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- Blumenthal, Barbara, 1969-, et al.
(författare)
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A GIS-based multivariate approach to identify flood damage affecting factors
- 2024
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- This paper investigates causal factors leading to pluvial flood damages, beside rainfall amount and intensity, in two Swedish cities. Observed flood damage data from a Swedish insurance database, collected under 13 years, and a set of spatial data, describing topography, demography, land cover and building type were analyzed through principal component analysis (PCA). The topographic wetness index (TWI) is the only investigated variable that indicates a significant relationship with to the number and amount of insurance damage. The Pearson correlation coefficient is 0.68 for the number of insurance damages and 0.63 for amount of insurance damages. With a linear regression model TWI explained 41% of the variance of the number of insurance flood damages and 34% of variance of amount of insurance flood damage.Future studies on this topic should consider implementing TWI as a potential measure in urban flood risk analyses.
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| 2. |
- Andersson, Jan-Olov, 1966-
(författare)
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A GIS-based landscape analysis of dissolved organic carbon in boreal headwater streams
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In boreal catchments, stream water chemistry is influenced and controlled by several landscape factors. The influence of spatially distributed variables is in turn dependent on the hydrological scale. Headwater streams have larger variability of water chemistry, and thus together represent a large biodiversity, and therefore need to be monitored in official environmental assessments. One objective of this study was, using Geographical Information Systems (GIS), to analyse co-variation between landscape variables and water chemistry and to determine which of the landscape variables have a major influence on the concentration of dissolved organic carbon (DOC) in headwater streams. Another objective was to find a simple method for predicting sources of DOC, using official map data and publically available GIS applications. Totally 85 headwater catchments (0.1-4 km2) in the county of Värmland, western south Sweden, were used in the study. Water chemistry was analysed for water sampled at low, medium and high flows, and landscape variables were extracted from official map data sources: topographic maps, a digital elevation model (DEM, 50 m grid), and vegetation data. Statistical analyses showed that topography (mean slope and mean topographic wetness index (TWI)) and wetland cover often correlated well with DOC in headwater catchments. Official map data could satisfactorily extract landscape variables (mean slope, mean TWI) that were useful in predicting stream water chemistry (DOC). A high-resolution elevation model, which was generated by interpolation of photogrammetric data, was used to calculate and evaluate two different wetness indices and their ability to predict the occurrence of wetlands in six catchments of different sizes and topography. The SAGA (System for Automated Geoscientific Analyses) wetness index (SWI) gave substantially better results than the TWI. The effects of resolution of DEMs on calculations of the SWI were investigated using 5, 10, 25 and 50 m grids. The results showed that SWI values increased with increasing cell size. The near linear increment of mean values for resolutions 10-50 m suggests a independence of terrain type and catchment size, which supported previous findings that indicated that mean slope and mean wetness index calculated from coarse elevation models may be used for prediction of DOC in headwater streams.
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| 4. |
- Andersson, Jan-Olov, 1966-, et al.
(författare)
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Spatial variation of wetlands and flux of dissolved organic carbon in boreal headwater streams
- 2008
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Ingår i: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; :22, s. 1965-1975
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Tidskriftsartikel (refereegranskat)abstract
- In order to investigate the relation between water chemistry and functional landscape elements, spatial data sets of characteristics for 68 small (0·2–1·5 km2) boreal forest catchments in western central Sweden were analysed in a geographical information system (GIS). The geographic data used were extracted from official topographic maps. Water sampled four times at different flow situations was analysed chemically. This paper focuses on one phenomenon that has an important influence on headwater quality in boreal, coniferous forest streams: generation and export of dissolved organic carbon (DOC). It is known that wetland cover (bogs and fens) in the catchment is a major source of DOC. In this study, a comparison was made between a large number of headwater catchments with varying spatial locations and areas of wetlands. How this variation, together with a number of other spatial variables, influences the DOC flux in the streamwater was analysed by statistical methods. There were significant, but not strong, correlations between the total percentages of wetland area and DOC flux measured at a medium flow situation, but not at high flow. Neither were there any significant correlations between the percentage of wetland area connected to streams, nor the percentage of wetland area within a zone 50 m from the stream and the DOC flux. There were, however, correlations between catchment mean slope and the DOC flux in all but one flow situations. This study showed that, considering geographical data retrieved from official sources, the topography of a catchment better explains the variation in DOC flux than the percentage and locations of distinct wetland areas. This emphasizes the need for high-resolution elevation models accurate enough to reveal the sources of DOC found in headwater streams.
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| 5. |
- Andersson, Jan-Olov, 1966-, et al.
(författare)
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Using official map data on topography, wetlands and vegetation cover for prediction of stream water chemistry in boreal headwater catchments
- 2009
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Ingår i: Hydrology and Earth System Sciences. - : Copernicus GmbH. - 1027-5606 .- 1607-7938. ; 13, s. 537-549
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Tidskriftsartikel (refereegranskat)abstract
- Abstract. A large part of the spatial variation of stream water chemistry can be related to inputs from headwater streams. In order to understand and analyse the dominant processes taking place in small and heterogeneous catchments, accurate data with high spatial and temporal resolution is necessary. In most cases, the quality and resolution of available map data are considered too poor to be used in environmental assessments and modelling of headwater stream chemistry. In this study 18 forested catchments (1–4 km2) were selected within a 120×50 km region in the county of Värmland in western Sweden. The aim was to test if topographic and vegetation variables derived from official datasets were correlated to stream water chemistry, primarily the concentration of dissolved organic carbon (DOC), but also Al, Fe and Si content. GIS was used to analyse the elevation characteristics, generate topographic indices, and calculate the percentage of wetlands and a number of vegetation classes. The results clearly show that topography has a major influence on stream water chemistry. There were strong correlations between mean slope and percentage wetland, percentage wetland and DOC, mean slope and DOC, and a very strong correlation between mean topographic wetness index (TWI) and DOC. The conclusion was that official topographic data, despite uncertain or of low quality and resolution, could be useful in the prediction of headwater DOC-concentration in boreal forested catchments.
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| 9. |
- Vigerland, Sarah, et al.
(författare)
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Long-term outcomes and predictors of internet-delivered cognitive behavioral therapy for childhood anxiety disorders.
- 2017
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Ingår i: Behaviour Research and Therapy. - : Elsevier. - 0005-7967 .- 1873-622X. ; 90, s. 67-75
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: This study investigated the long-term outcomes of internet-delivered cognitive behavior therapy (ICBT) for children with anxiety disorders, and potential pre-treatment predictors of treatment outcome.METHOD: The sample included eighty-four children (8-12 years old) with anxiety disorders, from both a treatment group and a waitlist control (after participants had crossed over to treatment) of a previous randomized controlled study. Participants were assessed at post-treatment and three- and twelve-months after treatment using a semi-structured interview and parent ratings. Pre-treatment data were used to investigate predictors of treatment outcome at three-month follow-up.RESULTS: Intention-to-treat analysis showed that treatment gains were maintained at twelve-month follow-up, including clinician rated severity of the principal anxiety disorder, parent rated anxiety symptoms and global functioning, with mainly large effect sizes (Cohen's d = 0.63-2.35). Completer analyses showed that suspected autism spectrum disorder was associated with less change in symptom severity. No other pre-treatment measures significantly predicted treatment outcome.CONCLUSION: This study suggests that internet-delivered CBT can have long-term beneficial effects for children with anxiety disorders. Predictors of treatment outcome need to be evaluated further.TRIAL REGISTRATION: Clinicaltrials.gov; NCT01533402.
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