River engineering

About: River engineering is a research topic. Over the lifetime, 435 publications have been published within this topic receiving 10286 citations. The topic is also known as: Channelisation.

More room for water

Abstract: Watercourses are among the basic natural phenomena that characterize the environment. On the one hand, the water regime limits the anthropogenic use of space; on the other hand, it enriches landscape. The problem of allowing the space that ‘belongs’ to water to be used for intensive anthropogenic uses has been dealt with by the oldest known civilizations. With the growing population, industrialization and urbanization, the inundated areas and wetlands have been consumed and, through river engineering, watercourses have been regulated such that the space belonging to water has been reduced. Since ancient times, and more intensively from the mid-19th century, riverbeds have been shortened and narrowed, and levees have been built for flood protection; this resulted in the serious reduction of flood plains and wetlands. The surfaces ‘taken’ from rivers were intended primarily for agriculture and urban development. The middle of 19th century saw the emergence of such regulation works on the Rhine River, and in the first half of the 20th century, in the United States (de Bruin 2005 and Cassidy 1962). Similar developments occurred worldwide. After World War II, the Netherlands greatly increased its arable land by polder development, land that has been taken from the lakes and rivers (Tol and Langen 2000). A similar situation occurred in Denmark, the United Kingdom, Belgium, Germany and France, where such works were developed from the late 19th century. At the end of the 20th century, many rivers in Europe were in highly confined channels. The situation was similar in Slovenia. Major projects and developments on the Mura, Drava, Sava and Ljubljanica rivers were carried out in the first half of the 20th century. In the second half of the 20th century, we dealt mainly with drainage of agricultural land. A special levy was introduced to compensate for agricultural land in construction. The collected funds were available for agricultural land management and supported the implementation of water management projects, such as the regulation of the Ljubljana Marshes, the Pesnica River and the Vipava River. Twenty years ago the maintenance of embankments of regulated natural watercourses was brought to a halt, and the new practice was seen as eco-friendly maintenance of watercourses. Many river banks were overgrown with bushes and the space for water was only further reduced. In some places, the vegetation in the narrow channels completely obscured the surface of the water (Fig. 1). The serious damages due to the recent floods and, last but not least, fatalities, are the price that we pay today; examples are the floods of the Gradascica and Vipava River in 2010. To make matters worse, the pressure on the water land is increasing in urban areas. A particular problem is the culverting of streams for urban purposes. It is ecologically extremely inappropriate; open water disappears from the environment in which it can only be enriched. Channels are diverted and small streams are put in culverts, despite the requirements of the Water Framework Directive. Water land which was often flooded is now occupied by roadways and parking lots.

The development of abandoned side-channels: ecological implications and future perspectives

Abstract: River–floodplain habitats have been strongly affected by damming and river regulation, which have initiated longterm trends towards terrestrialization and fragmentation. We studied the terrestrialization processes in the Donau-Auen National Park over the last 80 years by means of airborne images. The aggradation of side-arms is an ongoing process. The main parameters affecting the terrestrialization process are river bed degradation, the connectivity to the main river and the size and shape of the water bodies. As smaller water bodies silt up faster than larger ones, the process of terrestrialization speeds up. From a nature conservation point of view, inhabitants of small temporary water bodies such as amphibians and molluscs are particularly affected. First results of river engineering projects to re-connect abandoned side-channels show that the trend may be impeded. But for a sustainable solution of the problem the stop of river bed degradation is indispensable.