By Naveen Goveas

Mangaluru, Aug 22: Over the past decades there has been a substantial change in the weather records worldwide, putting citizens living in urban areas in deep worry. Flood waters have destroyed homes and businesses and scenes like this are seen all over the world. While rainfalls have become intense, our urban infrastructure has limitations with little room for water to flow.

While we build roads, we forget to provide enough space to construct wide storm water drains which allow water to flow. Our current infrastructure repeatedly fails during heavy spells of rain and water-logging has become a common sight. Adding more concrete will not solve the problem unless we adopt some innovative methods, give priority while planning our future infrastructure. This article focuses on various types of flood management techniques which are already applied in many other cities especially western countries.

Causes of floods

Floods are caused by many factors such as heavy precipitation, severe winds over water, unusual high tides, tsunamis or failure of dams, retention ponds or other structures that contain water. Periodic floods occur in many rivers, forming a surrounding region known as the flood plain. During rains, some of the water is retained in ponds or soil, some is absorbed by grass and vegetation, some evaporates and the rest travels over the land as surface runoff. Floods occur when ponds, lakes, riverbeds, soil and vegetation cannot absorb all the water. Water then runs off the land in quantities that cannot be carried within stream channels or retained in natural ponds, lakes, and man-made reservoirs. River flooding is often caused by heavy rain.

Effects of floods

Flooding has many impacts. It damages property and endangers the lives of humans and other species. Rapid water runoff causes soil erosion and concomitant sediment deposition elsewhere, such as further downstream or down a coast. The spawning grounds for fish and other wildlife habitats can become polluted or completely destroyed. Some prolonged high floods can delay traffic in areas which lack elevated roadways. Financial losses due to floods are typically in crores of rupees each year.

How can we avoid and reduce floods

There are many solutions that can minimize flood occurrences. Water management systems can in fact, reduce this catastrophic event in urban areas:

• Roof Gardens: They absorb the 50% of rainwater, reducing the quantity of water that is disposed off in the sewer.
• Sustainable Urban Drainage Systems (SUDS).
• Underground basins for water storage:  Reduces the quantity of water in the sewers, they naturally filter polluting materials and restore the natural hydrological balance of water in urban areas. 

Roof gardens

Rooftop plants, including green roofs and roof gardens, along with rainwater collectors and rain gardens can help slow things down and sustain the impact of heavy rain. The idea is to replace some of the trees, grass, hollows and wetlands that have been lost to concrete, and so mimic a more natural flow of water. Green roofs have the capacity to capture an average of 70 per cent of rainfall over a given time, relieving underground storm water systems and releasing the rain water back into the atmosphere. Urban ‘roof gardens’ can be created in public spaces, which capture and store seasonal flood water which creates urban green space and wildlife habitat. Carefully designed soak ways, planted with water loving vegetation, can provide an attractive and practical solution to encourage water passage and storage. 

Sustainable urban drainage systems (SUDS) 

The SUDS approach is to look at water in the urban environment in a completely different view point. Instead of hiding water underground, or behind concrete walls and channels, it brings it back into the community. SUDS combine natural principles such as trapping and slowing down of rainwater by vegetation with engineering and drainage principles which capture and remove floodwater before it becomes a problem. SUDS use these principles to help reduce ‘flash’ flooding in urban areas whilst also creating areas of habitat for wildlife, removing pollution and helping to replenish underground drinking water supplies. With SUDS, rain water is captured as soon as it falls, and is managed above ground rather than being drained into sewage and underground foul water systems. By managing the water where it falls, it also reduces the impact of flood water on people who live in low lying urban areas.

Underground basins for water storage

Increasing underground water storage capacity and simultaneously decreasing flood danger. The underground tank itself is almost always of one-piece design and is normally constructed from either high density polyethylene or GRP .The tank is accessed from the ground via an inspection cover for maintenance purposes, though in most cases, once an underground tank is installed it needs very little human interference. Once installed, it takes up no space at ground level so imposes little restriction on the design of the garden, as lawn, paving etc. can be laid over the top of it. Getting water in to it is generally easier as the pipe work can be routed below ground as required. Water stored below ground is kept cold and dark so there is no potential for growth of algae.

In my opinion the government should take unprecedented steps to implement the above mentioned sustainable methods. Our coastal cities which witness heavy rainfall need to have these kinds of methods to reduce the amount of water reaching the sea. Smart cities must have smart flood control methods in order to have less damage to the property and human life.

Naveen Goveas

(Naveen Goveas, from Moodbidri, is currently working as a Mechanical Engineer for infrastructure valves division at DCSERVE LLC in Dubai. He holds a Mechanical Engineering degree from MIT Manipal. He has a vast experience in various sectors like fire fighting, portable water, waste water drainage systems etc.  He also has special interest in organic farming.)