Swiss Competences in River Engineering and Restoration

The world is like a river, running along in its bed, this way and that, forming sandbanks by chance and then being forced by these to take a different course. Whereas this all proceeds smoothly and easily and gradually, the river engineers have great difficulties when they seek to counteract this natural behaviour (Goethe). Goethe recognized that the dynamics of a river can only be controlled to a limited extent by channel modifications and rigid river training works. The term “dynamics” refers to vari¬ations in hydromorphology over space and time due to flood discharges and sediment trans¬port. These processes regularly lead to the destruction of habitats, especially in riparian areas, and the creation of space for new habitats. Dynamic watercourses require a lot of space. For example, naturally meandering rivers may migrate laterally within a belt of roughly 5–6 times the width of the channel bed. In the valleys of the Swiss Alps and Pre-Alps the rivers origi¬nally divagated over the entire valley floor. To reclaim land for urban development and agriculture as well as to provide flood¬ing, watercourse alterations were carried out over the last two centuries in Switzerland. Efforts were thus made to impede the dynamics; rivers and streams were channelized, and channel bed widths were optimized with regard to sediment transport. This resulted in monotonous watercourses, with almost no variation in hydraulic or morphological characteristics. Recognizing the ecological deficit of the Swiss, a new approach in the strategic plan¬ning of flood protection projects was promoted by the Swiss Government which gave the basis for the first restoration programs more than 40 years ago. Since then much has been achieved. Nevertheless, today’s challenge of river engineers, in collaboration with environmental scientists, is to restore the channelized rivers under the constraints of high urbanization and limited space. The behaviour of river systems is a result of the complex interaction between flow, sediments, morphology and habitats. Furthermore, rivers pro¬vide important sources of water supply and energy production in addition to a means of transportation. Each year the Swiss Commission for Flood Protection (KOHS) of the Swiss Association for Water Management (SWV) organizes a symposium where professionals, officers of public administrations and researchers exchange their experiences on special topics and on-going projects. In 2014 this symposium was organized as a special session of the seventh Interna¬tional Conference on Fluvial Hydraulics “River Flow 2014” at École Polytechnique Fédérale de Lausanne (EPFL), Switzerland. Aside from the Swiss participants, scientists and profes¬sionals from all over the world were informed about the Swiss competences in river engineer¬ing and restoration. In the presented book, invited and selected contributions regarding the latest tendencies and key-projects in Switzerland are presented to an international commu¬nity of river engineers and researchers, hoping that they can enrich flood protection and river restoration projects all over the world.