As exposed by this writer as early as four years ago in my column with The Daily Guardian in October 6, 2008 headlined: Reservations and Misgivings on the Jica Flood Control Project”, which I will partially quote: “If the end portion is straightened and concretized as in the Jica Flood Control Project in Iloilo City, then it (the rivers) will vent its ire UPSTREAM in Pavia, San Miguel, Sta. Barbara and Cabatuan.” Now it is proven that the four-km STRAIGHT floodway from Tacas to the sea had caused the tremendous erosion on the river banks and bridges upstream of the Jica Flood Control Project. The straight floodway defies nature’s way of creating rivers which are SINUOUS and WINDING. The straight floodway enhances speed of flow because there is no frequent bend where the river can dissipate excess flow energy to maintain a slow and safe river flow.
Because of this exposé by this writer and with the prodding of Governor Art Defensor Sr. and Mayor Cads Gorriceta, DPWH had initiated repair measures here in Pavia as in the Tigum Bridge, Tulay Ng Pangulo Bridge and in Maliao Creek. The problem now is that in the process of repairing the eroded base of Tulay Ng Pangulo bridge, the foundation gave way a week ago causing the bridge to tilt on one side. Since that time on, work has stopped because the contractor has not returned.
The onset of the rainy season is very imminent. When the first flood comes and the Tulay Ng Pangulo is not repaired, then it will surely totally collapse in the river. Urgent measures should be done NOW to correct the tilting and reinforce the base before the rain comes this June. The contractor had started in the right direction by using the Gabion system (a French design using large stones or boulders then wrap it with mesh wire to protect river banks) but it has miscalculated the eroded bank that when they started excavating right under the bridge, the foundation gave way causing this dangerous tilt of the bridge.
While the Municipal government of Pavia appreciates the repair efforts of DPWH, still to this writer these repairs are just palliative or “band aid” solution. DPWH should admit that the root cause of all these abnormal river erosion during flooding is the straight floodway. Up to this writing DPWH will not accept that the straight floodway produces a SIPHON effect so that water flow of rivers upstream of the project have tremendously increased in speed. All the people living along the banks of Tigum, Maliao and Aganan river will attest to this.
Once DPWH admits that it is the straight floodway that caused all the erosion woes upstream, then they can do remedial measures to RETARD river flow, short of destroying the straight floodway and return it to a sinuous or winding channel. Flow RETARDERS can be installed like boulder humps as in subdivision roads to slow down cars, channel constrictors also made of boulders and many others which I believe the DPWH engineers are expert on this. Maximizing water load of the Jaro River without flooding Jaro area will also reduce water load of the straight floodway. The Jaro River is a natural meandering and sinuous river created by nature so the water speed is not as fast as in the straight floodway. The comment of the Iloilo Flood Control Project (IFCP) staff is that the Jaro River should be widened first! This Japanese mentality of structure mania approach is never the solution to flooding and erosion.
A river is like a human being that reacts to the load (water and sediments) given by the watershed. Within reasonable limits, it can adjust its width, depth and meander if there is an increase in its load. Beyond its equilibrium capacity, the river fights back by destroying its banks and overflows to the plains. It is not within the power of man to create a straight river that is harmless to the environment.
May 18,2013 12:52 AM
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