|
|
|
Poster Session 3
|
Flood hazard map and land development priority map
Developed using NOAA AVHRR and GIS data
Interactive effect of flood-affected frequency and flood depth for the development of flood hazard map:
Two flood hazard maps were developed for flood-affected frequency and flood depth, respectively, considering the flood hazard rank from 1 to 27. In these two hazard maps, 56.31% pixels exhibited the same hazard ranks and 43.69% were different, because flood-affected frequency and flood depth were considered independently. Comparing between the hazard maps of flood-affected frequency and flood depth, higher rank for a pixel was assigned for that pixel for the new developed hazard map. Watercourses were not included to the developed flood hazard map. Therefore, the drainage map was overlaid onto the hazard map, and final hazard map with watercourses is shown in Figure 4.
Development Priority Map for Flood Countermeasure
The major cities of Bangladesh are extremely highly populated area. The planning of river works for flood countermeasure should be undertaken by considering the economical effects of the infrastructure and the importance of the concerned area. Therefore, using flood hazard map and population density map land development priority map was developed. Digital population data was prepared using population map of Bangladesh. Urban and industrial areas show high dense of population, while agricultural low land and agricultural flat-plain show low dense of population. According to the population density, the population digital data was categorized into five zones. The area which shows the population density 1 to 500 per square kilometer was considered as zone 1, similarly, the areas which show the population density 501 to 1000, 1001 to 2500, 2501 to 4000 and over 4000 were considered as zone 2, zone 3, zone 4 and zone 5, respectively. Similarly, hazard ranks of flood hazard map were categorized into five groups. Hazard rank 1, 2 and 3 is grouped as 1, then similarly, 4 and 6 is 2, 8 and 9 is 3, 12 and 18 is 4, and 27 is 5. This new hazard grouped map was superimposed with population digital categories map and finally the land development priority map was developed using the ranking matrix of two dimensional multiplication modes. Figure 5 shows the land development priority map for flood countermeasure based on pixels. The ranks of land development map are ranging from 1 to 25. Higher ranks indicate the higher priority has to be given for the development for flood countermeasure. This development priority map shows the rank of priority on the basis of pixel. Comparing between the hazard map (Fig. 4) and the development priority map (Fig. 5), it is understood that some high hazardous areas do not show the high rank for the development. The northeast part of the Meghna river and southwest lower parts of Bangladesh show high hazard ranks whereas development map shows the low ranks for the development of the same areas. Some part of Dhaka and Narayanganj districts show the higher development rank due to the high dense population. Dhaka is the capital city of Bangladesh. Study showed that Dhaka city was highly affected during the 1988 flood (Sado & Islam 1997).
Figure 4: Flood hazard map
(Monochrome fig. produced from original color fig.)
Figure 5: Land development priority map
Conclusions
Flood hazard assessment were undertaken considering the interactive effect of flood-effected frequency and flood water depth, those were estimated from NOAA AVHRR images of 18 September 1988, 31 October 1995 and 18 September 1998, and finally a new flood hazard map for Bangladesh was developed. Flood hazard map represents the magnitude of flood damage for each pixel. Land development priority map for flood countermeasure were developed based on each pixel. Although flood hazard ranks for some urban areas are comparatively less than the hazard for some rural areas, development should be undertaken for those urban areas (higher dense populated area) on first priority basis. The results described in this study should provide helpful information for flood control planning and the construction and development of flood countermeasures. Flood hazard map and land development priority map also help the responsible authorities to better comprehend the inundation characteristics of the flood plains, the protection of which is their responsibility. Relief and aid operation can be performed by using flood hazard map for further future events.
References
- Bhattacharyya, N. N., 1997. Floods of the Brahmaputra river in India. Water International, 22(4), pp. 222-229.
- Islam, M. M. & Sado, K., 2000a. Flood hazard assessment in Bangladesh using NOAA AVHRR data with geographical information system. Hydrol. Process. 14(3), pp. 605-620.
- Islam, M. M. & Sado, K., 2000b. Development of a flood hazard maps of Bangladesh using NOAA-AVHRR images with GIS. Hydrological Science Journal, 45(3), pp. 337-356.
- Kale, V. S. & Pramod, H., 1997. Flood hydrology and geomorphology of monsoon-dominated rivers: the Indian Peninsula. Water International, 22(4), pp. 259-265.
- Kundzewich, Z. W. & Takeuchi, K., 1999. Flood protection and management: quo vadimus?. Hydrological Science Journal, 44(3), pp. 417-432.
- Muramoto, Y., 1988. Investigation of the flood disaster caused by heavy rainfall in Bangladesh during the 1987 monsoon season. Report of Scientific Research for Natural Disaster, no. B-62-5, Ministry of Education, Tokyo, Japan.
- Nishat, A., 1998. A discussion on flood management in Bangladesh. The 1998 Deluge-Developing Coping Capacities, Workshop on the 1998 flood, Nagorik Durjug Mokabela Uddogh, Dhaka, Bangladesh.
- Oberstadler, R., Honsch, H. & Huth, D., 1997. Assessment of the mapping capabilities of ERS-1 SAR data for flood mapping: case study in Germany. Hydrol. Processes,11, pp. 1415-1426.
- Sado, K. & Islam, M. M., 1997. Satellite remote sensing data analysis for flooded area and weather study: case study of Dhaka city, Bangladesh. J. Hydraul. Engng., JSCE, 41, pp. 945-950.
- Schultz, G. A., (1994). Meso-scale modelling of runoff and water balance using remote sensing and other GIS data. Hydrol Sci. J. 39(2), pp. 121-141.
- World Bank, 1989. Bangladesh Action Plan for Flood Control. 91, Asian Region, Country Department-1, World Bank, Washington DC, USA.
|
|
|
|
|
|
|
