River basin flood adaptation for coastal urban slums. Mithi river basin, Dharavi slum

From Firenze University Press Journal: Ri-vista

Anubhav Goyal, CIAUD, Research Centre for Architecture, Urbanism and Design, Lisbon School of Architecture, Universidade de Lisboa

Sérgio Barreiros Proença, CIAUD, Research Centre for Architecture, Urbanism and Design, Lisbon School of Architecture, Universidade de Lisboa

Maria Matos Silva, CIAUD, Research Centre for Architecture, Urbanism and Design, Lisbon School of Architecture, Universidade de Lisboa

Slums are informal neighbourhoods characterized by overcrowding and poor infrastructure. “[…] a contiguous settlement where the inhabitants are characterized as having inadequate housing and ba-sic services. A slum is often not recognized and addressed by the public authorities as an integral or equal part of the city” (UN Habitat, 2003, p. 8). In developing countries of global south, urban slums host a large proportion of population. Here, ‘global south’ is simplistically referred to in the terms of ge-ography, to consolidate the group of countries fac-ing disadvantages on the basis of economic system, the Brandt line, as a way of geographically classify-ing the countries into relatively richer and poorer nations. “The Global south is not an entity that exists per se but has to be understood as something that is created, imagined, invented, maintained, and rec-reated by the everchanging and never fixed status positions of social actors and institutions” (Kloß, 2017).Globally, in 2018, 23.5 percent of urban population lived in slums. The absolute number of people living in slums grew to over 1 billion, with 80 percent at-tributed to three regions: Eastern and South–East-ern Asia (370 million), Sub–Saharan Africa (238 mil-lion) and Central and Southern Asia (227 million) (UN Habitat, 2019). At national level, according to the Census of India in 2011, nearly 17 percent of urban population i.e. more than 65 million people lived in slums (Census of India, 2011). In Mumbai, which hosts Dharavi slum along the Mithi River, nearly 54 percent of urban population lives in slums (Census of India, 2001). Mostly, the slums occupy land unsuitable for formal development. Therefore, the low lying marshy are-as along the river basins or coastal mangroves near large cities are particularly pressured by this form of occupation. As a direct cause, the physical location makes them at a greater risk of flooding. A particular flood can result from many combinations of me-teorological, hydrological and human factors (Matos Silva, 2016, p. 81). It is realized that coastal urban slums are more vulnerable towards risks induced by climate change and sea level rise. Flooding is not just related with heavy rains or extreme climatic events but is also related with the ability of the built area of an urban slum to absorb the excess water or prevent the overflowing of water. “Uncontrolled urbanization has rapidly consumed rural land and sys-tematically encroached on water bodies, floodplains and wetlands, resulting in a fragmented ecosys-tem” (Claudia Rojas et al., 2015, p. 177). Due to ab-sence of adequate formal flood adaptation meas-ures, infrastructure and basic services urban slums lack the ability to prevent or absorb excess water. The dwellers are imposed with the impact of recur-ring floods from extreme climate events such as cy-clones, tidal surges etc. According to IPCC, there is high confidence that “Coastal systems and low-ly-ing areas will increasingly experience submergence, flooding and erosion throughout the 21st century and beyond, due to sea level rise” (Pachauri et al., 2014, p. 74). Also is predicted by 2100, about 70 per-cent of the coastline worldwide are projected to ex-perience sea level change within 20 percent of the global mean. In this sense, it is essential, to inves-tigate and avail the ability of adaptive public space such as river basin that exist with the coastal urban slums in addressing the floods. A river is a process that is governed by changing wa-ter levels, shifting seasons, erosion and sedimen-tation. “It creates land and water from ubiquitous wetness, defining them on either side of a line. It is one of the first acts of design, setting out a ground of habitation with a line that has largely been naturalized in features such as the coastline, the river-bank, and the water’s edge” (da Cunha, 2019). The river environment is not static rather a dynamic process. River basins, inscribed in a geographical area, face a continuous conflict between the mush-rooming slums and the environmental needs. We can consider that in river basins there exists a spatial interplay between the floods and the measures of adaptation and mitigation. Restoration and conservation of coastal and riparian ecosystems as al-ternatives to infrastructural measures are increasingly being explored (Barbier et al., 2011) (Borsje et al., 2011). A constant adaptation subsists in coast-al slums in close relation with water. River basin is “the entire geographical area drained by a river and its tributaries” (Sanghani, 2009, p. 3). It plays as a significant landscape infrastructure towards build-ing blood resilience for coastal slums.The objective of the paper is to investigate and ex-amine the research question of how this physical space in wetlands can be turned into an adaptive interplay between the water and adaptation measures by the local slum dwellers to address floods. The methodology involves observation and inter-pretation from the case of Mithi River basin, Dharavi slum in Mumbai, India. The drawings are derived from the spatial assessment of the case, assisting towards the development of a compre-hensive systematization, a typological framework of effective measures and innovative design elements that further could be conceptualized into the design of future flood resilient coastal urban slums.

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