Rock slope failures often result from progressive rock mass damage which accumulates over long timescales, and is driven by changing environmental boundary conditions. In deglaciating environments, rock slopes are affected by stress perturbations driven by mechanical unloading due to ice downwasting and concurrent changes in thermal and hydraulic boundary conditions. Since in-situ data is rare, the different processes and their relative contribution to slope damage remain poorly understood. Here we present detailed analyses of subsurface pore pressures and micrometer scale strain time series recorded in three boreholes drilled in a rock slope aside the retreating Great Aletsch Glacier (Switzerland). Additionally, we use monitored englacial water levels, climatic data, and annually acquired ice surface measurements for our process analysis. Pore pressures in our glacial adjacent rock slope show a seasonal signal controlled by infiltration from snowmelt and rainfall as well as effects from the connectivity to the englacial hydrological system. We find that reversible and irreversible strains are driven by hydromechanical effects from diffusing englacial pressure fluctuations and pore pressure reactions on infiltration events, stress transfer related to changing mechanical glacial loads from short-term englacial water level fluctuations and longer-term ice downwasting, and thermomechanical effects from annual temperature cycles penetrating the shallow subsurface. We relate most observed irreversible strain (damage) to mechanical unloading from ice downwasting. Additionally, short-term stress changes related to mechanical loading from englacial water level fluctuations and hydromechanical effects from pore pressure variations due to infiltration events were identified to contribute to the observed irreversible strain.

Predicting the impact of changing climate and anthropogenic influences on stream discharge dynamics and baseflow conditions requires insight into the main factors that regulate storage and transfer of water from hillslope aquifers to surface streams. Classically, it is assumed that above a certain scale, hydrological laws involved at small-scale can be simplified, allowing the representation of the landscape and its subsurface in models as a homogeneous hillslope with effective slope, length and hydraulic properties. From a comprehensive analysis of hydrological, geological and geomorphological databases available in the Swiss Alps we provide evidence that such simplification might lead to inaccurate estimates of streamflow dynamics at baseflow. We reveal that recession behavior strongly deviates from that predicted by idealized homogeneous theories. A correlation analysis allows us to identify which key features of the landscape might control this deviation, with particular attention to slope, drainage density, depth to bedrock, and lithology as the main drivers. We summarize the current knowledge of physical mechanisms that could lead to complex hydrological behavior in Alpine contexts, and we finally discuss implications in defining modeling strategies for the Critical Zone community.