Stabilisation of the banks and environmental enhancement of the urban section of the Torrente de Bunyola

The project

In the late-19th century, the Balearic Islands only had a single river, on the island of Ibiza, which always ran until it finally disappeared due to increased exploitation of the aquifers around it as tourism continued to grow.  

What there are plenty of in the Balearic Islands are watercourses known as torrentes: stream beds which remain dry for most of the year and which collect surface water at times of heavy rainfall or sudden thaws.

Spain has regions that are highly affected by problems of drought, whereas other areas suffer the hardships of highly localised intense rainfall events. The Balearic Islands enjoy a typically Mediterranean climate.  The heaviest rainfall is recorded in the months of October and November; the driest months of the year are June and July.

The periodic appearance of heavy rainfall, which in only a few hours can reach levels that exceed the average for the entire year, translates into sudden rises in the level of these streams, which, depending on the intensity, can drag everything that they encounter along with them: topsoil, stones, rocks, trees, undergrowth, etc., leading to flooding, and any towns or villages located close to these streams can be affected by blocked roads and power outages, homes and commercial premises can be affected, and sadly flooding of this kind can even lead to a loss of life.

Much of the land in the Balearic Islands (around 85%) is relatively flat and lies less than 200 m above sea level, although in the Sierra de Tramuntana this rises to 1,400 m, and the highest rainfall levels occur specifically in this mountain range, specifically in the central and eastern part.

Bunyola is a municipality on the island of Mallorca in the foothills of the Sierra de Alfábia, which forms part of the Serra de Tramuntana mountain range, and its torrent runs parallel to the MA-2100 road, crossing it several times before heading into Bunyola itself. Here it runs through the north part of the urbanised area, and even crosses the Palma-Puerto de Soller railway track.

This all makes it a potentially vulnerable area. The fact that the watercourse runs through where people live and work makes maintenance necessary on the walls of the banks, which range in height from 4 m to 6.5 m, vary in terms of construction and are in a deficient state of conservation.

The aim of this project is to prevent any erosion that occurs in episodes of heavy rainfall from causing the walls to collapse and form major obstructions, which could lead to the surrounding urban area becoming flooded, with the consequences that such an event would bring.