Urban Flood Risk Assessment: Integration of Decision Making and Machine Learning

Urban flood risk mapping is an important tool for the mitigation of flooding in view of human activities and climate change. Many developing countries, however, lack sufficiently detailed data to produce reliable risk maps with existing methods. Thus, improved methods are needed that can improve urban flood risk management in regions with scarce hydrological data. Given this, we estimated the flood risk map for Rasht City (Iran), applying a composition of decision-making and machine learning methods. Flood hazard maps were produced applying six state-of-the-art machine learning algorithms such as: classification and regression trees (CART), random forest (RF), boosted regression trees (BRT), multivariate adaptive regression splines (MARS), multivariate discriminant analysis (MDA), and support vector machine (SVM). Flood conditioning parameters applied in modeling were elevation, slope angle, aspect, rainfall, distance to river (DTR), distance to streets (DTS), soil hydrological group (SHG), curve number (CN), distance to urban drainage (DTUD), urban drainage density (UDD), and land use. In total, 93 flood location points were collected from the regional water company of Gilan province combined with field surveys. We used the Analytic Hierarchy Process (AHP) decision-making tool for creating an urban flood vulnerability map, which is according to population density (PD), dwelling quality (DQ), household income (HI), distance to cultural heritage (DTCH), distance to medical centers and hospitals (DTMCH), and land use. Then, the urban flood risk map was derived according to flood vulnerability and flood hazard maps. Evaluation of models was performed using receiver-operator characteristic curve (ROC), accuracy, probability of detection (POD), false alarm ratio (FAR), and precision. The results indicated that the CART model is most accurate model (AUC = 0.947, accuracy = 0.892, POD = 0.867, FAR = 0.071, and precision = 0.929). The results also demonstrated that DTR, UDD, and DTUD played important roles in flood hazard modeling; whereas, the population density was the most significant parameter in vulnerability mapping. These findings indicated that machine learning methods can improve urban flood risk management significantly in regions with limited hydrological data.

The 2020 national seismic hazard model for the United Kingdom

We present updated seismic hazard maps for the United Kingdom (UK) intended for use with the National Annex for the revised edition of Eurocode 8. The last national maps for the UK were produced by Musson and Sargeant (Eurocode 8 seismic hazard zoning maps for the UK. British Geological Survey Report CR/07/125, United Kingdom, 2007). The updated model uses an up-to-date earthquake catalogue for the British Isles, for which the completeness periods have been reassessed, and a modified source model. The hazard model also incorporates some advances in ground motion modelling since 2007, including host-to-target adjustments for the ground motion models selected in the logic tree. For the first time, the new maps are provided for not only peak ground acceleration (PGA) but also spectral acceleration at 0.2 s (SA0.2s) and 1.0 s for 5% damping on rock (time-averaged shear wave velocity for the top 30 m Vs30 ≥ 800 m/s) and four return periods, including 475 and 2475 years. The hazard in most of the UK is generally low and increases slightly in North Wales, the England–Wales border region, and western Scotland. A similar spatial variation is observed for PGA and SA0.2s but the effects are more pronounced for SA0.2s. Hazard curves, uniform hazard spectra, and disaggregation analysis are calculated for selected sites. The new hazard maps are compared with the previous 2007 national maps and the 2013 European hazard maps (Woessner et al. in Bull Earthq Eng 13:3553–3596, 2015). There is a slight increase in PGA from the 2007 maps to this work; whereas the hazard in the updated maps is lower than indicated by the European maps.

Mapping the biotic degradation hazard of wood in Europe – biophysical background, engineering applications, and climate change-induced prospects

Construction using timber has seen a resurgence in light of global climate mitigation policies. Wood is a renewable resource, and engineered wood products are proving to be competitive against concrete and steel while having several advantages. However, while the renewable nature of wood in construction is a beneficial property for climate mitigation policies, the process of biodegradation introduces a challenge for service life planning. A review of hazard mapping is presented while developing contemporary hazard maps, occurrence maps and projected hazard maps for 2050 using representative concentration pathways (RCP) 2.6 and 8.5. The risk of timber decay is expected to increase in most of Europe as the temperatures rise, with a decrease expected in dryer regions. Termites are likely to experience a range expansion as more areas become suitable, while human activity and an increase in extreme weather events like floods are expected to facilitate dispersion. Marine borer species already present a risk in most European coastal regions; however, the effect of changes in water temperatures are likely to shift the boundaries for individual borer species. Overall, warmer climates are expected to increase the metabolic activity of all of these organisms leading to a general reduction in service life.

