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Comparison of methods for predicting regolith thickness in previously glaciated terrain, Stockholm, Sweden
KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.ORCID iD: 0000-0002-3614-671X
KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.ORCID iD: 0000-0003-1736-0718
KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
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2014 (English)In: Geoderma, ISSN 0016-7061, E-ISSN 1872-6259, Vol. 226, 116-129 p.Article in journal (Refereed) Published
Abstract [en]

Knowledge about regolith thickness is important in several civil and environmental engineering fields. However, subsurface characteristics such as regolith thickness are difficult to determine through surface investigations and maps at regional scales. This paper presents four methods for estimating regolith thickness in a GIS environment for previously glaciated terrain with high frequency of rock outcrops: linear regression (LR) using topographical covariates; inverse distance weighting (IOW) interpolation of regolith thickness point data from well drillings: a trigonometrical approach (TA) developed for this study which uses outcrop slopes and distance between outcrops; and a simplified regolith model (SRM). The SRM is a model modified from TA which estimates the regolith thickness based on outcrops, slopes and the distance to outcrops in eight directions. The methods were compared for three study areas (Tyreso, Vallentuna and Osteraker) in Stockholm County, Sweden. Based on the results in this paper, LR proved to be the most accurate method for regolith thickness estimation, measured through root mean square error values. Whereas IDW was the most accurate method in terms of error within 2 m, which would make it a suitable model if and when large datasets of regolith point data are available. When drilling data is scarce then both the TA and SRM methods can be used for regolith estimations. However, the SRM proved to be a more accurate regolith thickness model compared to TA. SRM shows promising results and could be used at a preliminary stage in engineering projects where little or no data is available prior to detailed field investigations in previously glaciated terrain.

Place, publisher, year, edition, pages
2014. Vol. 226, 116-129 p.
National Category
Earth and Related Environmental Sciences
Identifiers
URN: urn:nbn:se:kth:diva-147399DOI: 10.1016/j.geoderma.2014.03.003ISI: 000336467500013Scopus ID: 2-s2.0-84897441618OAI: oai:DiVA.org:kth-147399DiVA: diva2:731789
Funder
Formas, 2009-1285
Note

QC 20140702

Available from: 2014-07-02 Created: 2014-06-27 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Subsurface dams in water resource management: methods for assessment and location
Open this publication in new window or tab >>Subsurface dams in water resource management: methods for assessment and location
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Natural groundwater storage can be improved by constructing a subsurface barrier that is a subsurface dam, in order to capture the subsurface flows and raise the groundwater levels (GWLs) in the sediment layers. Subsurface dams are preferable to surface dams because of lower evaporation, higher functionality, lower cost of construction, lessened risk for contamination and the possibility of utilizing land over the dam. Therefore subsurface dams constitute an affordable and effective method for the sustainable development and management of groundwater resources. The aim of this research project was to develop and test methods for the assessment and location of subsurface dams in water resources management. From previous experiences it has been established that locating suitable sites for construction of subsurface dams plays an important role in the overall success of these dams. Therefore, in order to locate suitable sites, two approaches were followed. The first was the Boolean approach using topographical, geological and landcover data in a geographic information system (GIS) environment for a previously glaciated terrain near Stockholm. The results of the Boolean approach were complemented by a groundwater balance model and a topographic wetness index (TWI). The second approach involved spatial multi-criteria analysis (SMCA) applied to a region with different geological and hydrological conditions. SMCA was applied in Northern Pakistan using factors such as topography, geology, landcover, soil thickness and TWI. Two weighting techniques, the analytic hierarchy process (AHP) and the factor interaction method (FIM), were employed and compared. The Factor removal technique was employed to assess the sensitivity of the model for each factor. Aquifer thickness is an important factor while planning subsurface dams and data regarding the soil thickness is often not available at larger scale. Therefore a simplified regolith model (SRM) was developed for estimating the regolith thickness in previously glaciated terrain with a high frequency of rock outcrops, based on a digital elevation model (DEM) and an optimized outcrop search algorithm. In order to analyse the dynamics of the groundwater flow, a transient 3D groundwater flow model was developed for a subsurface dam. Methods applied to locate suitable sites for the construction of subsurface dams showed some promising results and need to be applied and tested in areas with different hydrological and geological conditions. The Boolean approach is a simple method that could be used during early planning stages for locating suitable sites for the construction of subsurface dams. The SMCA framework enabled the integration of knowledge for decision making, where the weights had a more significant influence on the results than the choice of the weighting method. AHP was considered to be the more robust model for assigning weights in this study. The factor removal technique showed that the modeling results were least sensitive to soil depth and most sensitive to land cover for the construction of subsurface dams. SRM showed reasonable results and could be used in engineering projects prior to detailed field investigations in formally glaciated terrain when borehole data is not available. The groundwater flow modelling results helped to develop some sustainable pumping scenarios to demonstrate the benefits of the subsurface dam. Groundwater flow model results also facilitated the selection of a suitable site for placing a subsurface dam in order to maximize the groundwater storage upstream. It was concluded in this project that the subsurface dams could sustainably be used to mitigate the water supply issues in formerly glaciated humid terrain such as in Sweden and dry climatic areas such as in Pakistan. Moreover, subsurface dams can play an important role in water resources management in coastal areas of formerly glaciated terrain, where saltwater intrusion is a rising environmental issue. Also in dry climatic areas like in Pakistan, methods such as SMCA could make the planning step more robust before the actual construction of dams. Themethods and findings presented in this thesis can be considered to be one tentative step of scientific contribution for better analysis, assessment and the location of subsurface dams.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. xiv, 38 p.
Series
TRITA-LWR. PHD, ISSN 1650-8602 ; 2016:01
Keyword
Subsurface dams, Groundwater, GIS, Regolith thickness, Groundwater
National Category
Water Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-181937 (URN)978-91-7595-837-8 (ISBN)
Public defence
2016-03-03, F3, Lindstedtsvägen 26, KTH, Stockholm, 14:00 (English)
Opponent
Supervisors
Note

