Philippines Information Agency 18 Nov 11;
TACLOBAN CITY, Leyte, Nov. 18 (PIA) -- The Mines and Geosciences Bureau (MGB) of the Department of Environment and Natural Resources (DENR) called on local government units to consider the setting up of mangrove plantations as natural and nonstructural blockade to flooding during heavy rains and typhoons.
“To mitigate the effects of natural disasters, it is significant that the local government units should consider going “green” by planting mangroves along coastal areas and riverbanks which will provide communities protection from runoffs and flooding,” MGB-8 Director Roger A. De Dios underscored.
The pronouncement was made in relation to the report of the Geohazard Mapping and Assessment Team (GMAT) of the MGB after the conduct of rapid geohazard mapping and assessment survey in a 1:10,000 scale map of the 44 built-up barangays of Borongan City in Eastern Samar.
The team led by MGB-8 Chief Geologist James S. Leones observed that flood generally occurs during inclement weather and high tide on most communities of Borongan City due to flat and lowland topography and its being surrounded by major rivers that include Can-obing, Loom, Borongan, Maypangdan and Tabunan.
The team’s recommendation was that aside from dikes, retaining walls, groins and breakwaters, officials should also consider mangrove plantations as natural and nonstructural blockade to flooding during heavy rains and typhoons.
The mangrove plantations help in stabilization of banks and prevent soil erosion during floods and reduce sedimentation of ponds during flood. Field, laboratory and numerical studies show that mangrove forest and other coastal vegetation of certain density can reduce wave height considerably and protect the coast from erosion, as well as effectively prevent coastal sand dune movement during strong winds.
Healthy coastal forests such as mangroves and saltmarshes can serve as a coastal defense system where they grow in equilibrium with erosion and accretion processes generated by waves, winds and other natural actions.
Geologist Leones encouraged local officials to address the indiscriminate cutting of trees, improper solid waste disposal and the provision of adequate and efficient drainage system.
As a coastal community proximate to the Pacific Ocean, Borongan City is not spared from the threat of tsunami, Leones said.
The report stated that destructive tsunami waves are likely to surface should an earthquake of 7.0 or more magnitude will occur at the Philippine Trench east of Eastern Visayas.
The GMAT also provided landslide threat advisory to inform barangay officials on areas vulnerable to landslides with its corresponding recommendations. (PIA 8)
