Rationale• Watersheds are primary sources of quality water fordomestic, irrigation, hydropower, industrial, fisheryand recreational uses.• Excessive logging, shifting cultivation etc. havetriggered the degradation of watershed- accelerated soil erosion; siltation/sedimentationofrivers, lakes and waterways; and, water pollution.• Information on the site conditions of the Watershedis wanting.
RationaleThe Bued river watershed drains towardsRosario in La Union, Sison, San Fabian, SanJacinto and Mangaldan in Pangasinan.
RationaleThe historic and scenic Kennon Road islocated in this watershed where beautifulwaterfalls, hot springs and the famouszigzag road can be seen.
RationaleThe communication facility for northernLuzon is sited at Mt. Sto. Tomas while thereare other ecotourism spots found upstreamlike the Camp John Hay, Philippine MilitaryAcademy, and the Philippine EconomicZone.
RationaleDuring heavy rainfall/adverse weather conditions,Bued River contributes high volume of flood watersto low lying areas like when typhoon Ondoy andPeping hit the area where some properties weredestroyed and endangering the lives of people.
• Why conduct vulnerability assessment?- Tool in planning for sustainable developmentof watersheds and its natural resources- It identifies strength and weaknesses of thewatershed in relation to the identified hazards- It provides decision-makers with informationas to where and when interventions should bemade>to reduce/prevent damage or enhancecoping capacity of an ecosystem
4. To formulate mitigating measures to reduce damagecaused by natural and man-made hazards as well asimprove the condition of the watershed; and5. To review and recommend policy directions forsustainable management of the Bued river watershedwithin Benguet Province.
Creation of Regional TechnicalWorking Group for VulnerabilityAssessmentCoordination with Stakeholders
STARTAssessment of WatershedCharacterization DocumentsYESNOa) Biophysicalb) Socio-economic assessmentHazard Identificationand AnalysisCritical Factor AnalysisEnvironmental / GIS AnalysisMitigation Opportunities
MethodologyB. Data GatheringReconnaissanceSurveySecondary Data• Temporal (rainfallamount)• Spatialinformation(topographic map,soil map, landusemap, politicalboundary, raingage station, roadnetworks, rivers,etc)
B. Data GatheringPrimary Data• Water resources (Quality, Quantity)• Soil parameters (pH, OM, soil texture, soil profile)• Flora and Fauna• Socio-economic data• Location of infrastructures• Location of monitoring stations, landslide andflood-prone areas
C. Hazard identification and MappingHazards occurring in the watershed were identifiedHazard information from MGB, PAGASA and otheragenciesHazards and its contributory factors weredetermined through FGD with watershed occupantsand other key informants.Generation of Thematic Maps (contour, soil,landuse, rainfall, geology, fault lines, roads, rivernetworks, etc.)
D. Identification of Critical FactorsE. Hazard MappingF. Analysis of Factors
A. Description of the BuedRiver Watershed– It is located in Benguetbetween 120º30’45” to120º38’50” E longitude and16º14’00” to 16º24’30” Nlatitude.– It covers 6 barangays ofTuba: Camp 1, Tabaan Sur,Twin Peaks, Camp 3, Camp4, and portion of Poblacion– Small portions of BarangaysVirac and Ampucao inItogon, Benguet– 25 Barangays in southernpart of Baguio City
A. Description of Bued River Watershed– Total area is about 14,302 hectares– Mean elevation is 1,091.25 masl– Highest elevation is 2240 masl– The lowest elevation is 180 masl– Type I Climatic type
A. Description of the Bued River Watershed– The dominant slope class category is from 25-34.9%,followed by 35-45%– The mean slope is 31.96%Slope Area (ha) %Class0 –13.9% 2224.05 15.5514 –24.9% 3010.94 21.0525 –34.9% 3775.27 26.4035 –45% 3509.44 24.54> 45% 1782.36 12.46
Watershed Geo-morphological FeaturesParametersValueArea14,302 hectaresElongation ratio 0.738Circularity Ratio 0.458Compactness coefficient (K c) 0.677Max. elevation2240 maslMin. elevation180 maslLocal relief2060 mMean slope 31.96%Stream length (total) 149 km. (24.36km-main)Drainage density 1.04 km of streams/ km 2Aspectsouthwest
Hazard IdentificationWatershed characterization and Focus GroupDiscussion with occupants in the watershedrevealed two major hazards with serious effect inthe area. These are:1. Landslide2. Forest/grassland fire
GIS-Approach Landslide Analysis*Overlaying*Every thematic map has different weight andinfluencing factor. Relative weights wereassigned and rated by the team experts.
