scholarly journals Flood modeling can make a difference: Disaster risk-reduction and resilience-building in urban areas

Author(s):  
Jorge A. Ramirez ◽  
Umamaheshwaran Rajasekar ◽  
Dhruvesh P. Patel ◽  
Tom J. Coulthard ◽  
Margreth Keiler

Abstract. Surat, India is a coastal city with a population of approximately 4.5 million people that lies on the banks of the river Tapi and is located 100 km downstream from the Ukai dam. Given Surat's geographic location the city is repeatedly exposed to flooding caused by large emergency dam releases into the Tapi river combined with high tide water levels. Flood events of this type occur twice a decade, but their frequency and magnitude may increase due to the urbanization, encroachment in flood plain and climate change. A first step towards strengthening resilience in Surat requires a robust method for mapping flood exposure at fine spatial resolution. Here, in this study we have developed such a method for Surat using a reduced-complexity hydrodynamic model to simulate flooding, but is easily transferable to other urban locations. Our method features three distinct phases that involve: (1) modelling dam release discharge from the Ukai dam arriving at Surat, (2) modelling flooding within Surat caused by the combination of dam release and tides, and, (3) identifying Surat critical infrastructure, population, and income groups exposed to flooding. Our flood model of Surat utilizes topography produced using elevation data collected from an extensive survey. Within the city we have modelled flood scenarios that represent the uncertainty in flood peak discharge and duration resulting from possible climate change. These scenarios include catastrophic conditions that flood 50 % of the city and expose > 60 % of the population and critical infrastructure to deep flooding. Finally, we highlight how our modelling has contributed to changes in flood risk management within the city following a major flood and resulted in actions that have increased community resilience to flood hazard.

Water ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2616
Author(s):  
María Hernández-Hernández ◽  
Jorge Olcina ◽  
Álvaro-Francisco Morote

The effects of climate change on rainfall in the Mediterranean region are manifested in an overall decreasing trend, and greater irregularity in annual volumes and the city of Alicante is no exception. In addition, there has also been a spread of the urbanised area, which has led to an increase in the flood risk in urban areas (due to a greater runoff and the occupation of flood hazard areas) and drought events due to an increase in the water demand. In light of these new scenarios, the Mediterranean cities should design adaptation systems based on rainwater harvesting within the framework of a circular economy. This study analyses the integration of rainwater in flood and water demand management in the city of Alicante (Southern Spain). In recent years, this city has developed infrastructures in order to use these resources. To do this, different databases have been analysed (rainfall and volume of water collected in the green infrastructure systems). The results reveal that stormwater has become highly important in urban water management in Alicante as the city is now using a resource that previously went to waste and created problems (flooding and pollution). By way of conclusion, it is worth mentioning that the incorporation of rainwater for urban use in Alicante has reduced the pressure on traditional resources in satisfying water demand and has also acted as a measure for adapting to climate change.


2017 ◽  
Author(s):  
Mook Bangalore ◽  
Andrew Smith ◽  
Ted Veldkamp

Abstract. With 70 percent of its population living in coastal areas and low-lying deltas, Vietnam is highly exposed to riverine and coastal flooding. This paper examines the exposure of the population and poor people in particular to current and future flooding in Vietnam and specifically in Ho Chi Minh City, using new high-resolution flood hazard maps and spatial socioeconomic data. The national-level analysis finds that a third of today’s population is already exposed to a flood, which occurs once every 25 years, assuming no protection. For the same return period flood under current socioeconomic conditions, climate change may increase the number exposed to 38 to 46 percent of the population. Climate change impacts can make frequent events as important as rare ones: the estimates suggest a 25-year flood under future conditions can expose more people than a 200-year flood under current conditions. Although poor districts are not found to be more exposed to floods at the national level, the city-level analysis of Ho Chi Minh City provides evidence that slum areas are highly exposed. The results of this paper show the benefits of investing today in flood risk management, and can provide guidance as to where future investments may be targeted.


