Growing soil erosion risks and their role in modulating catastrophic floods in North Africa

Abstract

Intensifying hydroclimatic changes in North Africa are causing unprecedented floods, droughts, and land degradation patterns that are increasingly associated with human casualties, socioeconomic instabilities, and outflow migrations. These patterns’ and their future forecasts remain largely unquantified, aggravating the impacts on several populous areas. To address this deficiency, we employ pixel-based remote sensing data correlation analysis and soil loss modeling to constrain the uncertainties on the decadal hydroclimatic and ecosystem changes in North Africa. Using cloud-based big data analysis in Google Earth Engine, we establish the convolution between precipitation patterns and surface textural characteristics, evaluating the spatial distribution of soil erosion risks at the continental scale. Our investigation uses a multi-step approach, integrating risk areas derived from soil erosion with high-resolution population data, offering critical insights into zones of different vulnerabilities. Our results unveiled a significant escalation in soil erosion anomalies over the past two decades. In particular, 15 % of the areas receiving precipitation in all of North Africa are currently at medium to high risk of soil erosion versus only 7 % in 2002. These risks are concentrated in urban areas, where each year, ∼29,000 people become highly vulnerable to these hazards, up from ∼22,000 in 2002. These increases are primarily associated with the surge in semi-unformal urban settings and the rise in rain aggressiveness and storminess. These factors, combined with the poor public perception of the imminence of these risks, create hotspots where the impacts are becoming insurmountable, as considered herein for the case of the recent catastrophic floods in Derna, Libya, used as a validation site. We conclude that increased soil erosion will modulate the impacts of upcoming catastrophic floods. As such, a pressing change in urban and land use policies in expansive areas of North Africa is called for to increase their resilience to upcoming hydroclimatic fluctuations.