REIMAGINING THE ROLE OF NATURAL CHANNELS IN URBAN DEVELOPMENT FOR PLUVIAL FLOOD MITIGATION

Abstract

For long, the cities depended on grey infrastructure for draining stormwater. However, incidences of pluvial flooding are increasing, and existing grey infrastructure is unable to take up the additional stormwater load. Consequently, planners are forced to think of new and sustainable alternatives for stormwater management. A natural drainage system can supplement the urban stormwater drainage systems, but so far, the cities have not utilised this possibility. This research adopted the exploratory approach to investigate the city development trajectory, and in the process, aimed to identify the reasons that have impeded the inclusion of natural channels in urban drainage. Six developing cities in the Greater Mohali Region (India), with a vast network of natural channels, were selected for investigation. Systemic analysis of their development plans revealed that the planners intend to safeguard the seasonal natural channels and utilise them for drainage. Contrary to this, from the land use land cover change detection of the cities, it is found that most of these channels are now extinct as they have been reclaimed to provide land for housing, roads and agriculture. Conclusively, it is hypothesised that seasonal channels can be safeguarded by converting their seasonal functionality to year-long functionality. Hypothesis testing is facilitated by exploring the symbiotic relationship between leisure valley (greenspaces) and N-choe (seasonal natural channel) in the city of Chandigarh (India). This case study shows that seasonal channels and their function can be safeguarded by changing their land use from water bodies to greenspaces, and hence the hypothesis is confirmed. To convey the symbiosis of greenspaces and seasonal natural channels, this research has coined a new term, greenswale, which is defined as 'the stretch of greenspaces laid over a natural channel, ephemeral or intermittent, having stormwater detention and conveyance as primary functions during precipitation'. This study has added a new nature-based solution to the inventory of sustainable stormwater management measures.