Studie av faktorer som påverkar skredutbredningen vid Norsälven, Värmland
(2014) In Examensarbeten i Geologi vid Lunds universitet GEOL01 20141Department of Geology
- Abstract (Swedish)
- Ett förändrat klimat som en funktion av den pågående globala uppvärmningen kan i Sverige komma att leda till en ökning av naturkatastrofer i form av bland annat skred. Längs Norsälven i Värmland har det vid flera tidigare tillfällen inträffat skred och området har nu valts ut av Statens Geotekniska Institut (SGI) för att under 2013-2014 användas som ett pilotprojekt inom ett regeringsuppdrag för skredriskkartering.
Då flera av de inträffade skreden är starkt bakåtgripande i de sediment som omger Norsälven, med de största inträffade skreden inom ett avsnitt 17 000–21 000 m från älvens mynning i Vänern, är det av intresse att undersöka vilken eller vilka faktorer som påverkar utbredningen av dessa skred. Bland ett stort antal faktorer... (More) - Ett förändrat klimat som en funktion av den pågående globala uppvärmningen kan i Sverige komma att leda till en ökning av naturkatastrofer i form av bland annat skred. Längs Norsälven i Värmland har det vid flera tidigare tillfällen inträffat skred och området har nu valts ut av Statens Geotekniska Institut (SGI) för att under 2013-2014 användas som ett pilotprojekt inom ett regeringsuppdrag för skredriskkartering.
Då flera av de inträffade skreden är starkt bakåtgripande i de sediment som omger Norsälven, med de största inträffade skreden inom ett avsnitt 17 000–21 000 m från älvens mynning i Vänern, är det av intresse att undersöka vilken eller vilka faktorer som påverkar utbredningen av dessa skred. Bland ett stort antal faktorer valdes slänthöjd, sensitivitet och andelen siltjordar ut som lämpliga att undersöka med avseende på deras betydelse för skredutbredning.
Resultaten från studien visar bland annat att det finns stora förekomster av extremsensitiva jordar och kvicklera längs Norsälven fram till 16 000 m från dess mynning. Resultaten visar även att slänthöjd, som varierar kraftigt inom intervallet 3-43 m höjd, med de högre värdena uppmätta inom området 12 000–24 500 m, är av stor betydelse. Siltjordar dominerar inom intervallet 15 000–21 000 m från älvens mynning, medan leriga sediment är dominerar i områdena norr och söder om detta intervall.
Studien visar att det i området söder om 16 000 m från älvmynningen främst är sensitiviteten, i kombination med en hög slänthöjd, som bidrar till stora bakåtgripande skred. I det intervall längs älven där de största skreden är uppmätta indikerar resultaten istället att det är en hög andel silt, i kombination med en hög slänthöjd, som påverkar skredens utbredning.
För framtida studier skulle det behövas ytterligare undersökningar där bland annat portryck och grundvattenförhållanden längs älven utreds för att på så sätt få en klarare bild över hur dessa faktorer påverkar skredutbredningen. (Less) - Abstract
- The oncoming climate change due to the progressing global warming may in Sweden lead to an increase in natural disasters, among other e.g. in the form of landslides. Alongside the river Norsälven in Värmland there has on several occasions occurred landslides and this area has now been selected by the Swedish Geotechnical Institute (SGI) to be used during the period 2013-2014 for a pilot project for mapping of landslide risks as part of a government commission.
Since several of the landslides that have occurred were regressive, with the largest landslides occurring within a section from 17 000 to 21 000 meters from the river's mouth in Lake Vänern, it is of interest to investigate which factors are most important for the initiation and... (More) - The oncoming climate change due to the progressing global warming may in Sweden lead to an increase in natural disasters, among other e.g. in the form of landslides. Alongside the river Norsälven in Värmland there has on several occasions occurred landslides and this area has now been selected by the Swedish Geotechnical Institute (SGI) to be used during the period 2013-2014 for a pilot project for mapping of landslide risks as part of a government commission.
