Flood hazard map and land development priority map
Developed using NOAA AVHRR and GIS data
Dr. Md. Monirul Islam
Research Fellow, Tropical Marine Science Institute
National University of Singapore
14 Kent Ridge Road, Singapore 119223
Tel: 65 874 4649, Fax: 65 872 4067
E-mail: tmsmmi@nus.edu.sg
Singapore
Dr. Kimiteru Sado
Professor, Kitami Institute of Technology
165 Koen-cho, Kitami 090-8507
Tel. 81 157 269492, Fax. 81 157 239408
E-mail: sado@hp712.civil.kitami-it.ac.jp
Japan
Keywords: NOAA AVHRR data, Flood-affected frequency, Population density, Flood
hazard map, Land development priority map
Abstract:
In this paper flood hazard map and land development priority map for Bangladesh were developed using the flood events of 1988, 1995 and 1998 data with the digital data of physiographic divisions, geologic divisions, land cover classification and population density those were used as Geographical Information System (GIS) data. The techniques to construct a map for land development on the priority basis against the flood damages were described. Flood-affected frequency and flood depth were considered as hydraulic factors, and special attention were paid on population density for the land development priority map. Flood hazard assessment was undertaken using National Oceanographic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) with GIS. Flood-affected frequency and flood depth were estimated using NOAA AVHRR images. Flood hazard ranks were categorized using the flood affect on land cover classifications, physiographic and geologic divisions.
Introduction
There have been many destructive floods in Bangladesh including very severe floods of 1987, 1988 and 1998. The 1988 flood set new record for flooded area while 1998 flood set new record for its long duration. In 1988, Bangladesh experienced one of the worst floods in living memory, and then the study team comprised a core group of international consultants provided by UNDP, the Asian Development Bank, the European Economic Community and the world bank (World Bank 1989) and local experts who investigated the flood damages and its remedy. Bangladesh lies in the downstream area of the three river basins of the Ganges, Brahmaputra and Meghna. The three mighty rivers the Ganges, Brahmaputra and Meghna, enter Bangladesh from India through northwest, north and northeast of the country, respectively. High magnitude of floods strike on a regular basis in these three river basins in Bangladesh, India and its peninsular (Bhattacharyya 1997; Islam & Sado 2000a;b; Kale & Pramod 1997; Kundzewich & Takeuchi 1999; Muramoto 1988) because of the passage of depression and cyclone storm during the monsoon season. Bangladesh has limited control over the Ganges, Brahmaputra and Meghna rivers, moreover, for adequate and timely flood forecasting, Bangladesh sometimes depends on information from surrounding countries. The frequently occurring floods are very costly in terms of human hardship and economic loss. Therefore, the ability to estimate damages associated with the flood events are very important and necessary to evaluate future alternate flood control policies. In a round-table discussion following 1998 flood event, experts from different fields recommended the need for flood hazard maps for proper planning and management for future flood disaster (Nishat 1998). In our previous studies (Islam and Sado 2000 a; b) we have developed flood hazard maps only using 1988 event. Therefore, in this study we focus on the historical events of 1988 and 1998 severe floods and 1995 medium flood. NOAA AVHRR data are found very useful for monitoring large surface phenomena, such as floods, in the fields through out the world on local, regional and international scales while ERS, MOS, Landsat and SPOT has been used to observe regional or local floods. Furthermore, the routine measurement and the estimation of hydrological parameters including flood-related parameters could be useful in the areas ranging from global scale to local or regional scales, depending on the spatial resolution and recurrent period (Schultz 1994). The time of acquisition of satellite data does not generally coincide with the time of flood peak or maximum inundated area. The data and time of data collection and recurrent periods of satellite imaging are important for investigation of satellite data (Oberstadler et al. 1997). Therefore, in this paper result of analysis of NOAA AVHRR data, from the series of NOAA satellite 10 and 12, are used for the flood hazard assessment in Bangladesh and the construction of flood hazard map and land development priority map.
Figure 1. Schematic concept of model
Flood Hazard Assessment
Study proved that the combination by land cover, physiography and geology is the best combination of GIS data for each of the flood hazard map performed for flood depth and flood-affected frequency (Islam & Sado 2000b). Therefore, flood hazard assessments were undertaken using land cover, physiographic and geologic features and drainage network data. Land cover classification was carried out using dry season's NOAA AVHRR image of 20 January 1988. Land cover data, drainage network data, physiographic and geologic features were used as GIS data. Flood depth and flood-affected frequency were used as hydraulic parameters of the floods. A model was considered for the assessment of the flood hazard, which is shown in Figure 1.
