FLOOD STUDIES IN AND AROUND ALAKNANDA BASIN

Abstract

The study was taken up with the main objective to understand the flood problem in and around Alaknanda basin. In order to achieve this objective, as a first step, entire Alaknanda basin right from Devprayag to Mana was visited from May 23-26, 2013. The basin came into lime light after June 16-17, 2013 Kedarnath flood disaster. On 16 and 17 June 2013, heavy rains together with moraine dammed lake (Chorabari Lake) burst caused flooding of Saraswati and Mandakini Rivers in the Alaknanda basin.In this disaster, more than 10,000 human lives were lost and Kedarnath temple was damaged. Apart from this road network of entire Alaknanda and Bhagirathi basins also got damaged.In order to understand the possible causes of this hydrological disaster in and around Alaknanda basin, the annual maximum 24 hourly rainfall data of 35 rainguage stations of Uttarakhand were analysed and return period of June 2013 event was estimated. Trend, Independence, Stationarity and 1-lomogenity tests were applied before carrying out the analysis. The iso-pluvial (lines connecting equal depth of rainfall) maps, covering the entire Uttarakhand state, have also been prepared using GIS software. In Alaknanda basin there are six commissioned 1-lydro Electric Projects. Eightprojects are in the advanced stage of construction and 24 projects are in different stages of planning. In the present study impact of 2013 flood on one of the projects of the valley has also been studied. In present work, annual peak rainfall and flow data of Joshimath for a period of 40 years (1971-2010) have also been used to estimate100, 500 and 1000 years return period floods in order to compare the magnitude of 2013 flood in terms of return period. The analysis has been carried out to check whether the design flood of the VPI-IEP is adequate or not in the light of recent flood.