Cellular automata and Agent-based models in response to different environmental problems: a review on French research over the last ten years

Cellular Automata (CA) and Agent-Based Models (ABM) are used to better assess patterns and processes result-ing from environmental interactions using simple rules. Over the last ten years, the applications have been carriedout on various complex systems: flash floods, fire propagation, river meandering, landscape evolution... The fre-quent use these applications demand are supported by an array of advances in field outside of physical geographyas physics, computer sciences and mathematics. This communication presents common, singular and innovativeapplications observed in French research. On one hand, the CA RuiCells aims at understanding the spatial hy-drological behaviours in all points of one catchment, linking impacts due to basin forms and slopes through localto global scales (Delahaye et al., 2007). The CA Soda has been developed to measure erosion at fine scale, lessthan a few meters (Vallette, 2006). Smoothed-particules can also be implemented in CA to improve dynamics orhydrological fluxes (Drogoul, 1995). On the other hand, ABM appears in geomorphology after first initiatives inecology, sociology or human geography in the 1990's. Modules of CATCHSCAPE allow to simulate the hydrolog-ical system with its distributed water balance, irrigate schemes management, crop and vegetation dynamics (Bécuet al. 2008). For alluvial plains, ABM can also be used to simulate processes between independent interacting enti-ties which behave according to the local environment (Teles et al., 1999). At the opposite, many models have beendeveloped in other countries, as for simulating erosive thresholds (Favis-Mortlock, 1998), lava dynamics (Avolioet al., 2006), fluvial meandering (Coulthard and Van de Wiel, 2006), evolution of coasts (Dearing et al., 2005) anddunes (Thomas and Nicholas, 2007). Consequently, this communication addresses the debate on two questions:why French geomorphologist researchers are late in applying CA and ABMs, and is the simplification in processeshad led to change research questions or to offer new perspectives

Risk as a process: a history informed hazard planning approach applied to the 2018 post-fire debris flows, Montecito, California

Historical information about floods is not commonly used in the US to inform land use planning decisions. Rather, the current approach to managing floods is based on static maps derived from computer simulations of the area inundated by floods of specified return intervals. These maps provide some information about flood hazard, but they do not reflect the underlying processes involved in creating a flood disaster, which typically include increased exposure due to building on flood-prone land, nor do they account for the greater hazard resulting from wildfire. We developed and applied an approach to analyze how exposure has evolved in flood hazard zones in Montecito, California, an area devastated by post-fire debris flows in January 2018. By combining historical flood records of the past 200 years, human development records of the past 100 years, and geomorphological understanding of debris flow generation processes, this approach allows us to look at risk as a dynamic process influenced by physical and human factors, instead of a static map. Results show that floods after fires, in particular debris flows and debris laden floods, are very common in Montecito (15 events in the last 200 years), and that despite policies discouraging developments in hazard areas, developments in hazard zones have increased substantially since Montecito joined the National Flood Insurance Program in 1979. We also highlight the limitation of using conventional Flood Insurance Rate Maps (FIRMs) to manage land use in alluvial fan areas such as Montecito. The knowledge produced in this project can help Montecito residents better understand how they came to be vulnerable to floods and identify action they are taking now that might increase or reduce their vulnerability to the next big flood. This science-history-centric approach to understand hazard and exposure evolution using geographic information systems (GIS) and historical records, is generalizable to other communities seeking to better understand the nature of the hazard they are exposed to and some of the root causes of their vulnerabilities, in other words, both the natural and social processes producing disasters

Social and Hydrological Responses to Extreme Precipitations: An Interdisciplinary Strategy for Postflood Investigation