2020 ◽  
Vol 3 (1) ◽  
pp. 77-88 ◽  
Author(s):  
M. A. Cardoso ◽  
R. S. Brito ◽  
M. C. Almeida

Abstract Urban areas are complex, vulnerable and continuously evolving, with interacting strategic services, assets and stakeholders. Potential effects of climate dynamics on urban areas may include the aggravation of current conditions, with identification of new hazards or risk drivers. These challenges require an integrated and forward-looking approach to sustainable urban development. Several tools and frameworks for assessing resilience have already been developed in different fields of study. However, aiming to focus on climate change, urban services and infrastructure, some specific needs were identified. In this light, a resilience assessment framework was developed to direct and facilitate an objective-driven resilience diagnosis of urban cities and services; to support decisions on selection of resilience measures and development of strategies to enhance resilience to climate change; to outline a path to co-build resilience action plans; and to track the progress of resilience in the city or in the service over time. The paper presents an outline of the structure of the framework and details the approach used in its development, including engagement tools and actions undertaken to assure stakeholder involvement in its development, validation and testing.


Geosciences ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 127 ◽  
Author(s):  
Julian Hofmann ◽  
Holger Schüttrumpf

In times of increasing weather extremes and expanding vulnerable cities, a significant risk to civilian security is posed by heavy rainfall induced flash floods. In contrast to river floods, pluvial flash floods can occur anytime, anywhere and vary enormously due to both terrain and climate factors. Current early warning systems (EWS) are based largely on measuring rainfall intensity or monitoring water levels, whereby the real danger due to urban torrential floods is just as insufficiently considered as the vulnerability of the physical infrastructure. For this reason, this article presents a concept for a risk-based EWS as one integral component of a multi-functional pluvial flood information system (MPFIS). Taking both the pluvial flood hazard as well as the damage potential into account, the EWS identifies the urban areas particularly affected by a forecasted heavy rainfall event and issues object-precise warnings in real-time. Further, the MPFIS performs a georeferenced documentation of occurred events as well as a systematic risk analysis, which at the same time forms the foundation of the proposed EWS. Based on a case study in the German city of Aachen and the event of 29 May 2018, the operation principle of the integrated information system is illustrated.


2020 ◽  
Author(s):  
◽  
Mpumelelo Dolo

Water is regarded as the most important substance found on earth. There is no substitute for it. The daily running of production businesses, industrial firms and agricultural production that help sustain the economy of countries are largely dependent on the availability of water for them to function. The importance of water cannot be over emphasised. The food which is consumed daily depends on water; it can therefore be safely concluded that without water there would be no food, and without food there would be no life. Despite the importance of water in relation to human life, animals and plants, research studies show that the its availability becoming increasingly deficient around the globe. Water levels of major dams and rivers around the world are dropping, limiting the supply of potable water to those dependent on them. Global warming is one factor that is influencing the dropping of water levels, through evaporation. Other factors include climate change, drought and population growth. In South Africa, the government has been fighting a continuous battle of trying to address the backlog of water infrastructure, particularly in the areas which were disadvantaged by the apartheid government. These areas include rural areas, small towns (semi-urban) and townships. The Eastern Cape province in South Africa is top of the list from a backlog point of view. Rural dwellers migrate to urban areas for various reasons such as better education, better health care, job opportunities and more efficient services. Water supply is one of the services which is more adequately supplied in the cities compared to the rural areas. Even though the supplied water in the urban areas of the Eastern Cape is not the best standard when compared to other cities around the country or the world, it is still at an acceptable standard. Thus, this study was conducted to seek ways of improving the supply of water in the urban and rural areas of the Eastern Cape. The availability and the quality of water differs between the urban and rural areas. The purpose of this study was to seek ways of bridging the gap between these areas while improving the standard of water supply in both rural and urban areas. While working towards improving the lives of the Eastern Cape people, the study also seeks to promote water preservation and awareness to the people of the province. In order to find better alternatives which have been tested in various places around the world, an in-depth literature review was conducted in the study. This functioned as an effective comparison of what is obtained in different places around the world and the context of this study, which is the Eastern Cape. A survey method was used to gather data regarding the problems surrounding water supply and options that could be adopted to remedy those problems. The survey was conducted in the form of a self-observation assessment, questionnaire for households in urban and rural areas and interview sessions with prominent government entities and local technical service providers. The survey covered the whole spectrum of individuals and groups that play a major role in the supply and usage of water. The study was conducted within three municipalities of the Eastern Cape. These municipalities cover approximately two-third of the Eastern Cape considering the size of population in those areas. The municipalities covered by the study were: Amathole District Municipality (ADM), Buffalo City Metropolitan Municipality (BCMM) and OR Tambo District Municipality (ORTDM). The findings from the study showed that indeed the standard of water supply between urban and rural areas was not equal. This relates to the purification methods, the convenience of collecting water by users, the quality of infrastructure being constructed (due to good or poor monitoring during construction) and the quality of the water as well as operation and maintenance response from the various service providers. Moreover, it was found that there was an acceptable level of awareness by citizens when it comes to using water, and precautions to save it were being taken by some. However, some dominant factors such as poor management, poor infrastructure resulting in leaks, climate change, run-offs and population growth were putting a strain on the existing water resources which is not coping with the increasing demand by people. Recommendations made in the study to balance the supply of water in rural areas and urban areas include: improving the purification of water so as to achieve a standard quality within the Eastern Cape; that rural areas be allowed to have an option of having yard or house connections, particularly those who are willing to pay rates at a scale suiting their class or standard; and that water service providers make it their responsibility to extend reticulation networks if there is expansion or development of more houses in rural areas in order to keep the distance minimal to standpipes


