not really! there are technologies that can convert these pesky aquatic plants into renewable energy (oil & gas) and potable water. if government funds can only be diverted to projects using the technology, energy demand (for transport fuel and domestic cooking gas) can be supplemented and precious water can be recovered for domestic consumption.
the real culprit why the growth reached this situation is precisely the manggahan floodway itself. as i understand the purpose of the floodway is for containment and control of the flood waters, which remains closed until floodwaters need to be released to ease flooding in residential areas.
this scenario is a perfect condition to grow aquatic plants as nutrients from domestic, commercial and industrial waste continue to flow and reside in the floodwaters. aquatic plants feeds on the nutrients overload, hastened by sunlight. if one is only observant, these pesky aquatic plants grow very fast during summer where there is plenty of sunlight and floodways closed.
a simple solution is to implement a routine schedule of water releases (say every 2 weeks and when rain comes) from the floodways to replenish the stagnant water and remove the nutrients.