MANILA, Philippines (AP) — Lashed each year by typhoons and stuck with outdated drainage systems, the Philippine capital has been hit by ever-worsening floods. Population growth, inadequate infrastructure, corruption, deforestation and even trash build-up combine to exacerbate the impact. It's a trend experts expect to continue.

MANILA, Philippines – The entire Metro Manila has been placed under a state of calamity due to heavy rain and flood brought by the southwest monsoon or habagat enhanced by Typhoon Carina (Gaemi).

Unlike in Taiwan, the typhoon – known locally as Carina – didn’t make landfall in the Philippines, but its powerful outer bands dumped more than 300 mm (12 inches) of rain in the Manila region and parts of the main island Luzon, prompting officials to declare a “state of calamity” in the capital on Wednesday and evacuate tens of thousands of people.

Intense rainfall in the catchments forced dam managers to open floodgates, compounding flooding from urban rainfall. Floodwaters carry debris and waste through cities and homes. When they recede, they leave behind a higher risk of disease.

At least 22 cities and municipalities have declared a state of calamity. The move will allow the release of emergency funds and hasten rehabilitation efforts. A shear line — the point where warm and cold air meet — triggered heavy rains in parts of the country last week, causing the floods, the state weather bureau said.