Suitability Assessment of Small Dams’ Location as Nature-Based Solutions to Reduce Flood Risk in Mataniko Catchment, Honiara, Solomon Islands

Abstract

As global temperatures rise, flooding and storm surges caused by extreme weather threaten people’s safety and nations’ development. Nature-based Solutions (NBS) are practical actions to support resilience to reduce flood risk and are applied in many countries. As the NBS approach mentions, small check dams made of gabion and wood can retain runoff and temporarily create detention basins to reduce the magnitude of floods and provide additional water resources. However, previous dam suitability research emphasized the criteria selection and decision method evolution, which costs time on the complex calculation and does not fit the NBS small dams. This research aims to optimize the site selection workflow of small dams in vulnerable informal settlements by utilizing Remote Sensing (RS), Geographic Information Systems (GIS), and Multi-Criteria Evaluation (MCE). Several thematic layers, such as land use, river density, building distance, vegetation cover index, slope, and elevation factors, were chosen to identify the suitable area in Mataniko catchment, Honiara. More importantly, it provides a more efficient model builder that can be replicated in ArcGIS 10.8, which contributes to visualizing scenarios of the inundation area of small dams at different heights. As a result, this study tested up to 35 potential small dams with 2.5 and 5 m wall height in the flood-prone Vara Creek and selected nine small dams with 5 m height and 15 small dams at 2.5 m as the best locations according to the volume and area. Overall, it is an efficient tool for designers to communicate with different stakeholders and applies to other developing countries facing frequent floods. Moreover, it provides a prototype and evidence of NBS action to address the flood issue.