Hazard Map

The country of Bangladesh is frequently hit by devastating cyclones and other natural disasters on a yearly basis. The location and physical geography of this country has much to do with this incidence of disasters. The low delta region makes it susceptible to numerous floods and cyclone storm surges. The high wind speeds of the cyclone and these large amounts of water associated with it can destroy everything in its path.

The local communities on the coastal regions need to be aware of the danger that these storms pose. Preventative methods such as predicting surge heights and flooded areas are helpful in saving the lives of these people. Studies have been done to collect and analyze cyclone data in order to provide these people with information. Several hazard maps are shown to identify the areas with a potential of risk.

Figure 1.

http://banglapedia.search.com.bd/Maps/MN_0131D.GIF

 

The high risk areas for storm surges are tied closely with the elevation of the shore (Figure 1 storm surge hazardand Figure 2). The areas near the cities of Chittagong and Cox’s Bazar are located directly in the high risk area for surge water heights above 1 meter. Because of the steeper gradient on this shore, the water doesn’t travel as far as it would on the other shores of Bangladesh. On these shores, the moderate risk areas are at a distance of approximately 25 km from the shore and the high risk is within 10 km.

 

The largest losses of life occurred at Chittagong and Cox’s Bazar because they are large urban centers directly on the coast in southern Bangladesh. The hazard map for the potential surge of 650cm in these areas shows the distance decay that occurs up to 5 km away from the coast (Figure 3). This is because the storm surge is generally estimated to diminish in depth by .3 - .6 meters for every mile that it moves inland (Pielke, 1997). The elevation of the rest of the coast, however, is much less.

Figure 3.

http://www.itc.nl/ilwis/applications/application03.asp

This storm surge profile can be analyzed with land surface and elevation data to estimate the intensity and destruction of the water. This data is shown for the study area just south of Chittagong (Figure 4).

Figure 4.

http://www.itc.nl/ilwis/applications/application03.asp

Due to the low elevation of Cox's Bazar, this area shows up as pink on this map. This indicates a total high of the storm surge that will hit land. The surge generally decays as it moves inland. This storm surge data is also used to estimate the total deaths that could occur if a storm surge such as one with a hight of 510 cm were to hit (Figure 5).

Figure 5.

http://www.itc.nl/ilwis/applications/application03.asp

This map indicates that in there is an extreme risk in living near Cox's Bazar. The casualty rate for the 1991 cyclone was similar to this storm surge model. Reports indicate that there was up to a 70 percent casualty rate in the area of this city. Other areas some distance away suffered approximately a 30 percent casualty rate (Itc.nl, accessed May 5, 2005).

Another view at the casualty rate that is possible is to look at the population density of coastal Bangladesh (Figure 6). This map shows that most of coastal Bangladesh is relatively sparsely populated, but the people that live there need to be aware of the risk from a storm surge. The cities of Chittagong and Cox's Bazar are especially vulnerable areas for a large loss of life.

Figure 6.

http://www.bangladeshgov.org/bdmaps/bdpopdensity.jpg

UW-Eau Claire Home