T.G. Johnson

Bio: T.G. Johnson is an academic researcher from Technische Universität München. The author has contributed to research in topics: Flood myth. The author has an hindex of 1, co-authored 1 publications receiving 17 citations.

Causes, impacts and patterns of disastrous river floods

Abstract: Disastrous floods have caused millions of fatalities in the twentieth century, tens of billions of dollars of direct economic loss each year and serious disruption to global trade. In this Review, we provide a synthesis of the atmospheric, land surface and socio-economic processes that produce river floods with disastrous consequences. Disastrous floods have often been caused by processes fundamentally different from those of non-disastrous floods, such as unusual but recurring atmospheric circulation patterns or failures of flood defences, which lead to high levels of damage because they are unexpected both by citizens and by flood managers. Past trends in economic flood impacts show widespread increases, mostly driven by economic and population growth. However, the number of fatalities and people affected has decreased since the mid-1990s because of risk reduction measures, such as improved risk awareness and structural flood defences. Disastrous flooding is projected to increase in many regions, particularly in Asia and Africa, owing to climate and socio-economic changes, although substantial uncertainties remain. Assessing the risk of disastrous river floods requires a deeper understanding of their distinct causes. Transdisciplinary research is needed to understand the potential for surprise in flood risk systems better and to operationalize risk management concepts that account for limited knowledge and unexpected developments. River floods have direct and indirect consequences for society, and can cause fatalities, displacement and economic loss. This Review examines the physical and socioeconomic causes and impacts of disastrous river flooding, and past and projected trends in their occurrence.

Geostatistical Analysis of the Spatial Correlation between Territorial Anthropization and Flooding Vulnerability: Application to the DANA Phenomenon in a Mediterranean Watershed

Abstract: Climate change is making intense DANA (depresion aislada en niveles altos) type rains a more frequent phenomenon in Mediterranean basins. This trend, combined with the transformation of the territory derived from diffuse anthropization processes, has created an explosive cocktail for many coastal towns due to flooding events. To evaluate this problem and the impact of its main guiding parameters, a geostatistical analysis of the territory based on GIS indicators and an NDVI (Normalized Difference Vegetation Index) analysis is developed. The assessment of the validity of a proposed methodology is applied to the case study of the Campo de Cartagena watershed located around the Mar Menor, a Mediterranean coastal lagoon in Southeastern Spain. This area has suffered three catastrophic floods derived from the DANA phenomenon between 2016 and 2019. The results show that apart from the effects derived from climate change, the real issue that amplifies the damage caused by floods is the diffuse anthropization process in the area, which has caused the loss of the natural hydrographic network that traditionally existed in the basin.

Assessing the past and adapting to future floods: a hydro-social analysis

Abstract: Floods are extreme events affecting millions of people worldwide and causing loss worth billions. The magnitude and frequency of floods are likely to increase with altered climate, and developing countries tend to suffer the most because of low resilience and adaptive capacity. This research aimed to analyze existing and preferred future flood adaptation strategies in a flood-prone West Rapti River (WRR) Basin of Nepal, using hydrological analysis and flood modelling, and a social survey of 240 households (HHs) and several focus group discussions (FGDs). The specific objectives were to (1) understand the rainfall-flood behaviour of the basin in a simplistic way, (2) carry out flood modelling to generate inundation maps for informing the local people, and (3) identify flood adaptation strategies based on people’s perception. Flood inundation maps are generated for four scenarios based on return periods: scenario I (2 years), scenario II (20 years), scenario III (50 years), and scenario IV (100 years). Results show that the southern parts of three rural municipalities (Duduwa, Narainapur, and Rapti Sonari) get inundated almost every year irrespective of the flood magnitude. This information was presented to local communities before administering the HH survey and FGDs so that they could make informed decisions. During the survey, the preference of people’s adaptation strategies for the four flood scenarios was explored and prioritized. Our findings suggest that peoples’ thoughts and preferences for adaptation strategies changed with exposure to flood magnitudes. For example, “bamboo mesh with sand filled bags”—simplest and least expensive adaptation strategy—was preferred for a less severe flood while a complex and expensive technique “reservoir/flood regulating structures” was preferred for a devastating flood scenario. Thus, this study has highlighted firstly, the importance of inundation maps to understand and inform the local people about floods and their impacts; and secondly, the value of information to the people enabling them to make informed decisions. The novelty of this empirical study lies in a multi-disciplinary assessment framework which integrates scientific information, stakeholder knowledge, and local people’s perceptions of flood risks and adaptation strategies for the future. Such an approach of hydro-social analysis has the potential for replication in flood-prone regions globally, with similar bio-physical and socio-economic conditions.

Resilience issues and challenges into built environments: a review

Abstract: . This paper proposes a review of existing strategies and tools aiming at facilitating the operationalization of the concept of resilience into built environments. In a context of climate change, increased risks in urban areas and growing uncertainties, urban managers are forced to innovate in order to design appropriate risk management strategies. Among these strategies, making cities resilient has become an imperative. This injunction to innovation fits perfectly with the urban, economic, political, social and ecological complexity of the contemporary world. As a result, the concept of resilience is integrated into the issues of urban sprawl and the associated risks. However, despite this theoretical and conceptual adequacy, resilience remains complex to integrate into the practices of urban planners and territorial actors. Its multitude of definitions and approaches has contributed to its abstraction and lack of operationalization. This review highlights the multitude of approaches and methodologies to address the bias of the lack of integration of the concept of resilience in risk management. The limit is the multiplication of these strategies which lead to conceptual vagueness and a lack of tangible application at the level of local actors. The challenge would then be to design a toolbox to concentrate the various existing tools, conceptual models and decision support systems in order to facilitate the autonomy and responsibility of local stakeholders in integrating the concept of resilience into risk management strategies.