Use of NOAA/AVHRR data for flood monitoring in Mekong river delta

Hoang Minh Hien
Satellite Meteorology Division, National Centre for Hydro-meteorological Forecasting, Hydro-meteorological Service of Vietnam.
Tel. : 84-4-8261187 Fax: 84-4-8254278
E-mail: hmh@netnam.vn

The Mekong river delta is one of the most important agricultural lands in Vietnam. Every year it faces flooding and water logging which cause a lot of problems and damages. The NOAA/AVHRR Data have been used to monitor floods in this area. The method of Sheng Yongwei (1996) has been modified, using information from different channels of NOAA/AVHRR data, including visible and infrared split window channels to remove cloud influences, including cloud shadows, when cloud cover is not very serious.

The quantitative split window channel threshold value has been given for an identification of waterbodies and land surface under semi-transparent clouds. By this way, much wider ground areas for any condition of the weather, for any kind of cloud systems can be analysed and detected. The techniques for objective defining the threshold values and automatically running the program for flood monitoring have been developed. A technique for identifying the image pixels with different rate of mixing between water and land has been developed, too.

A case study for flood monitoring in the Mekong river delta in the late 1997 year has been carried out and the results of flood monitoring on 15 November 1997 are shown in the paper as a demonstration.