GEOPHYSICAL CHANGES DETECTION BY REMOTE SENSING IN ALAMINOS RIVER PANGASINAN, PHILIPPINES

摘要

Geophysical changes of the river outlets, riverbanks and coastlines in Alaminos, Pangasinan were measured using Google Earth from 2009 to 2014. On the other hand, actual measurements were gathered using South Total Station (NTS-362R6L) in 2015. The insight of the residents regarding feature changes of the river were obtained through one on one interview. Root Mean Square Errors (RMSE) were computed for measurement and horizontal positional accuracy of Google Earth. To perceive the effects of sea levels, historical data (2004-2015) from Bolinao, Philippines Tide Chart at online tides and currents predictions were also analyzed. Alaminos river outlets decreased in width size due to natural factor and human activities. Alaminos riverbank increased in width size which could be possibly due to natural calamities and weak bank resistance brought about by the frequent flooding caused by heavy rains and the emergency released of water from San Roque Dam. Generally the north and south coasts of Alaminos River increased and expanded. Rise in sea level is also a probable cause of changes wherein heights of low tides in Pangasinan Gulf is increasing overtime. The computed RMSE was low which indicate positional accuracy and measurement of Google Earth in the study area.