Natural Hazards and Earth System Sciences

Numerical-model-derived intensity–duration thresholds for early warning of rainfall-induced debris flows in a Himalayan catchment
Sudhanshu Dixit, Srikrishnan Siva Subramanian, Piyush Srivastava, Ali P. Yunus, Tapas Ranjan Martha, and Sumit Sen
Nat. Hazards Earth Syst. Sci., 24, 465–480, https://doi.org/10.5194/nhess-24-465-2024, 2024
Rainfall intensity–duration (ID) thresholds can aid in the prediction of natural hazards. Large-scale sediment disasters like landslides, debris flows, and flash floods happen frequently in the Himalayas because of their propensity for intense precipitation events. We provide a new framework that combines the Weather Research and Forecasting (WRF) model with a regionally distributed numerical model for debris flows to analyse and predict intense rainfall-induced landslides in the Himalayas.

The role of citizen science to assess the spatiotemporal pattern of rainfall events in urban areas: a case study in the city of Genoa, Italy
Nicola Loglisci, Giorgio Boni, Arianna Cauteruccio, Francesco Faccini, Massimo Milelli, Guido Paliaga, and Antonio Parodi
Nat. Hazards Earth Syst. Sci. Discuss., https//doi.org/10.5194/nhess-2024-24,2024
Preprint under review for NHESS (discussion: open, 1 comment)
This research analyzes the meteo-hydrological features of August 27th and 28th 2023 event occurred in Genoa city. Rainfall observations were taken using either official or rain gauge networks based on citizen science. The combined analysis highlights a spatial variability of the precipitations, which cannot be captured by the current spatial density of the authoritative stations. Results show that at minimal distances the variations in cumulated rainfall over sub-hourly duration are significant.

Improving the fire weather index system for peatlands using peat-specific hydrological input data
Jonas Mortelmans, Anne Felsberg, Gabriëlle J. M. De Lannoy, Sander Veraverbeke, Robert D. Field, Niels Andela, and Michel Bechtold
Nat. Hazards Earth Syst. Sci., 24, 445–464, https://doi.org/10.5194/nhess-24-445-2024, 2024
With global warming increasing the frequency and intensity of wildfires in the boreal region, accurate risk assessments are becoming more crucial than ever before. The Canadian Fire Weather Index (FWI) is a renowned system, yet its effectiveness in peatlands, where hydrology plays a key role, is limited. By incorporating groundwater data from numerical models and satellite observations, our modified FWI improves the accuracy of fire danger predictions, especially over summer.

Understanding flow characteristics from tsunami deposits at Odaka, Joban Coast, using a deep neural network (DNN) inverse model
Rimali Mitra, Hajime Naruse, and Tomoya Abe
Nat. Hazards Earth Syst. Sci., 24, 429–444, https://doi.org/10.5194/nhess-24-429-2024, 2024
This study estimates the behavior of the 2011 Tohoku-oki tsunami from its deposit distributed in the Joban coastal area. In this study, the flow characteristics of the tsunami were reconstructed using the DNN (deep neural network) inverse model, suggesting that the tsunami inundation occurred in the very high-velocity condition.

Climate change impacts on regional fire weather in heterogeneous landscapes of central Europe
Julia Miller, Andrea Böhnisch, Ralf Ludwig, and Manuela I. Brunner
Nat. Hazards Earth Syst. Sci., 24, 411–428, https://doi.org/10.5194/nhess-24-411-2024, 2024
We assess the impacts of climate change on fire danger for 1980–2099 in different landscapes of central Europe, using the Canadian Forest Fire Weather Index (FWI) as a fire danger indicator. We find that today's 100-year FWI event will occur every 30 years by 2050 and every 10 years by 2099. High fire danger (FWI > 21.3) becomes the mean condition by 2099 under an RCP8.5 scenario. This study highlights the potential for severe fire events in central Europe from a meteorological perspective.

