Ecology, Environment and Conservation Paper

USING SPATIAL INTERPOLATION WITH BARRIERS TO ASSESS THE SPREAD OF FLOOD INUNDATION ON DIFFERENT LAND USE TYPES IN DUC THO DISTRICT, HA TINH PROVINCE, VIETNAM

Pham Quy Giang and Nguyen Thi Tham

Abstract

In Vietnam, every year, floods cause the submersion of large areas of land, especially agricultural land in flood plains. Flood mapping is important for adaptation and mitigation plans and is usually done by interpolation method using flood depth data. However, normal interpolation is inappropriate when barriers such as dykes exist causing interruption and discontinuity on the surface. The objectives of this study were to apply IDW Interpolation with Barriers to map the spread of flood inundation on land and to calculate the level and area of flood inundation for different types of land use in Duc Tho District of Ha Tinh Province, Vietnam. The inundation map of land-use types was established by overlaying the interpolated flood inundation map and land use map, which was divided into two areas including the outside and inside areas of La Giang dyke. Results showed that the interpolation was accurate as all the employed statistics including R2 , RMSE, and MAPE got acceptable value for both the outside-dyke and inside-dyke areas. The outside-dyke area was found to have an inundation area of 2,945.93 ha, which accounted for 65.05% of the total natural land area and the inundation depth was mostly over 2.0 m. The inundation areas of agricultural land, nonagricultural land, and unused land were 1,916.26 ha, 946.28 ha, and 83.39 ha, respectively. For the inside-dyke area, the total area of inundation was 7,003.74 ha, accounting for 43.91% of the total natural land area and the inundation depth was also mostly over 2.0 m. The inundation areas of agricultural land, non-agricultural land, and unused land were 5,314.46 ha, 1,627.65 ha, and 61.64 ha respectively. The findings indicate serious flood submersion upon agricultural land, and it should therefore be given priority in flood prevention and adaptation plans. The method of IDW with Barriers applied in this study has shown high accuracy. Thus, it is recommended to be applied to other areas with different topographic and flooding characteristics to further assess its strength and suitability.