The extent and dynamics of permafrost are tightly linked to the distribution and movement of water in arctic landscapes. As the Arctic warms more rapidly than the global average, profound changes are expected in both permafrost and hydrology; however, much is still not known about the interactions between these two systems. The aim of this thesis is to provide new knowledge on the links between permafrost and hydrology under varying environmental conditions and across different scales. The objectives are to (i) determine how permafrost distributions and patterns in morphology are linked to hydrology, (ii) determine how groundwater flow influences ground temperature dynamics in permafrost landscapes, and (iii) explore the mechanisms that link permafrost to groundwater and streamflow dynamics. A range of methods have been applied within the four studies (papers I-IV) comprising the thesis: geophysical (ground penetrating radar and electrical resistivity tomography) and GIS techniques for mapping and analyzing permafrost distributions and related morphology; numerical modeling of coupled heat and water fluxes for mechanistic understanding permafrost-hydrological links; and statistical analyses for detecting trends in streamflow associated with permafrost thaw. Combining these various methods here allows for, and may be considered a prerequisite for, novel insights to processes. The thesis also presents statistical analyses of field observations of ground temperatures, ground- and surface water levels, as well as lake and shore morphological variables. Discontinuous permafrost peatlands are heterogeneous environments regarding permafrost distributions and thickness which is manifested in surface systems such as lake geometries. In these environments, lateral groundwater fluxes, which are not considered in most permafrost models, can significantly influence ground temperature dynamics, especially during high groundwater gradient conditions. River discharge data provide a potential for monitoring catchment-scale changes in permafrost, as the magnitude and seasonality of groundwater fluxes feeding into streams are affected by the distribution of permafrost. This thesis highlights the need to understand water and permafrost as an integrated system with potential internal feedback processes. For example, permafrost thaw can lead to increases in groundwater discharge which in turn can lead to increased heat transfer through the ground, resulting in further acceleration of permafrost thaw rates. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Manuscript.</p>

Spatial data management within the environmental field has a large range of application possibilities and comes with great advantages. In this study methods and technologies for spatial data management of soil contamination has been assessed in Geographical Information Systems (GIS), in order to identify in which way spatial data applications and tools can contribute with valuable information for these type of projects. The spatial assessment has been applied on a case study site in Kagghamra, Stockholm, exposed to high levels of contaminants, arsenic in particular. Subjects that have been evaluated are arsenic contamination distribution pattern, estimation of volume contaminated soil and amount of samples needed for spatial analyses. Furthermore, two versions of an exploratory soil sensitivity estimation model based on site specific ground and landscape parameters as well as literature references have been developed. The data management included large quantities of primary and secondary data of the commination levels as well as geological and ground properties. First hand collected geophysical field data obtained from Electromagnetic (EM) and Induced Polarisation (IP) measurements was also interpreted. The benefits of using geophysical measurements in soil contamination projects has been investigated. In this case the benefits were few due to difficult measuring conditions with disturbance noise. Spatial interpolations with the Natural Neighbour  (NN) technique are proven to be useful in transforming point contamination data into continuous layers. From the interpolation surfaces (arsenic distribution map) a variety of information can be extracted, such as a first hand volume estimation of contaminated soil, possibilities of reduction in amount of field sampling or to investigate statistical information and relations to different site specific ground conditions. The soil sensitivity estimation models are combined maps consisting of data layers that are relevant for the arsenic behaviour and interaction in the subsurface. Site specific Model (1) is based the data layers Soil type, Iron level, Soil depth, Slope  and illustrates mainly areas exposed to high concentrations of arsenic as high sensitivity areas. The more general, literature supported Model (2) also includes Vegetation cover and Topographic Wetness Index (TWI) and is not related highly to the arsenic distribution in the site area, but could contribute with general implications of sensitive areas if applied on a another, larger site area. Efficient management of large data quantities, economic and time saving benefits from less physical sampling and good representation and visualisation possibilities of the site conditions, as a tool for stakeholder communication and decision-making are the main contributions from the spatial data management.

