When a little town north of Copenhagen was buffeted by a once-in-a-generation flood, the estimated cost of building canals and dams to prevent it happening again was put at 100-million Danish Kroner.
Even for a rich country, R200-million is a lot of money to fix a stream – and for something that not might not happen again in a lifetime.
By taking a holistic approach, engineering consulting company NIRAS managed not only to cut R100-million off the bill, they provided the residents of the Sillebr area in Frederikssund with a magnificent park.
A delegation of Southern African water experts on a study tour heard from the company’s representatives that the whole process of transforming the river valley took four years from planning to delivery.
The construction phase of the project took just elevens months.
The Southern Africans are traveling at the invitation of the Danish Ambassador to South Africa, Rene Dinesen, on behalf of the Danish Ministry of Foreign Affairs.
Covering just over one square kilometre, the Sillebro Ådal project has a 35km-square catchment area.
Sillebro Ådal avoids the old-fashioned approach of canals and pipes. Instead of channelling large amounts of fast-moving water into narrow canals, NIRAS has succeeded in engineering a solution that has technical components like filters and pipes, but they are concealed and the vital elements of flood-mitigation are much more subtle.
Chemicals and oil are filtered out of the water, using a combination of methods.
As Henrik Lynghus, the marketing director at NIRAS explained on a site visit, “We have managed the river flow with ponds, overflow systems, controlled seepage and filters.”
Lots of vegetation was removed when the river course was altered but much more was planted, and these additions were all chosen for their ability to absorb water and stem the flow. Several reed beds were added.
Where the river used to run arrow-straight, it now curves its way from the top pond towards the bottom of the little valley where the river has to narrow sharply to pass through an area with quite a high density of buildings.
A civil engineer, Lynghus works within his company’s section called ‘Climate change adaptation, water and nature’.
His enthusiasm for the ‘nature’ part of his brief is clear when he outlines the benefits of the completed Sillebr Ådal project.
“We have enhanced nature”, he says. The ponds will provide places to swim – and skate on when the real winter weather kicks in, something the visiting Africans were very happy to be avoiding.
A network of winding paths cater to walkers and cyclists. Gradual gradients ensure that people in wheelchairs can use the park. There is even a specially designed pier so that disabled people can fish. The ponds will attract birds in the spring and at specific points, water flow has been designed to be heard.
“The sound of water is good for the human heart”, says Henrik.
NIRAS has about 1 400 employees and operates in every part of the world. It has African offices in Eygpt, Ethiopia, Uganda, Kenya, Tanzania, Mozambique and South Africa.