Spatial flood frequency analysis of ephemeral rivers in Northwest Namibia based on cloud computing of Landsat time series

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Title:Main Title: Spatial flood frequency analysis of ephemeral rivers in Northwest Namibia based on cloud computing of Landsat time series
Description:Abstract: Drylands cover approximately 40% of the Earth’s land surface and are home to over a quarter of the global population. Despite the deficit of surface water, rare but strong precipitation events are the fundamental driver for geomorphic activity in arid regions. A quantification of the frequency and magnitude of episodic river discharge is essential for a robust characterization of flood hazards and, thus, better understanding of the poorly studied hydromorphodynamics in deserts. However, observation data from gauges are sparsely distributed and, if existent, often do not cover a sufficiently long seamless time series or feature extensive gaps. This applies, for instance, to the remote Northwest Namibia, where more than a dozen ephemeral rivers drain the Kunene Highlands towards the Skeleton Coast, yet daily river flow data for a period of several decades is only available from the Hoanib. Hence, we propose a workflow based on the Landsat multispectral satellite imagery archive to detect flood events and their spatial impact since 1984 in a high resolution (30 m) for the entire Kunene Region (~144 km²). To cater for the limitations related to a revisit time of 16 days and potential impracticality of scenes due to cloud cover, we calculated spectral indices allowing for the detection of both inundated areas during flooding (e.g., Normalized Difference Water Index) and effects sustained after flood recession (e.g., Tasseled Cap Wetness to detect increased soil moisture). The large remote sensing dataset is processed via cloud computing using the Google Earth Engine. As a novel approach, we try to implement a frequency analysis directly in the Google Earth Engine environment after attributing the spectral imprints of floods to their magnitudes. For this purpose, a statistical relationship is developed between the daily record of the gauging station at the Hoanib and the spatiotemporal multispectral surface characteristics along the river course and floodplains. By transferring this relationship to the other ephemeral streams, spatially highly resolved recurrence intervals for areas affected by floods of different magnitudes can be derived for the entire Kunene Region.
Identifier:https://doi.org/10.5194/egusphere-egu23-12947 (DOI)
Responsible Party
Creators:Janek Walk (Author), Bruno Boemke (Author), Tobias Ullmann (Author)
Funding Reference:Deutsche Forschungsgemeinschaft (DFG): CRC 1211: Earth - Evolution at the Dry Limit
Publisher:EGU
Publication Year:2023
Topic
CRC1211 Topic:Remote Sensing
Related Subproject:C2
Subjects:Keywords: Geomorphology, Satellite remote sensing, Meteorology, Arid Zone
Geogr. Information Topic:Environment
File Details
Filename:EGU23-12947-print.pdf
Data Type:Text - Event Paper
File Size:289 KB
Date:Submitted: 10.01.2023
Mime Type:application/pdf
Data Format:PDF
Language:English
Status:Completed
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Download Permission:Free
General Access and Use Conditions:According to the CRC1211DB data policy agreement. © Author(s) 2023. CC Attribution 4.0 license.
Access Limitations:According to the CRC1211DB data policy agreement. © Author(s) 2023. CC Attribution 4.0 license.
Licence:[Creative Commons] Attribution 4.0 International (CC BY 4.0)
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Specific Information - Publication
Publication Status:Published
Review Status:Not peer reviewed
Publication Type:Event Paper
Issue:12947
Volume:EGU23
Number of Pages:1 (1 - 1)
Event:EGU General Assembly 2023
Event Type:Conference
Event Location:Vienna, Austria
Event Duration:23rd of April, 2023 - 28th of April, 2023
Metadata Details
Metadata Creator:Janek Walk
Metadata Created:02.05.2023
Metadata Last Updated:02.05.2023
Subproject:C2
Funding Phase:2
Metadata Language:English
Metadata Version:V50
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