Since the solution employed participatory methods, this will entail some considerable costs since data gathering, focus group discussioms, and numerous workshops and meetings must be conducted. The CCA&M interactions can even reduce costs while providing multiple benefits (Ayers & Huq, 2009; Biesbroek, Swart, & van der Knaap, 2009). Although it is generally believed that adaptation and mitigation are difficult to integrate because they are taken on different time and geographical scales, many successful cases have been reported, especially at the local level (Berry et al., 2015). For more informed decision-making on the optimal mix of CCA&M measures, detailed quantification of benefits from taking management actions is valued. In the case of the Silang-Sta. Rosa subwatershed, such benefits include the decrease in the number of damaged assets (e.g. buildings, infrastructure) and in the damage to economic activities (e.g. agriculture, manufacturing). It is ideal that these benefits can be accounted for in monetary terms, allowing the benefits to be compared with the costs of the actions. Future research needs exist in this kind of cost-benefit assessment. GHG emission reduction/avoidance can also be considered as a benefit of management actions.

Applying readily available data and techniques—participatory GIS and hydrological modeling—in a simple step-by-step procedure (i.e PWLM) makes this approach practical and applicable to various locations and institutions where limited expertise and resources are available. The GIS and remote sensing analyses conducted under the pilot project do not necessarily require a large amount of data, and most of them are publicly available (e.g. satellite images, population data, rainfall projections). The information about flooding and land-use can be obtained locally from consultation with local stakeholders. If the support from local experts in the relevant field of science (e.g. University of the Philippines Los Baños in our pilot project) is secured, similar data collection and analyses can be fully conducted at the local level. Our approach can be best described as a “partial” PGIS approach in a sense that all technical aspects of GIS were undertaken by experts (i.e. our study team) and that other stakeholders than local government representatives (e.g. local residents, companies) were not included (Canevari-Luzardo et al., 2015).

The existence of national policies and guidelines (e.g. CLUP guidebook (Housing and Land Use Regulatory Board, 2013, 2015)) stipulating the inclusion of climate factors within land-use planning engages the commitment of local governments. The local governments in the Silang-Sta. Rosa have revised their CLUPs based on the study result (e.g. flood hazard maps, climate change countermeasures), some of which are currently under review by local assemblies according to E. Creencia of the City of Santa Rosa (personal communication, 31 January 2017). The city uses estimated flood hazard in its LCCAP as a basis to take countermeasures, including the regulation on deforestation, which contributes to both adaptation and mitigation by alleviating runoff and avoiding CO2 emissions at the same time (City of Santa Rosa, 2016).

Implementing this climate change solution does not have direct environmental impacts.