Application of Hydro-Meteorological and Gis Based Hydraulic Model in River Training Works of the Marine River with Particular Reference to Food Security

Abstract

Marine River is one of the major Tributaries of Bagmati River originated from Mahabharat hills lying in south-western part of the Sindhuli Disrict. Total river length is about 68 km and the total basin area is about 544 km 2 . Annual rainfall in the basin area varies from 1,724 mm (driest year) to 3,320 mm (wettest year) with 2,580 mm as the annual average value. Statistical analysis showed that the 24 hour maximum rainfall for 15 years, 25 years and 100 years return periods are 369.9mm, 448.3mm and 583.8mm respectively. This showed the region is more susceptible to flood. A major flood disaster has occurred in Marine River on 19-21 July, 1993 which was caused by intensive rainfall in the central region of Nepal. At that time the rainfall of Hariharpur Garhi was 482.2 in record. Along with this the floods of 1899, 1985 and other minor floods had swept away a couple of villages, killed a number of people and livestock and damaged agricultural land and standing crops, and other infrastructures in the past. Flood of 15, 25 and 100 years return period estimated by Modified Dickens method were 1213.62m3/s, 1391.3m3/s and 1872.16m3/s respectively which were taken as the different design discharges for each to be compare to the river training works which was proposed for the protection of inundated land. A one-dimensional hydraulic model in HEC-RAS was developed and executed which enabled the analysis of flooding under different scenarios. Suitable structural methods for flood control identified were levees along the banks. The proposed river training structures in the Marine River explicitly demonstrates the relationship among the three parameters, viz, rainfall intensity, reclaimed land and economic value with respect to food security. Hydraulic models coupled with Geographic Information System (GIS) are powerful tools for quantitative and qualitative monitoring of spatial and temporal variation of flows in the river. The dynamic capability of GIS interfaced models which provide impressive visual perception in the sense of spatial and temporal variation of the modeling results in different scenarios for planners, could be used as a decision making tool for river training and sustainable integrated water resource management. For the purpose three different scenarios for each of the return period floods were analyzed. The comparative study showed the value of reclaimed agricultural land are 218.52, 224.79 and 251.50 hector for 15, 25 and 100 year return period flood securing the food (rice) for 15.8%, 16.3% and 18.2% of the total population of the basin considering the per capita rice consumption to be 93.4kg/yr taking into account that the hybrid rice is cultivated