Inscriere cercetatori

Site nou !

Daca nu va puteti recupera parola (sau aveti alte probleme), scrieti-ne la pagina de contact. Situl vechi se gaseste la adresa old.ad-astra.ro

Facebook

Embanking the Lower Danube: From Natural to Engineered Floodplains and Back

Domenii publicaţii > Ştiinţele pământului şi planetare + Tipuri publicaţii > Capitol de carte

Autori: Constantinescu, S., Diana Achim, Ioan Rus, Liviu Giosan

Editorial: Paul F. Hudson, Hans Middelkoop , Springer, Geomorphic Approaches to Integrated Floodplain Management of Lowland Fluvial Systems in North America and Europe, p.265-288, 2015.

Rezumat:

Anthropogenic intervention along the Danube floodplain has occurred in various degrees since ancient times. Early in this history, small and localized changes were linked to fishing as floodplain lakes and channels constituted a permanent and trusted source of fish. Large-scale, intense changes occurred primarily during the communist period when most of the floodplain was used for agriculture. As a result of this phase, 3250 km of artificial levee were constructed on the main course of the Danube, of which more than 1100 km are located in Romania. By the end of the 1980s, the area affected by anthropogenic intervention in the floodplain amounted to 433,957 ha, represented by 56 embanked enclosures. Only a small part (79,943 ha) remained under natural conditions, primarily the mouths of tributaries and the “Small Islet of Brăila”. In time, the narrowing of the streambed by anthropogenic levees led to an increase in current velocity and significant erosion of the riverbed. The damming of Danube at the Iron Gates Gorge and of its major tributaries led to the creation of 340 artificial lakes along their courses and lowered drastically Danube’s sediment discharge that feeds the current floodplain. In addition, fertilizer-aided intensive agriculture on the floodplain has fundamentally changed its soil regime.

Our study examines the recent history of the Lower Danube’s floodplain, using a comparative cartography approach. Maps published in the late nineteenth century (1880–1884) show no significant human influence upon the river system. By the mid twentieth century the shift from a natural regime to a human controlled system has reached its peak as evident from contemporary maps (1960–1980). Recent satellite and aerial images (2005) continue to exhibit extensive human impacts, 30 years after the large Iron Gates I and II dams were built. Islets along the Danube course have directly reflected all these hydrological changes over time.

Many of the artificial levees along the Lower Danube are currently severely damaged and require restoration works. In April 2006, the Danube levels reached historical values and caused significant damage. Floods occurred downstream of Iron Gates Dam not because water overtopped the levees but because of their natural failure through pipping. An optimal solution for navigation and economic use should take into account many factors: the reduction of solid discharge over the entire Danube basin, the narrowing the stream bed, the need for a buffer zone for floods, as well as agricultural and fishing activities, the natural ecosystem and the services it provides. As the human-controlled transformation of the Lower Danube floodplain suggests, changing the functionality of a system could be a one-way route and as a return to the initial, natural state may be impossible.

Cuvinte cheie: fluvial geomorphology, Human impacts

URL: http://link.springer.com/chapter/10.1007/978-1-4939-2380-9_11