Establishment and Operation of Lower Mekong River Basin Regional Flash Flood Guidance System - A Project Funded by Agency for International Development/ Office of Foreign Disaster Assistance

As in many parts of the world, flash floods are destructive in the countries of the Lower Mekong River Basin (LMB). To respond to regional and national needs and in order to address the problem of flash flood in each member state of the Mekong River Commission (MRC), the MRC and the US Agency for International Development (USAID), Office of US Foreign Disaster Assistance (OFDA) implemented a flash flood guidance system for the LMB. The Hydrologic Research Centre (HRC) in San Diego in cooperation with the U.S. National Weather Service (U.S. NWS) jointly implemented a flash-flood mitigation programme in Cambodia, Lao PDR, Thailand and Vietnam. Based on HRC's experience, and with financial support of the USAID/OFDA, a system was established based, on remote sensing of critical meteorological parameters and available global and local spatial data sets rather than implement a series of systems based on in-situ automatic and/or manual hydrometeorological monitoring networks.

The MRC Flash Flood Guidance System (MRCFFGS) is designed as a diagnostic tool for meteorological and hydrologic services to analyze weather-related events that can initiate flash floods (e.g., heavy rainfall, rainfall on saturated soils), thereby allowing its users to make a rapid evaluation on the potential for a flash flood for a specific location. The system provides values of flash flood guidance and flash flood threat for small stream basins - the basins most prone to flash flooding .The system is not based on simply identifying areas of heavy rainfall. The technical method that would be used to produce this guidance is the same that has been proven over the last 30 years via operational application by the U.S. National Weather Service. This method is based on physically related hydrologic modeling involving soil water accounting and capacity of the draining channel at a level of minor flooding (bankfull) conditions. Evaluations of the threat of flash flooding may be done over hourly to six-hourly time scales (depending on timely reporting of hydrometeorological data). Satellite rainfall estimates (Hydroestimater) have been used together with available in-situ rainfall gauge data to obtain bias-corrected estimates of current rainfall volume over the region. It used these bias-corrected satellite rainfall data to update soil moisture estimates and to evaluate flash flood threat.

The development of the system was initiated in 2005. The system, including the delivery of capacity building for the MRCFFGS operators of 4 national line agencies, was fully completed by August 2009. By the end of October 2009 the MRCFFG System was accepted for operational purposes by MRC's Regional Flood Management and Mitigation Center (RFMMC) in Phnom Penh, Cambodia. Daily monitoring of the MRCFFG has been conducted since, and information of flash flood risk areas, thereby indicating the name of villages, districts and provinces, were updated daily in the MRC website. Since October 2009 until now the MRCFFG System successfully detected several flash flood risk areas, especially during the sever weather conditions, such as low pressure, ITCZ or tropical storms, and provided this information on time to the concerning line agencies and public, as well as to the MRC website .