Comparing ‘geomorphic design’ and conventional waste rock deposits at a mining site in northern Sweden.

Today, mining products are crucial to the development of various sectors of the economy. Although mining companies are trying to reduce their impact on the planet by aiming for green mining, huge waste rock deposits are placed around mining areas without specific guidelines to allow for ecological recovery. Waste rock deposits are usually formed to optimize the storage volume per area, with a stable terrace shape, according to the closure plan. Although this form is stable in the short term, the structures tend to erode through the development of gullies, driven by fluvial erosion, producing onsite (loss of vegetation and topsoil) and offsite (river pollution) effects. In order to reduce these impacts and leave a more sustainable landscape, geomorphic restoration of waste rock deposits have been undertaken at several sites, mainly in semi-arid environments where fluvial processes driven by rainfall events dominate. Here we present preliminary results of the first monitoring and comparison between geomorphic restoration waste rock deposit, with two main objectives: 1) compare the erosive response of the geomorphic and conventional site and 2) compare the advantages and disadvantages of the different surveying methods in a mining context.

The Svappavaara mining site is managed by LKAB and is located in northern Sweden. A 4-hectare geomorphic restoration started in 2022 and was completed in July 2023 after the addition of topsoil (till). The conventional terraced waste rock deposit was started in 2023 and completed in summer 2024. Surveys to assess geomorphic changes at both sites were carried out using photogrammetry with a DJI P1 camera, DJI L1 LiDAR camera and ground control points (GPS and total station). Comparable surveys within the geomorphic site were assessed in October 2023, June 2024 and October 2024 and will continue until spring 2026. Image errors that were obtained from 10 GCP ranged between 1.8 and 3 cm on the vertical axis. We use Geomorphic Change Detection software to compare the different digital elevation models generated by the surveys to determine erosion and deposition. As a control, a pond was constructed immediately downstream of the monitoring station to trap sediment and calculate the total export from each site.

Preliminary results from the surveys suggest initially high erosion rates at the geomorphic site with a declining trend. Erosion rates at the conventional site remain at an initially moderate level without a decreasing trend. Erosion at the geomorphic site followed expected patterns in channels and some rills on hillslopes. However, erosion at the conventional site exhibited the start of gully formation. We show how varying patterns of snowmelt and rainfall impact erosion patterns.

Errors in the vertical axis were 2.1 to 1.8 cm with GPS and total station, while RTK and no GCP accounted for a 3 cm error. LiDAR with RTK had an error of 5 cm. These results have implications for understanding the stabilization of new landforms and drainage systems after disturbance, and will provide important baseline data for mining companies planning to use geomorphic design rather than conventional waste dumps.