Airborne remote sensing as a tool for monitoring topographical and hydrological changes on northern degraded and restored peatlands
Thesis event information
Date and time of the thesis defence
Place of the thesis defence
Martti Ahtisaari auditorium (L2)
Topic of the dissertation
Airborne remote sensing as a tool for monitoring topographical and hydrological changes on northern degraded and restored peatlands
Doctoral candidate
Master of Science (Technology) Lauri Ikkala
Faculty and unit
University of Oulu Graduate School, Faculty of Technology, Water, Energy and Environmental Engineering Research Unit
Subject of study
Environmental Engineering
Opponent
Doctor Lauri Markelin, Finnish Geospatial Research Institute
Custos
Associate Professor Hannu Marttila, University of Oulu
Remote sensing as a tool for monitoring elevation and hydrological changes on drained and restored peatlands
The possibilities of airborne remote sensing in peatland monitoring are studied in the doctoral thesis. A significant share of peatlands is degraded due to drainage and land use. Monitoring is needed for understanding the status and change of peatlands, reducing their environmental impacts and evaluating the restoration success. Remote sensing enables extending the conventional monitoring data, which is typically limited to single points, to spatially continuous datasets. Remote sensing methods for monitoring peatland topography and hydrology are reviewed in the thesis from the available literature. In addition, selected remote sensing and data processing methods were demonstrated on cultivated peatlands as well as in restoration sites once drained for forestry.
In drainage, the water naturally belonging to the peatland has been directed to the ditch network. Thus, the peat has dried, and it has begun to degrade, which has caused subsidence. In the thesis, the subsidence was shown to significantly increase the flood risk on cultivated riverside peatlands. The average annual flood area increased two–threefold during the past 24–51 years. Whereas in restoration, the ditches are infilled, which makes the peatland water table rise. However, the flow routes do not necessarily fully recover, since the land has encountered uneven subsidence, most of it located along the ditches. Thus, the flow routes typically remain on the ditch lines despite the infilling. In the thesis, the quantitative impact of restoration on the flow routes and wetness was shown. The restoration promoted uniform rewetting of the studied sites. The mean wetness increased by 3–7% during the 1–10 months after the restoration.
Remote sensing is well applicable in peatland monitoring, providing advanced large coverage and/or high-detail monitoring data. Each method, however, includes specific technical challenges and development needs. The production of the data can be fluent and flexible but ensuring sufficient quality might be laborious. For many areas, open data, such as national aerial imageries and digital terrain models, can be utilized. The results of the thesis and the developed methods can be applied to guide peatland management and improve restoration practices.
In drainage, the water naturally belonging to the peatland has been directed to the ditch network. Thus, the peat has dried, and it has begun to degrade, which has caused subsidence. In the thesis, the subsidence was shown to significantly increase the flood risk on cultivated riverside peatlands. The average annual flood area increased two–threefold during the past 24–51 years. Whereas in restoration, the ditches are infilled, which makes the peatland water table rise. However, the flow routes do not necessarily fully recover, since the land has encountered uneven subsidence, most of it located along the ditches. Thus, the flow routes typically remain on the ditch lines despite the infilling. In the thesis, the quantitative impact of restoration on the flow routes and wetness was shown. The restoration promoted uniform rewetting of the studied sites. The mean wetness increased by 3–7% during the 1–10 months after the restoration.
Remote sensing is well applicable in peatland monitoring, providing advanced large coverage and/or high-detail monitoring data. Each method, however, includes specific technical challenges and development needs. The production of the data can be fluent and flexible but ensuring sufficient quality might be laborious. For many areas, open data, such as national aerial imageries and digital terrain models, can be utilized. The results of the thesis and the developed methods can be applied to guide peatland management and improve restoration practices.
Last updated: 23.1.2024