Development of integrated landscape framework at land-water interface for water sensitive urban design in the eastern fringe of Dhaka metropolitan area

Abstract

Dhaka, the capital of Bangladesh has seen unprecedented urban growth for the last couple of decades. Thereafter, landcover changed by increasing built-up areas have caused huge destruction on the natural landscape particularly on waterbodies. The natural land and water system of the Bengal Delta has always played an important role in structuring the city’s settlement pattern and maintaining the overall hydrological, ecological equilibrium. The Eastern fringe, which is the remaining spontaneous territory of Dhaka Metropolitan Area (DMA), is rapidly converting from local homestead to urbanized land through diminishing existing waterbodies and agricultural lands. Local people in this area are utilizing the natural landscape for production, flood mitigation, and enhancement of an open space network. But the city’s present development activities do not respect this deep geo-morphological nature of the territory nor incorporate these into built-up areas. As a result, the city has failed to preserve these essential natural landscapes and resulting in adverse effects on the urban hydrological and ecological environment, especially in flooding scenarios.

To address the present urban crisis associated with water, it is essential to search for strategies to protect the mandatory waterbodies and integrate those in the land development process. The land-water interface, a transitional strip around the water edge, buffers the waterbodies from human activities and prevents them from being converted into built-up areas. To identify the potential landscape elements, the land-water interface of 5 sample locations from the Eastern fringe with an area of 1.50 sq km each were analyzed using different landscape parameters for hydro-ecological performances. The transitional strips were extracted for two main seasons- summer and monsoon, because of extreme water level fluctuation and its impacts on the land-water interface. In the frame of analysis, the sample locations of the study area have been surveyed, observed, mapped, and analyzed in both quantitative and qualitative manners, to have a detailed understanding of the principles of local land-water integration. Numerous landscape elements, practices, and processes, which have been extracted from the analysis were further examined and correlated through cases for classifying the generalized landscape characters along with their embedded influencing factors. The research identified that the local land-water interface maintains significant landscape characteristics like area, width, and slope gradient of waterbodies, landuse patterns, circulation networks, hydrological features, drainage patterns, water edge conditions, meanders, water storage, soil condition, and agricultural patterns in their spontaneous development. Incorporating these landscape elements, the study derives urban design guidelines for ‘providing space for water’, ‘maintaining natural landform’, ‘preserving natural landscape’, ‘retaining local landuse patterns, and ‘applying local knowledge’ for interface utilization to ensure desired hydro-ecological performances. Finally, a landscape framework with urban design guidelines has been developed integrating these landscape elements with the ascertained principles for effectively structuring the water edge that can be applied to the current planning and design policy of the city and in similar contexts towards a water-sensitive urban design.