Real-time coastal flood hazard assessment using DEM-based hydrogeomorphic classifiers

Deltas, estuaries, and wetlands are prone to frequent coastal flooding throughout the world. In addition, a large number of people in the United States have settled in these low-lying regions. Therefore, the ecological merit of wetlands for maintaining sustainable ecosystems highlights the importance of flood risk and hazard management in these regions. Typically, hydrodynamic models are used for coastal flood hazard mapping. The huge computational resources required for hydrodynamic modeling and the long-running time of these models (order of hours or days) are two major drawbacks that limit the application of these models for prompt decision-making by emergency responders. In the last decade, DEM-based classifiers based on Height Above Nearest Drainage (HAND) have been widely used for rapid flood hazard assessment demonstrating satisfactory performance for inland floods. The main limitation is the high sensitivity of HAND to the topography which degrades the accuracy of these methods in flat coastal regions. In addition, these methods are mostly used for a given return period and generate static hazard maps for past flood events. To cope with these two limitations, here we modify HAND and propose a composite hydrogeomorphic index for rapid flood hazard assessment in coastal areas. We also propose the development of hydrogeomorphic threshold operative curves for real-time flood hazard mapping. We select the Savannah river delta as a testbed, calibrate the proposed hydrogeomorphic index on Hurricane Matthew and validate the performance of the developed operative curves for Hurricane Irma. Validation results demonstrate that the operative curves can rapidly generate flood hazard maps with satisfactory accuracy. This indicates the high efficiency of our proposed methodology for fast and accurate estimation of hazard areas for an upcoming coastal flood event which can be beneficial for emergency responders and flood risk managers.

Managing Flood Hazard in a Complex Cross-Border Region Using Sentinel-1 SAR and Sentinel-2 Optical Data: A Case Study from Prut River Basin (NE Romania)

In this study, an alternative solution for flood risk management in complex cross-border regions is presented. In these cases, due to different flood risk management legislative approaches, there is a lack of joint cooperation between the involved countries. As a main consequence, LiDAR-derived digital elevation models and accurate flood hazard maps obtained by means of hydrological and hydraulic modeling are missing or are incomplete. This is also the case for the Prut River, which acts as a natural boundary between European Union (EU) member Romania and non-EU countries Ukraine and Republic of Moldova. Here, flood hazard maps were developed under the European Floods Directive (2007/60/EC) only for the Romanian territory and only for the 1% exceeding probability (respectively floods that can occur once every 100 years). For this reason, in order to improve the flood hazard management in the area and consider all cross-border territories, a fully remote sensing approach was considered. Using open-source SAR Sentinel-1 and Sentinel-2 data characterized by an improved temporal resolution, we managed to capture the maximum spatial extent of a flood event that took place in the aforementioned river sector (middle Prut River course) during the 24 and 27 June 2020. Moreover, by means of flood frequency analysis, the development of a transboundary flood hazard map with an assigned probability, specific to the maximum flow rate recorded during the event, was realized.

