Estimation and Prediction of Riverbank Erosion Susceptibility and Shifting Rate Using DSAS, BEHI, and REBVI Models: Evidence from the Lower Ganga River in India

doi:10.21203/rs.3.rs-1097959/v1

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Research Article

Estimation and Prediction of Riverbank Erosion Susceptibility and Shifting Rate Using DSAS, BEHI, and REBVI Models: Evidence from the Lower Ganga River in India

https://doi.org/10.21203/rs.3.rs-1097959/v1

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published 12 Jun, 2023

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The process of riverbank erosion (RE) is often accelerated by natural events and anthropogenic activities leading to the transformation of this natural process to natural hazard. The present study aims to estimate bank erosion rate and prediction of the lower Ganga River in India using digital shoreline analysis system (DSAS) model. The prediction of RE susceptibility mapping has been generated using three ensemble models such as DSAS, bank erosion hazard index (BEHI), and river embankment breaching vulnerability index (REBVI). For the study satellite images and field data (bank materials, geotechnical parameters, embankment structure, hydraulic pressure etc.) have been used to recognize the river bank position and BEHI and REBVI scores. During 1973-2020, the average bank erosion and accretion rate was found 0.059 km/y and 0.022 km/y at the left bank while 0.026 km/y and 0.046 at the right bank respectively. The prediction results illustrated that the very high vulnerable condition of 06 villages and 21 villages for high vulnerable due to left bank erosion. BEHI and REBVI scores have been the significant performance of understanding and identification of RE vulnerable areas. The long-term (2020-2045) average erosion and deposition rate was predicted at 0.135 km/y and 0.024 km/y at the left bank and 0.043 km/y and 0.045 km/y at the right bank respectively. The prediction accuracy and validation of models were measures by statistical techniques such as student’s t-test, RMSE, and R² values. This study would be help planners and decision makers the spatial guidelines to understanding future trends of bank erosion and shifting rate for land-use planning and management strategies to protect riverbank.

Planetary Science

Atmospheric Sciences

Erosion-accretion

DSAS model

BEHI

REBVI

Alluvial channel

remote sensing

Table 1 Previous literatures of the study area.

Sl. No.	Study Area	Applied Method	References
1.	Upstream and downstream of farakka barrage (The Ganga River)	Manual and traditional polygons superimpose or overlay methods were used for the cross section creation and EA measurement.	Thakur et al., (2011)
2.	Upstream and downstream of farakka barrage (The Ganga River)	Traditional and Manual methods were used for EA measurement.	Das (2011).
3.	Upstream and downstream of farakka barrage (The Ganga River)	Manual and traditional polygons superimpose or overlay methods were used for EA measurement.	Sinha and Ghosh, (2012)
4.	The left bank site of river Ganges of the Malda district.	Manual and traditional polygons superimpose or overlay methods were used for the cross section creation and EA measurement.	Mukherjee and Pal, (2017).
5.	The left bank site of river Ganges of the Malda district.	Manual and traditional polygons superimpose or overlay methods were used for EA measurement.	Mondal and Mandal, (2018)
6.	The Ganga River From Bhagalpur to Lalgola.	Manual and traditional polygons superimpose or overlay methods were used for the channel shifting measurement.	Pal and Pani, (2019).
7.	The left bank site of river Ganges of the Malda district.	Traditional and Manual methods were used for transects creation and EA calculation.	Majumdar and Mandal, (2020)
8.	The Ganga River From Bhagalpur to Farakka	Manual and traditional polygons superimpose or overlay methods were used for EA measurement.	Raj and Singh, (2020)
9.	The Ganga River From Sahibganj (Jharkhand) to Jalangi (West Bengal)	Traditional and Manual methods were used for reach division creation.	Ashwini et al., (2020)
10.	Upstream and downstream of farakka barrage (The Ganga River)	Manual and traditional polygons superimpose or overlay methods were used for EA measurement of different blocks boundary.	Sarif et al., (2021)

Table 2 Data type used for different purposes and respective sources.

Data type	Specification				Purpose	Sources of data
Secondary data	Satellite Images	Acquisition date	Path/Row	Spatial Resolution (in m)	For bankline extraction	http://earthexplorer .usgs.gov
	Landsat-1 MSS	23.11.1973	129/043	60
	Landsat-5 TM	08.12.1987	129/043	30
	Landsat-5 TM	22.12.1997	129/043	30
	Landsat-7 ETM	16.01.2007	129/043	30
	Landsat-8 OLI-TIRS	15.12.2020	129/043	30
Primary data	Bank height, bank full height, root depth, root density, surface protection, bank angle, soil texture, base width, bank slope, and water weight.				For BEHI and REBVI score calculation	Primary survey

Table 3: Guidelines for measuring complete BEHI (After, Rosgen, 2001).

Table 4 DSAS model based mean and stander deviation of erosion-accretion of both bank

Years	Left bank							Right Bank
	Erosion		Accretion		NET	NAT	NST	Erosion		Accretion		NET	NAT	NST
	Mean	SD	Mean	SD	NET	NAT	NST	Mean	SD	Mean	SD	NET	NAT	NST
1973-1987	0.129	0.082	0.104	0.121	661	357	329	0.061	0.066	0.119	0.123	548	382	526
1987-1997	0.072	0.064	0.020	0.018	484	474	389	0.019	0.030	0.061	0.062	394	462	600
1997-2007	0.106	0.099	0.037	0.029	481	428	438	0.049	0.067	0.026	0.046	442	459	555
2007-2020	0.168	0.139	0.021	0.024	455	494	398	0.079	0.111	0.056	0.051	296	757	403
2020-2025	0.089	0.047	0.032	0.019	473	434	440	0.045	0.040	0.060	0.063	313	544	599
2025-2035	0.151	0.141	0.019	0.018	506	477	364	0.043	0.49	0.026	0.025	318	616	522
2035-2045	0.164	0.149	0.021	0.011	597	438	312	0.031	0.035	0.045	0.041	417	474	565

SD = Stander deviation, NET = Number of Erosion Transect, NAT= Number of Accretion Transect, NST= Number of Stable Transect

Table 5 DSAS model-based results of RMSE and student’s t-test

Transects Number	Bankline Position (Actual 2020 and predicted 2020)	RMSE	(p<0.05) Two-tail
0-336	Left bank	0.492	0.314
0-364	Right bank	0.124	0.129
337-673	Left bank	0.131	0.165
365-728	Right bank	0.247	0.436
674-1009	Left bank	0.921	0.203
729-1092	Right bank	0.171	0.709
1010-1347	Left bank	0.819	0.019
1093-1456	Right bank	0.510	0.208