Review on Agricultural Flood Disaster in China

Agricultural flood disaster is generally accepted as an important branch of disaster science. Based on reviewing literatures related to agricultural flood, related concepts are formulated and previous research and existing facts are sorted and summarized. Afterwards, directions for future research are discussed integrating impacts of climate warming.According to affected crops and occurrence times, agricultural flood disaster in China can be divided into spring waterlogging, summer waterlogging and grown or harvested in the summer and autumn waterlogging, which have impacts on the overwintering crop, sowing crop and autumn harvest, respectively. The formation of agricultural flood and its intensity are induced by comprehensive effects of weather, crop flooding tolerance, topography, soil structure and human activities. In the context of climate warming, an increasing tendency is detected in the hazard rate and stricken area of China's agricultural flood, however, the regional disparity is significant. Agricultural flood disaster decreases in north China, while it increases in the south part. Two fundamental aspects must be linked to explain the spatiotemporal characteristic of agricultural flood. The first one is the disaster weather itself, i.e., the frequency and intensity change of extreme precipitation. The second one is the characteristic of the crop affected, such as crop growth and development speed, the crop boundary, crop strains, cropping system and planting area, which indirectly influence the formation and development of agricultural flood disaster. The occurrence mechanism of flood on crop yield are the comprehensive result of many processes, including the physical damage caused by the flood struck, physiological damage of watered out and ecological hazard because of environment change. Field survey, modeling experiment and numerical simulation are currently the dominant tools available to investigate agricultural flood disaster. Agricultural flood level indexes such as the morphology index, waterlogging degree index, meteorological index and agriculturalmeteorological index are used to systematize effects of flood on agriculture. Impacts of agricultural flood is multidisciplinary, including affecting the agricultural production environment, affecting the ecophysiological processes of crop, crop growth and development and inducing diseases and pests. It suggests that three broad areas be addressed to improve the simulating ability, and attentions should be paid to future impacts of flood on crop yields. First, multidisciplinary agricultural flood index is required under the background of climate change. Second, a comprehensive risk assessment of the disaster needs to be conducted considering knowledge of the disaster process. Finally and the most importantly, data representative of actual disaster is needed to evaluate the influence of climate warming on the agricultural flood.