Seabed surface sediments vary with active geomorphodynamics and sediment remobilization processes. Understanding relations between geotechnical sediment properties and sediment mobilization processes can potentially improve predictions of coastal erosion and hazard mitigation. Portable free fall penetrometers have emerged as an economic and useful tool for rapid geotechnical site characterization and uppermost sediment layer investigation. Acoustic methods have been used to assess seabed layering, scour evolution, and seabed morphology. However, there still exist major limitations in using these methods for classification and characterization of seabed sediment surface layers in the context of local sediment dynamics. Therefore, the goal of this research is to advance field data collection methods and field data availability towards advancing the current understanding and prediction of nearshore sediment dynamics. Geotechnical and geophysical measurements were conducted at different sites: Delaware Bay, Delaware; Pea Island, North Carolina; York River, Virginia; Potomac River, Maryland; Guadalupe River, Brazos River, Colorado River, Texas with different soil types and properties, hydrodynamic conditions, and morphological settings. The data collected was utilized to address the research goals through: (1) combining geotechnical and acoustic measurements to get better insight on sediment dynamics and erodibility, (2) proposing a framework that utilizes PFFP data to classify soil and estimate certain sediment properties (relative density and friction angle for sand and undrained shear strength for clays), relevant for local sediment dynamics, and (3) investigating how relevant geotechnical properties are reflected in acoustic, and specifically chirp sonar measurements. The findings of this research support the capability of portable free fall penetrometer to estimate sediment properties in topmost layers for different soil types such as friction angles, with an accuracy of ± 1° and undrained shear strength values, with <10% mismatches. Geoacoustic parameters such as acoustic impedance can also be calculated from acoustic measurements and correlated to certain sediment properties such as porosity and bulk density. Combining both measurements can yield better site characterization and accurate estimation of sediment properties for a better prediction of sediment dynamics. / Doctor of Philosophy / As the impacts of climate change seem to worsen, the likelihood of extreme events increases. This includes more frequent and severe events such as erosion, storm surges, melting glaciers, and sea level rise that impacts coastlines and coastal infrastructure. The increase in water levels increases the frequency of coastal hazards and flooding. These events result in devastating consequences, economically and environmentally, and disrupt people's lives all over the world. To adapt and reduce the severity of these consequences, there is a need to capture the changes in seabed, and a better understanding of seabed properties and their erodibility. This requires a reliable site characterization and an accurate estimate of seabed properties, which remain a challenge for different marine environments. There exist different site investigation methods to estimate seabed sediment properties that fall under geotechnical or geophysical types. One of the common geotechnical methods is a Portable free fall penetrometer (PFFPs), that presents a robust and economical tool for a rapid site assessment of topmost seabed layers. Geophysical tools, and mainly acoustic methods, are also often used to complement geotechnical methods due to their ability to cover vast areas in efficient time. However, both methods still face limitations in assessing seabed layers and properties. Therefore, the objective of this research is to develop a framework that paves the way for a reliable assessment of seabed properties using geotechnical and geophysical methods. Both methods were utilized for data collection in different locations across the US: Delaware Bay, Delaware; Pea Island, North Carolina; York River, Virginia; Potomac River, Maryland. Three additional sites Guadalupe, Brazos River, and Colorado Rivers, Texas were surveyed post hurricane Harvey that resulted in extreme flooding events. The measurements are collected from different coastal environments. This better account for the diversity in seabed to achieve a more generalized and well-integrated methodology to assess seabed layers under different conditions.

The complex and non-linear fluvial river dynamics are characterized by repeated periods of fluvial erosion and re-deposition in different parts of the floodplain. Understanding the fluvial architecture (i.e. the three-dimensional arrangement and genetic interconnectedness of different sediment types) is therefore fundamental to obtain well-based information about controlling factors. However, investigating the fluvial architecture in buried floodplain deposits without natural exposures is challenging. We studied the fluvial architecture of the middle Weiße Elster floodplain in Central Germany, an extraordinary long-standing archive of Holocene flooding and landscape changes in sensitive loess-covered Central European landscapes. We applied a novel systematic approach by coupling two-dimensional transects of electrical resistivity tomography (ERT) measurements and closely spaced core drillings with spatially resolved measurements of electromagnetic induction (EMI) of larger floodplain areas at three study sites. This allowed for (i) time and cost-efficient core drillings based on preceding ERT measurements and (ii) spatially scaling up the main elements of the fluvial architecture, such as the distribution of thick silt-clay overbank deposits and paleochannel patterns from the floodplain transects to larger surrounding areas. We found that fine-grained sand and silt-clay overbank deposits overlying basal gravels were deposited during several periods of intensive flooding. Those were separated from each other by periods of reduced flooding, allowing soil formation. However, the overbank deposits were severely laterally eroded before and during each sedimentation period. This was probably linked with pronounced meandering or even braiding of the river. Our preliminary chronological classification suggests that first fine-grained sedimentation must have occurred during the Early to Middle Holocene, and the last phase of lateral erosion and sedimentation during the Little Ice Age. Our study demonstrates the high archive potential of the buried fluvial sediments of the middle Weiße Elster floodplain and provides a promising time and cost-effective approach for future studies of buried floodplain sediments.