Active volcanism in Colombia and the role of the Servicio Geológico Colombiano

The Servicio Geológico Colombiano (SGC) was created in 1916 and has been dedicated to the research and monitoring of active volcanoes in the country since the disaster resulting from the eruption of Nevado del Ruíz Volcano in 1985, where more than 25000 people died due to lahars. Today the SGC has three Volcanological and Seismological Observatories in the cities of Manizales (SGC-OVSM), Popayán (SGC-OVSPop), and Pasto (SGC-OVSP), from where 23 active volcanoes are monitored. The three observatories manage an instrumental network of about 740 stations (permanent and portable) as well as signal repeaters, and cover the disciplines of seismology, geodesy, geochemistry, and potential field, amongst others. Volcanic hazard assessment is also carried out by the SGC, producing hazard maps and reports. These tasks are complemented by programs for promoting geoscience knowledge transfer to the public, developed through different strategies. Although at this time, data derived from volcanic monitoring are not available online, the SGC is analysing this need, for implementation in the near future. El Servicio Geológico Colombiano (SGC) fue creado en 1916, y se ha dedicado a la investigación y monitoreo de los volcanes activos en el país desde el desastre resultante de la erupción del volcán Nevado del Ruíz en 1985, donde más de 25000 personas murieron debido a la ocurrencia de lahares. Hoy en día, el SGC tiene tres Observatorios Vulcanológicos y Sismológicos en las ciudades de Manizales (SGC-OVSM), Popayán (SGC-OVSPop) y Pasto (SGC-OVSP), desde donde se monitorean 23 volcanes activos. Los tres observatorios manejan una red instrumental de aproximadamente 740 estaciones (permanentes y portátiles), como también repetidoras de señal, y cubren las disciplinas de sismología, geodesia, geoquímica y campos de potencial, entre otras. La evaluación de la amenaza volcánica también es realizada por el SGC, produciendo mapas e informes. Estas tareas se complementan con programas para promover transferencia de conocimientos geocientíficos al público, desarrollados a través de diferentes estrategias. Aunque en este momento los datos derivados del monitoreo volcánico no están disponibles en línea, el SGC está analizando esta necesidad para su implementación en un futuro cercano.

Hazard assessment studies and multiparametric volcano monitoring developed by the Instituto Geológico, Minero y Metalúrgico in Peru

Urban development in the areas surrounding active volcanoes has led to increasing risks in southern Peru. In order to evaluate the hazard, the Instituto Geológico, Minero y Metalúrgico (INGEMMET) created a Volcano Observatory (OVI) to carry out detailed geological investigations to understand eruption histories and provide volcanic hazard maps. The generation of geological information on volcanoes has allowed the identification of scenarios and zoning of potentially impacted areas. This information has also allowed OVI to implement surveillance networks giving priority to the volcanoes that pose the greatest risk to the population, infrastructure, and economic activities. Since 2006, OVI has been running volcanic monitoring networks with a multidisciplinary approach, improving real-time transmission, and making timely forecasts. Based on geological information and the risk posed by the volcanoes, the greatest efforts have been made to monitor Sabancaya, Misti, Ubinas, and Ticsani volcanoes. Following the order of priorities, monitoring of Coropuna, Huaynaputina, Tutupaca and, Yucamane volcanoes has also been developed. In addition, OVI carries out routine education activities and diffusion of information that serve to manage volcanic risk in Peru. El desarrollo urbano en zonas aledañas a volcanes activos ha conllevado a la generación de riesgos cada vez mayores en el sur del Perú. Con la finalidad de evaluar el peligro, el Instituto Geológico, Minero y Metalúrgico (INGEMMET) creó un observatorio vulcanológico (OVI) para realizar estudios geológicos detallados que permitan conocer las historias eruptivas y elaborar mapas de peligros volcánicos. La generación de información geológica sobre los volcanes ha permitido la identificación de escenarios y la zonificación de áreas con potencial a ser afectadas. Esta información también ha permitido al OVI implementar sus redes de monitoreo priorizando los volcanes que representan mayor riesgo para la población, la infraestructura y las actividades económicas. Desde el año 2006, el OVI viene implementando redes de vigilancia volcánica con un enfoque multidisciplinario, mejorando la transmisión en tiempo real y realizando pronósticos oportunos. En base a la información geológica y el nivel de riesgo de los volcanes, se han puesto los mayores esfuerzos en monitorear los volcanes Sabancaya, Misti, Ubinas y Ticsani. Siguiendo el orden de prioridades, el OVI ha comenzado, también, el monitoreo de los volcanes Coropuna, Huaynaputina, Tutupaca y Yucamane. Además, el observatorio desarrolla actividades permanentes de educación y difusión de la información que sirven a la gestión del riesgo volcánico en el Perú.

