BMP'S IN MEDITERRANEAN RIVERS RESTORATION IN EUROPE

摘要

The Mediterranean climate is got a dry summer, temperate winter with and a very big variation in it's rainfall that use to be pouring rains Rainfall intensity and distribution along the year provide very specific characteristics to the rivers. Though one may find some big and plentiful rivers, most of them present a quite different behaviour: pouring rains, dry periods of time, "ramblas" or avenues that only have water a few days per year, sediment and changes in the ordinary channel... The low land near Mediterranean rivers used to coincide with intensive populates areas. This situation has created some conflicts with hundreds of people killed during flooding. So today the reality of these rivers is canalization, dam, marsh, reduction of his original natural width, invasion of not native plants like Arundo donax, Ahilantus altissima, Senecio inaquidens... In the last 10 years the use of soil bioengineering techniques are beginning to be more usual in this rivers with the aim to improve the environment quality but also maintaining the hydraulic protection. This works are done for: Protect infrastructures located in the rivers against water impact during flooding. Increase the natural capability of wetlands to improve water quality. Plant repopulation in rivers with a high level of impacts. Increase the habitat biodiversity by modelling the flux of water. Control the water flow in relation with sediment transport. All this techniques had been use in a demonstrative project of Sant Boi de Llobregat. A landscape improvement of the Right Canal was carried out within the project. The sphere of activity is around 420 I.m. of canal. The vegetation growing within the canals is poor in natural value and the erosion of the slopes create big problems. The work had been design in 2001 and executed in 2003 and is specially interesting for the use of different bioengineering technologies (permanent reinforcement blankets, coir rolls, rock rolls, fascines...) A second sample is the works design and executed in 2005 in the river Ripoll with flooding of 6m/s water flow and the use of fibre rolls that will have a second phase just now. This projects show the potential of bioengineering techniques in Mediterranean climates and the potential of the use of some native plants for erosion control like Vitex agnus-castus, Iris pseudacorus...also against not native plants.