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Hydrological Modelling Of Seti Catchment And Vulnerability Analysis Of Pokhara City, Nepal

Congress: 2015
Author(s): Sanam K Aksha
Virginia Tech University1

Keyword(s): Sub-theme 11: Key vulnerabilities and security risks,
AbstractIntroduction:
Floods are considered as one of the most common and widely distributed natural risks to physical properties and human lives and have caused significant damages on a global as well as in local scales in recent decades. In Nepal, floods are caused by different mechanisms alone and in combination: continuous rainfall and cloudburst, snowmelt and rainfall combine, glacial lake outburst floods (GLOFs), landslide dam outburst floods (LDOFs), floods due to the infrastructure failure, and sheet flooding or inundation in lowland areas caused by blockage built against the flow. Although flood is damaging property and claiming human lives frequently each year in Nepal, there are very few studies done to find out the physical as well as social causation of this disaster. Moreover, Himalayan region is characterized by limited availability of data and many of the Nepalese rivers are either poorly gauged or ungauged due to complexity of terrains, and lack of technical manpower and financial resources. This study aims to perform hydrological modelling to simulate the stream flow of Seti river catchment and to analyze how vulnerability has been changed in Pokhara over the time.

Methods/Materials:
HBV-light model together with remote sensing and geographic information system were used to achieve these objectives. In addition, hydro-meteorological data and census data were analysed and interviews were carried out to understand the current situation.

Results and Discussion:
The model is able to produce Nash--Sutcliffe efficiency of 0.809 for the calibration period and 0.618 for validation period. The scatter plot observation found efficiency of 0.8181. The model simulated river flow consistently for the study period except few underestimations of low flows. The analysis of Landsat images of the Pokhara of shows the significant increase of settlement from 6.33% to 51.71% between 1975 and 2013 which is also verified by census data and field interviews.

Conclusion:
In overall, the HBV-light model can be applied to Nepalese catchment to simulate flows where data deficiency is one of the major problems. Having history of previous mega flood events, there is urgency to prepare disaster preparedness plans and policies to reduce significant losses from the future flood events and other disasters.

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