A Hydrometeorological Flood Forecasting Chain for the Red and Ca rivers (China, Laos and Vietnam) Part I—Investigated Areas and Model Setup

As a result of two research projects conducted over the years from 2005 to 2011, this paper describes the configuration of a coupled hydrometeorological flood forecasting system set up for the Red river basin (169,000 km2 at the outlet) and the Ca river basin (23,830 km2 at the outlet), across China and Vietnam, and Laos and Vietnam, respectively. The research objectives were to setup a hydrometeorological chain to forecast the discharge flowing into reservoirs and at some control sections for flood control in downstream areas of the Red river and Ca river. These areas include the heavily populated Northern Delta of Red river and, for the Ca river, the Vinh area. Both these areas are in fact experiencing a rapid population and economic development. The distributed hydrological model DIMOSHONG, which implements a modified Green and Ampt or an SCS—type routing scheme of the soil–water content, is forced by Quantitative Precipitation Forecasts provided by the BOLAM and the MOLOCH meteorological models or by raingauge observations. The forecasting chain has an Extended Kalman Filtering updating module based on hydrometric measurements now available in real-time for two pilot stations installed in Ghenh Ga section and Nam Dan section, in the Red and Ca rivers, respectively. Several floods in the basins, including the August 1971 and October 2010 catastrophic ones which flooded the Red river and the Ca river regions, were simulated providing useful results in view of improving flood alert systems.