QC 20160210

Available from: 2016-02-10 Created: 2016-02-09 Last updated: 2016-02-10Bibliographically approved
2. Geo-environmental considerations in transport infrastructure planning
Open this publication in new window or tab >>Geo-environmental considerations in transport infrastructure planning
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Transport infrastructure constitutes one of the key factors to a country’s economic growth. Investment in new transport infrastructure might cause potential environmental impacts, and if a project has several alternative corridors open for suggestion then each alternative corridor will have a different impact on the environment. The European Commission has stated that the natural resources are important to the quality of life. Therefore, the efficient use of resources will be a key towards meeting future climate change and reduction in greenhouse gas (GHG) emissions. This implies that in an evergrowing global society the resource efficiency as well as the choice of transport infrastructure corridor becomes even more important to consider. The aim of this research project was to contribute to early transport infrastructure planning by the development of methods for and implementation of easy understandable geological criteria and models for decision support. Moreover, the intention was to assess how geological information can be developed and extracted from existing spatial data and coupled with other areas of interest, such as ecology and life cycle assessment. It has previously been established that geological information plays an important role in transport infrastructure planning, as the geological characteristics of the proposed area as well as the possibilities of material use influences the project. Therefore, in order to couple geological information for early transport infrastructure planning, four studies (Paper I-IV) were undertaken where methods were developed and tested for the inclusion of geological information. The first study (Paper I) demonstate how optional road corridors could be evaluated using geological information of soil thickness, soil type and rock outcrops, bedrock quality and slope in combination with ecological information. The second study (Paper II) shows how geological information of soil thickness and stratigraphy can be combined with life cycle assessments (LCA) to assess the corresponding greenhouse gas emission and energy use for the proposed road corridors. The difficulty of using expert knowledge for susceptibility assessment of natural hazards, i.e. flooding, landslide and debris flow, for early transport infrastructure planning was presented in the third study (Paper III). In this study the expert knowledge was used in a multi-criteria analysis where the analytic hierarchy process (AHP) was chosen as a decision rule. This decision rule was compared to the decision rule weighted linear combination (WLC) using two different schemes of weighting. In all the mentioned studies the importance of soil thickness information was highlighted. Therefore, the fourth and final study (Paper IV) presented a new methodology for modelling the soil thickness in areas where data is sparse. A simplified regolith model (SRM) was developed in order to estimate the regolith thickness, i.e. soil thickness, for previously glaciate terrain with a high frequency of rock outcrops. SRM was based on a digital elevation model (DEM) and an optimized search algorithm. The methods developed in order to couple geological information with other areas of interest is a tentative step towards an earlier geo-environmental planning process. However, the methods need to be tested in other areas with different geological conditions. The combination of geological information in GIS with MCA enabled the integration of knowledge for decision making; it also allowed influencing the importance between various aspects of geological information as well as the importance between geological information and other fields of interest, such as ecology, through the selected weighting schemes. The results showed that synergies exist between ecology and geology, where important geological considerations could also have positive effects on ecological consideration. Soil thickness was very important for GHG emission and energy whereas stratigraphical knowledge had a minor influence. When using expert knowledge the consistency in the expert judgements also needs to be considered. It was shown that experts tended to be inconsistent in their judgements, and that some consistency could be reached if the judgements were aggregated instead of used separately. The results also showed that the developed SRM had relatively accurate results for data sparse areas, and that this model could be used in several projects where the knowledge of soil thickness is important but lacking. It was concluded that geological information should be considered. By using GIS and MCA it is possible to evaluate different aspects of geological information in order to improve decision making.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. 44 p.
Series
TRITA-LWR. PHD, ISSN 1650-8602 ; 2016:07
Series
TRITA-LWR PHD, ISSN 1650-8602 ; 2016:07
Keyword
Roads, Railways, Geology, GIS, Decision support, Modelling
National Category
Earth and Related Environmental Sciences
Research subject
Land and Water Resources Engineering
Identifiers
urn:nbn:se:kth:diva-192918 (URN)978-91-7729-124-4 (ISBN)
Public defence
2016-10-14, Kollegiesalen, Brinellvägen 8, Stockholm, 14:00 (English)
Opponent
Supervisors
Projects
Environmental assessment of road geology and ecology in a system perspective
Funder
Swedish Research Council Formas, 242-2009-1285, 2014 - 754
Available from: 2016-09-23 Created: 2016-09-22 Last updated: 2016-09-23Bibliographically approved

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Karlsson, CarolineAli, ImranMörtberg, Ulla

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