City-scale high-resolution flood models and the role of topographic data: a case study of Kathmandu, Nepal
Topographic data is a fundamental input to flood hazard models and controls the quality of the outputs. However, open-access global digital elevation models (DEMs) are dated and limited to 30 m resolution, which hinders modelling efforts in urban or topographically complex environments. We used the...
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Taylor & Francis Group
2024-01-01
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| Series: | Geocarto International |
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| Online Access: | https://www.tandfonline.com/doi/10.1080/10106049.2024.2387073 |
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| author | C. Scott Watson Januka Gyawali Maggie Creed John R. Elliott |
| author_facet | C. Scott Watson Januka Gyawali Maggie Creed John R. Elliott |
| author_sort | C. Scott Watson |
| collection | DOAJ |
| description | Topographic data is a fundamental input to flood hazard models and controls the quality of the outputs. However, open-access global digital elevation models (DEMs) are dated and limited to 30 m resolution, which hinders modelling efforts in urban or topographically complex environments. We used the flood prone and expanding city of Kathmandu, Nepal, to evaluate the impact of topographic data source and resolution on flood model outputs. All DEMs evaluated featured spatially correlated topographic sinks with depths exceeding 20 m that required hydrological conditioning before being used in flood modelling. Incomplete hydrological conditioning appeared related to the overestimation of flood extent and therefore limited agreement when comparing a global 90 m resolution flood hazard model with a bespoke city-scale model at 10 m resolution (F1 score = 0.40). Instead, we found that the height above nearest drainage (HAND) metric was better able to replicate the higher resolution flood map as an indicator of flood susceptibility requiring only topographic information as an input. We also found that the computationally efficient FastFlood model was able to match the inundation extent (F1 score = 0.79) and flood depths (mean absolute error and root mean square error of 0.46 and 0.76 m respectively) of a published 10 m physics-based flood hazard model whilst requiring 212 times less computation time. Our analysis demonstrated that mapping city-scale flood inundation required hydrologically conditioned high-resolution topographic data but not physically complex flood models, highlighting the need for greater availability of high quality open access topographic data. |
| format | Article |
| id | doaj-art-30753ea0e2cf42fe836db6fe120ce763 |
| institution | OA Journals |
| issn | 1010-6049 1752-0762 |
| language | English |
| publishDate | 2024-01-01 |
| publisher | Taylor & Francis Group |
| record_format | Article |
| series | Geocarto International |
| spelling | doaj-art-30753ea0e2cf42fe836db6fe120ce7632025-08-20T01:59:21ZengTaylor & Francis GroupGeocarto International1010-60491752-07622024-01-0139110.1080/10106049.2024.2387073City-scale high-resolution flood models and the role of topographic data: a case study of Kathmandu, NepalC. Scott Watson0Januka Gyawali1Maggie Creed2John R. Elliott3COMET, School of Earth and Environment, University of Leeds, Leeds, UKPractical Action, Kathmandu, NepalJames Watt School of Engineering, The University of Glasgow, Glasgow, UKCOMET, School of Earth and Environment, University of Leeds, Leeds, UKTopographic data is a fundamental input to flood hazard models and controls the quality of the outputs. However, open-access global digital elevation models (DEMs) are dated and limited to 30 m resolution, which hinders modelling efforts in urban or topographically complex environments. We used the flood prone and expanding city of Kathmandu, Nepal, to evaluate the impact of topographic data source and resolution on flood model outputs. All DEMs evaluated featured spatially correlated topographic sinks with depths exceeding 20 m that required hydrological conditioning before being used in flood modelling. Incomplete hydrological conditioning appeared related to the overestimation of flood extent and therefore limited agreement when comparing a global 90 m resolution flood hazard model with a bespoke city-scale model at 10 m resolution (F1 score = 0.40). Instead, we found that the height above nearest drainage (HAND) metric was better able to replicate the higher resolution flood map as an indicator of flood susceptibility requiring only topographic information as an input. We also found that the computationally efficient FastFlood model was able to match the inundation extent (F1 score = 0.79) and flood depths (mean absolute error and root mean square error of 0.46 and 0.76 m respectively) of a published 10 m physics-based flood hazard model whilst requiring 212 times less computation time. Our analysis demonstrated that mapping city-scale flood inundation required hydrologically conditioned high-resolution topographic data but not physically complex flood models, highlighting the need for greater availability of high quality open access topographic data.https://www.tandfonline.com/doi/10.1080/10106049.2024.2387073Flood hazardtopographydigital elevation modelshydrological correction |
| spellingShingle | C. Scott Watson Januka Gyawali Maggie Creed John R. Elliott City-scale high-resolution flood models and the role of topographic data: a case study of Kathmandu, Nepal Geocarto International Flood hazard topography digital elevation models hydrological correction |
| title | City-scale high-resolution flood models and the role of topographic data: a case study of Kathmandu, Nepal |
| title_full | City-scale high-resolution flood models and the role of topographic data: a case study of Kathmandu, Nepal |
| title_fullStr | City-scale high-resolution flood models and the role of topographic data: a case study of Kathmandu, Nepal |
| title_full_unstemmed | City-scale high-resolution flood models and the role of topographic data: a case study of Kathmandu, Nepal |
| title_short | City-scale high-resolution flood models and the role of topographic data: a case study of Kathmandu, Nepal |
| title_sort | city scale high resolution flood models and the role of topographic data a case study of kathmandu nepal |
| topic | Flood hazard topography digital elevation models hydrological correction |
| url | https://www.tandfonline.com/doi/10.1080/10106049.2024.2387073 |
| work_keys_str_mv | AT cscottwatson cityscalehighresolutionfloodmodelsandtheroleoftopographicdataacasestudyofkathmandunepal AT janukagyawali cityscalehighresolutionfloodmodelsandtheroleoftopographicdataacasestudyofkathmandunepal AT maggiecreed cityscalehighresolutionfloodmodelsandtheroleoftopographicdataacasestudyofkathmandunepal AT johnrelliott cityscalehighresolutionfloodmodelsandtheroleoftopographicdataacasestudyofkathmandunepal |