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Hydrodynamic + Sediment Transportation

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The aquatic and wetland ecosystems adjacent to river basins of the Doņana Marshes in Spain, the Elbe Riverland in Germany and the Po River Delta in Italy are the three areas of study where the technology and applications of the project RAMWASS are applied.

The Marsh Area of Doņana (Spain)

The marsh area of Doņana, one of the three large eco-systems of the Doņana Park, covers some 27.000 Ha. It was considerably damaged and reduced in size by human occupation of the marsh area during the XXth century and its hydrological capacity gravely affected. Work has been carried out in recent years to restore the original hydrological function of the marshland to ensure its survival.

The Doņana marsh has suffered from several human-induced hazards. The most recent one is the Aznalcollar earth dam failure on April 25 1998 releasing some 5 million tons of mining pollution flood directly on a large part of Doņana marsh area, killing birds and fossils and polluting the water course.

The marsh in Doņana has taken place as result of the culmination of the lagoon created by the closing of the estuary of the Guadalquivir River during the Quaternary Age. The continued sediment contribution coming from the incident streams (La Rocina, El Partido, Canyada Mayor) forms its present topography, where it is observed a great plain located to an average of 3.6m over the sea level and slope around 0.01%. The extensive plain is only altered by small elevations and depressions, those conform a smooth hydraulic - network. This network determines the hydraulic behavior of the marsh (flow directions and velocity, sedimentation processes, water quality) and it causes the existence of a great diversity of environmental paces, and this gives rise to a much differentiated fauna and a flora along the space and the time. This diversity is motivated by the annual variation of the marsh.

Nowadays, the river banks upstream the marshes are occupied and therefore reduced by urbanization processes. This occupation has destabilized the sediment contribution of the basin which is accelerating the marsh disappearance. This fact combined with the present interest of the European Commission in preserving natural environments with a great ecological value such as Doņana Park, leads to the need for understanding the hydrodynamics of the Doņana marsh. Contributing to theses efforts by means of the development of innovative risk assessment management tools, such as the RAMWASS DSS, is one of the paramount objectives of the project.

The Elbe Riverland

The Elbe is a river of outstanding importance in the middle of Europe. With a length of 1,091 km, it is one of the longest rivers in Europe and the largest natural valley in Germany, www.elbebadetag.de/index.php?id=85&L=1. Two third of the catchments area with 148.000 kmē belongs to Germany. The mean annual discharge into the North Sea is about 877mģ/s. For 50 years the Elbe was a political border between East and West, and so very little building construction took place on its banks.

Because of this, the Elbe Valley provides excellent conditions for biodiversity. Their variability with regard to both natural and cultural aspects and biotopes, and the wide variety of plant and animal species to be found there have given this river international importance as biosphere reserve. The lower Middle Elbe is situated entirely within the Biosphere Reserve "Elbe Riverlands". Regular floods of the river Elbe form landscape and determine land-use. Sustainable agricultural land use plays a vital role in the conservation of this unique treasure. 6.000 - 7.000 ha of the flood plain in the biosphere reserve are regularly flooded pastures and meadows. But the floods not only bring nutrients but also pollutants which causes problems for agriculture.

In August 2002 an extreme flood caused damages of high amount. High waters re-suspended high amounts of sediments and transported them to inundation areas, thus leading to contamination of large areas with toxic compounds like heavy metals and persistent organic pollutants.

The end-user in Germany will be the authorities for the biosphere reserve of the lower part of the river Elbe. There exists already a close collaboration of the working group "Ecosystem Functioning and Global Change" at University of Lüneburg and this authority. The new RAMWASS DSS will be an extremely useful tool for the risk assessment and management of hazards in the biosphere reserve of the Elbe Riverlands.

The Po River Delta Biosystem

The Po river is the largest river in Italy and has a huge delta occupying a large area in the region Emilia Romagna. The delta comprises several arms of the river itself, marshland and smaller lagoons.The Delta is a biosystem and is actually a natural park, (www.parks.it/parco.delta.po.er). The delta is threatened by erosion, in particular apparent erosion, i.e. apparent landward movement of the coastline due to surface subsidence, and do diminished sediment transport.

Already in the 1950s and 1960 the delta experienced abnormally large surface settlements (in places over 3m) due to production of natural gas dissolved in the underlying aquifers. The ensuing surface subsidence resulted in the Po River flooding several times the area with great damage to life and property. Even after close down of the wells the subsidence continued for a substantial period. Recently gas is extracted from gas fields both offshore and onshore south of the delta, sufficiently close to possibly disturb the newly found environmental equilibrium of the delta. The aspects we want to follow up and study with the RAMWASS DSS are hence erosion, apparent erosion, subsidence due to water and hydrocarbon extraction from the subsoil, compaction of the soils due to natural effects or human activity and general, behavior of the soil under surface loads, e.g. embankments necessary to counter balance the loss of surface elevation over the mean sea level. Typical hazards are again flooding of these areas and disturbance to the ecosystem. To follow the evolving coastline of the delta we will exploit series of satellite photographs over recent years (which exist, but have to be acquired) and during the project period. This will give a picture of the dynamics of the region. In parallel CISM will model with their in-house finite element software the observed surface subsidence. This is a time consuming task, requiring collection of a huge amount of data. This modeling may be in part substituted with Artificial Neural Networks, trained with reference to well documented field studies. Such networks would make a rational management of these areas much easier (e.g. planning of new elevations of dykes etc.). In conclusion the use of the RAMWASS DSS will be essential for a better understand the erosion, compaction and subsidence of the Po river delta area, as well as for understand the necessary prevention, mitigation and remediation measures.