Flood Risk Management Plans in Volcanic Islands: Analysis, Discussion, and Lessons Learned in the Canary Islands

 Floods are risks arising from natural phenomena such as torrential rainfall over short periods or rising sea levels. In limited territories, like islands, these phenomena reduce geographical space and have severe environmental and economic consequences. The Canary Islands (Spain) is a territory where numerous floods have occurred throughout history. The regional authorities have undertaken Flood Risk Plans as part of the Hydrological Programme for the archipelago. Climate change and the Canary Islands’ orography make them prone to adverse weather phenomena like heavy rains and the gradual disappearance of coastal territories due to wave action and progressive rising sea levels. These factors have prompted this review of Flood Risk Plans in the Canary Islands, Spain. Furthermore, an assessment of the archipelago’s hydrological and orographic conditions has been conducted to contextualize the islands’ situation regarding flood risks. The results obtained indicate that there is a need for greater control through hydrological planning to minimize the impacts of episodes of torrential rains. In addition, studies related to extreme wave events should be improved to size maritime infrastructures correctly. A lack of preventive actions has been detected, involving: (i) assessment and prevention of floods using computer models and simulations, (ii) actions in eroded areas of basins, (iii) cleaning up watercourses, (iv) assessment of hydraulic infrastructures that cross watercourses, such as crossing works, bridges, speed bumps on tracks or agroforestry roads, and (v) effective coordination for the planning, management, and performance of hydrological and forestry projects between the Forestry and Hydraulic Authorities. Flood effects also increase after large forest fires, especially if action is not taken immediately after the fire by building barriers with burnt material and masonry dikes. Due to the real risks posed by Flooding in the Canary Islands, which has caused historical problems in the archipelago, the Regional Administration has created a “Flood Risk Plan” for each of the islands, where the primary information has been collected. This plan includes the following aspects: selection of the potentially floodable and high-risk areas of the hydrographic basins; evaluation of risks derived from runoff; delimitation of flood zones; selection of potentially floodable coastal areas; studying climate evolution; studying the influence of climate change on sea levels and other aspects considered relevant in the case of coastal and rainwater flooding. Risks have been classified as river flooding, flash flooding, and flooding due to the sea. Civil works must also be conducted to channel ravines to allow the natural flow of water. Wire meshes should be placed on the unstable slopes of the islands to trap small rocks that may fall after episodes of heavy rains. Moreover, urban planning needs to consider areas at risk of flooding to take the appropriate measures. Finally, the most crucial factor is that all the public authorities are aligned and pursue a common goal so that water, coastal, and urban planning can help minimize flood risks.

Tienes el texto completo:

10.1007/978-3-031-43169-2_7