The municipality of Santa Cruz de Tenerife is among the numerous cities globally impacted by this phenomenon. Notable for its intense rainfall events occurring over brief time spans, coupled with its steep and wide ravines, as well as its unplanned expansion, the capital is susceptible to flash flooding.
Moreover, the rise in heavy rainfall attributed to climate change, alongside the trend of increasingly erratic precipitation, is significantly exacerbating the issue.
Flooding is regarded as the most prevalent and devastating natural threat on an international scale. In many mountainous volcanic islands, flash floods are particularly common, occurring suddenly due to the limited capacity of the basins and the steepness of the terrain, linked to rapid runoff processes.
This type of flooding is also prevalent in arid or semi-arid coastal regions, particularly in locales with close mountain ranges, where small river basins frequently remain dry.
Santa Cruz de Tenerife encounters considerable challenges concerning urban flooding. According to the study ‘Identification of urban areas prone to flash floods: The case of Santa Cruz de Tenerife’, 1,023 risk points have been detected. The primary concern is inadequate drainage capability, primarily a result of drainage infrastructure not being designed to cope with peak flows during flood events, underscoring the pressing necessity to integrate non-structural strategies, such as hazard analysis (evaluation of return periods and peak flows), with structural solutions, namely the development of scientifically sound drainage systems.
The rapid urban growth of the city, along with flaws in urban planning, has contributed to the establishment of settlements in vulnerable areas. The aforementioned research illustrates the critical impact urban expansion has on heightening flood risk, not merely by occupying flood plains but also by diminishing runoff capacity due to soil sealing.
From a flood risk perspective, two crucial types of areas exist within the urban drainage framework. One group consists of the main channels, which manage greater flows than their tributaries, while the other encompasses occupied or removed channels, which are devoid of adequate drainage systems, making them highly exposed and vulnerable areas.
This analysis emphasises that inadequate planning or management not only heightens exposure and susceptibility to flooding but also modifies and worsens risk by creating new areas vulnerable to this threat. Therefore, effective maintenance of waterways is vital to mitigate these risks.
