Water volume estimates of shallow desert lakes are the basis for water balance calculations, important both for water resource management and paleohydrology/climatology. Water volumes are typically inferred from bathymetry mapping; however, being shallow, ephemeral, and remote, bathymetric surveys are scarce in such lakes. We propose a new, remote‐sensing‐based, method to derive the bathymetry of such lakes using the relation between water occurrence, during >30 year of optical satellite data, and accurate elevation measurements from the new Ice, Cloud, and Land Elevation Satellite‐2 (ICESat‐2). We demonstrate our method at three locations where we map bathymetries with ~0.3 m error. This method complements other remotely sensed, bathymetry‐mapping methods as it can be applied to: (a) complex lake systems with subbasins, (b) remote lakes with no in‐situ records, and (c) flooded lakes. The proposed method can be easily implemented in other shallow lakes as it builds on publically accessible global data sets.

Was the catastrophic flooding in Derna, Libya—one of the deadliest hydrometeorological disasters on record—an inevitable outcome of rare weather conditions, or did the design of the infrastructure fail to account for probable risks? On 10 to 11 September 2023, Storm Daniel, a Mediterranean tropical-like cyclone, caused heavy rainfall that led to the collapse of two dams and more than 5000 casualties in Derna. Using a combination of atmospheric reanalysis, satellite data, and hydrologic modeling, we overcame key limitations typical of data-scarce, high-variability regions and revealed that despite the catastrophic impact, the return periods of the rainfall and flood were only a few decades. Hydraulic simulations revealed that the dam failures amplified the damage nearly 20-fold compared to a dam-free scenario. With extensive and timely implications, our findings underscore the importance of uncertainty-aware risk assessment and highlight the value of distributed flood prevention and early warning systems in mitigating risks in vulnerable regions.

The geomorphic response of channels to base‐level fall is an important factor in landscape evolution. To better understand the complex interactions between the factors controlling channel evolution in an emerging continental shelf setting, we use an extensive data set (high‐resolution digital elevation models, aerial photographs, and Landsat imagery) of a newly incising, perennial segment of Nahal (Wadi) HaArava, Israel. This channel responds to the rapid and progressive lowering of its base‐level, the Dead Sea (>30 m in ~35 years; ~0.5–1.3 m yr⁻¹). Progressively evolving longitudinal profiles, channel width, sinuosity, and knickpoint retreat during the last few decades were documented or reconstructed. The results indicate that even under fast base‐level fall, rapid delta progradation on top of the shelf and shelf edge can moderate channel mouth slopes and, therefore, largely inhibit channel incision and knickpoint propagation. This channel elongation stage ends when the delta reaches an extended accommodation within the receiving basin and fails to keep the channel mouth slopes as low as the channel bed slopes. Then, processes of incision, narrowing, and meandering begin to shape the channel and expand upstream. When the down‐cutting channel encounters a more resistant stratum within the channel substrate, these processes are restricted to a downstream reach by formation of a retreating vertical knickpoint. When the knickpoint and the channel incise to a level below this stratum, a spatially continuous, diffusion‐like evolution characterizes the channel's response and source‐to‐sink transport can be implemented. These results emphasize the mouth slope and channel substrate resistance as the governing factors over long‐term channel evolution, whereas flash floods have only local and short‐lived impacts in a confined, continuously incising channel. The documented channel response applies to eustatic base‐level fall under steepening basin bathymetry, rapid delta progradation, and lithologic variations in the channel substrate.