Philippines: Sipalay Flood Control Project
The City of Sipalay is one of the cities in the province of Negros Occidental, Philippines, located in the most southwestern part of Negros Island . The place has a long history of land use that contributed to the degrading state of its watersheds. Being a highly mineralized area, mining exploration has been the first and major industrial venture that has resulted in the operation of two mining companies since 1957. Both mining operations though, have been suspended in 2001 until to date.
In 1960 up to the early 1980, three logging companies were also operating in Sipalay and the adjoining municipalities. The combined operations of mining, logging and kaingin (slash & burn) farming, has resulted in significant changes in the upland landscape. Open -pit method of mining has exposed many areas to erosion and generated a lot of earth spoils and mining waste which find their way into Sipalay river. Although mine -tailing ponds have been established, breaching and spillage still occur releasing large volumes of mine tailing into the river system and were subsequently deposited in the coastal area. Much of the accretion occurring along the coast is attributed to the mining waste that accumulated over the years in the coastal zone. In addition, logging activities have brought about the denudation of the watershed, reduced its capacity to prevent flash floods and increase the level of erosion.
Flood Occurrence and Damages Assessment
Four serious typhoon/flooding events; Nov.1990, Aug.1994, Oct.1998 and Nov.2001 resulted to disruption in the overall socio-economic environment, namely:
a. Fatality or death due to drowning, extreme injuries:
b. Morbidity cases from wounds and illness related to flood water exposure
c. Indirect effect on environmental health from contamination of water sources and exposure to polluted waters.
d. Damage to housing and personal properties, and consequent dislocation of families.
Moreover, flood relief operations and assistance entail the utilization of resources that runs into millions of pesos, which otherwise could have been channelled to more productive and other pressing needs of the city government.
Formulation of Flood Mitigation Measures
In the light of the continuing and worsening problem of flooding and devastation, the city government initiated measures spearheaded by the City Mayor Oscar C. Montilla. The City council then passed a Resolution on August 2002 approving the hiring of the services of a consultancy group to conduct a thorough study of the flooding. The hydrographic survey of the Sipalay river and the topographic survey of the flood plain of the city provided a more in-depth analysis of the flood occurrences in the area. Thus, a two-fold set of measures was adopted to be implemented over the short to medium and long terms.
1. Short to medium term measures:
• the dredging of the Sipalay river channel from its mouth up to about a kilometre and a half upstream in order to increase the present capacity of the channel to facilitate more efficient transport of water towards the sea. (Maintenance dredging)
• construction of a cut-off channel upstream to shorten the Sipalay river channel by about one kilometre and produce a man -made oxbow lake corresponding to the present northbound bend
• Widening of cut-off channel
• The rivetment and slope protection works at critical river sections
• The necessity of reinforced dikes along the eroding outer side of Sipalay river
2. Long term measures:
• Land use policy/policy reform
• Institutional development
• Community mobilization/preparedness programs
Mitigation Measures Implementation by Project Components
A. Ground civil works:
Early part of 2002, the construction of dikes, elevation of river banks and cut-off channel went underway immediately after securing all pertinent Environmental Compliance Certificate. This was made possible because of the substantial number of construction equipment of the city government namely, big bulldozers, wheel loaders, backhoe excavators, road rollers and a fleet of dump trucks.
B. Dredging works
The dredging component of the project was the biggest challenge because of an instant high capital financial outlay requirement. Also, a special type of equipment is needed to do various jobs. The perceived financial burden to the city for the purchase of the said machine created a strong opposition from some members of the city council hence, the recourse at that time was for the city government to rent a dredger as recommended by other dredging contractor and equipment dealers. It was at this juncture that a Finnish- made dredging machine, the Watermaster, was presented to the council en-banc. The unique features for multi applications namely, suction and backhoe dredging, pile driving, the capability of moving in and out of the water without crane assistance was thoroughly scrutinized by the city council with the technical assistance of city engineers. Afterwards, the Bids and Award Committee insisted on seeing the machine operating on the site.
Hence a visit to the jobsite at San Fernando, in the province of Panpanga was arranged, where three Watermaster machines of the Department of Public Works and Highways (DPWH) were working. The machine performance sits well with the expectation of the visiting group and after a confirmatory review of the investment, operating cost vis a vis return of investment, the group finally recommended the purchase of one (1) unit for the project.
In May 2003, the Watermaster Classic III was delivered to Sipalay City and after the assembly and test run, operators and maintenance technical training was conducted by Watermaster factory engineer at the site and dredging operations started.
While dikes on the west side of the river were built by filling materials to elevate river bank, widening and excavating river channels and other civil works were done as planned using available land- based equipment.
On the other hand, the Watermaster started dredging the bay area at the river mouth and continually moved upstream. Dredged material was pumped on the shore line to reclaim and elevate the land.
After dredging for sometime, it worked in opening up the new 400m- long river channel towards upstream. Here, the Watermaster backhoe dredging was applied, hereby lifting the materials from the channel centre on the sides. Excavators on the sides assisted in finalising the new channel banks. During the work, the channel had 0-1 m water depth all the time, but this did not cause any problem to the Watermaster.
Environmental and Social Impact of the Project
The major part of the project was completed in one year time and its mitigating effects were already felt with the heavy rains/typhoon in 2004 and 2006. The city was spared the perennial flooding and devastation to the relief and security of the general populace. The current status of the project still requires some reinforcement and improvement. But by far, it has already tremendously alleviated the sufferings of the city inhabitants which could not have been possible without the crucial dredging operation of the Watermaster.
To date Watermaster has already logged-in over 11 000 working hours and has dredged vast amount of silt and sand. It is still continually on its maintenance dredging operation in the bay area at the mouth of the river.
The project, apart from arresting the devastation as a result of flooding, has also provided means of livelihood to the locals who are hauling and selling the dredged sands to be used in the manufacture of concrete hollow blocks. The widening and continuous dredging on the mouth of the river have provided easy access to the small fishermen going in and out from the mooring place making it easier for them to sell their catch.
The widened and longer shoreline brought about by the continuous dredging reclamation induces private entrepreneurs to set up of shops for dining and entertainment during night time which boosted local tourism. Such economic activities raise hopes for a better future for the city.
Source: watermaster, December 30, 2010