Thursday, July 26, 2007

Will There be a Flood?

With so much rain the last few days, flood is on my mind. At a dinner last night I talked with a Water Engineer (someone who works at the Water Modelling Institute in Dhaka.) Here are some things he said:

1. It is too early to say if there will be flooding this year. Apparently the rainfall-to-date is about average.

2. A main reason for flooding is the simultaneous cresting of the Padma, Jamuna and Meghna rivers (or sometimes Jamuna and Meghna.) If this happens (mid-August, my friend thought) we will get Flooded.

3. The roads and alleys in Dhaka which go underwater during heavy rain are not "Flooded" per se - the water experts consider them drainage-congestion-induced waterlogging.

4. When Dhaka gets flooded water enters from the rivers through the drainage system.

5. Waterlogged places often get sewage mixed into the water because the sewage system is not isolated but rather designed so that normal rainwater enters and pushes the sewage out. So too much water allows the sewage into the streets. Ugh. Isn't it possible to build a one-way valve?

6. Dhaka once had a wonderful canal system that did not requires drains. Much has been written on this lately. I guess waterlogged streets remind people of the good old days.

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