Preparation of Flood Hazard Map for Bagmati River within Kathmandu Valley

Project Description

The main objective of the study is to prepare a flood hazard map of Bagmati River within Kathmandu valley for floods of various return periods.

Assignment Description

Data, report collection and it's review; • Identification of data source and information collection for the study purpose on hazard, past flood, land use, hydrology, and socio-economic status of the project area including it's review in the context of the study scope and objectives; • Prepare Digital Elevation Model (DEM) using satellite imageries stereo-pair image (Kathmandu Valley area about 665 sq. km) • Engineering survey of the river in selected area/location for establishing control points to run the hydrodynamic models; • Evaluate and estimation of Manning's; • Hydrological analysis, compute catchment flows for various return periods (25, 50 and 100 years), and establish stage-discharge relationships as required from measured discharges and cross-section survey for the boundary sections; • Setting up and running hydrodynamic model "HEC-RAS"; utilize cross-section extracted from DEM/field survey as appropriate; • Generate scenarios of flooding for main river and its major tributaries (Manahara, Dhobikhola, Sishnumati, Nakkhu) using output of HEC-RAS and HEC-GeoRAS; • Prepare flood maps for various return period floods using output of HEC-RAS, with application of Geographic Information System (GIS), and HEC-GeoRAS; • Validation of the flood hazard map using field information; • Assessment and recommendation of the top width of the main river and its major tributaries to be maintained at different sections for flood passage; • Photographic documentation of fieldworks and vulnerable areas; • Preparation and submission of Inception Report and presentation; • Preparation and submission of Draft Report and presentation; • Preparation and submission of Final Report.