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Does Mumbai Devasting Drainage System Has Any Solution?
In this, we are going to compare drainage systems in India (especially coastal cities) with the world’s best urban drainage in Tokyo. We are intending to show is it possible to rectify the problems generally faced by our business capital Mumbai in monsoon and also the financial losses during those three-four monsoon months. Statistically speaking Tokyo and Mumbai possess nearly same conditions in an aspect of rainfall average but though there is no incident heard that Tokyo is facing flood-like conditions. Govt. of Japan and the University of Tokyo together proposed a plan of an advance drainage system that consists of 5 major water banks and one pumping plant which is connected by a 6.3km long massive tunneling system. On contrary, in Mumbai (Storm Water Drains) SWD department which is fairly based on just roadside, below footpath, open/closed drains, box drains, major gutters, minor gutters, and outfalls. But these are not enough to control heavy rainfall. So, if we focus to modify our older drainages and providing water treatment plant which will give an option for reuse of this wastewater in industries, so it will be great for
the concept Make In India.
Infrastructure improvement, intense rainfall, flooding, stormwater runoff model,
By the year of 1995, the University of Tokyo in association with the Government of Japan proposed a unique plan of advance drainage system in Tokyo, which further proved to be one of the greatest achievements in the drainage system which was able to sustain severe flood. In Tokyo, the drainage system is focused on the policy of Collect and Discharge but we are intending to use the policy Collect and Reuse for our cities like Mumbai. By making some modifications in the current Storm Water Drainage (SWD) system of Mumbai such as diversions from major gutters and the drainage flow through those diversions should flow into the tunneling system which should be constructed with reference to the advance drainage system of Tokyo. In India, a major problem in industrialization is the requirement of water, and to rectify this problem we can use the idea of reuse of wastewater which just drains out from roadside drainage and which ultimately solves the problem of floodage and industrial requirements.
Existing Drainage Condition in Mumbai
Proposed Working Of Tokyo System
1. The city Tokyo consist of 5 rivers of which Edo river is the greatest one, the underground drainage system has 5 major water banks that collect flood water of river Naka, Kurumatsu, Otoshifurutone. These water banks are connected by a 6.3km long underground tunneling system which ends at no. 1 water bank beside which drainage pump station is located.
2. Bank- The five banks from no.1 to no.5 are interconnected to each other to underground tunnel and used for taking in floodwater from the river including Naka, Kuramatsu, Otoshifurutone. On top of that, they play an important role in maintenance and management of the outer underground discharge channel, by being intake areas for vehicle and by installing ventilation system.
3. Inflow Facility- flood water is taken into the outer underground discharge channel at the overflow level provided on the embankment of the river including Naka, Kuramatsu, and Otoshifurutone. If the water level of each river surpasses the height of the overflow level flood water will go into the inflow facility on its own. The height of the overflow level is set too much the same height as that of the lowest nearby ground so that it can function sufficiently to cope with even small to mid-size floods.
4. Tunnel-This is an underground river constructed to lead the floodwater flowing in from Naka, Kuramatsu, Otoshifurutone Rivers and others to Edo River. The tunnel connecting five banks is constructed along route 16 at a depth of 50m below ground level. It has an inner diameter of approximately 10m, and an overall length of 6.3km. It can drain flood water at a speed of up to 200m³.
5. Drainage Facility- The Showa drainage pump station is the heart of the water discharge tunnel on the outskirt of the metropolitan area, and has two roles. One role is to drain the floodwater that random from the underground tunnel, from the pressure adjusting water tank through a giant pump and the drainage sluiceway to the Edo River. The other role is to operate and centrally monitor each inflow
6. Drainage Sluiceway- This facility is used for draining floodwater from the water discharge tunnel on The Outskirts of The Metropolitan Area. Flood water sucked up by the pump station is drained into the Edo River through six drainage sluiceways, each 5.4m×4.2m. It has another function of preventing backwater coming from the Edo river.
Implemention in Mumbai
Mumbai receives seasonal rainfall for four months of average 2000mm. The SWD system of Mumbai comprises of a hierarchical network of roadside surface drains (about 2000 km mainly in the suburbs), underground drains and laterals (about 440km in the island city area), major and minor gutters (200km and 87km resp.) and 186 outfalls, which discharge all the surface runoff into rivers and seas.
The discharge of all the stormwater and treated sewage is into the Arabian Sea. Most of the key reasons for flooding apart from tidal variations, flat gradients, mudfats are manmade inappropriate levels of outfalls, poor placement of gullies, loss of holding ponds due to lands development over the years and increase in runoff coefficient and encroachment on drains, enhance silting and choking of a drain due to sewage inflows and garbage dumping in drains poor structural conditions etc.
1. The whole Storm Water Drainage system of Mumbai is based on the gravity effect, i.e. there is no pump station for drain water which results in blockages of gutters due to which flows on the road instead of underground tunnels.
2. So as per the BRIMSTOWAD report if we provide more diversions to major gutters which ease the flow of sewerage.
3. Our suggestion for SWD is if we increase number diversions of major gutters though they will not withstand severe water flow, so by constructing a separate underground water tunneling system around Mumbai which will be connected by all out-lets of gutters and discharge that sewerage into proposed new water banks instead of Arabian Sea. This collected drain water must be treated at the
pump station which should be located at the end of the proposed underground tunneling system which should be based on Tokyo’s drainage system.
Storm Drainage Department Local Drain Network
|Drain hierarchy/type||Iceland City||Western suburbs||Eastern suburbs||Total|
Roadside open drain
Closed pipes or Dharpa Drains
Existing Condition of Mumbai
1. Rapid development of urban areas- By reuse of drainage water
2. Change of lifestyle- Use of wastewater by recycling which enhances the growth of industries.
3. Climate monitoring- Reduce environmental risk and prevention from polluted water causing diseases.
4. Flood control- By introducing a pump station.
Tokyo present drainage system
Knew the Facts
How it will help in accordance to “MAKE IN INDIA FOR RURAL PROSPERITY”?
1. As if our major business capital MUMBAI is free from major drainage problems ultimately this wastewater can be made usable for industrialization by treating this water in water treatment plant which consumes only 0.5 liters of crude oil to treat 1000liter of water which can further save our daily water from dam or any resources.
2. As most of the times, we ignore to establish any industry or a plant at a rural place due to shortage of water but by this project, we must be assured that lot much amount of water can be used for the thermal plant by which rural may turn to urban which leads make in India.
3. The treated water which has been provided to any industrial plant in rural areas, the raised fund from those industries can be used in favor of rural prosperity.
Many coastal cities like Mumbai need an advance drainage system, which can withstand severe storm and rainfall. Also, such kinds of projects help to reduce financial losses that occur during monsoon. Mainly if this collected water reused properly then there will not be any issue related to the water crisis and on the other hand there will be a great push for industrial growth in undeveloped regions. The cleanliness of the metro cities also can be achieved effectively with efficient drainage.
- Planning section. Planning and coordination division, Bureau of Sewerage, Tokyo Metropolitan Government, 2-8-1, Shinjuku-ku, Tokyo, 163-8001, Japan.
- Files- Chief Engineer (Storm Water Drains), Mumbai, www.mcgm.gov.in
- Environmental Science Center, The University of Tokyo.
- Ministry of land, infrastructure, transport & tourism of Japan, www.mlit.go.ac