Temporal change in channel form and hydraulic behaviour of a tropical river due to natural forcing and anthropogenic interventions

ABSTRACT

Assessing the degradation of river channels is crucial in the Anthropocene era, particularly in the deltaic areas worldwide. The present study aims to investigate the degradation of the Mathabhanga-Churni River giving emphasis on the temporal change of channel morphology and hydraulic behaviour and comparing the current situation with the historical past based on planform morphology and meander geometry of 118 meander loops, and width, depth, cross-sectional area, and hydraulic behaviour (velocity, discharge, stream power) at 47 cross-sections. The absence of lateral dynamicity, the static character of channel sinuosity during the last century (1913–2018), and the constant meander morphology reflects the static meander geometry and degradation of the river. The reduction of average channel width, depth, and cross-sectional area supports the falling trend of channel forms. Findings on hydraulic behaviour indicate declining discharge (~50% reduction during 1915–2018) that induces the present-day downscaled velocity and lowered stream power. Neotectonics (eastward tilting of the Bengal delta) and anthropogenic stressors such as stream crossings, agriculture on river beds, brickfields, and urbanisation have a severe impact on the hydromorphology of the channel, turning the active river into a stagnant and polluted channel.

KEYWORDS:

• Hydro-morphological change
• Mathabhanga-Churni river system
• planform geometry
• river decay

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The datasets used and/or analysed during the current study are available from the corresponding author [AI] on reasonable request.

Additional information

Funding

The first author of this paper [BS] would like to acknowledge Indian Council of Social Science Research (ICSSR) for their financial support vide File number [RFD/2017-18/ENVI/GEN/324] to carry out this research work.