Determining process of occasional flooding from channel hydrological characteristics of Chel Basin, North Bengal (India)
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Determining process of occasional flooding from channel hydrological characteristics of Chel Basin, North Bengal (India) Debarshi Ghosh1
Received: 11 January 2019 / Revised: 5 September 2019 / Accepted: 10 September 2019 Korean Spatial Information Society 2019
Abstract Occasional flooding has a distinct impact on fluvial dynamics of a channel. It brings new thresholds of adjustment for hydraulic conditions of a channel. The task of estimation of peak discharge during occasional floods is very complex, as the water recedes very quickly. The flood and rainfall design techniques (Gumbel’s frequency distribution) are the relevant solutions for peak discharge estimation at an un-gauged station of measurement. This paper aims to estimate the volume of peak discharge during the phase of occasional floods at ‘t’ recurrence intervals (5, 10, 20, 50 and 100 years) which are 148.87221, 158.58408, 167.9592, 179.9475, and 218.8758 cumecs. The separate yield of peak runoffs from small 3rd-order basins has been estimated by rational method on 2 years (162.70 cumecs) and 10 years (212.60 cumecs) probabilities of recurrence. While deriving probable peak flood discharge, various temporal hydrological relationships regarding rainfall– runoff and stage–discharge have been established by curvefitting method in linear and power regression models. The temporal study (2015–2017) reveals some interesting hydrological results, including (a) 1284.21–1522.22 Ha m day–1 channel runoff causes discharge greater than 150 cumecs, (b) effect of basin lag influences the runoff curve and (c) the water stage above 2.5 m gauge height indicates occasional floods. The rainfall as system input indicates high spatio-temporal variation ranges, between 200 and 5500 mm, as maximum annual average. This approach fundamentally assembles the rainfall–runoff–
& Debarshi Ghosh [email protected] 1
Dhupguri Girls’ College (affiliated to University of North Bengal), Dhupguri, Jalpaiguri, West Bengal, India
discharge trio relation in estimating the design for peak occasional flood discharge for Chel Basin. Keywords Discharge Gauge height Intensity–duration– frequency curve Flood probability Runoff Occasional flood Peak discharge
1 Introduction A flood is an unusual high stage of water due to runoff from rainfall and melting of snow in quantities too great to be confined in the normal water surface elevations of the river or stream [1, 2]. That is, a flood is any relatively high flow that overtops the natural or artificial banks in any reach of a stream [2]. Reliable estimates of the magnitude and frequency of floods are essential for flood insurance studies, flood-plain management, and the design of transportation and water conveyance structures, such as roads, bridges, culverts, dams, and levees [3, 4]. The process of flooding is related with the increase in relative heights of water column or the stage. It can be determined from the peak flows in flow duration curves. Flooding is an integral part of the channel process that sometimes causes the
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