|
|
THE
BOLINAO-BANI-ALAMINOS COASTAL SYSTEM: A GIS-BASED
EVALUATION OF WATERSHED SEDIMENTATION POTENTIAL AND
POSSIBILITIES FOR MANGROVE AND UPLAND MITIGATING
PROGRAMS
M. Bernadette
B. de Venecia 1,2 , Laura T. David 1,
Erlinda E. Salamante 1, Joel B. Abunda
3, Napo Cayabyab 4, Severino
G. Salmo III 1, Rene N. Rollon 4,
Evangeline T. Magdayao 1,and Cesar L.
Villanoy 1 |
|
1 The Marine Science
Institute, University of the Philippines, Diliman, Quezon City
1101
2 University of Asia and the Pacific, Pearl Drive,
Ortigas Center
3 Bureau of Agricultural Research, Department of
Agriculture, Diliman, Quezon City
4 Institute of Environmental Science and Meteorology,
University of the Philippines, Diliman, Quezon City 1101
Corresponding author: M.B. de
Venecia; Present address: The Marine Science Institute,
University of the Philippines, Diliman, Quezon City; telefax
922-3957; devenecia@upmsi.ph
ABSTRACT
A current environmental concern is
the perceived shallowing bathymetry of the Bolinao-Bani-Alaminos
coastal system – site of a major mariculture industry in
Pangasinan. Its broader problem of coastal sedimentation could
have several factors: upland deforestation, which increases
erosion; deforestation of mangroves, which inhibits sediment
trapping; high density of mariculture structures, which slows
sediment flushing out of the bay; and accumulation of excess
aquaculture feeds. This study makes use of geographic
information systems to evaluate the sedimentation potential of
the Alaminos of the Bani watersheds that influence these coastal
waters.
Upland areas of severe erosion were associated with grasslands
and shifting cultivation practice. Agricultural activity
dominates the coastal plains. Information on slope, land cover,
precipitation, and soil erosion were integrated to evaluate the
relative erosion potential (REP) of the watersheds. The REP
values indicate low upland sedimentation threat levels, likely
attributed to low relief of the areas. Information on mangrove
cover was determined to evaluate current sediment trapping
potentials. Only 0.5 % of the estimated probable original
mangrove cover remains. The conversion of mangroves to
fishponds, may have drastically reduced the sediment trapping
capacity of the coastal interphase. Previous studies have shown
that the high density of mariculture structures results in poor
flushing of coastal waters. This could result in the
accumulation of excess feeds released in aquaculture.
Upland reforestation as a resource management strategy takes on
low priority. Mangrove reforestation, regulation of mariculture
structures, and re-evaluation of aquaculture feed utilization
are projected areas of high priority for a mitigation program to
address coastal sedimentation.
|
|
