Why it will take some time for Laguna Lake floodwaters to subside?

Ateneo Innovation and Entrepreneurship



Many people living near the coast of Laguna Lake are inundated because of the high level of floodwater/lakewater at Laguna Lake.  It will take at least 3 months, if the rain stops, to get rid of water in Taguig, Angono, Taytay, Pateros and ther low lying coastal areas.

Why?  Because of the dynamics of the floodway, Napindan channel system.

l.  The floodway was builtto save Manila (and Malacanang) from flooding, thus floodwater
from Marikina river were diverted to the Manggahan floodway  and Laguna Lake.  The impounding storage area is the Laguna lake.

2.  The Laguna Lake is drained via the Napindan channel which drains to the Pasig River and eventually to Manila Bay.  The distance from Laguna Lake to Manila Bay is long.

3.  The draining of the Laguna Lake has to be carefully tittered otherwise,  there will be more flooding.  The Napindan channel will be opened to drain to Pasig River/Manila Bay when it is low tide.  But that must be timed in such a way that the Pasig River level has gone down.(and drained to the Manila Bay)  There is a narrow window (only 4 hours) to drain the lake thus it takes eons to remove water by this draining method;  a hot weather can speed up evaporation though.

The original plan calls for a spillway that is much nearer but could not push through because of the objection of the  residents.  Since the distance is shorter (some 5km vs the Napindan channel of l0+ km) draining the lake would be faster.   However, that would take 5 to 10 years planning if ever we get people to say yes?

Wikipedia on Manggahan floodway

UP Diliman Study of Manggahan floodway, Cambridge and informal settlers



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