Overcoming Floods:Improving local land-use planning to

address climate changeArlene Arcillas

City MayorSanta Rosa, Laguna, Philippines

Silang-Santa Rosa Subwatershed, PhilippinesArea shaded in red (above), topography (right)

Target area

Silang

Santa Rosa

Binan

Cabuyao

• Multiple cities in 120 km2• Rapid economic growth• Population growth and

migration (570,000 people)• Massive land use changes

in past 2 decades• Flooding, environmental

degradation, pollution, waste

Weather-related disasters: FloodingSa

nta

Ro

sa,

The

Ph

ilip

pin

es

Sep

. 20

06

wit

h T

yph

oo

n M

ilen

yo

(Photos: E. C. Creencia)

The Methodology

Scenario develop-

ment

Risk assess-ment

Counter-measure develop-

ment

Climate-sensitive land-use planning

Participatory Watershed Land-use Management

STEP1: SCENARIO DEVELOPMENTFocus group discussion & participatory mapping:

To understand future development & land-use

Current Land Use (2014) Future Land Use Plan (2025)*

*Future land use plan map based on the results of a participatory land use mapping session with representatives from four local government units (LGUs)

Mapping current & future land-use

STEP2: RISK ASSESSMENTFlood-hazard projection

10 year Rain Return Period Based on Ambulong

Station RIDF (Rainfall Intensity-

Duration Frequency Curve) which has a 54 years recordPrepared by HydrometeorologicalData Application Section (HMDAS)

Rainfall: Typhoon Ofel(Int. Name: Son-Tinh) Oct. 25, 2012

Duration: 12 hoursAmount: 224.4 mmIntensity: 18.67 mm/hrCollected using Tipping Bucket Rain

Gauge installed in Silang, Cavite (Upstream)

FUTURE SCENARIO (2025) Simulation using 10 min. Time step

More than 20% increase in the area likely to be affected

Flood area2014 vs2025

Institute for Global Environmental Strategies

9

STEP 3: COUNTERMEASURESThrough consultation with LGUs

Proposed provisional priority measures1. Zoning enhancementTo avoid and alleviate climate impact, and to sequestrate carbon dioxide

2. River rehabilitationTo increase water retaining capacity

Enforce development controls in areas highly susceptible to flooding.

Strengthen building codes in high-risk areas (e.g. floodwalls, elevated flooring).

Devise a relocation plan for informal settlers residing in flood-prone areas.

Mandate runoff mitigation measures (e.g. tree planting, water-permeable paving) where development/land-conversion is made.

Improve enforcement of zoning ordinances. Harmonize land-use among local governments to

manage the river basin as a whole.

All areas Regular river cleanup

Upstream area Protection and improvement through

replanting of endemic and indigenous plant species

Midstream area Rehabilitation of easement and riverbanks Construction of slope protection along

riverbanks Downstream area

Dredging of sediments Solid and liquid waste management Planting of endemic and indigenous plant

species Improvement of drainage

3. Capacity developmentTo strengthen the ability of local government to design and implement climate actions Needs assessments on climate change adaptation and mitigation and disaster preparedness and

management Development of campaign materials and training modules Conduct of trainings and events to increase awareness and preparedness

Memorandum of agreement (MOA) for cooperation

Establishment of Council for

Integrated Watershed Management

December 2, 2014

Catalyzed by 5-year WWF Hydrology Project

Inter-city cooperation for harmonizing land-use

Adaptation benefits of taking actions• Preservation of existing vegetation & development with runoff mitigation

measures reduce rainfall runoff, leading to less intense and less frequent flooding.

• In the best-case (runoff neutral) scenario, population affected by flood in 2025 will be reduced by 20% (down from 226,410 to 183,349).

• Exposure of people to floodwater could be further reduced by restricting development and/or reinforcing building standards in flooded areas.

Land-use in the Silang-Santa Rosa subwatershed as of (a) 2014, (b) 2015 in business-as-usual scenario,

and (c) 2025 in runoff-neutral development scenario. with flooded areas indicated in red

(a) (b) (c)

Mitigation benefits

CO2 of 528,142 tons avoided if current vegetation preserved

2014 Above-ground Biomass 2025 Above-ground Biomass

Change in C storage: 2014-2025

STEP4: CLIMATE-SENSITIVE LAND-USEImproving Comprehensive Land-use Plan (CLUP)

• Update CLUP, paying attention to CCA&M– LGUs in Silang-Santa Rosa sub-watershed

use flood-hazard maps & countermeasures to improve CLUPs

– Project data used for local climate change action plan of Santa Rosa

– Lake Laguna Development Authority use project results in master plan

• Comply with laws and policies– Republic Act 7160 (Local Government

Code of 1991)

– Climate Change Act of 2009 (RA 9729)

– National Disaster Risk Reduction and Management Act (RA 10121)

Photo: Meeting with Santa Rosa City Officials and

Consultants to improve CLUP incorporating climate change

actions based on project findings

Contributing to risk governance

• Science (e.g., flood hazard projection) provides basic information for appropriate risk governance (e.g., countermeasure development).

• Flood alleviation and prevention measures are integrated into local land-use development planning.

• Inter-city cooperation helps manage watershed as a whole through collective planning.

• Integrated Watershed Management Council serves as a mechanism to facilitate cooperation among LGUs.

Contributing to national agenda

• Share experiences and lessons learned with other subwatersheds in Lake Laguna basin.

• Conduct feasibility study to explore possibility of scaling up the project.

• Help materialize national agenda e.g., Communities for Resilience (CORE), Ecotown, and Ridge-to-Reef initiatives.

(Source: Climate Change Commission)

Conclusion/key messages

• Participatory Watershed Land-use Management can help address weather-related disasters such as floods, integrating climate change actions into local planning.

• Application of this approach indicates that planned land-use conversion and projected climate change are likely to increase the intensity of flooding in the study area.

• Zoning enhancement (e.g., development controls and runoff mitigation) could alleviate the probable impact of climate change.

• Harmonization of land-use within the subwatershed is critical for an effective integration of climate change responses.

• Providing other subwatersheds with experiences and lessons learned to tackle similar problems, the Silang-Sta.Rosa pilot contributes to advancing risk governance, and the CORE, Ecotown, and Ridge-to-Reef initiatives.

THANK YOU