2 6 ▁September ▁ 2 0 0 9 ▁at ▁about ▁ 6 : 0 0 ▁pm ▁P ST , ▁Ty ph oon ▁O nd oy ▁hit ▁Metro ▁Man ila ▁and ▁dump ed ▁one ▁month ' s ▁ra inf all ▁in ▁less ▁than ▁ 2 4 ▁hours , ▁causing ▁the ▁Mar ik ina ▁River ▁system , ▁including ▁the ▁Mang g ah an ▁Flo od way , ▁to ▁burst ▁its ▁banks ▁rapidly . ▁Al ong ▁with ▁flo oding ▁along ▁other ▁river ▁systems , ▁ 8 0 ▁percent ▁of ▁the ▁National ▁Capital ▁Region ▁became ▁flo oded . ▁Also ▁flo oded ▁were ▁ 2 5 ▁nearby ▁provinces . ▁In ▁Metro ▁Man ila ▁alone , ▁ ▁of ▁dirty ▁water ▁forced ▁people ▁to ▁ev acu ate ▁their ▁homes . ▁By ▁the ▁ 3 0 th ▁of ▁September ▁at ▁least ▁ 4 5 0 , 0 0 0 ▁inhabitants ▁had ▁been ▁disp la ced , ▁with ▁at ▁last ▁ 3 8 0 , 0 0 0 ▁forced ▁into ▁makes h ift ▁sh el ters ; ▁ 2 4 6 ▁people ▁were ▁reported ▁dead . ▁It ▁is ▁believed ▁that ▁blocked ▁pip es , ▁a ▁poor ly ▁maintained ▁se wer age ▁system , ▁and ▁un collect ed ▁domestic ▁waste ▁were ▁major ▁factors ▁in ▁the ▁speed ▁with ▁which ▁the ▁flo od ▁waters ▁eng ulf ed ▁the ▁surrounding ▁area . ▁This ▁prompt ed ▁President ▁Gl oria ▁Mac ap ag al - Ar roy o ▁to ▁declare ▁a ▁State ▁of ▁National ▁Cal am ity ▁and ▁set ▁up ▁a ▁task ▁force ▁to ▁rescue ▁the ▁inhabitants .