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<front>
<journal-meta>
<journal-id journal-id-type="publisher">ISPRS-Archives</journal-id>
<journal-title-group>
<journal-title>The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences</journal-title>
<abbrev-journal-title abbrev-type="publisher">ISPRS-Archives</abbrev-journal-title>
<abbrev-journal-title abbrev-type="nlm-ta">Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci.</abbrev-journal-title>
</journal-title-group>
<issn pub-type="epub">2194-9034</issn>
<publisher><publisher-name>Copernicus Publications</publisher-name>
<publisher-loc>Göttingen, Germany</publisher-loc>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.5194/isprs-archives-XLIX-B4-2026-89-2026</article-id>
<title-group>
<article-title>Unsupervised Mapping of Flood-prone Areas in Ghana Using Sentinel-1 Time-Series</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Toffah</surname>
<given-names>Felix Enyimah</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Pirotti</surname>
<given-names>Francesco</given-names>
<ext-link>https://orcid.org/0000-0002-4796-6406</ext-link>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
<xref ref-type="aff" rid="aff3">
<sup>3</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>Department of Civil, Building and Environmental Engineering, Sapienza University of Rome, Via Eudossiana 18, 00184 Rome, Italy</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>Interdepartmental Research Center of Geomatics (CIRGEO), University of Padova, Viale dell’Universita 16, 35020, Legnaro, Italy</addr-line>
</aff>
<aff id="aff3">
<label>3</label>
<addr-line>Department of Land, Environment and Agro-Forestry (TESAF), University of Padova, Legnaro, Italy</addr-line>
</aff>
<pub-date pub-type="epub">
<day>04</day>
<month>08</month>
<year>2026</year>
</pub-date>
<volume>XLIX-B4-2026</volume>
<fpage>89</fpage>
<lpage>96</lpage>
<permissions>
<copyright-statement>Copyright: &#x000a9; 2026 Felix Enyimah Toffah</copyright-statement>
<copyright-year>2026</copyright-year>
<license license-type="open-access">
<license-p>This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit <ext-link ext-link-type="uri"  xlink:href="https://creativecommons.org/licenses/by/4.0/">https://creativecommons.org/licenses/by/4.0/</ext-link></license-p>
</license>
</permissions>
<self-uri xlink:href="https://isprs-archives.copernicus.org/articles/XLIX-B4-2026/89/2026/isprs-archives-XLIX-B4-2026-89-2026.html">This article is available from https://isprs-archives.copernicus.org/articles/XLIX-B4-2026/89/2026/isprs-archives-XLIX-B4-2026-89-2026.html</self-uri>
<self-uri xlink:href="https://isprs-archives.copernicus.org/articles/XLIX-B4-2026/89/2026/isprs-archives-XLIX-B4-2026-89-2026.pdf">The full text article is available as a PDF file from https://isprs-archives.copernicus.org/articles/XLIX-B4-2026/89/2026/isprs-archives-XLIX-B4-2026-89-2026.pdf</self-uri>
<abstract>
<p>Flooding is one of the most persistent natural hazards in Ghana, causing recurrent damage to infrastructure, livelihoods, and local economies. Despite its widespread impacts, most flood-related research has been concentrated on Accra, leaving many regions understudied. This paper addresses this spatial gap by integrating Earth Observation (EO) datasets to identify and characterise flood-prone areas across Ghana at a national scale. Precipitation patterns between 2015 and 2025 derived from the IMERG dataset showed a clear seasonal cycle, with major rainfall peaks from April to October, directly corresponding to observed flood events. This implies an associated annual seasonal cycle of flooding. Sentinel-1 Synthetic Aperture Radar (SAR) imagery was used for flood mapping using a change detection (ratio) approach on the backscatter coefficients. Results showed that flood is concentrated in the southern half of the country, particularly in Western, Western North and Eastern Regions, and hotspots around Kumasi in Ashanti and the Weija dam in Greater-Accra regions. Spatial patterns of the flood align closely with the national topography, with low elevation areas especially those beneath the Y-shaped mountain in the country more vulnerable. Technically, the study demonstrates the effectiveness of SAR-based change detection for flood mapping in data-sparse environments, while highlighting limitations relating to in-situ validation. The results underline the necessity of adopting engineering solutions to reduce flood impacts as a long term solution to the annual recurring flood observed in the country. From a policy perspective, the findings provide evidence to support flood risk management strategies.</p>
</abstract>
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