Strengthening Bangkok’s early warning system to respond to climate induced flooding

This report provides details of CTCNs project 'Strengthening Bangkok’s Early Warning System to respond to climate induced flooding'. The report provides the background hydrological setting, reviews the existing warning systems and final provides the following recommendations:  Better information on Dry Weather Flow (DWF) - There is a significant volume of inflow and infiltration into the drainage system. This volume is only estimated on basis of general data. Information that is more accurate will improve the accuracy of the hydraulic model and hence the quality of the flood forecast.  More accurate elevation information – The surface runoff into the drainage network as well as the surface flow when the drainage is surcharging are completely controlled by the slope and characteristics of the surface. A more accurate mapping will improve the accuracy of the hydraulic model and hence the quality of the flood forecast.  Reduce the time delay in access to SCADA information - The current time delay of 10-20 minutes of rainfall and water level data, affects the timeliness of the forecast. A reduced delay will make the forecasts available sooner, and this give more lead time for taking prevention actions.  Reduce the time delay in access to radar rainfall forecast data – A reduced delay will make the forecasts available sooner, and this give more lead time for taking prevention actions.  Deploy BMA radar – Two radars were installed a few years ago. Neither of these radars are yet calibrated based on on-line ground rain gauge data. It is recommended that BMA engage in getting the radar calibrated and engage the nowcast/forecast inherent features of these radars. Inclusion of these radars will reduce the time lag and enhance the forecast timeliness.