hig.sePublications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard-cite-them-right
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • sv-SE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • de-DE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Importance of river bank and floodplain slopes on the accuracy of flood inundation mapping
University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Urban and regional planning/GIS-institute. (geomatik / geomatics)ORCID iD: 0000-0002-3884-3084
University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Urban and regional planning/GIS-institute. (geomatik / geomatics)ORCID iD: 0000-0002-3906-6088
2012 (English)In: River Flow 2012: Volume 2 / [ed] Rafael Murillo Muñoz, Leiden, The Netherlands: CRC Press / Balkema (Taylor & Francis) , 2012, p. 1015-1020Conference paper, Published paper (Refereed)
Abstract [en]

Effective flood assessment and management depend on accurate models of flood events, which in turn are strongly affected by the quality of digital elevation models (DEMs). In this study, HEC-RAS was used to route one specificwater discharge through the main channel of the Eskilstuna River, Sweden. DEMs with various resolutions and accuracies were used to model the inundation. The results showed a strong positive relationship between the quality of theDEMand the extent of the inundation. However, evenDEMswith the highest resolution produced inaccuracies. In another case study, the Testebo River, the model settings could be calibrated, thanks to a surveyed old inundation event. However, even with the calibration efforts, the resulting inundation extents showed varying degrees of deviation from the surveyed flood boundaries. Therefore, it becomes clear that not only does the resolution of the DEM impact the quality of the results; also, the floodplain slope perpendicular to the river flow will impact the modelling accuracy. Flatter areas exhibited the greatest predictive uncertainties regardless of the DEM’s resolution. For perfectly flat areas, uncertainty becomes infinite.

Place, publisher, year, edition, pages
Leiden, The Netherlands: CRC Press / Balkema (Taylor & Francis) , 2012. p. 1015-1020
Keywords [en]
Flood Inundation, Geographical Information Systems (GIS), LiDAR, Digital Elevation Models (DEM)
National Category
Other Civil Engineering Ocean and River Engineering Remote Sensing Oceanography, Hydrology and Water Resources
Identifiers
URN: urn:nbn:se:hig:diva-12942ISI: 000347871500135Scopus ID: 2-s2.0-84867959207ISBN: 978-0-415-62129-8 (print)ISBN: 978-0-203-07635-4 (print)ISBN: 978-1-4665-7552-3 (print)OAI: oai:DiVA.org:hig-12942DiVA, id: diva2:553169
Conference
International Conference on Fluvial Hydraulics. River Flow 2012. San José, Costa Rica, 5-7 September 2012
Projects
DaGIS, GLOBESKvalitetsbeskrivning av geografisk information vid översvämningskartering
Note

Partly financed by the European Union through Swedish Agency for Economic and Regional Growth (Tillväxtverket) (project number 151092).

Available from: 2012-09-18 Created: 2012-09-18 Last updated: 2018-10-10Bibliographically approved
In thesis
1. Modelling, mapping and visualisation of flood inundation uncertainties
Open this publication in new window or tab >>Modelling, mapping and visualisation of flood inundation uncertainties
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Flood maps showing extents of predicted flooding for a given extreme event have wide usage in all types of spatial planning tasks, as well as serving as information material for the public. However, the production processes that these maps undergo (including the different data, methods, models and decisions from the persons generating them), which include both Geographic Information Systems (GIS) and hydraulic modelling, affect the map’s content, and will be reflected in the final map. A crisp flood boundary, which is a common way of representing the boundary in flood maps, may therefore not be the best representation to be used. They provide a false implication that these maps are correct and that the flood extents are absolute, despite the effects of the entire modelling in the prediction output. Hence, this research attempts to determine how flood prediction outputs can be affected by uncertainties in the modelling process. In addition, it tries to evaluate how users understand, utilise and perceive flood uncertainty information. 

Three main methods were employed in the entire research: uncertainty modelling and analyses; map and geovisualisation development; and user assessment. The studies in this work showed that flood extents produced were influenced by the Digital Elevation Model (DEM) resolution and the Manning’s  used. This effect was further increased by the topographic characteristic of the floodplain. However, the performance measure used, which quantify how well a model produces result in relation to a reference floor boundary, had also biases in quantifying outputs. Determining the optimal model output, therefore, depended on outcomes of the goodness-of-fit measures used.

 In this research, several ways were suggested on how uncertainties can be visualised based on the data derived from the uncertainty assessment and by characterising the uncertainty information. These can be through: dual-ended maps; flood probability maps; sequential maps either highlighting the degrees of certainty (certainty map) or degrees of uncertainty (uncertainty map) in the data; binary maps; overlain flood boundaries from different calibration results; and performance bars. Different mapping techniques and visual variables were used for their representation. These mapping techniques employed, as well as the design of graphical representation, helped facilitate understanding the information by the users, especially when tested during the evaluations. Note though that there were visualisations, which the user found easier to comprehend depending on the task given. Each of these visualisations had also its advantages and disadvantages in communicating flood uncertainty information, as shown in the assessments conducted. Another important aspect that came out in the study was how the users’ background influence decision-making when using these maps. Users’ willingness to take risks depended not only on the map, but their perceptions on the risk itself. However, overall, users found the uncertainty maps to be useful to be incorporated in planning tasks.