2015 ◽  
Vol 15 (19) ◽  
pp. 27041-27085
Author(s):  
K. Markakis ◽  
M. Valari ◽  
M. Engardt ◽  
G. Lacressonnière ◽  
R. Vautard ◽  
...  

Abstract. Ozone, PM10 and PM2.5 concentrations over Paris, France and Stockholm, Sweden were modeled at 4 and 1 \\unit{km} horizontal resolutions respectively for the present and 2050 periods employing decade-long simulations. We account for large-scale global climate change (RCP-4.5) and fine resolution bottom-up emission projections developed by local experts and quantify their impact on future pollutant concentrations. Moreover, we identify biases related to the implementation of regional scale emission projections over the study areas by comparing modeled pollutant concentrations between the fine and coarse scale simulations. We show that over urban areas with major regional contribution (e.g., the city of Stockholm) the bias due to coarse emission inventory may be significant and lead to policy misclassification. Our results stress the need to better understand the mechanism of bias propagation across the modeling scales in order to design more successful local-scale strategies. We find that the impact of climate change is spatially homogeneous in both regions, implying strong regional influence. The climate benefit for ozone (daily average and maximum) is up to −5 % for Paris and −2 % for Stockholm city. The joined climate benefit on PM2.5 and PM10 in Paris is between −10 and −5 % while for Stockholm we observe mixed trends up to 3 % depending on season and size class. In Stockholm, emission mitigation leads to concentration reductions up to 15 % for daily average and maximum ozone and 20 % for PM and through a sensitivity analysis we show that this response is entirely due to changes in emissions at the regional scale. On the contrary, over the city of Paris (VOC-limited photochemical regime), local mitigation of NOx emissions increases future ozone concentrations due to ozone titration inhibition. This competing trend between the respective roles of emission and climate change, results in an increase in 2050 daily average ozone by 2.5 % in Paris. Climate and not emission change appears to be the most influential factor for maximum ozone concentration over the city of Paris, which may be particularly interesting in a health impact perspective.


Water ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2658 ◽  
Author(s):  
Eduardo Martínez-Gomariz ◽  
Luca Locatelli ◽  
María Guerrero ◽  
Beniamino Russo ◽  
Montse Martínez

Pluvial flooding in Badalona (Spain) occurs during high rainfall intensity events, which in the future could be more frequent according to the latest report from the Intergovernmental Panel on Climate Change (IPCC). In this context, the present study aims at quantifying the potential impacts of climate change for the city of Badalona. A comprehensive pluvial flood multi risk assessment has been carried out for the entire municipality. The assessment has a twofold target: People safety, based on both pedestrians’ and vehicles’ stability, and impacts on the economic sector in terms of direct damages on properties and vehicles, and indirect damages due to businesses interruption. Risks and damages have also been assessed for the projected future rainfall conditions which enabled the comparison with the current ones, thereby estimating their potential increment. Moreover, the obtained results should be the first step to assess the efficiency of adaptation measures. The novelty of this paper is the integration of a detailed 1D/2D urban drainage model with multiple risk criteria. Although, the proposed methodology was tested for the case study of Badalona (Spain), it can be considered generally applicable to other urban areas affected by pluvial flooding.


2018 ◽  
Vol 56 (4) ◽  
pp. 59-68
Author(s):  
Anna Bilska

Abstract Climate change may have severe consequences for urban areas and many cities, such as those situated on deltas, are already threatened. The paper claims that the solution for endangered areas is the embedding of urban climate resilience. The concept of resilience is put forward to bring a broad perspective to a city with an indication that the city is a complex system with developed relations, both inward and outward. Social and institutional aspects of these relations are highlighted as they have the highest potential to make the city resilient. The paper indicates three fundamental features of embedding the resilience of urban areas to climate change: network building, a strategic approach and implementing urban projects. A practical application of these fundamental features is evaluated using the case study of Rotterdam. The research shows the reliability of these bases and indicates key characteristics of each fundamental feature: the network should be multidimensional with solid institutional and interpersonal relations, the strategy should have a holistic approach and project implementation needs the engagement of all the city actors.


2013 ◽  
Vol 6 (2) ◽  
pp. 81-87 ◽  
Author(s):  
T. L. A. Driessen ◽  
M. van Ledden

Abstract. The objective of this paper was to describe the impact of climate change on the Mississippi River flood hazard in the New Orleans area. This city has a unique flood risk management challenge, heavily influenced by climate change, since it faces flood hazards from multiple geographical locations (e.g. Lake Pontchartrain and Mississippi River) and multiple sources (hurricane, river, rainfall). Also the low elevation and significant subsidence rate of the Greater New Orleans area poses a high risk and challenges the water management of this urban area. Its vulnerability to flooding became dramatically apparent during Hurricane Katrina in 2005 with huge economic losses and a large number of casualties. A SOBEK Rural 1DFLOW model was set up to simulate the general hydrodynamics. This model included the two important spillways that are operated during high flow conditions. A weighted multi-criteria calibration procedure was performed to calibrate the model for high flows. Validation for floods in 2011 indicated a reasonable performance for high flows and clearly demonstrated the influence of the spillways. 32 different scenarios were defined which included the relatively large sea level rise and the changing discharge regime that is expected due to climate change. The impact of these scenarios on the water levels near New Orleans were analysed by the hydrodynamic model. Results showed that during high flows New Orleans will not be affected by varying discharge regimes, since the presence of the spillways ensures a constant discharge through the city. In contrary, sea level rise is expected to push water levels upwards. The effect of sea level rise will be noticeable even more than 470 km upstream. Climate change impacts necessitate a more frequent use of the spillways and opening strategies that are based on stages.


2020 ◽  
Author(s):  
Irena Nimac ◽  
Ivana Herceg Bulić ◽  
Maja Žuvela-Aloise

<p>Changes in surface and atmosphere characteristics in urban areas can alter radiation, heat and water balance and generate excessive heat load in those areas. One of the associated consequences is higher temperatures in built-up areas compared to the rural surrounding, also known as urban heat island (UHI). Here, summer heat load in Zagreb, the largest city of Croatia, is investigated. Summer season is in the focus of the study, not only because it is shown that trend in summer temperatures in Zagreb is stronger compared to the winter one, but also as it is the season when intense and prolonged extreme weather events, like heat-weaves, are likely to occur.</p><p>In this work, urban climate model MUKLIMO_3 with 100 m horizontal resolution is applied for a broader area of Zagreb. To explore the effect of climate change on the heat load, two separate experiments with the same land-use (corresponding to the current state of the city), but for different climate conditions are made. Daily data measurements for the period 1951–1980 are used as past climate, while 1981–2010 period represents the current climate conditions. Heat load is here estimated by a number of days with the maximum air temperature above 25 °C, i.e. by summer days. Both simulations indicated the lowest values of heat load in mountainous forest area accompanied by increased values in densely built-up regions and old city center. However, lower number of summer days is also found for green and blue areas within the city. The spatial pattern of difference in the number of summer days between considered periods is mainly influenced by orography with a much lower increase in the mountain area of the domain than in the lowland city region.</p>


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