A Green Approach to Mitigate Urban Flooding

By Tapaswini Mohapatra Samant Architect, Environment Designer, Sustainable Architect

Bioswales –A Newer –Better -Strom Water Management Strategy

New Delhi, June 21, 2018: As the monsoon is arriving the threat of urban flooding is going sturdy. Indian cities roads are all getting blocked with monsoon. None of the cities are left lagging in the race of urbanization so as the case of urban flood.

Urban flooding is not uncommon. All cities are now experiencing flooding frequently without any exception. Common consequences of urban development include the removal of vegetation and an increase in impervious surfaces and drainage networks, all of which increase precipitation runoff; this may result in more flooding. Urban flooding occurs when water flows into an urban region faster than it can be absorbed into the soil or moved to and stored in a lake or reservoir.

Many recent sustainable innovations are approaching to deal with urban flood and to prevent runoff near its source and to provide pollution and quantity control. Some of the strategies are as follows:

Create a ‘sponge city’ -passively absorb, clean and use rainfall in an ecologically friendly way

Green roofs/rooftop gardens.

Create flood plains and overflow areas for rivers.

Separating rainwater from the sewer system.

Install water infiltration and attenuation systems.

Keep the sewer system clean, so it can do its job.

Sustainable drainage: permeable pavement, sidewalks and gardens.eg: bioswales.

One of the strategy that can mitigate urban flooding & can enhance the beauty of the street by landscaping is called Bioswale.Bioswales are designed to redirect storm water, reduce flooding & making the city more green & clean.

A swale or bioswales is a stretch of vegetation that borders a paved area. You’ll often see swales separating dual-direction roads; or in-between a sidewalk and road. As an unpaved area, swales and bioswales provide permeable space in highly paved regions. Properly functioning swales feature highly permeable soil and vegetation, allowing storm water to collect, filter and drain into the earth.

How do they manage storm water?

Bioswales have four functions for storm water management: collection, conveyance, filtration and infiltration. These four traits reduce and delay peak run off volumes  as well as treat storm water quality.

Storm water is first collected in the trench, and if the water accumulates faster than it is carried away, then the water will pool. The reason why water accumulates in a bioswales and not in a gutter is that the vegetation adds roughness to the channel, greatly reducing the velocity. This effect delays the time of peak run off. The vegetation does more than reduce the velocity of the water, as plants filter suspended sediments from the water passing through them. While the plants remove these large particles, microbes in the soil digest organic nutrients which in high concentrations can be considered pollutants.

Corporate Comm India(CCI Newswire)