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Autor Principal:	Adhya, Dr. Sanghamitra
Formato:	Recurso digital
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Publicado:	Zenodo 2014
Subjects:	Flood risk management Urban sprawl encroachment Deforestation
Acceso en liña:	https://doi.org/10.5281/zenodo.20346808
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This paper analyses the effects of urban development on flood incidence and severity in Kalyani, a planned town in Nadia District, West Bengal, situated on the natural levee of the Hooghly (Ganga) River and integrated into the Kolkata Metropolitan Region. Conceived as a modern industrial–institutional township with an efficient drainage network and abundant open spaces, Kalyani has undergone rapid land‑use change, infilling of wetlands and ponds, and proliferation of unplanned settlements that increasingly undermine its original hydrological resilience. The study asks three questions: (i) how has urban development altered surface hydrology and drainage pathways in Kalyani; (ii) what is the relationship between these changes and the occurrence of floods and water‑logging; and (iii) what planning and engineering measures can reduce flood risk in the context of continued urban growth. Methodologically, the paper combines geospatial analysis, hydrological assessment and institutional review. Multi‑temporal satellite imagery, cadastral maps and municipal land‑use records are used to map changes in built‑up area, road networks, open spaces, tanks and low‑lying depressions over the last three to four decades. A digital elevation model (DEM) and terrain analysis support delineation of natural drainage lines, flow accumulation zones and potential ponding areas within Kalyani Municipality, while GIS‑based terrain models developed in earlier work are adapted to simulate flood‑prone areas under different rainfall–runoff scenarios. These spatial analyses are complemented by rainfall data, flood‑hazard information from state and national atlases, and field surveys documenting outfall conditions, drain cross‑sections, encroachments, siltation and local water‑logging hotspots. Interviews with municipal engineers and planners, along with reviews of urban development plans and storm‑water drainage reports for the broader corridor, provide insight into the design capacity and current limitations of drainage infrastructure. The findings indicate that urban development in Kalyani has significantly altered the natural hydrological regime. Expansion of built‑up surfaces and roadways has increased impervious area and storm‑water runoff, while the progressive filling of tanks, wetlands and low‑lying depressions has reduced local storage capacity and opportunities for groundwater recharge. Although Kalyani was originally endowed with a relatively well‑planned underground drainage system, rapid growth of unplanned settlements, informal constructions and paved courtyards has overloaded existing drains, many of which are now undersized, silted or physically encroached upon. GIS‑based flood simulations and field observations show that even moderate to heavy monsoon showers now produce recurrent water‑logging along key road corridors, institutional campuses and slum clusters, particularly where secondary drains discharge into clogged primary channels or lack adequate outfalls. While the Hooghly’s levee position reduces direct riverine flood risk under normal conditions, backwater effects and high river stages during extreme events can slow drainage, compounding pluvial flooding within the town. The Kalyani case reflects broader patterns observed in Indian cities, where unchecked urbanisation, loss of wetlands, inadequate storm‑water planning and poor maintenance have converted occasional flooding into near‑annual crises. National guidelines on urban flooding emphasise that congestion of drainage channels, encroachment on natural drains and absence of integrated land‑use–drainage planning are key drivers of urban flood vulnerability, all of which are increasingly evident in Kalyani’s fringe areas and informal settlements. The paper argues that the town’s transformation from a carefully laid‑out grid to a more fragmented, densified urban fabric has created a mismatch between design assumptions of the original drainage system and current hydrological reality. In response, the paper proposes a multi‑layered risk‑reduction framework. Priority measures include systematic mapping and protection of residual wetlands and low‑lying areas as urban retention basins; desilting, resizing and re‑aligning critical storm‑water drains; restoring and legalising natural drainage channels; and integrating flood‑risk layers into municipal land‑use zoning to restrict high‑density development in low‑lying pockets. Adoption of sustainable urban drainage systems (SUDS)—such as permeable pavements, rain gardens, roadside bioswales and rooftop rainwater harvesting—could reduce peak runoff and enhance infiltration, especially in institutional and residential sectors that still have some open space. Strengthening routine operation and maintenance, incorporating flood‑risk assessment into new infrastructure projects (such as road widening and housing schemes), and building local awareness around waste disposal and drain blockage are essential for long‑term resilience. The Kalyani case thus demonstrates how urban development, if not guided by hydrological sensitivity and proactive planning, can exacerbate flood risk even in a planned town, while also highlighting realistic pathways for corrective, GIS‑informed urban water management.

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