Assessment of crop damage due to flood using GIS technology

Abstract

Bangladesh has a reputation for being disaster-prone. Floods, cyclones, tornadoes and droughts strike with depressing regularity and intensity. None of these hazards are new, but in recent years, there have been some significant developments. On the one hanei, the potential for loss of life, damage to property and agriculture is increasing as population pressure forces people to occupy more marginal and exposed land. On the other hand, sophisticated satellite communication systems, computer softwares now offer better warnings of impending climatic shocks and the country should generally be better prepared to cope with emergencies and to mitigate their impact. This study is set to assess crop damage due to flood using the Geographic Information System (GIS) as a tool. A part of the Compartmentalization Pilot Project (CPP) under Flood Action Plan (F AP) in Tangail has been taken as the study area. One of the main objectives of this project is to boost crop production through water management by controlled flooding. Field survey was done to obtain the existing cropping pattern. Additional data such as land contour, crop damage functions were collected from the Bangladesh Water Development Board and CPP. Flood model results for water level series were collected from Surface Water Modelling Centre (SWMC). These information were used finally in the PC ARC/INFO GIS software to assess crop damage for different years. Results obtained in the system were compared with the field situation, though a detail damage information covering a number of years on such a small area (403 hectares) as the study area, is not available. However, for the year 1995 the damage information was available. The system result for the year 1995 for with project situation shows good match with the field situation. [n this year partial water management testing was performed in the study area. For other areas, both inside and outside the project area, where the flood water of \995 flood got its way to damage crop fields, damage scenario can be compared with that of 1991. Because the years 199\ and \995 experienced almost the same kind of flood having a return period of 5 years. The sy.stem result for the y. ear 1991 also shows:; year return period damage to crops which indicates that the system that has been developed in the GIS may be considered reliable. The study showed in case of the year 1995 that no damage to crops occurred during monsoon in the study area, which complied with the field situation. In this year when nood came, water levels in the crop fields were maintained according to the farmers necessity in 80% of cropping area. Analysis was done considering the target water levels which are designed to be maintained in the crop field according to the water management plan. The result showed good match with the field situation. In the study area in 1995 no damage to crops found during field survey. Analysis with the system developed in the GIS also assessed the same result. However, sometimes it is found that the system result is over estimated. This may have occurred due to lack of information about the plantation time in the actual field condition. If in a certain area the crop fields can be identified by proper monitoring activities when the monsoon comes, the system could have been applied more efficiently in assessing crop yield or crop damage. Another expected finding is that the cropping pattern in 1995 monsoon, which has been surveyed later on, is similar to the cropping pattern that has been obtained in the present study. Actual cropping pattern in the field in 1995 monsoon, which was found out in the survey, was expected as the farmers were trained to choose and plant crops according to CPP's water management target. However GIS can be used to find out suitable cropping pattern in project planning activities especially in water management projects. Finally recommendations are put forward to apply the GIS technique for assessing nood damage to other areas of the country.