THIRUVANANTHAPURAM: Redesigning of the Amayizhanjan canal is the key to preventing flash floods in the city, experts say. But that’s not all.
Haphazard urbanisation and ‘plastering’ of land becoming a fad are factors contributing to flash floods, says a study by Geology Cafe, a forum of geologists in the city.
‘’First and foremost, the very design of the Amayizhanjan canal - a discharge way with masonry walls on both banks and practically of uniform width and depth - is against natural law or law of river flow. The waterway needs redesigning with a larger cross section area downstream. This will increase the velocity of flow in the upstream reaches as well. There is no point in deepening it as it will violate the equilibrium profile, or the base level,’’ says the study by Geology Cafe members K P Thrivikramji, professor emeritus, Geology Department, Kerala University; and K P Jaikiran, assistant professor, Geology Department, Kerala University.
The most recent flash floods, caused by a single night’s rain on Friday, was unique as well as a warning bell. It was for the first time that many areas, especially residential ones, faced nature’s fury. ‘’The recent flash floods had a different reason. Storm water which reached the city through rivers as well as the actual rains received in the city caused it,’’ Jaikiran said.
It is also time to think of a ‘’new’’ Amayizhanjan canal or sub-surface pipeline network to carry the flood water, said the study. Small water retention structures like ponds and sub-surface reservoirs are essential on the slopes of the city to check the flow of rain water. Drainage routes should be kept free of sediment and refuse.
‘’Last, but not the least, plastering of land (such as concreting of front and backyards of houses) should be done away with. Such unhealthy constructions direct storm water from residential plots into public roads and drains. Large plots that can hold and permit rain water to soak into the ground should be encouraged to do so to reduce storm water overload in low lying areas,’’ says the study.