| The Pampanga River in Luzon Island is affected by floods almost every year to suspend local functions. Land classification revealed that Pampanga’s fluvial plain flanked by Sierra Madre and Zambales mountains with Mt. Pinatubo’s volcanic land, is divided into fan, alluvial surface (high, middle and low), back swamp, delta, meander scroll, and valley plain. Flood easily concentrates in this basin-like fluvial plain, and lower alluvial surface and delta located in the most downstream portion are easily inundated by enhanced floods due to land subsidence and tidal effects. Both back swamps of San Antonio and Candaba in the north and east of Mt. Arayat, respectively, are heavily inundated but take important roles as retarding basins. Interview survey revealed that inundation depth by typhoon Pedring and Quiel in 2011 became more than 2 m and continued more than a month at barangay San Agustin, Candaba municipality in the margin of Candaba swamp. Local residents there live stilt houses with almost 3-m-high pillars to adapt seasonal floods, mainly conducting rice cultivation in dry season and fishery in rainy season to get maximum benefits under the seasonally changing environment. Also, Calumpit municipality located in the end of lower alluvial surface, which is one of the most flood-prone municipalities in the region, experienced the suspension of municipal functions due to severe inundation of the municipal hall during 2011 floods. While floods are frequent during rainy season, drought often happens in irrigation sectors because of shortage of water resources and deficiency of irrigation management. Understanding local lifestyles and revealing characteristics of fluvial systems based on flow observation, topographic and subsurface geological information with past disaster records are important to predict and mitigate future water-related disaster risk. |
