## 8 Discussion and Further Required Research  
### Applicability of the Proposed Approach  
The approach introduced in this work is intended to be a high-level screening tool for identifying the greatest landslide impulse wave threats and thus helping prioritize resources for a more detailed and thorough analysis. The study is based on 3D hydrodynamic modeling and considers a wide range of water body geometries. Results demonstrate the reliability of a lake geometry-based approach for a first-order assessment of the danger posed by potential landslide-triggered impulse waves in mountain lakes. The suggested method finds its applicability in situations where the characteristics of the possible impacting volume are unknown, as only the geometrical properties of lakes are required. Unlike other methods, this approach does not require a deep knowledge of wave theory or the need for additional software. A reliable constraint on wave attenuation, as is provided by this approach, means that the initial wave amplitude needs only to be generally approximated. The method can be applied to lakes with diverse shapes and dimensions, subject to the limitation that the potential impacting volume has similar characteristics to the one adopted for the modeling in this work (Section 4). In the case of lakes with complex shapes, Equation (5) can be applied to sub-basins with specific geometrical properties to estimate the wave decay potential parameter _WDPP_, as has been done with the Chehalis Lake test case (Section 6). If Equation (5) is not applicable due to unknown lake-geometry parameters in Equation (2), _WDPP_ can be estimated using Equation (3) or Equation (4), which consider lake area or volume respectively. The equations in Table 3 provide flow depths expected at  
Figure 12: Alpine and perialpine lakes considered in this study and related _WDPP_ values obtained using the _ShpP_ relation (circles in the legend). Where _ShpP_ is unavailable, _WDPP_ was obtained using the water volume relation (squares in the legend, see also Figure 7b). Topographical background taken from Microsoft Bing Maps—2021 Microsoft Corporation Earthquake Geographics Bio (Accessed on 26 July 2021). the shoreline. However, because models with a maximum depth of less than 20 m were excluded from the later stages of the workflow, this method might overestimate the hazard potential for small shallow lakes. The Chehalis Lake example shows that analyzing singular sub-basins provides a more conservative estimate of flow characteristics compared to an analysis of the entire lake. As waves propagating from one basin to the next may have already attenuated, sub-basin-specific estimations using this approach can be deemed as worst-case scenarios. It is worth noting that the subdivision of sub-basins does not take into account wave propagation from one basin to another. However, this limitation is a minor issue because a wave entering a second sub-basin has already significantly attenuated, implying that the highest threat is already identified by intra-basin events. Nonetheless, wherever sub-basins join, complex variations in flow depth at the shoreline might be expected as impulse waves approach from the adjacent sub-basin. This is due to changes in bathymetry (e.g., a shallow sill as at Chehalis Lake, Figure 10), basin alignment (e.g., non-parallel valleys such as the western part of Lake Lucerne, Figure 1b), or both (e.g., the eastern part of Lake Lucerne, Figure 1b). In some instances, these effects might result in locally increased near-shore wave energy and run-up. As a consequence, although intra-basin wave generation gives a conservative assessment of near-shore wave threats, intra-basin waves may underestimate such threats where sub-basins join.