pp2 Findings

Institute for Environmental Conservation and Research (INECAR) Ateneo de Naga University, Naga CIty
Position Paper No. 2 Prioritize the protection of the town of Sogod and barangays located along the banks of Subang Daku River, Sogod, Southern Leyte
II. Findings
Meanders are created when the velocity of the river slows down after traveling fast from upstream in the mountain towards lesser slope downstream as the river moves towards the sea. This is more evident when the riverbed contains sediments of various sizes causing uneven flow of water resulting to meandering of the river channels. Sometimes, harder rock layers can obstruct the flow of water causing it to bend (see Figures 3 and 4). In Subang Daku, the meander slows down the release of silt to Sogod Bay because of the erosional and depositional behavior of the meander (Figure 21) that reduces the speed of water flow.
		Figure 21 (left): Location of areas of deposition (dep) and erosion (ero) in meandering river. The maximum velocities of each section are also indicated in the figure. (adapted from Plummer, McGeary and Carlson, 1999)
Figure 21 above shows that in a meandering stream, although there are areas of maximum speed that cause erosion of banks along concave bends, there is a reduction of speed of water flow due to obstruction and erosion along the concave path and where deposition of materials occurs along the convex bend of the meander. However, a meandering stream even when rechanneled/ straightened, most often revert to its old meanders (Montgomery, 1997). This is due to the condition of the slope upstream where the presence of sediments of various sizes and the energy of dropping water including obstruction along the path of water flow, caused bending of the direction of the river flow. Thus, the probable reasons why a portion of the road and banks in Barangay San Miguel has been destroyed are: a) increased in energy upstream as a result of rechanneling downstream and b) the river has been fragmented by quarrying operations creating channels that are directed towards the area of the barangay concerned. Figure 22, 23 and 24 below present some examples of the resulting fragmentation of Subang Daku River.

		Figures 22, 23 and 24: Some examples of fragmentation of river channels in Subang Daku causing channels to be cut-off and preventing aquatic organisms from going through its natural cycle of traveling along the river channels going upstream and vice versa. (1st picture captured from video documentary c/o SSDM Dec. 2001; last 2 pictures taken by Dr. E. G. Regis, May, 2002)

Figures 25 (left) and 26 (right): Effects on the river structure and ecosystem by quarrying are shown in these figures. Figure 25 show how deep the river basin has become. (pictures provided by SSDM)
		Figures 27 (left): Destruction of the road in San Miguel last December, 2001. Note the bend (pointed by a yellow arrow) of one of the channels that destroyed the road. This happened because of fragmentation of the river channels due to quarrying. Fragmented river channel created a section inclined in such as way that it would hit this part of the riverbank. (picture captured from video documentary, Dec. 2001)
Even if Shemberg says that the area in question is not part of their concession (which is some “300 meters below” the destroyed area), their quarrying operations have considerably reduced the amount of material in the river downstream as well as increased the river slope. Consequently, the speed of the water flow became much faster and stronger in eroding fine sediments which are carried to the sea. Similarly, the rechannelization has shortened and widened the river channel which caused it to carry higher volume of water at shorter distance, thus, facilitated the movement of sediments downstream eventually causing siltation of Sogod Bay (Figures 28A and 28B). In 1994, just after rechanneling done by Shemberg, large amount of silt was immediately released in Sogod Bay Figures 28A and 28B). At present, although unnoticed, siltation of Sogod Bay coming from Subang Daku is still going on and being dispersed in the bay. Such condition gives a false picture of what is really happening to the bay. It gives a wrong signal to Sogodnons and adjacent villages that everything is all right. Realization might come too late for remediation to mitigate a more serious problem which is the reduction in the productivity of the bay. The people that will most likely be impacted will be the fishermen and those that depend on the bay for cheap source of food.

*Figures 28 A(left) and 28 B(right). A is the view of the horizontal plume of silt coming out from Subang Daku river. B is a close-up view of the silt near the barge (used by Shemberg) that was docked near the mouth of the river. These pictures taken by the undersigned in the summer of 1994 just after rechanneling activities were initiated. (pictures taken by Dr. E. G. Regis, Summer, 1994)
D. Changes in river dynamics as a result of Ltrs. C contributed to the rapid siltation of Sogod Bay thereby affecting its fisheries and ecological relationship with Subang Daku Sogod Bay is home to a variety of fishes. It is a major fishing ground for the nine (9) municipalities surrounding the bay. “Mangku” (Euthynnus affinis) is its major fishery resource. Seasonal influx of Mangku has provided food and livelihood to the people of Sogod and nearby municipalities. The Study of Sogod Bay by Siliman University in 1994 mentioned that there are seven (7) finfish species that are pelagic and are harvested when they enter the bay. Recently, there have been reports of whaleshark sightings in the bay (http://www.whitetip.com/divingwshark.html). This rare mammal is already a protected species. Its food are the tiny crustaceans that are eaten like “soup”. As an ecosystem, Subang Daku performs a role that allows harmonious relationship with organisms thriving in Sogod Bay. However, some factors may have disturbed the lives and life cycles of aquatic organisms. These are: 1) noise such as those caused by grinding of rocks during quarrying operation; b) fragmentation of river system preventing travel of aquatic organisms through a continuous river channel; c) silt deposited in the sea which is facilitated by rechanneling activities (see explanation under rechanneling section). The resulting fragmentation and siltation of Sogod Bay may have disturbed the life cycle of some organisms that require movement between the sea and the freshwater ecosystem such as Subang Daku. For instance, the behavior of a certain crab named locally as “Kamwa”, has been reported by one of the local inhabitant who followed the crab upstream and found that the path the young traveled from the sea to upstream of Subang Daku reached until Barangay San Juan about 120 meters above sea level (asl). The behavior of this crab was that the adult laid eggs in the sea and when the eggs are hatched, the baby crabs traveled upstream. Other species observed and/or reported downstream were “Katang”, “Uang” (fresh water shrimp), a small mollusk (a gastropod) having some spines on its shell locally known as Odianga and two kinds of freshwater fishes. Rapid siltation of Sogod Bay is brought about by human activities, such as quarrying and rechanneling. These activities have also been mentioned in the study of Siliman University (1994), that “sand and gravel mining” (p. 40 of report) and “rechanneling and sand harvest near the mouth” (Table 3.3 p. 41), as other causes of degraded habitats and major water quality issues of the area. The same report mentioned mining (quarrying is a type of mining) as one of the harmful practices that the bay should be protected from. Quarrying however may be regulated through setting up of certain controls. This also holds true for rechanneling that require competent planning based on scientific evidences and not only on the opinion of some people. Thus, proper planning, regulations and monitoring, Subang Daku can be saved from further destruction. As a result. siltation of Sogod Bay will also be reduced, thus, help save its fishery resources which benefit a large number of people residing along its shore.

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