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Ice cliff distribution plays a major role in determining the melt of debris‐covered glaciers but its controls are largely unknown. We assembled a data set of 37,537 ice cliffs and determined their characteristics across 86 debris‐covered glaciers within High Mountain Asia (HMA). We find that 38.9% of the cliffs are stream‐influenced, 19.5% pond‐influenced and 19.7% are crevasse‐originated. Surface velocity is the main predictor of cliff distribution at both local and glacier scale, indicating its dependence on the dynamic state and hence evolution stage of debris‐covered glacier tongues. Supraglacial ponds contribute to maintaining cliffs in areas of thicker debris, but this is only possible if water accumulates at the surface. Overall, total cliff density decreases exponentially with debris thickness as soon as the debris layer reaches a thickness of over 10 cm. Plain Language Summary Debris‐covered glaciers are common throughout the world's mountain ranges and are characterized by the presence of steep ice cliffs among the debris‐covered ice. It is well‐known that the cliffs are responsible for a large portion of the melt of these glaciers but the controls on their formation, development and distribution across glaciers remains poorly understood. Novel mapping approaches combined with high‐resolution satellite and drone products enabled us to disentangle some of these controls and to show that the ice cliffs are generally formed and maintained by the surface hydrology (ponds or streams) or by the opening of crevasses. As a result, they depend both at the local and glacier scale on the dynamic state of the glaciers as well as the evolution stage of their debris cover. This provides a pathway to better represent their contribution to glacier melt in predictive glacier models. Key Points We derived an unprecedented data set of 37,537 ice cliffs and their characteristics across 86 debris‐covered glaciers in High Mountain Asia We find that 38.9% of the cliffs are stream‐influenced, 19.5% pond‐influenced and 19.7% are crevasse‐originated Ice cliff distribution can be predicted by velocity, as an indicator of the dynamics and state of evolution of debris‐covered glaciers

Watersheds are complex systems with multiple interactions between physical processes and human-induced socio-economic dynamics. Since the 2000s, numerous flooding and mudslide events have affected the territory in Normandy (France), leading to significant damages. Therefore, a public policy was adopted with the aim to reduce runoff and erosion, it includes: (i) the building of 4,000 hydraulic infrastructures (dams, fascines, hedges, etc.), (ii) the creation of turbidity water-treatment plants and, (iii) the conduction of animation and protection programs on soil and water resources. These investments are co-funded by several local authorities. This original research project aims evaluating the effectiveness of the above-mentioned public policy. Therefore, two complementary approaches are applied: (i) at the regional scale, the investments and damages between 2000 and 2017 were assessed and, (ii) for a pilot small scaled watershed (la Lézarde, 212 km²) a coupled modeling was conducted, taking hydro-sedimentary processes (flood envelopes, diffuse and concentrated erosion, karstic transfers) and associated socio-economic dynamics into account. Our results suggest that over the study period, at the regional scale 500 M€ were invested to reduce erosion/runoff impacts and, 300 M€ of damage were caused. Nevertheless, the effectiveness of the public policy since 2000s must be evaluated at the watershed scale using a Cost-Benefit Analysis (CBA) according to two main scenarios: S1 = pre-development (2000), and S2 = post-development (2017). The processes that govern the surface transfer are modeled for different design floods (Q10-50-100) coupling two semi-dynamic models (MikeSHE and Watersed), and the karstic transfer using a deep learning algorithm (Tensorflow). Additionally, three long-term scenarios (until 2050) are modeled taking into account the effects of climate change (RCP scenarios), the change in land use (-33% of grassland areas), and the modification of agricultural practices that limit runoff. These projections provide key elements for decision-makers to guide future public policies controlling runoff and erosion in this territory.