Mumbai and many parts if India have been hammered by torrential rains. While on one hand, high rainfall has reduced anxiety about water level in reservoirs, on the other hand there have been many reports of collapse of buildings and bridges. In a recent unfortunate incident, three young students lost their lives by drowning in a basement!

There is a mistaken belief in the mind of the common man that structures become weaker during monsoon. Most of the cases of collapse of bridges are not due to structural weakness of the bridge foundations, but on account of erosion of riverbed, known as ‘scour ’, in Bridge Engineering jargon. Excessive scour can be caused by sudden gush of flood water and locations in the foothills of mountain ranges are prone to this phenomenon. Increase in incidences of extreme weather events is claimed to be a consequence of global warming. It is likely that every monsoon season will have such extreme weather events leading to collapse of more bridges in sub-mountainous regions.

Collapsing buildings in urban regions is, however, not attributed to scour, but may be caused by reduction in the bearing capacity of the soil in saturated condition. Unauthorised addition of floors which causes extra bearing pressure coupled with reduced bearing capacity can result in such events. For collapse to take place, even small differential settlement is often enough. Dilapidated and distressed buildings which have little redundancy left in the structure are very sensitive to such changes. Lack of adequate drainage compounds the problem.

While one expects the ‘authorities’ to do something about it, we the citizens need to ensure that we do not add to the problem by littering, choking the drains, making unauthorized changes in structure etc.