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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.

India experienced more flood situations due to the increasing extreme rainfall events over the different Indian River Basins (IRBs) during the last few decades. An Extreme Value Theory (EVT) is used to examine trends of rainfall extremes over the IRBs using long-term observed high-resolution grid-based rainfall (1901-2019) of the India Meteorological Department. The analysis depicts that when generalized extreme value theory (GEV) is applied to annual maximum rainfall over IRBs, statistically significant uniform trends were not seen. The spatial variations in the annual maximum rainfall for the 10-, 30- and 100-year return levels show statistically significant increasing trends over the IRBs. The shifting trend of rainfall extremes from northeast towards the western river basins of IRBs in the last two decades and resulted in damage to life and property on the west coast. The decadal changes in average intensity of dry and wet condition at 12- months running time window reveals that the shifting and increasing pattern of the rainfall extremes events during the last decades of the 20th century (1981-2000) and current decades of the 21st century (2001-2019) over the western ghats and west-flowing river basin leads to several floods situations. This research highlights the significant increasing trend in extreme rainfall events over the IRBs, which may pose a grave risk to agriculture, human life, and predominantly on the vulnerable sections of the society.

Globally, changes in hydroclimate extremes such as extreme precipitation events influence water resources, natural environments, and human health and safety. During recent decades, India has observed an enormous increase in rainfall extremes during the summer monsoon (June to September) seasons. However, future extreme rainfall events have significant uncertainty at the regional scale. Consequently, a comprehensive study is needed to evaluate the extreme rainfall events at a regional river basin level in order to understand the geomorphological characteristics and pattern of rainfall events. In the above purview, the current research focuses on changes in extreme rainfall events obtained through observed gridded datasets and future scenarios of climate models derived through the Coupled Model Intercomparison Project (CMIP). The results highlight a significant rise in the extremes of precipitation events during the first half of the 21st century. In addition, our study concludes that accumulated precipitation will increase by five days in the future, while the precipitation maxima will increase from 200 to 300 mm/day at the 2-year, 50-year, and 100-year return periods. Finally, it is found that during the middle of the 21st century the 23.37% number of events will increase over the TRB at the 90th percentile.

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.