RATED THEMATIC MAPS (0-5)SLOPE MAPSOIL MAPRAINFALL MAPFAULT/ROCKFRACTURINGROAD/RIVER CUTTYPHOONFREQUENCYLITHOLOGYLAND COVERWEIGHT FACTORSLOPE MAPSOIL MAPRAINFALL MAPLITHOLOGIC MAPLAND COVER MAPROCK FRACTURINGRIVER CUT MAPROAD CUT MAPOCCUPANCYFARMING PRACTICEGROUND DISTURBANCEVulnerability due to Biophysical FactorsVulnerability due to Anthropogenic FactorsVULNERABILITY MAPSchematic Diagram of GIS assisted vulnerability assessment
*For assessing landslide vulnerability due to physical factors,the resulting thematic maps (slope, soil, geology/seismic, landuse, and climate) were assigned with corresponding hazardrating.*Then, relative weights were assigned and overlaid based on thefollowing relationship to compute for vulnerability:Landslide Vulnerability = [(Rated Slope Map * 0.25) + (RatedSoil Type/Morphology Map * 0.10) + (Rated Rainfall Map *0.15)+(Rated typhoon frequency Map * 0.15) + (RatedGeologic Formation/Geologic Age * 0.10) + (Rated RockFracturing/Fault line * 0.10) + (Rated Land Use/Cover Map* 0.15)]Landslide = [(0.90)(Biophysical Factors) +(0.10)(Anthropogenic Factors)]
Summary of Factors Affecting Vulnerability to Landslide(BUED RIVER WATERSHED)ITEM Weights Rating COMPUTED DESCRIPTIVERATING VULNERABILITYA. BIOPHYSICAL FACTOR 0.90 3.22* Slope and terrain 0.25 4.00 1.00 High* Soil 0.10 4.50 0.45 Very High* Rainfall 0.15 3.00 0.45 Moderate* Typhoon Frequency 0.15 4.00 0.60 High* Geologic Age 0.10 3.82 0.38 High* Land cover 0.15 2.65 0.40 Low* Rock fracturing/fault line 0.10 2.96 0.30 ModerateB. ANTHROPOGENIC FACTORS 0.10 0.39* Farming System 0.35 3.90 1.37 High* Ground Disturbance by human activities 0.35 4.40 1.54 Very High* Occupancy and habitations 0.30 3.20 0.96 ModerateOverall Computed Average Rating 3.60 High
Summary of Factors Affecting Vulnerability to FIRE(BUED RIVER WATERSHED)ITEM RATING DESCRIPTIVEVULNERABILITYA. BIOPHYSICAL FACTOR (40%)• Dry fuel materials• Vegetation• Slope and terrain• Aspect in relation to wind and exposure• Wind velocity and direction• Dry spell• Fire breaks• Natural barriers• Proximity to fire prone areas• Accessibility• Infrastructure3.563.563.892.673.784.223.003.114.334.223.78Average Biophysical Factors (40%) 1.46Highly vulnerableHighly vulnerableHighly vulnerableLow vulnerabilityHighly vulnerableVery highly vulnerableModerately vulnerableModerately vulnerableVery highly vulnerableVery highly vulnerableHighly vulnerable
Summary of Factors Affecting Vulnerability to FIRE(BUED RIVER WATERSHED)B. ANTHROPOGENIC FACTORS (60%)1. Socio-cultural• Access/property rights• Social kit• Leadership• Incendiarism2. Psycho-sociological• Awareness/knowledge• Beliefs• Perceptions• Attitudes3. Economic• Household/community economy• Markets and Prices• Capital Investment4. Technology5. Political/Institutional• Institutions• Policies2.781.781.892.442.782.111.782.672.442.783.563.003.002.89Low vulnerabilityNot vulnerableNot vulnerableLow vulnerabilityLow vulnerabilityLow vulnerabilityNot vulnerableLow vulnerabilityLow vulnerabilityLow vulnerabilityHighly vulnerableModerately vulnerableModerately vulnerableModerately vulnerableAverage Anthropogenic Factor (60%) 1.54Overall Computed Average Rating 3.00 Moderately vulnerable
Thematic Maps asModel Inputs
Typhoon Incidence Map
‣ The vulnerability assessment of the Buedriver watershed showed that the area is highlyvulnerable to landslides and moderatelyvulnerable to forest/grassland fires.
‣Through the geographic and spatial results,location of potential landslide areas andpotential fire-prone areas can be pinpointed.
The following results were obtained:1)Areas that needs rehabilitation weredetermined (i.e along Kennon Road);
2) More effective ways to respond to the needof the watershed in terms of policy anddecision-making as well as strategizingmitigation measures to minimize theoccurrence of landslides and forest fires arerecommended;
3) The result could be a useful bases by theLGUs in deciding the areas to be grantedpermit for resource extraction or in sitingdevelopment undertaking without adverseeffect to the watershed ecosystem and anaid in identifying areas where further studythat are both important and urgent can belocated.
