Flash floods in Mediterranean rivers are becoming more frequent

Last week, the first session on flood risk management took place in Vic and Gurb within the framework of the project LocAll4Flood, led by BETA Technological Centre – UVic-UCC. This session highlighted the importance of adapting and improving the population’s response capacity to these increasingly frequent events. The need to strengthen prevention through effective early warning systems and implement measures to mitigate the effects of flooding was also emphasized. These include modifying infrastructure, incorporating nature-based solutions, and improving territorial planning.

At the event, representatives from the Catalan Water Agency (ACA), the Vic City Council, the Gurb City Council, the Urban Guard, the Fire Department, Civil Protection of the Government of Catalonia, and the Osona County Council participated, along with the Center for the Study of Mediterranean Rivers (CERM), the Remei Neighborhood Association, the Vic Civil Protection Volunteers Association, and other experts. During the session, a practical exercise on flood management in the Osona region was carried out, which focused on the river Mèder, Torrent de Sant Jaume (which flows through Malla and Vic), and Torrent de l’Esperança (which borders Vic and Gurb). These river systems have very different hydrological dynamics, but which, in the event of sudden and intense rainfall, can lead to both river and pluvial flooding. A map has identified the most vulnerable areas in Vic and Gurb to improve their management and enhance early warning systems.

What’s happening in the Mediterranean basin?

The effects of climate change in the Mediterranean are more intense due to several factors: it is one of the regions warming most rapidly, with temperatures rising above the global average, leading to more frequent droughts. This faster warming is due to its geographic location, in addition to other factors such as deforestation and increased urbanization. Rising temperatures cause increased evaporation and increased humidity in the atmosphere, generating more intense and irregular rainfall. A clear example of flash flooding is the one that occurred in Valencia last October, highlighting the importance of taking preventive, adaptation, and mitigation measures to combat these phenomena.

Flash floods occur when intense rainfall causes water to overflow its banks in a short period of time, submerging normally dry areas. Streams with little or no flow become overwhelmed within hours, rapidly inundating nearby areas.

What can be done?

To improve prevention, it is essential to optimize warning systems so that messages arrive in a timely manner, as well as improve the response systems of the various entities involved in flood risk management. Work is already underway to develop early warning systems for the municipalities of Vic and Gurb. This system is based on a monitoring platform that uses sensors and real-time data on climate and environmental conditions, sourced from the Catalan Water Agency and the Meteorological Service of Catalonia, among others.

To improve adaptation, you can Measures such as conducting awareness campaigns to inform the public about flood risks in vulnerable areas can also be implemented. Surveys can also be conducted to determine public perceptions of whether they live in flood zones and the associated risks, as part of a preliminary study for designing the necessary educational materials. In addition, it is necessary to provide knowledge about what to do in an emergency, starting with schools and other community spaces.

Previously, floods were managed with “gray” infrastructure, such as dams and river diversions, which can be effective but are also costly and prone to failure. Furthermore, these facilities can affect natural habitats and sediment flow, impacting agriculture and coastal protection. “Nature-Based Solutions (NBS) are a good alternative for naturally mitigating flood risks. Some examples include the creation of lamination ponds, riverbank restoration, or increasing urban permeability by creating and expanding urban green areas“, says Meritxell Abril.

Faced with a clear climate situation, with increasingly frequent episodes of intense rainfall, the need to adapt the environment and urban infrastructure by renaturalizing it and planning its spaces to avoid construction in flood-prone areas is becoming clear. This is a complex task that requires structural changes and the involvement of experts, organizations, and society.