Since several of the landslides that have occurred were regressive, with the largest landslides occurring within a section from 17 000 to 21 000 meters from the river's mouth in Lake Vänern, it is of interest to investigate which factors are most important for the initiation and lateral spread of these landslides. Out of a large number of factors, slope height, sensitivity and the percentage of silt in the sediment along Norsälven were selected as suitable choices to investigate.
The results from this study show that there are large deposits of extremely sensitive soils and quick clay along Norsälven, up to 16 000 m from its mouth in the south. They also show that the slope height varies widely in the range of 3-43 m, with the higher values measured in between 12 000 to 24 500 m from the river mouth. Silty sediments dominate between 15 000 to 21,000 m from the river mouth, while clayey sediments are predominant in the areas north and south of this length interval.
The analysis further shows that in the area south of 16 000 m from the river mouth, it primarily is the sensitivity of the sediment, in combination with a high slope height, that contributes to large backward moving landslides. In the length section where the largest landslides have been identified, the contributing factors instead seems to be a high proportion of silty sediment, in combination with a high slope height that has been the driving mechanisms.
Further investigation is needed to examine pore pressure and groundwater conditions alongside the river in order to get a clearer picture of how these factors might affect and be important for regressive landslides in the area. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/4459577
- author
- Järvin, Sara LU
- supervisor
- organization
- alternative title
- Study of factors influencing the spread of landslides at Norsälven, Värmland
- course
- GEOL01 20141
- year
- 2014
- type
- M2 - Bachelor Degree
- subject
- keywords
- skred, sensitivitet, slänthöjd, kvicklera, Norsälven, silt, landslide, sensitivity, slope height, quick clay
- publication/series
- Examensarbeten i Geologi vid Lunds universitet
- report number
- 392
- language
- Swedish
- additional info
- Extern handledare Hjördis Löfroth, Statens Geotekniska Institut
- id
- 4459577
- date added to LUP
- 2014-06-12 13:10:13
- date last changed
- 2014-06-12 13:10:13
@misc{4459577,
abstract = {{The oncoming climate change due to the progressing global warming may in Sweden lead to an increase in natural disasters, among other e.g. in the form of landslides. Alongside the river Norsälven in Värmland there has on several occasions occurred landslides and this area has now been selected by the Swedish Geotechnical Institute (SGI) to be used during the period 2013-2014 for a pilot project for mapping of landslide risks as part of a government commission.
Since several of the landslides that have occurred were regressive, with the largest landslides occurring within a section from 17 000 to 21 000 meters from the river's mouth in Lake Vänern, it is of interest to investigate which factors are most important for the initiation and lateral spread of these landslides. Out of a large number of factors, slope height, sensitivity and the percentage of silt in the sediment along Norsälven were selected as suitable choices to investigate.
The results from this study show that there are large deposits of extremely sensitive soils and quick clay along Norsälven, up to 16 000 m from its mouth in the south. They also show that the slope height varies widely in the range of 3-43 m, with the higher values measured in between 12 000 to 24 500 m from the river mouth. Silty sediments dominate between 15 000 to 21,000 m from the river mouth, while clayey sediments are predominant in the areas north and south of this length interval.
The analysis further shows that in the area south of 16 000 m from the river mouth, it primarily is the sensitivity of the sediment, in combination with a high slope height, that contributes to large backward moving landslides. In the length section where the largest landslides have been identified, the contributing factors instead seems to be a high proportion of silty sediment, in combination with a high slope height that has been the driving mechanisms.
Further investigation is needed to examine pore pressure and groundwater conditions alongside the river in order to get a clearer picture of how these factors might affect and be important for regressive landslides in the area.}},
author = {{Järvin, Sara}},
language = {{swe}},
note = {{Student Paper}},
series = {{Examensarbeten i Geologi vid Lunds universitet}},
title = {{Studie av faktorer som påverkar skredutbredningen vid Norsälven, Värmland}},
year = {{2014}},
}