Deciphering climate-induced displacement in Somalia: A remote sensing perspective

In 2016, 865.5 km2 of the AOI flooded, primarily affecting the Belet Weyne, Saakow and Jowhar districts (Fig 7A). In 2017, floods affected the districts of Saakow and Jowhar, covering 2263.4 km2 (Fig 7B), whilst in 2018 several districts were flooded (including Hiiraan -Fig 6) with an area equal to 3552.1 km2 (Fig 7C). Lastly, in 2019 the total area flooded was 2657.9 km2. The flood was used as a base map alongside the population map to estimate the number of people affected by each flood event. Land Cover (LC) and LC change maps for drought and flood events The final environmental indicator comprised of the LC and LC change maps, which are crucial for assessing the impact of natural phenomena like floods and drought on agricultural food productions (like orchards and croplands) and human settlements (like towns and villages). First, LC maps were produced to show the Earth’s different land cover patterns in five different classes (soil/sparse vegetation, water, agriculture field, forest, and grassland/shrubland). Sentinel-2 Level 2A imagery was the primary data input for LC maps. A cutting-edge U-Net based algorithm produced LC maps during drought and flood events, enhancing detec- tion of different textural features seen in the base images. LC is a fundamental environmental variable for understanding the causes and trends of human and natural processes. LC refers to the physical material at the earth’s surface like grass, soil, impervious surfaces, and trees. The information extracted from the land cover features and their associated changes can help

Table 4. Demonstration of the mapping of the transition between two land cover classes to an integer value that was stored in the land cover change raster file. To From Agricultural Field Forest Grass/ Shrub Settlement Soil Water Agricultural Field 0 1 2 3 4 5 Forest 6 7 8 9 10 11 Grass/Shrub 12 13 14 15 16 17 Settlement 18 19 20 21 22 23 Soil 24 25 26 27 28 29 Water 30 31 32 33 34 35 https://doi.org/10.1371/journal.pone.0304202.t004 Fig 7. Annual aggregated flood maps of the study area generated from Sentinel-1 data. a. 2016 floods; b. 2017 floods; c.2018 floods; d.2019 floods. https://doi.org/10.1371/journal.pone.0304202.g007 PLOS ONE Deciphering Climate-induced Displacement in Somalia: A Remote Sensing Perspective PLOS ONE | https://doi.org/10.1371/journal.pone.0304202 August 9, 2024 14 / 27