Storm surge protection and new harbour environment in Svendborg

About the project

The Blue Edge (Den Blå Kant) will be the residents of Svendborg's new common harbour space between the city and the sea. Three sluiceways and a belt of fixed and mobile dikes along the outer perimeter of Svendborg Harbour will protect the area against storm surges of up to three meters above mean sea level.

Svendborg city lies elevated compared to the harbour. The project will therefore also establish several emergency flood channels leading stormwater runoff from the city directly into the harbour basin. The harbour basin can be used as a reservoir to protect the harbour area onshore against flooding during cloudbursts when the city sends cascades of water downhill.

Svendborg Municipality estimates the total project cost to be several hundred million kroner. The municipality therefore also expects the full project will take more than ten years to complete. Once complete, however, the harbour area of Svendborg will be able to withstand a 100-year storm surge event and a 100-year rainfall event.

First steps of The Blue Edge project already in the making

The first of three emergency flood channels have already been established along the
Frederiksgade street running from the city to the harbour. The city council has earmarked funds to finance the first of the three large sluices in the harbour. The first phase of the new urban space will be completed in 2021.

The first stage of The Blue Edge is also expected to be completed in 2021. By then, the urban space will have been upgraded with a new, wide footbridge to the harbour island of Frederiksø. On Frederiksø, new green spaces will have been established for outdoor relaxation, café seating and events.

The next stage of the project will involve storm surge defences protecting the southern part of the harbour. Svendborg Municipality has earmarked around DKK 37 million to build a sluice and fixed piers to keep out the sea. The municipality expects this part of the project to be ready by the end of 2023.

One of the emergency flood channels has already been established along the Frederiksgade street. The channel will guide future stormwater directly into the harbour basin via large conduits, pipes and outflows. Other sub-projects will be implemented over the next 10-15 years, as the municipality obtains financing.

A long dike, sluices and emergency flood channels to keep the harbour safe

Along the outer edge of the harbour, a dike will fend off the water masses during storm surges. The dike will have three sluices. From land, three emergency flood channels will protect the harbour area against water from cloudbursts, and the inner harbour basin will serve as a large reservoir. 

The Blue Edge project in Svendborg will include the establishment of a two-kilometre dike to protect the harbour against a water level of up to three meters above main sea level That's double the current quay height. The dike will consist of fixed concrete quays and openings that can be closed as needed.

The long, continuous dike will be established along the outer edge of the harbour. It will run across the Frederiksø island, which is situated inside the harbour, and which will therefore become a part of the dike.

Between Frederiksø and the northern and southern parts of the harbour area, three sluices will be established on the seabed. The sluiceways will be between 12 and 20 metres wide and can be closed in the event of a high-water alert.

In the southern part of the harbour, an openable bridge will be built on top of the sluice. This will provide a continuous path system across the water.

The defence structure will split Svendborg Harbour into two independent areas, one of which will be dammed in during high-water events.

To protect the harbour against flooding in connection with cloudbursts, three of the city's streets will be retrofitted as emergency flood channels. The streets in question already channel a great deal of rainwater towards the harbour. They will now be retrofitted with emergency flood conduits and wide grates along the edges. The new emergency flood channels will therefore consist of both open and covered water conduits.

At the same time, a previously closed-off stream running towards the harbour will be reopened. Furthermore, various projects for local drainage of rainwater will be established to keep some of the water in the city.

During cloudbursts, the emergency flood channels, and the reopened stream will send water towards the dammed in area of the harbour. This area can hold as much as 66,000 cubic metres of water. Should the water level increase by more than 0.5 metres inside the damming, a pumping station will pump some of the water out into the open area of the harbour.

During the work to establish flood protection for Svendborg, the city will be compartmentalised into four zones with permanent or temporary dikes. Each zone will be equipped with a pumping station, so that stormwater can be pumped out into the large harbour basin, if the zone faces flooding.

The total project will be able to protect the harbour of Svendborg against a 100-year storm surge event and a 100-year rainfall event.

Svendborg Municipality will develop the harbour area into an entirely new public urban space with a harbour bathing area, a harbour park and facilities for various activities and events. The harbour area will be safeguarded against storm surges but will still offer a view of the sea. 

From the onset, the municipality wanted to integrate their climate change adaptation project with the development of a new public urban space. An important criterion in the architectural competition in 2017-18 was that the project coupled climate change adaptation with the design of a new vibrant urban space.

The winning project forming the basis for the ongoing project, establishes new opportunities for recreation and relaxation along the harbour. Project manager Anna Als Nielsen describes the new urban spaces "like beads on a string creating a beautiful transition between industry, homes, culture and recreation".

The long dike will have built-in benches. The quaysides will be fitted with steps descending to the water's edge. People will be able to walk across the water on one of the sluice dams.

Because the long dike will be built along the outer edge of the harbour, the vista across the water from inside the harbour will not be lost.

The first stage of The Blue Edge project is already underway.  The first stage includes a new footbridge to the Frederiksø harbour island. The next stage of the project has been approved and will involve a storm surge protection solution for the most exposed part of the harbour. 

The municipality prepared an overall development plan for the harbour area in 2014. The municipality then issued an architectural competition on the basis of the plan in 2017.
Comprehensive efforts were made to encourage stakeholders to contribute ideas and identify needs.

Workshops and dialogue meetings were held with young people, local businesses, shipping companies, utility companies, private property owners, Svendborg International Maritime Academy, SIMAC, and many more. Furthermore, a large public meeting was held.

The municipality continuously cooperates with stakeholders in the project.
The winning project from the architectural competition is being monitored along the way, so that both technical solutions and financial aspects are continuously adapted to what is practicable.