Socio-economic damages caused by extreme floods have been increasing rapidly in recent years, mainly driven by changes in the climate and modulated by increasing human population in deltic areas and floodplains. The Cuvelai-Etosha Basin (CEB) in southern Africa, covering southern Angola and northern Namibia, experiences socially and economically devastating extreme floods. Yet, accurate information on past and current surface water changes and dynamics is lacking. Here, we estimate and map the surface water extents in the CEB and its surroundings (CEB + S) for 32 years (1990–2021) from Landsat data using random forest models to provide long-term baseline information on surface water changes and dynamics. Based on the reference data, a total of 15,677 ± 1080 km² have been inundated by surface water in the CEB + S during 1990–2021. This extent was accurately mapped by our local water extent product (mapped area = 16,273 km², user’s accuracy = 91.5 ± 2.5%, producer’s accuracy = 91.1 ± 6%). With user’s and producer’s accuracy of 91%, our overall water extent provides the first most accurate long-term baseline information on surface water inundation in CEB + S necessary for local spatial planning processes to minimise future negative impacts of floods in the basin. Interannual variability of surface water extent is, however, high, with water extent ranging from 520.8 ± 375.7 km² to 12372.3 ± 1154.7 km² during the 1990–2021 period. The largest annual water extents (>10,000 km²) were recorded in 2006, 2008, 2009, 2011, and 2017, whereas the smallest extents (<1000 km²) were recorded in 1992 and 2019. We found that over 40% of the area inundated in the CEB + S during 1990–2021 was inundated less than 9 times. With human population increasing rapidly in the CEB + S, rarely inundated areas with short water residence could become a prime target for human settlements, which may lead to huge socio-economic damages during extreme floods if no preventive measures are put in place. Globally available surface water maps from the Global Land Analysis and Discovery (GLAD) and European Commission’s Joint Research Centre (JRC) did not provide realistic surface water extent for CEB + S, especially during years with extreme floods. Therefore, locally adopted product for operational monitoring of surface water in the CEB + S is needed to provide accurate information for informing spatial planning processes and surface water resource management strategies in this endorheic basin and help minimise future negative impacts of floods.

近年来，特大洪水造成的社会经济损失迅速增加，主要受气候变化驱动，并受到三角洲地区和洪泛区人口增加的调节。南部非洲的 Cuvelai-Etosha 盆地 (CEB) 覆盖了安哥拉南部和纳米比亚北部，经历了对社会和经济造成破坏性的极端洪水。然而，缺乏关于过去和当前地表水变化和动态的准确信息。在这里，我们使用随机森林模型根据 Landsat 数据估计和绘制 CEB 及其周边地区 (CEB + S) 32 年（1990-2021 年）的地表水范围，以提供有关地表水变化和动态的长期基线信息。根据参考数据，共 15,677 ± 1080 km ²在 1990-2021 年期间，CEB + S 被地表水淹没。该范围由我们当地的水域范围产品准确绘制（绘制面积 = 16,273 km ²，用户精度 = 91.5 ± 2.5%，生产者精度 = 91.1 ± 6%）。由于用户和生产者的准确率为 91%，我们的整体水量范围提供了 CEB + S 地表水淹没的第一个最准确的长期基线信息，这是当地空间规划过程所必需的，以尽量减少未来流域洪水的负面影响。然而，地表水范围的年际变化很大，在 1990-2021 年期间，水范围从 520.8 ± 375.7 km ²到 12372.3 ± 1154.7 km ²不等。年最大水域范围（>10,000 km ²) 记录于 2006、2008、2009、2011 和 2017 年，而最小范围 (<1000 km ²) 记录于 1992 年和 2019 年。我们发现，在 1990 年至 2021 年期间，CEB + S 中超过 40% 的区域被淹没不到 9 次。随着 CEB + S 地区人口的迅速增加，很少被淹没且水位短的地区可能成为人类住区的主要目标，如果不采取预防措施，在极端洪水期间可能会导致巨大的社会经济损失。来自全球土地分析和发现 (GLAD) 和欧盟委员会联合研究中心 (JRC) 的全球可用地表水图并未提供 CEB + S 的真实地表水范围，尤其是在发生极端洪水的年份。所以，