Spring water anomalies before two consecutive earthquakes (Mw 7.7 and Mw 7.6) in Kahramanmaraş (Türkiye) on 6 February 2023
Sedat İnan, Hasan Çetin, and Nurettin Yakupoğlu
Nat. Hazards Earth Syst. Sci., 24, 397–409, https://doi.org/10.5194/nhess-24-397-2024, 2024
Two devastating earthquakes, Mw 7.7 and Mw 7.6, occurred in Türkiye on 6 February 2023. We obtained commercially bottled waters from two springs, 100 km from the epicenter of Mw 7.7. Samples of the first spring emanating from fault zone in hard rocks showed positive anomalies in major ions lasting for 6 months before the earthquake. Samples from the second spring accumulated in an alluvium deposit showed no anomalies. We show that pre-earthquake anomalies are geologically site-dependent.

Water depth estimate and flood extent enhancement for satellite-based inundation maps
Andrea Betterle and Peter Salamon
Nat. Hazards Earth Syst. Sci. Discuss., https//doi.org/10.5194/nhess-2024-22,2024
Preprint under review for NHESS (discussion: open, 1 comment)
The study proposes a new framework, named FLEXTH, to estimate flood water depths and improve satellite-based flood monitoring using topographical data. FLEXTH aims to reduce the impact of floods and is readily available as a computer code, offering a practical and scalable solution for estimating flood depths quickly and systematically over large areas. The methodology can reduce the impacts of floods and enhance emergency response efforts, particularly where resources are limited.

A regional-scale approach to assessing non-residential building, transportation and cropland exposure in Central Asia
Chiara Scaini, Alberto Tamaro, Baurzhan Adilkhan, Satbek Sarzhanov, Zukhritdin Ergashev, Ruslan Umaraliev, Mustafo Safarov, Vladimir Belikov, Japar Karayev, and Ettore Fagà
Nat. Hazards Earth Syst. Sci., 24, 355–373, https://doi.org/10.5194/nhess-24-355-2024, 2024
Central Asia is prone to multiple hazards such as floods, landslides and earthquakes, which can affect a wide range of assets at risk. We develop the first regionally consistent database of assets at risk for non-residential buildings, transportation and croplands in Central Asia. The database combines global and regional data sources and country-based information and supports the development of regional-scale disaster risk reduction strategies for the Central Asia region.

Current and future rainfall-driven flood risk from hurricanes in Puerto Rico under 1.5 and 2 °C climate change
Leanne Archer, Jeffrey Neal, Paul Bates, Emily Vosper, Dereka Carroll, Jeison Sosa, and Daniel Mitchell
Nat. Hazards Earth Syst. Sci., 24, 375–396, https://doi.org/10.5194/nhess-24-375-2024, 2024
We model hurricane-rainfall-driven flooding to assess how the number of people exposed to flooding changes in Puerto Rico under the 1.5 and 2 °C Paris Agreement goals. Our analysis suggests 8 %–10 % of the population is currently exposed to flooding on average every 5 years, increasing by 2 %–15 % and 1 %–20 % at 1.5 and 2 °C. This has implications for adaptation to more extreme flooding in Puerto Rico and demonstrates that 1.5 °C climate change carries a significant increase in risk.

Modelling hazards impacting the flow regime in the Hranice Karst due to the proposed Skalička Dam
Miroslav Spano and Jaromir Riha
Nat. Hazards Earth Syst. Sci. Discuss., https//doi.org/10.5194/nhess-2024-21,2024
Preprint under review for NHESS (discussion: open, 0 comments)
Our study examines how building the Skalička Dam near the Hranice Karst affects local groundwater. We used advanced modeling to analyze two dam layouts: lateral and through-flow reservoirs. Results show the through-flow variant significantly alters water levels and mineral water discharge, while the lateral layout has less impact.