Instituto Geofísico – Escuela Politécnica Nacional, the Ecuadorian Seismology and Volcanology Service

Ninety-eight Quaternary volcanoes have been identified in the Ecuadorian Andes and the Galápagos Islands, from them, nine experienced at least one eruption in the last twenty years. Additionally, about 35 % of the Ecuadorian population live in areas that could be affected by future volcanic eruptions. The Instituto Geofísico of the Escuela Politécnica Nacional (IG-EPN) monitors and evaluates Ecuador’s volcanic hazards: nineteen volcanic hazard maps and hundreds of related articles have been published as a result of its research. The monitoring networks include eighteen volcanoes, with more than 266 stations, which also form the basis for early warning systems at several volcanoes. Volcanic activity is widely communicated by the IG-EPN through periodic information published in different media (website and social networks). Ecuadorian volcanoes will erupt in the future and, therefore, the IGEPN continuously updates its monitoring and hazard assessment practices and improves communication channels and protocols to successfully fulfil its responsibilities. Noventa y ocho volcanes cuaternarios han sido identificados en los Andes ecuatorianos y Galápagos de los cuales nueve han experimentado erupciones al menos una vez en los últimos veinte años. Adicionalmente, alrededor del 35 % de la población ecuatoriana vive en zonas que podrían ser afectadas durante futuras erupciones. El Instituto Geofísico de la Escuela Politécnica Nacional (IG-EPN) monitorea y evalúa la amenaza volcánica del país y, como resultado de sus investigaciones, diecinueve mapas de amenaza volcánica y centenares de artículos científicos han sido publicados. Las redes de vigilancia comprenden dieciocho volcanes e incluyen más de 266 estaciones, que son parte también de los sistemas de alerta temprana. La actividad volcánica es comunicada amplia y periódicamente por el IG-EPN a través diferentes medios (página web y redes sociales). Comprendiendo que futuras erupciones ocurrirán en Ecuador, el IG-EPN continúa actualizando sus prácticas de vigilancia y evaluación de la amenaza, y mejorando sus protocolos de comunicación para cumplir exitosamente sus responsabilidades.

Volcanic monitoring and hazard assessment in El Salvador

The Salvadorean volcanic range forms part of Central America Volcanic Arc and is located on the Pacific ring of fire. El Salvador is a country with at least twenty Holocene-active volcanic structures and where most of the population, including the metropolitan area of San Salvador, live near a volcanic complex. Currently, there are six active volcanoes that are continuously monitored by the Observatorio de Amenazas y Recursos Naturales, which is part of the Ministerio del Medio Ambiente y Recursos Naturales. Volcano monitoring involves seismic, geochemical, and visual monitoring techniques, among others. In addition to volcano monitoring and with the aim of early warning of future eruptions, volcanic hazard maps and networks of local observers have been developed. These initiatives together with the general directorate of civil protection, seek to meet the goal of reducing risk from volcanic activity in El Salvador. La cadena volcánica salvadoreña forma parte del Arco Volcánico de América Central y está localizada dentro de la zona conocida como cinturón de fuego del Pacífico. El Salvador es un país donde se encuentran al menos 20 estructuras volcánicas que han estado activas durante el Holoceno y donde la mayor parte de la población, incluyendo la ciudad capital San Salvador, está ubicada en las proximidades de algún complejo volcánico. Actualmente, seis volcanes activos son continuamente monitoreados por el Observatorio de Amenazas y Recursos Naturales, que es parte del Ministerio del Medio Ambiente y Recursos Naturales. El monitoreo volcánico se realiza mediante técnicas de monitoreo sísmicas, geoquímicas, visuales, entre otras. Como complemento del trabajo de monitoreo, se han desarrollado mapas de amenaza volcánica y redes de observadores locales constituyendo así sistemas de alerta temprana ante futuras erupciones. Estas iniciativas, en conjunto con la dirección general de la protección civil, persiguen el objetivo de reducir el riesgo por actividad volcánica en El Salvador.