Water Sensitive Urban Design: Storm Water Management Practices as an Opportunity

INTRODUCTION

Cities have experienced tremendous expansion in the 20th century. Oftentimes this expansion has been uncontrolled, which has resulted in the shifting of non-urban to urban land use. For the first time, 2011 census data showed significant increase in the urban population in India which was slightly higher than the increase in rural population. India's National Population Commission (NCP) predicts that over the next 15 years (that is, by 2036), about 38.6 percent (600 million) of Indians will live in urban areas (Census of India 2011, 2020). The United Nations also emphasized that India's urban population will nearly double from 461 million to 877 million between 2018 and 2050 (UNO, 2018). With the increase in urban population there is tremendous pressure on land. This spread of the built up areas has significantly increased impermeable and paved surfaces which has reduced the infiltration rate. Flooding, erosion, and other water-related issues come from poor storm water and urban runoff management. This in turn affects our urban cycle. Under natural conditions, water acts as closed loop of precipitation, infiltration, runoff and evaporation. However, in urban areas this loop is disturbed. Urban water is contaminated and unable to permeate the earth because of paved surfaces, which results in rapid collection and drainage into public sewers that do not get the time to evaporate. Ultimately, it has negative effects on urban climate. All these issues clearly indicate the need for efficient solutions for urban water management (Hoyer, 2011).

CITIES AND WATER

Water emerges in cities as potable water, storm water and grey water managed by the municipality. Storm water must infiltrate the ground or paved surfaces (roofs, streets, etc.) to avoid flooding and keep side streets and buildings dry and safe (Hoyer, 2011). The findings states that around ―4.0 billion suggested by previous studies which estimated between 1.7 and 3.1 billion people‖ (NATIONS, 2021) . The existing water management practices are not helping cities in increasing the efficiency of water cycle and creating awareness of the importance of water resources.

LITERATURE REVIEW CONVENTIONAL APPROACH

Storm water management practices are constantly evolving. In Ontario, urban storm water has been managed for flood control purposes since the 1970s. In the 1990s, storm water management was also recognized as an important tool for improving water quality and reducing pollution of lakes and rivers. Since then, this practice has focused primarily on centralized storm water storage. This is also known as storm water treatment at the end of the pipe(Goulden et al., 2018).

1. Combined sewerage systems collect both wastewater and storm water in a single pipe network. Mixed water is transported to a wastewater treatment plant, where it is cleaned before being released into the river. 2. Separate sewerage systems: Wastewater and storm water are collected in two different sewerage systems. The wastewater is transported to a wastewater treatment plant, whereas the storm water pipe either discharges directly to the receiving water (in the absence of pollutants) or is treated separately before being discharged into the river. (Hoyer, 2011)

WATER SENSITIVE URBAN DESIGN (WSUD) AS SUSTAINABLE APPROACH

1. Protect local water sources (lakes, ponds and wetlands) to get additional water resources. 2. Landscape elements (e.g., vegetated ditches and buffer zones band, biological note system) are used to manage rainwater in public locations, especially open areas in cities. 3. Recycle and reuse wastewater naturally (low cost / low energy). 4. Enhance water conservation approaches at different scales (building / campus) - means by groundwater supply systems sources. Rainwater harvesting and in situ conservation are also significant in mitigating water scarcity. 5. By cooperating with professionals from many fields to present different viewpoints and skills, the urban cycle will be connected.(Water Management to Water Sensitive Planning-A Contemporary Approach for Sustainable Urban Development, n.d.) Table 1: Comparison Between Conventional Practices And Wsudp (Source: Author)

Figure 1: Conventional Approach

Figure 2: WSUD Approach

WSUDP PRINCIPLES

There are four water sensitive design principles: (1) cater to potable water demand; (2) reduce wastewater production; (3) rainwater treatment; (4) use of natural water resources as a feature of the landscape. In terms of technical solutions, water sensitive design basically offers strategies for rainwater accumulation, rainwater filtration and ultimately release of water into nature, it also connects social and technological aspects. These

a combination of both two (reservoir, storage tank).(Walsh et al., n.d.)