High-resolution projections of ambient heat for major European cities using different heat metrics
Clemens Schwingshackl, Anne Sophie Daloz, Carley Iles, Kristin Aunan, and Jana Sillmann
Nat. Hazards Earth Syst. Sci., 24, 331–354, https://doi.org/10.5194/nhess-24-331-2024, 2024
Ambient heat in European cities will substantially increase under global warming, as projected by three heat metrics calculated from high-resolution climate model simulations. While the heat metrics consistently project high levels of ambient heat for several cities, in other cities the projected heat levels vary considerably across the three heat metrics. Using complementary heat metrics for projections of ambient heat is thus important for assessments of future risks from heat stress.

Characteristics of spatial and temporal distribution of heavy rainfall and surface runoff generating process in the mountainous areas of northern China
Hui Yang, Xianglong Hou, and Jiansheng Cao
Nat. Hazards Earth Syst. Sci. Discuss., https//doi.org/10.5194/nhess-2024-8,2024
Preprint under review for NHESS (discussion: open, 0 comments)
For the last decade, a significant upward trend in the frequency of moderate and heavy rainfall events. The spatial variability of rainfall in the Taihang Mountain and the influence of elevation are both smaller when the rainfall during 24 h is lower than 50 mm. For runoff generation under saturated condition, the contribution of rainfall was only 58.17 %. While when the runoff coefficient was greater than 0.5, the surface runoff generating processes were entirely determined by rainfall.

Towards a global impact-based forecasting model for tropical cyclones
Mersedeh Kooshki Forooshani, Marc van den Homberg, Kyriaki Kalimeri, Andreas Kaltenbrunner, Yelena Mejova, Leonardo Milano, Pauline Ndirangu, Daniela Paolotti, Aklilu Teklesadik, and Monica L. Turner
Nat. Hazards Earth Syst. Sci., 24, 309–329, https://doi.org/10.5194/nhess-24-309-2024, 2024
We improve an existing impact forecasting model for the Philippines by transforming the target variable (percentage of damaged houses) to a fine grid, using only features which are globally available. We show that our two-stage model conserves the performance of the original and even has the potential to introduce savings in anticipatory action resources. Such model generalizability is important in increasing the applicability of such tools around the world.

The communication strategy for the release of the first European Seismic Risk Model and the updated European Seismic Hazard Model
Irina Dallo, Michèle Marti, Nadja Valenzuela, Helen Crowley, Jamal Dabbeek, Laurentiu Danciu, Simone Zaugg, Fabrice Cotton, Domenico Giardini, Rui Pinho, John F. Schneider, Céline Beauval, António A. Correia, Olga-Joan Ktenidou, Päivi Mäntyniemi, Marco Pagani, Vitor Silva, Graeme Weatherill, and Stefan Wiemer
Nat. Hazards Earth Syst. Sci., 24, 291–307, https://doi.org/10.5194/nhess-24-291-2024, 2024
For the release of cross-country harmonised hazard and risk models, a communication strategy co-defined by the model developers and communication experts is needed. The strategy should consist of a communication concept, user testing, expert feedback mechanisms, and the establishment of a network with outreach specialists. Here we present our approach for the release of the European Seismic Hazard Model and European Seismic Risk Model and provide practical recommendations for similar efforts.

Heat wave characteristics: evaluation of regional climate model performances for Germany
Dragan Petrovic, Benjamin Fersch, and Harald Kunstmann
Nat. Hazards Earth Syst. Sci., 24, 265–289, https://doi.org/10.5194/nhess-24-265-2024, 2024
The influence of model resolution and settings on the reproduction of heat waves in Germany between 1980–2009 is analyzed. Outputs from a high-resolution model with settings tailored to the target region are compared to those from coarser-resolution models with more general settings. Neither the increased resolution nor the tailored model settings are found to add significant value to the heat wave simulation. The models exhibit a large spread, indicating that the choice of model can be crucial.

