DEVISING MANNING’S “N” ROUGHNESS COEFFICIENT AS AN ANALYTICAL APPROACH TO ASSESS THE UPLAND FLOOD BUFFERING CAPACITIES OF RIVERINE MANGROVES

Mangroves are the primary protector of the coastal ecosystem against flood, surge or enormous waves. They can dissipate the negative impact of these natural hazards for the biotic and abiotic factors in the marine zone. The study provides an analytical approach in describing the buffering capacities of mangroves in the riverine system against upland flooding. The study utilized the Manning’s “n” Roughness Coefficient for irregular open channel to deliver a systematic procedure in estimating the buffering capacities of mangroves against flooding. The study was conducted in the mangrove ecosystem of Sukol River, Bongabong, Oriental Mindoro, Philippines. Based on the result of the study, using the regular condition of the water current in Sukol River as basis of estimation, the mangroves of the study site reduced the velocity of river water by 0.57 m/s with a discharge of 190.12 m3/s engaging a 2691.64 cfs flow rate. This is an implication that the mangroves influenced the movement of floodwater when they reached this ecosystem during the run-off. The test implies that Manning’s “n” Roughness Coefficient is an efficient tool in evaluating the capacities of mangrove ecosystem in buffering the upland flooding. The procedure using the abovementioned approach provides a more logical analysis in the role of mangroves to disintegrate upland flooding.