Egå is a neighbourhood of Aarhus, which is closely related nowadays to the outskirts of Risskov, Egå Marina and the lake Egå Engsø. The area is densely populated, low-lying and at high risk of flooding under increased precipitation. Since the 1950s, the area was an object of extensive drainage to gain more agricultural land. Two pumping stations were established at the existing natural stream at that time, Egå, in order to pump water out of the wetland and into a new channel that carried it to Aarhus Bay. Intensive farming was the dominating factor at Egå valley. Nowadays the stream has been partly restored to its natural state and represents an example of adaptation to climate change that has had multiple benefits.
After some years, it was realised that the intensive farming and the leaching of nitrogen in particular had negative consequences on the animal and plant life which led the Danish parliament to adopt the Action Plan for the Aquatic Environment II in 1998. Its purpose was to reduce nitrogen leachate to the aquatic environment. One of the means to achieve this was to restore original streams and wetlands.
One of the places where the Action Plan for Aquatic Environment II had been applied, with the colaboration of Aarhus municipality, was the Egå valley. The process included a removal of old stream dykes in 2006, which costed significant flooding of previously reclaimed areas. The result turned to be the establishment of Egå Engsø. The lake is 115 ha. with a mean depth of approximately 1m, where the deepest area is 1.7m. The water level can be raised by about 1m depending on the seasonal and rainfall conditions. Egå Engsø is providing both space and time for achieving a water balance. The lake acts as a holding lake, which helps to reduce high water levels downstream and in mean time extends the period during which the water table is slightly raised. Egådalen is characteristic water landscape element in the cityscape, which is very low-lying in comparison with the surrounding terrain.
The low-lying areas at the bottom of Egådal near Risskov are at risk of flooding, either through intense runoff from uplands or when high tide in Aarhus Bay occurs. Currently, the area is protected by levees and a pumping station at the Egå mouth in Aarhus Bay. The lake’s holding capacity is reduced if the water level in the lake is already higher than normal because of significant rainfall. This was the case during January, February and March in 2007, where lakes, streams and groundwater were at maximum capacity. Furthermore early March also saw a large amount of snowmelt, which increased the danger. This resulted in the highest sustained water flow rates in 10 years and Egå was close to exceed its capacity. Emergency teams from all over Denmark were called to the area to prevent a flood that could have major economic consequences. The event highlighted the need for further preventive measures.
Aarhus municipality has created a plan for the remaining reclaimed areas as a design for ‘possible future wetlands‘.
Those wetlands will have several functions and purposes:
~ reduction in nitrogen leaching into Aarhus Bay
~ further reduction of the risk of flooding in the lower part of the Egå system through attentuation
~ improvement in the natural environment by ensuring environmentally-conscious land management
~ improvement in recreational opportunities in conjuction with Egå Engsø.
The new wetland will function as a climate change adaptation project. Aarhus municipality’s investigations in the area show that it could hold large volumes of water, therefore reducing the risk of flooding around Risskov.
However, my project will take into consideration the plans that the municipality is already discussing and mostly focus on the improvement of the recreational value of the area. I will use the water as a mediator between natural and constructed form. The fieldwork was a significant part of the project’s progress. Most of the time during the project was used on developing the architectural strategy for the area around Egå valley and understanding the movement from Egå Engsø to Egå marina.