Coastal cliff failures hazard along the Safi coastline (Morocco): a methodology for shoreline change assessment and its forecast along with examination of the causes.

The coastal cliffs of the Jurassico–Cretaceous formation, outcropping along the coastal area of Safi (Morocco), are particularly vulnerable. A wide variety of instabilities and slope failure, impacts such slopes, inducing serious structural and human security risks and accelerating the retreat. This paper presents results of research conducted on shoreline change assessment and forecast and inspecting causes that produce and/or accelerate coastline change to propose optimal management and protection solutions. Net Shoreline Movement, Linear Regression Rate, and End Point Rate analysis were computed to examine shoreline change rate (2002–2020) using Landsat 7 ETM + and LOI data and Digital Shoreline Analysis System. The Kalman filter model is used to predict shoreline change (2030 and 2040). The estimated erosion and accretion rates between − 7.87 and 2.23 m/year highlight the main erosional trend, and reveal the feedbacks between the proportional advance (set-forwards or accretion) and the active landslides, high accretion rates are recorded in the landsliding segment. An attempt was made to identify the relationships between causal factors; to this end, a methodological development through field investigation and laboratory tests of the brown clay involved in all slope failures. Results of physicochemical and mineralogical tests showed that all clay samples had medium to high plasticity, and similar mineral compositions, mainly illite, vermiculite, mixed-layer illite-vermiculite of expandable phases, and permit to point out the strong relationship existing between landslide occurrence, cliff dynamic, and geotechnical and mineralogical properties of Brown clay. [ABSTRACT FROM AUTHOR]