Blogindlæg

Early surface water planning makes it easier to create sustainable drainage systems

3. jun. 2022

By Helena Åström, helena@scalgo.com

In Køge Nord, Denmark, a new urban development will use nature-based stormwater measures to create sustainable drainage and flood protection whilst providing recreational areas and improving biodiversity.

Køge municipality has planned the site in close collaboration with KLAR water utility, EnviDan engineering consultancy and Schønherr architects. In the early stages of the project, EnviDan used SCALGO Live to continuously incorporate inputs from stakeholders, assess how suggested changes or new details might impact drainage, and discuss how flood challenges might be resolved. One of the initial plans for the area is shown in Figure 1.

“Initially the municipality wanted to reserve the south-eastern corner for dwelling, as this part was assessed to be the most attractive due to its proximity to the train station”, Christian Bjoljahn from EnviDan says. “However, the analysis in SCALGO Live revealed a big, natural depression in this area. Because of this, it was decided to exploit the natural flow patterns and construct detention basins there.”

Figure 1: One of the first versions of the master plan for Køge Nord, emphasizing the desired main flow paths and detention zones. The idea was that surface runoff would either flow into detention zones along the main road (also called the cloudburst road) or be transported by the cloudburst road into the big detention zones in the south-eastern corner.

SCALGO Live also revealed that there is a natural catchment divide running east-west across the development area, shown in Figure 2, dividing it into two separate watersheds. The low-cost and sustainable solution was, therefore, to “go with the flow” and establish an additional detention pond in the northern part.

“From the initial analyses in SCALGO Live, we could see that a main watershed is flowing south towards the natural depression, but a secondary watershed is flowing north”, Christian explains, “and it would be very expensive to force surface water from the entire development site to flow south.”

Figure 2: Screen shot from SCALGO Live showing the overland flow paths and flooded zones in Køge Nord given a cloudburst event with a return period of 50 years, after adapting the master plan to the natural terrain. The black line indicates the flow directions along the main cloudburst road, the profile window depicts the terrain along the road.

EnviDan used SCALGO Live to provide fast and efficient “frontloading” of relevant information, hereby supporting the process from the beginning of the project. Christian concludes:

“Had it not been for an early and close collaboration between all the stakeholders, the adjustments might not have been made until much later, by which time it would have been complicated and more costly to resolve them.”

Want to know more about this project? Contact Sara (sara@scalgo.com) or Christian Bjoljahn (chb@envidan.dk).

If you would like to learn more about surface water management in city planning and local planning, you can watch the webinar Regnvandshåndtering i byudvikling og lokalplanlægning.