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Changes in climate cause significant alterations in morphometric parameters and may lead to hydro-meteorological hazards. In this study, an attempt has been made to identify drainage morphometric characteristics through topographic, geologic and hydrological information to assess the extreme weather events (flood) over the Gandak River Basin (GRB). The standardized precipitation index (SPI) and rainfall anomaly index (RAI) were used for deducing extreme rainfall incidences derived from the Tropical Rainfall Measuring Mission precipitation datasets. An assembled frequency distribution as well as trends in RAI and SPI was calculated to understand the hydro-climatological behaviour of the basin. During the monsoon season, the years 1998, 2007, 2011, 2013 and 2017 witnessed the extreme flood events. The variations in heavy and intense rainfall in short time can be linked to extreme flood events, which leads to channel shifting and modifications, can be deduced from provided asymmetric factors and sinuosity index. The results illustrated that both the monsoonal rainfall and the frequency of extreme rainfall over the basin are increasing, which could be a reason for a high severity and frequency of flood events in the GRB.

Watershed development and management is essential for the present as well as future constancy of water resources in a river basin. Watershed prioritization, planning and development are depending on the morphometric analysis of a basin. The drainages of a basin are mainly influenced on geomorphic appearances which show a dynamic role for monitoring the basin’s hydrology as per topographical characteristics. In this paper, the morphometric study was characterized by set of parameters i.e. linear, aerial and relief aspects of Varuna river basin (India) with the integration of geo-spatial techniques. The mean annual rainfall, Normalized Difference Vegetation Index, Digital Elevation Model and Land Use/Land Cover (LULC) were taken into account for this study. The annual rainfall pattern and its percentage departure were shown by high frequencies of drought conditions while the seasonality index depicts that mostly rainfall occurred in less than 3 months. Moreover, indices such as Standardized Precipitation Index and Standardized Precipitation Evapotranspiration Index were used to conclude past extreme drought conditions (1996–2002, 2010–2017) over the basin. LULC changes were monitored over the south-east and north-west part of river basin during the period 1977 to 2013. The results revealed that an increasing trend of urbanization was monitored due to a decrease in agricultural land by 40.71% in the lower part of the basin. Moreover, the overall study can be helpful to assess the quantitative depiction of basin geometry as well as land use pattern for future development of agricultural growth.

Geoinformatics-based morphological studies play a significant role in planning, designing, and development of river engineering structures. Quantitative morphometric parameters affect catchment streamflow pattern through their influence on concentration time, and geomorphic characteristics of a drainage basins play a vital role in controlling the basin’s hydrology. In the present paper, an effort has been made to assess the inferences of various linear, areal, drainage, and relief aspects of quantitative morphometric characteristics of the Narmada basin and its down (13) and upper watersheds (17) using ASTER DEM data in GIS platform. Total basin area of the Narmada is about 98,796 km2, and it is identified that the study area is an eighth order drainage basin. A total 31,211 stream segments including the Narmada river are identified, and it is clear that the cumulative stream length is higher in first-order streams and decreases as the stream order increases. The bifurcation ratio (Rb) of the Narmada basin is varied from 2 to 9, and it designates that the drainage pattern of the basin has been affected by the structural disturbances. The lowest value of elongation ratio in the basin indicates high relief and steep slope, while highest value specifies relatively plain land with low relief and low slope than other down watersheds. Sinuosity index of Narmada basin is 1.58, which shows that the Narmada river is meandering in nature.