Integrated assessment of extreme events and hydrological responses of Indo-Nepal Gandak River Basin
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Integrated assessment of extreme events and hydrological responses of Indo‑Nepal Gandak River Basin Pawan K. Chaubey1 · Prashant K. Srivastava1 · Akhilesh Gupta2 · R. K. Mall1 Received: 15 November 2019 / Accepted: 15 September 2020 © Springer Nature B.V. 2020
Abstract 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. Keywords Flood · Standardized precipitation index (SPI) · Rainfall anomaly index (RAI) · Morphometric · Gandak basin (Indo-Nepal region)
1 Introduction The Indo-Gangetic Basin (IGB) comprises several river streams and act as an important source for freshwater resources in the Indian region. The extreme rainfall events during South-west monsoon are mainly driven by Himalayan mountain ranges over Indo-Nepal regions in south-central Asia (Singh and Mal 2014; Mall and Srivastava 2012). Gandak River Basin (or GRB) holds a unique topography covered by glaciers snowfields and the mountainous terrain over the Nepal, while the downstream area forms an alluvial plain in India. Because of the complex nature of the mountainous ecosystem, it is often * R. K. Mall [email protected] 1
DST‑Mahamana Centre of Excellence in Climate Change Research, Institute of Environment and Sustainable Development, Banaras Hindu University, Varanasi 221005, India
2
Department of Science and Technology, New Delhi, India
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problematic to understand the hydrological responses and extreme precipitation events of GRB. In the past, many researchers documented the use of morphometric analysis for extreme event management as well as designing control measurements for flood and drought, etc. (Pophare and Balpande 2014; Choudhari et al. 2018; Nagalapalli et al. 2019; Mall et al. 2019). Morphometric is the analysis of the mathematical measurement of the earth’s surface, shape and dimension (Clarke 1966). Analysis of quant
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