WATER SENSITIVE URBAN DESIGN TECHNIQUES

1. GRASSED SWALES: The design of grassed swales or lawn gutters are designed to allow storm water to enter at more gradual and controlled rate, and acting act as a filter means to remove pollutants while allowing storm water to exit (Figure 3). Channels are a low-cost, low-maintenance option for removing scale, nutrients and contaminants. They increase the penetration of rainwater and visually add an aesthetic element to the site.(Virginia Stormwater Management Program (VSMP), n.d.) 2. RAIN GARDENS: A rain garden is a garden in which flowering plants and grasses (both preferably) that can survive in moist soil after heavy rains grow. But these are not gardens with stagnant water (Figure 4). Rainwater gardens collect runoff from rainwater, slow it down and enhance its penetration into the earth. These attractive gardens assist homes and businesses in reducing rainfall runoff, as a result pollutants carried away from roofs and hard surfaces are not swept into streams and lakes (Rain Gardens, n.d.). 3. INFILTRATION TRENCH: A shallow digging ditch filled with gravel or rubble is known as an infiltration trench, designed to filter rainwater through permeable soil into an aquifer of groundwater (Figure 5). In locations with poor rainwater drainage, it is frequently utilised to transport wastewater from impermeable surfaces like sidewalks and parking lots. (Infiltration Trenches, n.d.). 4. BIO-RETENTION SYSTEM: The bio-retention system consists of a soil layer with suitable non-invasive plants (preferably native plants). Rainwater that flows into the bio-settlement system is filtered through the soil bed before being transported downstream through the underground drainage system or infiltrating the existing underground soil layer (Figure 6). Bed vegetation planted in the soil allows for the absorption of pollutants and runoff water, and helps to maintain voids and associated soil infiltration rates in the bed (Fallis, 2013). 5. FLITER STRIPS IN PARKING LOTS: Filter strips are planted areas near to impermeable surfaces that are gently sloping. They're supposed to assist improve storm water quality by reducing the effects of sheet flow and velocity (Figure 7). They're also called boosting infiltration.(Stormwater Management - Filter Strips, n.d.).

CONCLUSION

―We forget that the water cycle and the life cycle are one.‖ — Jacques Yves Cousteau The goal of long-term storm water management is to reduce runoff by treating storm water as close to the point of origin as possible, ideally on-site. ―Treating‖ does not signify the collection and discharge of storm water in the public sewer system, rather it would be treated judicially to reduce the surface runoff and to increase the storm water infiltration rate. Past experiences have proven the misconduct of water which results today in downfall of water table and climatic crisis. This is because, conventional approach of water management proceeds towards the quick collection of storm water and drain it which reduces the infiltration rate and simultaneously affects the hydrological cycle adversely. This paper highlights the water sensitive techniques like infiltration trenches, swales and rain gardens at urban design level and then individual design level which can be adopted to make the cities sustainable, aiming for the Sustainable Development Goals-2030 which include clean water, sanitation, and sustainable cities, as well as community participation.

RECOMMENDATIONS

Storm water management includes management of water at terraces, ground, roads and pavements which are the catchment points of surface water. This surface water flows towards the drain. For the sustainable water sensitive management this surface water should be promoted towards the pervious surface to increase the infiltration rate. Apart from the design techniques mentioned above, several design considerations can be adopted at urban as well as individual level to make the cities sustainable and increase the infiltration rate such as 1. Creating contours to allow surface water to infiltrate into the ground effectively. filter rainwater through permeable soil into an aquifer of groundwater. 3. Using turf pavers on the pathways and on parking lots. It has high infiltration rates of storm water. This allows the paved area to work in tandem with Mother Nature, rather than against her. Along with these initiatives at individual level, the development authorities and concerned government bodies should make it mandatory to incorporate WSUDP strategies and techniques in all architectural and planning projects to effectively restore the hydrological cycle in cities.

REFERENCES

1. Census of India 2011. (2020). Population Projections for India and States 2011-2036, Census of India 2011, National Commission on Population Ministry of Health and Family Welfare India. https://main.mohfw.gov.in/sites/default/files/Population Projection Report 2011-2036 - upload_compressed_0.pdf 2. Fallis, A. . (2013). Bioretention systems. Journal of Chemical Information and Modeling, 53(9), 1689–1699. 3. Goulden, S., Portman, M. E., Carmon, N., & Alon-Mozes, T. (2018). From conventional drainage to sustainable stormwater management: Beyond the technical challenges. Journal of Environmental Management, 219, 37– 45. https://doi.org/10.1016/j.jenvman.2018.04.066

5. Infiltration Trenches. (n.d.). Retrieved February 12, 2022, from https://www.esf.edu/ere/endreny/GICalculator/InfiltrationIntro.html 6. NATIONS, U. (2021). UN World Water Development Report 2021. rain gardens. (n.d.). Retrieved April 4, 2022, from https://www.groundwater.org/action/home/raingardens.html 7. Stormwater Management - Filter Strips. (n.d.). Retrieved March 12, 2022, from https://www.lakesuperiorstreams.org/stormwater/toolkit/filterstrips.html

s/WUP2018-Report.pdf 9. Virginia Stormwater Management Program (VSMP). (n.d.). Retrieved March 5, 2022, from Virginia Stormwater Management Program (VSMP) 10. Walsh, C. J., Booth, D. B., Burns, M. J., Fletcher, T. D., Hale, R. L., Hoang, L. N., Livingston, G., Rippy, M. A., Roy, A. H., Scoggins, M., & Wallace, A. (n.d.). Principles for urban stormwater management to protect stream ecosystems. 11. Water Management to Water Sensitive Planning-A contemporary approach for sustainable urban development. (n.d.)

Guest Teacher, Department of Architecture, Aligarh Muslim University, Aligarh