Rain-on-snow responses to warmer Pyrenees: a sensitivity analysis using a physically based snow hydrological model
Josep Bonsoms, Juan I. López-Moreno, Esteban Alonso-González, César Deschamps-Berger, and Marc Oliva
Nat. Hazards Earth Syst. Sci., 24, 245–264, https://doi.org/10.5194/nhess-24-245-2024, 2024
Climate warming is changing mountain snowpack patterns, leading in some cases to rain-on-snow (ROS) events. Here we analyzed near-present ROS and its sensitivity to climate warming across the Pyrenees. ROS increases during the coldest months of the year but decreases in the warmest months and areas under severe warming due to snow cover depletion. Faster snow ablation is anticipated in the coldest and northern slopes of the range. Relevant implications in mountain ecosystem are anticipated.

Using integrated hydrological–hydraulic modelling and global data sources to analyse the February 2023 floods in the Umbeluzi Catchment (Mozambique)
Luis Cea, Manuel Álvarez, and Jerónimo Puertas
Nat. Hazards Earth Syst. Sci., 24, 225–243, https://doi.org/10.5194/nhess-24-225-2024, 2024
Mozambique is highly exposed to the impact of floods. To reduce flood damage, it is necessary to develop mitigation measures. Hydrological software is a very useful tool for that purpose, since it allows for a precise quantification of flood hazard in different scenarios. We present a methodology to quantify flood hazard in data-scarce regions, using freely available data and software, and we show its potential by analysing the flood event that took place in the Umbeluzi Basin in February 2023.

Revisiting regression methods for estimating long-term trends in sea surface temperature
Ming-Huei Chang, Yen-Chen Huang, Yu-Hsin Cheng, Chuen-Teyr Terng, Jinyi Chen, and Jyh Cherng Jan
Nat. Hazards Earth Syst. Sci. Discuss., https//doi.org/10.5194/nhess-2023-218,2024
Preprint under review for NHESS (discussion: open, 1 comment)
Monitoring the long-term trends in sea surface warming is crucial for informed decision-making and adaptation. This study offers a comprehensive examination of prevalent trend extraction methods. We identify ordinary least squares as suitable for general tasks yet highlight the need to address seasonal signal-induced bias, specifically the phase-distance imbalance. Our implementation, evaluated with simulated and realist data, provides a potential solution.

Meteorological Analysis of the Forcett-Dunalley Wildfire in 2013 in Tasmania, Australia
Ivana Čavlina Tomašević, Paul Fox-Hughes, Kevin Cheung, Višnjica Vučetić, Jon Marsden-Smedley, Paul Beggs, and Maja Telišman Prtenjak
Nat. Hazards Earth Syst. Sci. Discuss., https//doi.org/10.5194/nhess-2023-210,2024
Preprint under review for NHESS (discussion: open, 0 comments)
We have analyzed a severe wildfire event in Tasmania, Australia that also developed thunderstorm clouds. The drivers of this compound hazard were highly complex, which included climatic factors (above normal heavy rain seasons followed by heatwave), weather systems (fronts and high winds) to heighten fire severity and unstable atmosphere to develop thunderstorm clouds, all in coincidence. Such event has demonstrated the difficulty to assess wildfire risk in a warming climate.

Impact-based flood forecasting in the Greater Horn of Africa
Lorenzo Alfieri, Andrea Libertino, Lorenzo Campo, Francesco Dottori, Simone Gabellani, Tatiana Ghizzoni, Alessandro Masoero, Lauro Rossi, Roberto Rudari, Nicola Testa, Eva Trasforini, Ahmed Amdihun, Jully Ouma, Luca Rossi, Yves Tramblay, Huan Wu, and Marco Massabò
Nat. Hazards Earth Syst. Sci., 24, 199–224, https://doi.org/10.5194/nhess-24-199-2024, 2024
This work describes Flood-PROOFS East Africa, an impact-based flood forecasting system for the Greater Horn of Africa. It is based on hydrological simulations, inundation mapping, and estimation of population and assets exposed to upcoming river floods. The system supports duty officers in African institutions in the daily monitoring of hydro-meteorological disasters. A first evaluation shows the system performance for the catastrophic floods in the Nile River basin in summer 2020.