Abstract [sv]

Översvämningskartor som visar utbredningen av förutspådda översvämningar för vissa extrema händelser har stor användning i all typ av samhällsplanering, samt fungerar som informationsmaterial för allmänheten. Men, de produktionsprocesser som dessa kartor genomgår (inkluderande olika data, metoder, modeller och beslut från de personer som genererar dessa) och som innefattar både geografiska informationssystem (GIS) och hydraulisk modellering, påverkar kartornas innehåll, vilket även återspeglas i de slutliga kartornas utseende. En skarp översvämningsgräns, som är det vanliga sättet att visa gränsen i översvämningskartor, är därför antagligen inte det bästa sättet att representera utbredningen. Sådana gränser ger en falsk trygghet i att dessa kartor är korrekta och att översvämningsutbredningen är absolut, trots att hela processen att producera dem innebär osäkerheter. Denna studie försöker därför undersöka hur översvämningskartering påverkas av osäkerheter i modelleringsprocesser och hur dessa osäkerheter kan representeras, visualiseras och kommuniceras i kartorna. Dessutom försöker studien utvärdera hur olika användare förstår, använder och uppfattar översvämningskartor som innehåller osäkerhetsinformation.

Tre huvudmetoder har använts i denna studie: osäkerhetsmodellering och analys, kart- och geovisualiseringsutveckling samt användarstudier. Resultaten visar att översvämningsgränserna påverkades både av de digitala höjdmodellernas upplösning (cellstorlek) och markens friktion, representerat av Mannings 𝑛, men också av markens topografi. För att kvantifiera skillnaderna mellan modell och referensöversvämningsyta och därefter kunna välja den mest optimala modellen användes olika valideringsmetoder. Dessa lider dock också av olika brister, vilket gör att resultaten varierar beroende på den valideringsmetod som används.

I denna studie föreslås flera sätt att visualisera osäkerheter baserat på resultaten från osäkerhetsmodellering och karaktären av osäkerhetsinformation. Dessa utgörs av kartor med divergerande färgramp (sk. dual-ended colour maps), sekventiella kartor (som framhäver graden av säkerhet, respektive osäkerhet), binära kartor, överlagring av översvämningsgränser från olika modeller samt värdestaplar. Olika karteringsmetoder och visuella variabler användes för att representera informationen. Resultat från en användarstudie visade att dessa, samt utformningen av den grafiska representationen, underlättade förståelsen av informationen. Beroende på uppgiften finns det visualisering som är lättare eller svårare att förstå för kartanvändarna. Varje visualisering hade också för- och nackdelar med att kommunicera översvämningsosäkerhetsinformation. En annan viktig aspekt som kom fram i studien var hur användarnas bakgrund påverkar beslutsfattandet när de använde de olika kartorna. Användarnas vilja att ta risker berodde inte bara på kartan, utan också på deras uppfattning av risken i sig. Sammantaget visade det sig emellertid att osäkerhetskartorna är användbara för planeringsuppgifter.

Place, publisher, year, edition, pages
Gävle: Gävle University Press, 2018. p. 109
Series
Studies in the Research Profile Built Environment. Doctoral thesis ; 10
Keywords
cartography, flood, hydraulic modelling, GIS, map, uncertainty, visualisation, GIS, hydraulisk modellering, karta, kartografi, osäkerhet, visualisering, översvämning
National Category
Computer and Information Sciences Other Earth and Related Environmental Sciences Civil Engineering
Identifiers
urn:nbn:se:hig:diva-27995 (URN)978-91-88145-33-8 (ISBN)978-91-88145-34-5 (ISBN)
Public defence
2018-12-10, Lilla Jadwigasalen (12:108), Kungsbäcksvägen 47, Gävle, 15:00 (English)
Opponent
Supervisors
Available from: 2018-11-13 Created: 2018-10-10 Last updated: 2018-11-13

Open Access in DiVA

Brandt_and_Lim_2012(776 kB)700 downloads
File information
File name FULLTEXT01.pdfFile size 776 kBChecksum SHA-512
fa480ad4116cdce8ecd08fc1251b873dd31882d8b79419f237ef42d1adc68e2a9e4d9f05f16e67cdc20ebc95be72c3d9b349c399d0ba4a681675207472d544b3
Type fulltextMimetype application/pdf

Other links

Scopushttp://www.crcpress.com/product/isbn/9780415621298

Authority records BETA

Brandt, S. AndersLim, Nancy Joy

Search in DiVA

By author/editor
Brandt, S. AndersLim, Nancy Joy
By organisation
Urban and regional planning/GIS-institute
Other Civil EngineeringOcean and River EngineeringRemote SensingOceanography, Hydrology and Water Resources

Search outside of DiVA

GoogleGoogle Scholar
Total: 700 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 1835 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard-cite-them-right
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • sv-SE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • de-DE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf