Development of a low-cost methodology for data acquisition and flood risk assessment in the floodplain of the river Moustiques in Haiti

Over the past two decades, Haiti was struck by 30 storm events and 40 floods, affecting over 3.5 million people. Being the poorest country in the Northern hemisphere, it is unable to allocate funds to risk assessment and management. Therefore, this research developed a low-cost methodology to analyse flood risk in data-sparse regions. The floodplain of the river Moustiques was chosen as study area. First, a methodology was developed and input data were gathered from existing data, literature, field data, and open source data. Then, a flood risk assessment was performed for the area. The resulting economic risk map and social risk map indicate that the region is at risk for nearly 2 million USD and has potentially 60 casualties per year. Although the assessment was performed as a quantitative analysis, the resulting maps should be interpreted qualitatively, as the values could not be validated. Nonetheless, the results clearly indicate the high-risk areas where measures should be taken. Furthermore, this research shows the potential of citizen science, in the form of a questionnaire survey conducted in the floodplain. This low-cost and fast acquisition method provided many different input data for flood risk assessment, from population data to damage factors and validation information on historic flooding

Analyzing the sensitivity of a flood risk assessment model towards its input data

The Small Island Developing States are characterized by an unstable economy and low-lying, densely populated cities, resulting in a high vulnerability to natural hazards. Flooding affects more people than any other hazard. To limit the consequences of these hazards, adequate risk assessments are indispensable. Satisfactory input data for these assessments are hard to acquire, especially in developing countries. Therefore, in this study, a methodology was developed and evaluated to test the sensitivity of a flood model towards its input data in order to determine a minimum set of indispensable data. In a first step, a flood damage assessment model was created for the case study of Annotto Bay, Jamaica. This model generates a damage map for the region based on the flood extent map of the 2001 inundations caused by Tropical Storm Michelle. Three damages were taken into account: building, road and crop damage. Twelve scenarios were generated, each with a different combination of input data, testing one of the three damage calculations for its sensitivity. One main conclusion was that population density, in combination with an average number of people per household, is a good parameter in determining the building damage when exact building locations are unknown. Furthermore, the importance of roads for an accurate visual result was demonstrated

Risk assessment in the Caribbean: modeling a GIS-based Flood risk Tool for Jamaica

The Caribbean is known to be one of the most hazard-prone regions in the world. Although the growing intensity of these disasters increases the concern of decision makers, researchers have not yet succeeded in developing an accurate multi-hazard risk assessment tool to locate the high-risk areas. Many single-hazard risk analyses adequately estimate the risk of one hazard, but the complexity of the relation between the different types of hazards causes difficulties in developing one risk analysis to assess all hazards. This research aims to develop such a model for the Caribbean. In a first step, a flood risk tool was developed for Jamaica. After optimizing this tool, the methods will be used for other hazard types. In a final step, all single-hazard tools will be combined into one multi-hazard risk assessment. To generate the flood risk tool, a new methodology based on minimizing risks rather than building water defences, was used. In the Flemish Region in Belgium, this method is already used in a tool called LATIS, and has proven that using a risk-based methodology helps tremendously in finding the most cost-efficient measures to reduce risk. For Jamaica, the lack of data was and is a big concern. Since there was only minimal rainfall data available, flood hazard maps could not be generated. Therefore, a risk map could not yet be computed, only a vulnerability map and a damage map could. Furthermore, the available damage functions did not cover all elements at risk. Before regenerating the damage map, these functions will have to be reassessed. However, the vulnerability map that was produced shows promising results in indicating the high-risk areas, which are the most important factor in the decision making process. Further research will focus on the flood hazard maps and the damage functions, before applying this method to other natural hazards

Development of a 3D dynamic flood WebGIS visualisation tool

Low elevation coastal areas are vulnerable to the effects of sea level rise and to an increase in the frequency and severity of storm surge events due to climate change. Coastal urban areas are at risk because coastal flooding causes extensive damage to energy and transportation infrastructure, disruptions to the delivery of services, devastating tolls on the public's health and, occasionally, significant loss of life. Although scientists widely stress the compelling need to mitigate and adapt to climate change, public awareness lags behind. Because WebGIS maps (web-based geographic information systems) quickly convey strong messages, condense complex information, engage people in issues of environmental change, and motivate personal actions, this paper focusses on searching the ideal flood assessment WebGIS method to encourage people to mitigate and adapt to climate change. Surveys demonstrated that 3D visualisations have an enormous added value because they are more vivid and therefore more understandable and make it easier to imagine the consequences of a flood than 2D visualisations. In this research, the WebGIS will be created using Ol3-Cesium and open layers to visualise a flood event by dynamic layers in a 2D/3D environment

