CS(AR)-28/97-98 : Flood studies in Satluj basin

Abstract

Flood in monsoon months is a major problem in northern rivers in India in spite of various flood control measures adopted against the floods. Large floods inundate vast expanse of land adjoining the river course. Flood inundation/ flood plain features mapping and river planform measurements are done for Satluj. The river lies in the Indus system. A part of the river reach (181 km) in Punjab downstream from Roopnagar is selected for planform study. An upstream reach of 50 km in the study area is selected for inundation study. Flood inundation mapping is done for flood of September 1988 using digital image processing technique. IRS LISS II digital data and FCC at the scale of 1:250000 are used. Softwares used are ILWIS 2.2 and PC- ERDAS 7.5. The ILWIS is used in data encoding, image rectification and output. ERDAS is used for image processing and GIS manipulation. Mainly areas on the right flank of the river are inundated. On the left flanks storage of rainwater on depressions occurs. A flood damage analysis is done by assigning a qualitative damage scale of numbers 1 to 10 in increasing order of damage. The land use and cover (next season) and flood inundation maps are assigned weights for the analysis. The results will be useful for further investigation in field and for planning flood control measures.

Percentage areas with low and high flood damage are respectively 2.2 and 11.9. The areas are respectively 20 and 110 sq. km. The Large high flood damage class is due to the presence of 90% agricultural land. The 'high damage' area is over estimated since the crop map for the flood season is not used. The causes of the flood are over topping of the banks, floods in the hill torrents and occurrence of low lying areas with poor drainage. Flooding has occurred predominantly on right flank of the river up to the Bist Doab and Nawhashar canals. Hill torrents cause sand casting. Hydrometeorology of the flood of Sept. 1988 and conveyance capacity of the canalised Satluj downstream of Roopnagar headworks are also described.