Erosion and sediment shortage

As discussed in Section 3.3, mangroves have largely disappeared and replaced man-made fishponds, pushing the original coastline into Manila Bay. Due to the loss of mangrove areas, the North Manila Bay Delta coastal area holds way fewer natural sediments than 70 years ago. This could mean:

  • The sediments supposed to be deposited are being hindered from arriving in North Manila Bay Delta upstream of the rivers.

  • Sediments are directly transported into Manila Bay due to the canalized rivers and therefore do not get a chance to deposit in the North Manila Bay Delta.

  • Due to the removal of mangroves and the shortage of sediments, erosion is a frequently occurring problem. The pace of the process depends on both continuing events (sediment shortage) and instantaneous events (storm waves). The process impacts the current man-made structures in the area, as can be seen in figures below.

  • The ongoing subsidence changed the erosion/sedimentation balance towards more erosion.

Examples of erosion of man-made structures.