Making the Case for Nature-Based Solutions and Green-Grey Integration across Four Priority River Basins

Project Context

The Philippines is highly exposed to floods and sedimentation risks, with four major river basins – Pampanga, Jalaur, Buayan-Malungon, and Apayao-Abulug – among the most flood-prone in the country. The Government of the Philippines, with ADB support, is preparing the Enhanced Integrated Flood Resilience and Adaptation Investment Program, a multi-tranche financing facility (MFF) spanning approximately ten years. While the Program’s primary interventions centre on large-scale grey infrastructure, it also integrates nature-based solutions and non-structural measures such as early warning systems to address the upstream drivers of flood risk and sedimentation, including stabilising critical slopes, reducing erosion, enhancing water retention, and supporting livelihoods.

The watershed management component, to be implemented by the Department of Environment and Natural Resources (DENR), is a critical part of this broader program. With an indicative financing envelope of USD 500 million, it is expected to deliver scaled-up forest and landscape restoration, diversified rural livelihoods, improved watershed governance, and mobilised sustainable financing mechanisms across the four priority basins. ICEM has been engaged by ADB to prepare the strategic framework and pre-feasibility investment package for the watershed component, with a particular focus on making the case for nature-based solutions and green-grey integration as a cost-efficient approach to flood risk management.

Objectives

The assignment aims to:

  • Develop a strategic prioritisation framework for the watershed management component of the MFF across four priority river basins, identifying hotspots and establishing the evidence base for nature-based solutions as a cost-efficient complement to grey flood infrastructure.
  • Prepare a pre-feasibility investment package for the first MFF tranche, providing the analytical foundation for ADB and Government appraisal and defining the sequencing logic for subsequent tranches.
client:
Asian Development Bank (ADB)
LOCATION:
Philippines
TIME:
March 2026
to September 2026

TAGS

Biodiversity, Environmental Economics, Project description, Water
Philippines
Nature-based Solutions
Current Projects

Activities

ICEM’s technical work is delivered across four phases:
  • Watershed Diagnostics and Hotspot Identification: Consolidating existing basin, watershed, flood, sediment, and land use data; undertaking basin-wide diagnostics to characterise dominant degradation processes; and applying GIS-based spatial analysis and a structured hotspot identification process across the four priority basins, validated with government counterparts.
  • Intervention Identification and Investment Sequencing: Developing a list of watershed management and nature-based solution interventions, applying a natural capital framing to define risk-reduction functions and benefits, and using a multi-criteria analysis (MCA) framework to prioritise and sequence interventions across MFF tranches in consultation with stakeholders.
  • Field Validation: Conducting targeted field visits to selected hotspot areas, refining priority interventions based on field findings, and engaging local stakeholders to validate prioritisation results and investment sequencing logic.
  • Pre-Feasibility Assessment and Investment Package: Conducting pre-feasibility screening for Tranche 1 interventions, preparing indicative cost estimates and investment rationale, assessing financing options including innovative sustainable finance mechanisms, and defining implementation arrangements and next steps for subsequent MFF tranches.

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Designing Integrated Climate Adaptation Investments to Protect Coastlines and Secure Livelihoods in a Low-Lying Atoll Nation

  • Philippines

Making the Case for Nature-Based Solutions and Green-Grey Integration across Four Priority River Basins

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Integrating Gender-Responsive EbA Approaches into Watershed Restoration and Flood Risk Management in Nepal

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