The reproducibility of SfM algorithms to produce detailed Digital Surface Models: the example of PhotoScan applied to a high-alpine rock glacier

In geomorphology, PhotoScan is a software that is used to produce Digital Surface Models (DSMs). It constructs 3D environments from 2D imagery (often taken by Unmanned Aerial Vehicles (UAV)) based on Structure-from-Motion (SfM) and Multi- View Stereo (MVS) principles. However, unpublished computer-vision algorithms used, contain random elements which can affect the accuracy of the outputs. For this letter, ten model runs with identical inputs were performed on UAV imagery of a rock glacier to analyse the magnitude of the variation between the different model outputs. This variation was quantified calculating the standard deviation of each cell value in the respective DSMs and derivatives (curvature). Places with steep slope gradients have considerably more DSM variation (up to 10 cm) but stay within the range of the model’s accuracy (10 vertical cm) for 88 – 96% of the area. The edges of the model also show a larger variability (0.10 – 3 m), related to a lower number of overlapping images. These results should be accounted for when performing a geomorphological research at centimetre scale using PhotoScan, especially in areas with a complex relief. Using medium-quality runs, additional oblique viewpoints and respecting a minimum of five overlapping images can minimize the software’s variations

Flood risk mapping worldwide : a flexible methodology and toolbox

Flood risk assessments predict the potential consequences of flooding, leading to more effective risk management and strengthening resilience. However, adequate assessments rely on large quantities of high-quality input data. Developing regions lack reliable data or funds to acquire them. Therefore, this research has developed a flexible, low-cost methodology for mapping flood hazard, vulnerability and risk. A generic methodology was developed and customized for freely available data with global coverage, enabling risk assessment worldwide. The default workflow can be enriched with region-specific information when available. The practical application is assured by a modular toolbox developed on GDAL and PCRASTER. This toolbox was tested for the catchment of the river Moustiques, Haiti, for which several flood hazard maps were developed. Then, the toolbox was used to create social, economic and physical vulnerability maps. These were combined with the hazard maps to create the three corresponding flood risk maps. After creating these with the default data, more detailed information, gathered during field work, was added to verify the results of the basic workflow. These first tests of the developed toolbox show promising results. The toolbox allows policy makers in developing countries to perform reliable flood risk assessments and generate the necessary maps

Constitutive serotonin transporter reduction resembles maternal separation with regard to stress-related gene expression

Interactive effects between allelic variants of the serotonin transporter (5-HTT) promoter-linked polymorphic region (5-HTTLPR) and stressors on depression symptoms have been documented, as well as questioned, by meta-analyses. Translational models of constitutive 5-htt reduction and experimentally controlled stressors often led to inconsistent behavioral and molecular findings, and often did not include females. The present study sought to investigate the effect of 5-htt genotype, maternal separation, and sex on the expression of stress-related candidate genes in the rat hippocampus and frontal cortex. The mRNA expression levels of Avp, Pomc, Crh, Crhbp, Crhr1, Bdnf, Ntrk2, Maoa, Maob, and Comt were assessed in the hippocampus and frontal cortex of 5-htt +/- and 5-htt +/+ male and female adult rats exposed, or not, to daily maternal separation for 180 minutes during the first two postnatal weeks. Gene- and brain region-dependent, but sex-independent, interactions between 5-htt genotype and maternal separation were found. Gene expression levels were higher in 5-htt +/+ rats not exposed to maternal separation compared to the other experimental groups. Maternal separation and 5-htt +/- genotype did not yield additive effects on gene expression. Correlative relationships, mainly positive, were observed within, but not across, brain regions in all groups, except in non-maternally separated 5-htt +/+ rats. Gene expression patterns in the hippocampus and frontal cortex of rats exposed to maternal separation resembled the ones observed in rats with reduced 5-htt expression, regardless of sex. These results suggest that floor effects of 5-htt reduction and maternal separation might explain inconsistent findings in humans and rodents.</p