JALAWAAYU

Flood Susceptibility Analysis in West Rapti River Basin Using Frequency Ratio Model

2022-08-30T13:49:48+0545

Floods are recognized as lethal natural events, which result in devastating natural and human losses. So, identifying flood susceptible zones is crucial to adopt necessary mitigation strategies beforehand. With the advent of GIS tools and modelling techniques, mapping of such zones has become easier and more precise; yet, flood prone countries like Nepal have not been able to embrace such tools for flood risk management. With a compelling need to address this situation, this paper employs Frequency Ratio model to analyze flood susceptibility in the West Rapti River Basin. The model, created with the help of 77 flood points and tested with 30 points to obtain 80.7% accuracy, maps the flood hazard zones in the area and identifies the lower Terai and settlement regions as high-risk areas. With the increasing threat of changing climate in the future, this study also propounds better preparation of flood inventory maps in the future for more precise susceptibility analysis models and better flood risk management.

Flood Hazard Mapping Using a Multi-Criteria Decision Analysis Approach Over the Indrawati River Basin

2022-11-01T12:45:33+0545

Floods are devastating natural hazard responsible for direct mortality, deterioration of crops, and damage to infrastructure and property. So, their study is crucial for watershed management and mitigation of flood hazards. The main objective of this study was to create a scientifically valid flood hazard map of the Indrawati River Basin (IRB) through the use of the multi-criteria decision analysis approach. Topographical Wetness Index (TWI), Elevation (EL), Slope (SL), Precipitation (PPT), Land Use/Land Cover (LULC), Normalized Difference Vegetation Index (NDVI), Distance from the River (DRI), Distance from the Road (DRO), Drainage Density (DD), and Soil Type (ST) were chosen as flood triggering factors based on literature review, data availability, and catchment characteristics. The analytic hierarchy process (AHP) method was used for determining the relative weight of each flood causative factor. All these factors were resampled into a 30 m × 30 m pixel size. Based on an evaluation of satellite imagery, 30 flood points were identified in the IRB, and these points were used as the testing dataset for validating the outcome. Based on results, the IRB has been classified into five different flood susceptible zones; very low, low, moderate, high, and very high. According to the study, 13%, 26%, 30%, 23%, and 8% of the total area are in very low, low, moderate, high, and very high flood susceptible zones, respectively. The Area Under the Curve (AUC) value for the success rate was 0.792. The results of this study will be crucial for concerned parties to design early warning systems and flood risk reduction measures for flood preparedness.

Application of SWAT Hydrological Model to Simulate Flow of Seti-Gandaki Basin

2022-11-02T15:39:40+0545

The Soil and Water Assessment Tool (SWAT), a semi-distributed hydrological model, has been used for the Seti-Gandaki River Basin (SGRB) to simulate streamflow. Further, SWAT was assessed to study water balance of the basin. This study primarily focuses on different features of hydrological modeling like multi-site calibration and validation of the streamflow with a view to check the reliability of the model in the high precipitation basin of Nepal. The statistics performance of the model is evaluated using various statistical test like Nash-Sutcliffe, RMSE, and Kling Gupta Efficiency (KGE). Moreover, the study used various statistical parameters like Nash-Sutcliffe efficiency (NSE), Percentage Bias (PBIAS), Coefficient of Variation (R2), ratio of the root mean square error to the standard deviation of measures data (RSR), and Kling Gupta Efficiency (KGE) to evaluate the performance of the model and carryout
0.93(0.89), -0.04(-21.87), 0.95(0.94), 0.26(0.34), and 0.85(0.76), respectively, for calibration (and validation) at Damauli station. The mean annual flow and annual precipitation at SGRB was observed to be 209 m3/s and 2866 mm, respectively. About 20% of annual precipitation seems to be lost as evapotranspiration. The statistics results showed that the model performed better for daily and monthly periods. Overall, the versatility and reliability of SWAT is an appropriate hydrological modeling tool for water resources over the study region. The output of the study can be helpful for the planning and management of water resources in high precipitation basins.

Glacier Area, Mass and Associated Glacial Lake Change in Kawari basin, Western Nepal

2022-11-01T16:50:03+0545

Due to ongoing global climate change, the glaciers in the Himalaya are shrinking and the glacial lakes are increasing in number and area. This study investigates the glacier area change, mass balance and associated glacial lake evolution in the headwaters of Kawari basin, western Nepal using optical remote sensing images. The results indicate that eleven glaciers in the study area have shrunk by 1.64 km² between 1994 and 2021. In the same period, due to glacier recession glacial lake formed and expanded by 0.0103 km2 yr^-1 reaching 0.34±0.042 km² in 2021. Surface elevation change of glaciers revealed that the ablation zone of glacier thinned up to -8.18 m between 2000 and 2019. The specific mass balance of eleven glaciers was calculated to be -0.3 m w. e. yr^-1from 2000 to 2019. The study of glaciers is important as they are visible signals of climate change, and their changes often impact water resources and mountain hydrology.

A Meteorological Analysis from the Southern Slope of Mt. Everest, Nepal

2022-12-27T17:02:11+0545

Mt. Everest is the highest mountain in the world, with an elevation ending at 8848.86 m above sea level, providing unique opportunity for direct observation of the upper troposphere. Utilizing the data from recently established five automatic weather stations (AWSs) network along the Everest climbing route, as part of the National Geographic and Rolex Perpetual Planet Expedition to Mount Everest 2019, from June 2019 to May 2020, this study investigates the meteorological environment over the southern slope of the Mt. Everest. Precipitation, temperature, radiations (income and outgoing short wave and long wave radiation), wind speed and direction along with derived variables like Lapse Rate, Precipitation Gradient, 6.11 hPa Isoline, and zero-degree Isotherm are analyzed with the aim of understanding altitudinal variation. Precipitation is mainly concentrated in monsoon with highest in Phortse (530 mm). Analysis of temperature lapse rate shows the highest lapse rate (-5.6 ? km^-1) in monsoon and lowest in post-monsoon (-7? km^-1). The precipitation analysis reveals that the vertical and horizontal precipitation gradient for monsoon is -63 mm km-1 and is -8.6 mm km^-1however, during the post-monsoon, precipitation increased by 0.75mm km^-1 and 4.6 mm km^-1, respectively. Similarly, westerly winds dominate during winter in upper station while it’s nearly uniform for lower stations. Radiation, likewise, are highly correlated between the stations, with incoming shortwave being the highest in the upper station, South-Col. Both isoline and isotherm lines are observed at around 6000 m above sea level. The one-year data has revealed some of the interesting pictures of high-altitude meteorology, but long-term data with fewer data gaps should be required to confirm these patterns.