Climate Change and Climate Variability
Climate change and landscape modification have induced higher flood risk in the delta. Magnitude and frequency of the incoming water flow have been altered by more intensive rainstorms in the upstream watersheds. The probability of the extreme tidal level series at the delta outlet have also changed due to sea level rise (SLR). The extreme high water level, a design basis for flood protection in coastal engineering, is commonly quantified by a one-dimensional (1-d) hydrodynamic model. However, without considering the variations of model inputs, the extreme high water level can be severely underestimated contributing to large costs in the delta area with dense population and economy. This research aims to estimate the delta high water level under the changing environment by accounting variations in the inputs to the 1-d model. Pearl River Delta (PRD) in South China, a prosperous delta with the flood regime greatly modified, has been used in the study. The time-varying moment (TVM) has been applied to estimate the incoming inland flow as well as the outlet extreme tidal level. A 1-d model has been set up for the PRD, and forced by four scenarios generated from the TVM results on a year-2050 projection basis, i.e. 100 or 50-year flood meeting a 100-year tide, and 100 or 50-year flood with a 50-year tide. Without taking the trend into consideration, the underestimated in 100-year flood is 17.51%, and up to 14.07% in 100-year tide. Meanwhile, the tidal increase in the Pearl River Estuary is higher in the northeast, and lower in the southwest. According to the increase of extreme water level under the impact of the increasing flood and tides, stations in the PRD can be divided into three groups. Among these three groups, the most affected group is located around the southwest outlets, and the least affected one, lying around the northeast outlets. Besides, extreme water levels in stations that are 22 km away from outlets are tide-domain, while the ones that are 45 km away from outlets are flood-domain. This research has not only introduced a methodology for extreme water level estimation in the environmentally altered delta, but also quantified the spatial variation of the degree of water level change. This research will provide the quantitative support to flood protection in the delta area.
Sun Yat-sen University
Wednesday, January 4
10:00 AM – 5:00 PM