Wednesday, September 06, 2006
Keeping your compound dry
Water-logging in compounds is increasingly becoming a problem hard to tackle in the urban areas of Kerala. Not only in cities, but also in regions that were slowly getting urbanised, water-logged compounds are creating headaches for house owners every monsoon.
The reasons for increasing levels of water-logging are many. They are not too hard to find, given the topsy-turvy nature of our urban development. "Lack of any proper planning in providing a drainage is the major cause of water-logging," points out the Kochi-based architect G. Jaigopal. Add to this the high ground water table in many parts of the State, especially in the coastal areas like Ernakulam. The city and suburbs have one of the highest water tables in Kerala.
High water table
"In many areas in Kochi, the ground level is often lower than the mean sea level, resulting in a high water table," Mr. Jaigopal points out. In such places, the rainwater does not sink into the ground. Coupled with the groundwater, it becomes almost a lake. The only problem being that the lake is formed right in front of your house.
"In planned towns, each compound is assigned different levels. If your compound is at a certain level, the next plot is given an assigned level lower or higher than yours, according to the slope of the land. The water from all the plots are diverted through sloping drains towards the nearest canal or stream or river or any other water body. But, here, we have absolutely no planning regarding such matters," points out Mr. Jaigopal.
"On the other hand, we compete with each other in rising the level of our own plots than the neighbours," with the result that an entire area gets waterlogged."
He points out that providing proper drainage is the basic way to prevent water-logging. "The issue of water-logging can be handled at two levels," points out Sebastian Jose, Kochi-based architect. In his opinion, draining off all the rainwater that falls on your plot is not quite advisable. "It should be the last resort," he says.
Recharging groundwater
"Most city plots have small surface areas, so the collection of water from direct rainfall is comparatively lesser than the water collected from the roof." Mr. Jose advises making use of the excess water for recharging the groundwater levels. Using sand piles to help the water get absorbed into the ground is one technique for increasing the re-charging. As the soil in Kochi is mostly clay, the absorption of water is also very less. But, using sand can increase the absorption levels. Make a sand pile and direct the water into it. Sand acts as a filter.
In city plots, even underground storage tanks for storing the rainwater could be built, with the house being situated on top of it. However, Mr. Jaigopal points out that using excess water for recharging the soil and water sources is highly difficult in areas with a high water table. "But, there are plenty of options in areas with a low water table."
Proper drainage
Providing a proper drainage is highly important, he points out. There can be different ways of providing drainage. Open drain is one idea. Another is, sub surface drainage. The sub-surface drain will not be visible over the surface, but will collect water through open joints. Maintenance is easier for such drains. Clogging, especially plastic clogging, is another issue causing water-logging. The maximum peak rainfall in an area in one hour should be considered ideally, for designing the drains for that area. However, water will not be absorbed by clay or rock. Hence in areas with clay or rocky sub-surface, groundwater recharging is very difficult.
Unproven method
A theoretical possibility of deep borewell recharging has been evolved, but it is yet to be practically proved, says Mr. Jaigopal. According to this theory, water can be recharged into deep underground through borewells. This water may, in turn, help to increase the water table of an area with rocky sub-surface or with a low water table.
