New lake in the town of Gedved helps fend off water from private properties

About the project

In the small town of Gedved north of Horsens, Jutland, the Danish Nature Agency has established an almost 42-hectare stormwater wetland area, including a restored Gedved Lake.

The purpose of the project is to reduce the amount of nitrogen that ends up in Horsens Fjord. At the same time, the project has improved the natural habitat, i.e. by introducing a wildlife corridor.

Horsens Municipality has also designed the new stormwater wetlands to serve as a buffer during heavy precipitation events. Downstream of the new wetlands, properties near Gedved Mill used to be troubled by flooding.

However, after establishment of the new lake, even the record amounts of rain during the autumn of 2019 did not cause problems. How substantial a precipitation event the lake can cope with has not been calculated.

It took many attempts, but Gedved Lake has now finally been restored. To begin with, the primary goal was to restore the lake as a part of the landscape. Later, the aim was to curb discharges of nitrogen into the aquatic environment as well as to create more connected natural habitats. Most recently, climate-proofing and carbon sequestration became important focus areas.

Gedved Lake takes up 30 hectares of the new stormwater wetlands that were inaugurated in April 2019. As early as in 1992, the former Vejle County made a first attempt at restoring Gedved Lake. Another attempt was made in the 2000s.

With funding from the European Agricultural Fund for Rural Development (EAFRD) and the Ministry of Environment and Food of Denmark, restoration of the lake is now a reality. The Danish Nature Agency has established voluntary agreements with landowners. Farmers have been financially compensated for allowing their farmland to be rewilded.

The current project involving the new lake was commenced in 2013. Horsens Municipality introduced climate change adaptation into the project during the detailed planning phase in 2017.

Downstream from Gedved Lake by Gedved Mill is a cluster of houses that have stood knee-deep in water on several occasions.

Horsens Municipality used the aquatic-environment improvement project to ensure protection for these properties against unwanted rainwater.

Like many other water bodies in Denmark, Horsens Fjord is receiving too much nitrogen.

In the 1990s, therefore, the former Vejle County wanted to restore Gedved Lake, so that the lake could hold back some of the nitrogen.

Today, nature restoration is the responsibility of the central and local governments. As applications for the current project were being processed by the authorities, in 2017 Horsens Municipality became aware that the new lake could be an important piece of the puzzle in climate-proofing this area.

The properties around the mill used to experience flooding when the Elling Bæk watercourse overflowed its banks during heavy rainfall.

The new lake can hold more than 720.000 cubic metres of water.

Drains were relocated to lead water from the fields out into the lake. An open watercourse was established to lead water from the lake. Furthermore, an old, more than 500-meter-long drain is now serving as a spillway in situations with heavy downpour.

Gedved Lake, with its 30 hectares, makes up a large part of the approx. 42-hectare new stormwater wetlands.

Around 7,100 cubic metres of soil was excavated to make place for the lake. The lake has an average depth of 2.4 meters, is around 5 meters deep at its deepest point, and holds 721,000 cubic metres of water.

During heavy downpours, the water table can rise as much as 10 centimetres above normal. In these situations, the lake can hold as much as 60,000 cubic metres additional water.

“The lake could probably hold even more water,” explains Anne Gro Thomsen, project manager at the Danish Nature Agency. “But that’s not something we aimed for, because it’s not our primary objective with the lake,” she said.

The farmland around the new Gedved Lake has been drained since the 1950s. Today, all the drains have been redirected to lead the water into Gedved Lake.

What is now Gedved Lake used to be low-lying, pump-drained areas along the Holtvad Bæk watercourse. The pump is now silent, and Holtvad Bæk runs through the lake.

Another watercourse, Elling Bæk, passes two thirds of its water volume on to the new lake during heavy rainfall. This helps reduce the water volume along the critical stretch through the mill complex.

Part of the Holtvad Bæk watercourse used to be culverted as a more than 500-meter-long drain. The culverted section has been maintained and a spillway has been established by the lake’s outlet. This 

emergency spillway is activated during extreme precipitation events.

Horsens Municipality did not have any real alternatives to establishing the new lake. Adapting the area to climate change would otherwise have required lowering a listed dam construction by Gedved Mill and widening the Elling Bæk watercourse throughout the area.

The restoration of Gedved Lake is one out of two projects along the same continuous stretch of watercourse. In another stormwater wetland project in the water system, the Danish Nature Agency has re-meandered the Tolstrup Å watercourse, raised the watercourse bed and discontinued drainage of the area along the watercourse.

Also, in this project, the goal was to detain nitrogen. However, Tolstrup Å can also help detain water during heavy precipitation.

Climate change adaptation projects often offer added benefits (added value) in the form of more natural landscapes, recreational enjoyment, carbon sequestration, and health. However, climate change adaptation is the added benefit in the Gedved Lake project.

The reestablishment of Gedved Lake and the re-meandering of Tolstrup Å, which both lie north of Horsens, are examples of a type of project that we are now seeing in many other parts of Denmark.

The Danish Nature Agency has a total of 13 current stormwater wetlands projects totalling 1,600 hectares, i.e. 16 square kilometres. Together, these projects will reduce the overall discharge of nitrogen to the aquatic environment by 184 tonnes nitrogen annually. The projects are part of efforts to realise the river basin management plans that will ensure Denmark meets the requirement of the EU Water Framework Directive for a good aquatic environment in Europe.

The wetlands projects are typically on low-lying farmland. As these areas are restored to wetlands that can detain water, they also ensure less runoff and, thus, reduced risk of flood events downstream.

In the case of the restored Gedved Lake, even extreme rainfall during the autumn of 2019 did not give rise to flooding at Gedved Mill downstream. Enjoying their properties in all kinds of weather and without getting their feet wet is a whole new experience for property owners near the mill.

The Gedved Lake project succeeded in uniting agriculture and nature conservation interests. This was because farmers received a compensation amount or a sales price that they found reasonable. This meant that all the farmers affected by the project backed the project. Other landowners made land available voluntarily.

The restoration of Gedved Lake was based on voluntary agreements with the farmers affected by the project as well as other landowners.

With funding from the rural development funds, the central government was able to give farmers the compensation they requested.

Those farmers who chose to sell off their land to the state, have the first option to buy back the same land once the final land registration is in place for the wetlands.

The project included an EIA screening. A rural zone permit was granted for the establishment of the lake along with authorisation under the Watercourse Act to remeander the watercourse. Furthermore, the project was granted exemption under the Nature Protection Act to make changes to so-called section-3 land. The Museum Act also came into play, as a Stone Age settlement was discovered during excavations for the lake.

Some of the affected farmers had bad experiences from the earlier attempt by Vejle County to re-establish Gedved Lake. This time, therefore, the authorities were careful to approach things differently.

Earlier attempts to re-establish the lake were halted, not only because of the lack of adequate compensation. The process was also halted because some farmers experienced a poor process and lacked clear agreements regarding the scope.

In the current project, some of them were therefore concerned that a system of paths, for example, may be registered on their land, without their knowledge and acceptance.

To this Anne Gro Thomsen, project manager from the Danish Nature Agency, said “We do what we say! And we say what we do!” It was all about building trust.

Also, the Danish Nature Agency chose to divide the project into two phases: First the establishment of the lake and then a decision on public access to the new natural area. The Gedved community council will play a large role in this matter, together with the municipality and the final owners of the area.