Blog post

Planting forest to protect ground water and increase biodiversity

Jul 7, 2021

by Jonas Ribergaard Rasmussen (jrra@cowi.com) and Helena Åström (helena@scalgo.com)

Across Europe, re-creating forest areas (also known as afforestation) is being used for climate mitigation, ground water protection and natural flood management.

In Denmark, for example, the Danish Nature Agency has been restoring nature so that wildlife and flora can thrive and groundwater can be protected from further contamination by pesticides and chemicals.

In the example that follows, we show how COWI’s consulting engineers use SCALGO Live to help the Danish Nature Agency design and define afforestation projects.

The project is from an 18-hectare, abandoned cornfield near the True Forest just outside the city of Aarhus. It required COWI to create realistic scenarios for bringing water from old drainage pipes back to the surface.

This meant, among other things, reforming terrain and achieving the goals of afforestation by creating natural ponds and natural surface water flow while also adhering to the legal requirement of securing continued drainage from upstream catchments.

Here is how SCALGO Live helped them do it.

Step 1: Starting from scratch

“What did we know about this area?” says Jonas Ribergaard Rasmussen, project manager at COWI.

“Not much”

“In a project like this one, we don’t always know a lot at the start in this project we only had an old drainage map from Aarhus Municipality which gave us an idea of what could be hidden beneath the surface. Together with people from the Nature Agency, I identified all visible wells in the project area. Then I brought that data directly into SCALGO Live,” he says.

The project area, an old corn field, is being transformed into a forest with natural streams and ponds to increase biodiversity and protect ground water.

Step 2: Mapping hidden pipes

Based on the old drainage map and all identified well points, SCALGO Live helped visualise where the underground pipes were located.

This gave planners a starting point for understanding the current sub-surface flow paths and catchments.

Green lines and dots represent identified drainage pipes and wells in the area. Data was brought into SCALGO Live.

Step 3: Understanding surface water characteristics

“The task was then to figure out where we could bring water to the surface without affecting the neighbours and without flooding their property. Also, you are not allowed to stop the free flow of water from upstream catchments, so it was important that surface water drainage was both natural and effective,” says Jonas Ribergaard Rasmussen.

The flow path analysis in SCALGO Live was used to describe natural conditions for surface water flow. As shown in the picture below, old drainage pipes follow the calculated flow paths quite well.

The flow paths were then used as a guideline for placing natural streams and ponds. Where flow paths run through forested areas, streams were re-directed. The dotted black circle shows a location where the flow paths crosses a forest, and hence, re-direction of the stream was needed.

Purple lines show flow paths from SCALGO Lives analysis. Green lines are old pipes and wells. The dotted black circle shows an area where the flow path crosses a forest, Here, the stream should be re-directed.

Step 4: Imagining new scenarios

Using the terrain editing tools in SCALGO Live, COWI planners could then begin to design and visualize how surface water would flow on terrain.

While edits are made SCALGO Live automatically computes how much soil that must be moved to create the suggested design of meandering streams and small ponds.

“Before SCALGO Live you would be working in a GIS map to get an overview, while all the data would be computed separately in an excel sheet. Every time you made one little change to depths or paths, you would have to go back and recalculate everything from the beginning. Now you can do it all in one software. And you can do it on-the-fly, which saves us a lot of time says Jonas Ribergaard Rasmussen.

The terrain editing tools make it easy to change the elevation model. The black lines show where terrain edits have been placed to create small streams. The elevation profile in the upper left corner shows the cross-section of the streams.

Step 5: Communicating the results

Besides being used as a planning tool, SCALGO Live also helped communicate project ideas to clients. The advantage of interactive analyses and visualisations is that it is easy for planners to explain their findings and engage with stakeholders.

“We have had regular meetings with the client, and it has been very easy to share screens and show the stages step-by-step to get input directly so we could get it right the first time,” says Jonas Ribergaard Rasmussen.

The blue lines show the final plan where ponds and streams work together to create natural drainage and better biodiversity, and actively contribute to the afforestation goals. Where a purple line, i.e. the initial flow path analysis, is shown, the final stream has been re-directed.

Want to learn more about how SCALGO Live can help you understand, design and communicate when working with nature restoration? Contact Jonas (jrra@cowi.com) or Helena (helena@scalgo.com)