‣ In terms of forest fire, several documentsproved that in the Philippine context, that theoccurrence of forest/grassland fire isgenerally anthropogenic in nature.
BASED ON THE RESULTS OF THE STUDIES, THEFOLLOWING RECOMMENDATIONS AREFORMULATED:1. The study should be further validatedby gathering more data on the actualoccurrence of landslide and fire;
2. Watershed Management Planningshould consider vulnerabilityassessment results.
3. Result of Vulnerability Assessment shouldbe presented to local LGUs so it can beincorporated in the community andmunicipal comprehensive land use plan(CLUPs). This would ensure saving of livesand properties and government money;
4. Infrastructures and settlements must beavoided in areas with moderate to highlandslide vulnerability (steep slopes, unstablegeology and near fault lines) specifically withinthe stretch of barangays Camp 4 and TwinPeaks;
5. There is a need of continuousmonitoring of landslides (DENR andLGUs);
RECOMMENDATIONS6. Upper slopes of roads constructed insteeper slopes must be supported withripraps;
7. LGUs and other government agencies(DPWH, DENR) must install warning signson the hazard prone areas to warnprospective developers and investors;
8. In road construction, appropriateengineering measures such as retainingwalls, drainage canals and diversion ofwater to prevent scouring of slopes shouldbe implemented particularly in road cutareas to prevent the occurrence oflandslide;
9. Intensive IEC campaign must be done through“barangay pulong-pulong”. GIS maps of landslideproneareas should be displayed in the municipaland barangay halls to inform stakeholders of thedangers and possible occurrence of landslides inthe areas. Community training, extension andorganizing activities should be conducted toimprove the management and protection of thewatershed.
10. The Watershed Management Plan shouldfocus in developing interventions/projectsin identified hazard-prone areas. Possibleinterventions include:
a. Installation of simple rainfall monitoringdevise to inform the populace on the amountof rainfall falling in the watershed. Oncethreshold is reached, warning should begiven to inform the residents near steepslopes for possible occurrence of landslide;
. Use of indigenous or adaptable/compatibleforest tree species (i.e tuai, ficus sp.,alibangbang, akleng parang) in reforestinghighly vulnerable areas;
c. Planting of perennial crops or tree-vegetablecombinations and fire-resistant species infire-prone areas should be encouraged toforest occupants.
d. Conversion of forest land to vegetableproduction in vulnerable areas of thewatershed should be stopped by concernedagencies (DENR, DA, DAR, LGUs).Appropriate agro-forestry cropping schemeshould be adopted by the community in theirvegetable gardens. Other environmentfriendlylivelihood (i.e bamboo propagation/production, apiculture, “trash-to-cash”) shouldbe introduced.
e. Roadside/banks should be cleared ofdebris and other dried, flammablematerials to minimize accidental fires.
RECOMMENDATIONS11. Slash-and-burn farming should only be donein moderately sloping areas (below 15percent slopes). Opening of new clearingsshould be avoided.
RECOMMENDATIONS12. Monitoring of the adoption of the result ofthe vulnerability assessment should beconducted to the LGUs concerned.END
Class Rating of Various Themes.CLASS RATING SLOPE(%)VeryHighMONTHLYRAINFALL(mm)TYPHOONINCIDENCECLIMATECHANGEGEOLOGICAL AGE DIST. FRMFAULTLINE (km)5 >50 >500 5 VH Recent; QuaternaryAlluvium, Pliocene-QuaternaryHigh 4 30.1-50 400.1-500 4 H Pliocene-Pleistocene, UpperMiocene-PlioceneModerate3 18.1-30 200.1-400 3 M Oligocene 3Low 2 8.1-18 100.1-200 2 L Undifferentiated(Sedimentary andMetamorphicrocks)4VeryLow1 0-8
Class Rating of Various ThemesCLASS RATING SOIL MORPHOLOGY LAND USE/ LANDCOVERVery High 5 Tropudults withTropudalfs; mountain soilsHigh 4 Entropepts withDystropeptsCultivated/sparselyvegetatedGrassland/50-70%sparsely vegetatedRoad/RiverCut>5030.1 -50Moderate 3 Tropudalfs with Tropepts Brushland 18.1 -30Low 2 Tropopsamments withTroporthentsVery Low 1 Tropaquepts withEntropepts, Tropepts andOxisolsMixed forest/40-50%forestPrimary forest/close canopy8.1 -180 - 8
Vulnerability Class for LandslideLANDSLIDE VULNERABILITY RATINGCLASSVery Highly Vulnerable >4.2Highly Vulnerable 3.5 – 4.19Moderately Vulnerable 2.8 – 3.49Low Vulnerability 2.1 – 2.79Not Vulnerable