The Impact of Climate Change on Invisible River Floods: a Case Study of Beni Slimane City, Médéa Wilaya, Algeria

Objective: This study aims to investigate the complex flooding dynamics in the city of Beni Slimane, Algeria, with a focus on the dual impact of flash floods and the less visible "invisible floods" caused by the Oued Alaim during intense rainfall events. The objective is to understand how these flooding mechanisms affect urban infrastructure and public health, and to inform risk management strategies. Method: A case study approach was used, incorporating hydrological assessments, field observations, and analysis of rainfall and flood event data. Particular attention was given to the interaction between stormwater, wastewater discharge, and the Oued Alaim’s flow behavior during heavy precipitation. Results and Discussion: The findings reveal that Beni Slimane is exposed to two distinct types of flooding. Flash floods, triggered by sudden surges in the Oued Alaim, are highly visible and destructive. However, the study also highlights the occurrence of "invisible floods," where rising river levels obstruct the outflow of wastewater and stormwater drainage systems. This results in backflow and accumulation that eventually surfaces in residential areas, especially affecting homes with basements. The combination of unregulated wastewater discharge and inadequate drainage infrastructure exacerbates both types of flooding, posing significant environmental and health challenges. Implications of the Research: The study underscores the urgent need for targeted urban planning interventions in Beni Slimane. These should include improved wastewater management, enhanced stormwater infrastructure, and climate-resilient design to mitigate the impact of both visible and invisible flooding. The findings also provide a framework for risk assessment and infrastructure adaptation in similar urban environments affected by climate change. Originality/Value: This research introduces the concept of "invisible floods" in the context of urban hydrology, highlighting a frequently overlooked aspect of flood risk in cities with inadequate drainage systems. It offers a novel perspective on the interaction between climate change, urban infrastructure, and hydrological processes, contributing valuable insights to the field of flood risk management and urban resilience planning.