International audienceThis paper describes and illustrates a methodology to conduct postflood investigations based on interdisciplinary collaboration between social and physical scientists. The method, designed to explore the link between crisis behavioral response and hydrometeorological dynamics, aims at understanding the spatial and temporal capacities and constraints on human behaviors in fast-evolving hydrometeorological conditions. It builds on methods coming from both geosciences and transportations studies to complement existing post-flood field investigation methodology used by hydrometeorologists. The authors propose an interview framework, structured around a chronological guideline to allow people who experienced the flood firsthand to tell the stories of the circumstances in which their activities were affected during the flash flood. This paper applies the data collection method to the case of the 15 June 2010 flash flood event that killed 26 people in the Draguignan area (Var, France). As a first step, based on the collected narratives, an abductive approach allowed the identification of the possible factors influencing individual responses to flash floods. As a second step, behavioral responses were classified into categories of activities based on the respondents' narratives. Then, aspatial and temporal analysis of the sequences made of the categories of action to contextualize the set of coping responses with respect to local hydrometeorological conditions is proposed. During this event, the respondents mostly follow the pace of change in their local environmental conditions as the flash flood occurs, official flood anticipation being rather limited and based on a large-scale weather watch. Therefore, contextual factors appear as strongly influencing the individual's ability to cope with the event in such a situation

Milling time and public perception of Cell Broadcast tsunami alerts tested on the French Mediterranean coast on 19 January 2024

There is limited research on public perception, intended responses and message understanding in the situation of Cell Broadcast mobile alerts, especially in France as the Cell Broadcast has been recently developed (since June 2022). This original dataset has been completed during a tsunami trial conducted on 19 January 2022, by using an online questionnaire, with a short URL link directly included in mobile alert messages, displayed along the French Mediterranean coast (with 189 municipalities and 9 departments). The aim is to further evaluate what people do and think upon receiving Cell Broadcast alerts, that deliver an attention-grabbing message directly on the screen of mobile phones of people located in the at-risk zones. The Tsunami Evacuation Zones (TEZ) have been designed as the Cell Broadcast zone, by considering at fine scale all the areas characterized by a height of 0 to 5m above sea level and up to 200m inside river mouths. A first notification was sent in the TEZ from 09:30 to 10:30, and a second from 10:35 to 10:50 to close the test. A total of 9,446 totally-completed answers have been collected during 2 days even if 82.9% (n=7,825 answers) were already collected at 11:00. The sample consists of 24 questions, designed by an interdisciplinary research team (including geographers, designers and psychologists researchers), to respond to a dual challenge: 1) firstly, to evaluate the participants’ immediate reactions to the Cell Broadcast messages, displayed with sound tone (that may provoke anxiety, fear or stress, particularly if individuals are confused by such type of alert), and 2) second, to estimate the intended milling time (i.e., the time one person declared before he decides to evacuate) and to measure its influence for evacuation planning. Other variables (age, professional status, location during alert reception) completed the dataset and can be used as socio-demographic parameters as well as explanatory variables in case of more complete statistical analyses. The 9 Prefectures, the French Ministry of Interior and the researchers team were involved before the test (to produce the Tsunami Evacuation Zones and to design the alert messages), during the test (to observe reactions of recipients, but only at local scales) and after the test (to present results to the practitioners and disseminate the scientific lessons that can be addressed with this questionnaire). This original dataset serves as a critical resource for researchers, policymakers, and emergency managers focused on optimizing Cell Broadcast alerts and defining alert messages. It is particularly suited to enhance the effectiveness and understanding of tsunami Cell Broadcast alerts.THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

Floods 2 : risk management

Crowdsourcing and crisis-mapping are concepts supported by the involvement of a large number of persons that enable, in a voluntary way, consolidation of information collected in situ during the course and progress of a phenomenon (such as a flood for example). The term 'volunteerism' is generally used to refer to activities that are non-obligatory (there is no contractual, familial or friendship obligation between the helper and the helped, nor coercion). Data collected is often of a geographical nature, and the tools used for collection (internet, mobile technologies), and publication of this data (websites, map platforms), enable it to be shared instantly and quickly. When floods occur, this input can help to assess the seriousness of a situation, and to guide disaster relief operations for victims

Introduction to the thematic issue: "Quantitative hydro-geomorphology"

Co-Guest Editors would like to thank the authors who answered this call for papers and the eighteen anonymous reviewers. We also want to deeply thank Gilles Arnaud-Fassetta, Editor in Chief of the journal Géomorphologie: relief, processus, environnement for his confidence and his availability. Since a few decades hydro-geomorphologists use quantitative tools to estimate flows, water or sediments passing across river basins. They focus on the upstream/downstream interactions and on the numerou..