characteristics of the flat river network area are studied by mathematical models. Some hydrodynamic models of Shanghai in China were established by the MIKE11 modeling system, however, the model couldn't be applied to flood forecasting without a rainfall-runoff model (Xu, 2003; Yan, 2007). Using the same numerical software, a detailed model of the Rideau Valley Watershed was constructed, and is being used for various purposes of watershed management (Ahmed, 2010). More than that, the water environmental mathematic model of Pinghu city in China provided an effective method to simulate the effect of reducing pollution load on water quality (Qian, 2013; Yin, 2011). The above indicates that appropriate numerical models have positive practical performance of flood forecasting and controlling river pollution. In this paper, a coupled hydrodynamic and water quality model was constructed using the MIKE 11 modeling system, and then four cases were used to simulate the process of flood and water quality in the Hangjiahu (HJH) region.