G. Sterk

Bio: G. Sterk is an academic researcher from Delft University of Technology. The author has contributed to research in topics: Sanitary sewer & Combined sewer. The author has an hindex of 2, co-authored 2 publications receiving 139 citations.

Microbial risk assessment for urban pluvial flooding

Abstract: Public health risks of urban pluvial flooding have so far received little attention in technical discussions. In this paper, the results of pathogen measurements in the sewer system of Utrecht and an urban flooding experiment are presented and used in an application of Quantitative Microbial Risk Assessment, an existing risk analysis method for the quantification of infection probabilities. This method uses ingested doses of pathogenic organisms for the calculation of infection probabilities. Ingested dose estimations are based on pathogen measurements. These samples have been analysed for concentrations of Campylobacter, Cryptosporidium and Giardia. Dose-response relations from literature are used to calculate infection probabilities for flood events. The results show that mean probabilities of obtaining a Campylobacter or Giardia infection as a result of contact with urban flood water are 2.8% and 0.6% per event respectively for adults and at least 5.7% and 1.0% per event for children, respectively. Infection probabilities for Cryptosporidium are about 1000 times lower than for Giardia. The infection probabilities found indicate that the health risk of urban flooding is higher than that of swimming in recreational freshwater environments, based on a comparison to the values for ‘acceptable risk’ as defined by the WHO for bathing water.

Urban flood impact assessment: A state-of-the-art review

Abstract: Flooding can cause major disruptions in cities, and lead to significant impacts on people, the economy and on the environment. These impacts may be exacerbated by climate and socio-economic changes. Resilience thinking has become an important way for city planners and decision makers to manage flood risks.Despite different definitions of resilience, a consistent theme is that flood resilient cities are impacted less by extreme flood events. Therefore, flood risk professionals and planners need to understand flood impacts to build flood resilient cities. This paper presents a state-of-the-art literature review on flood impact assessment in urban areas, detailing their application, and their limitations. It describes both techniques for dealing with individual categories of impacts, as well as methodologies for integrating them. The paper will also identify future avenues for progress in improving the techniques.

Waterborne Pathogens: Detection Methods and Challenges

Abstract: Waterborne pathogens and related diseases are a major public health concern worldwide, not only by the morbidity and mortality that they cause, but by the high cost that represents their prevention and treatment. These diseases are directly related to environmental deterioration and pollution. Despite the continued efforts to maintain water safety, waterborne outbreaks are still reported globally. Proper assessment of pathogens on water and water quality monitoring are key factors for decision-making regarding water distribution systems’ infrastructure, the choice of best water treatment and prevention waterborne outbreaks. Powerful, sensitive and reproducible diagnostic tools are developed to monitor pathogen contamination in water and be able to detect not only cultivable pathogens but also to detect the occurrence of viable but non-culturable microorganisms as well as the presence of pathogens on biofilms. Quantitative microbial risk assessment (QMRA) is a helpful tool to evaluate the scenarios for pathogen contamination that involve surveillance, detection methods, analysis and decision-making. This review aims to present a research outlook on waterborne outbreaks that have occurred in recent years. This review also focuses in the main molecular techniques for detection of waterborne pathogens and the use of QMRA approach to protect public health.

Cumulative hazard: The case of nuisance flooding

Abstract: The cumulative cost of frequent events (e.g., nuisance floods) over time may exceed the costs of the extreme but infrequent events for which societies typically prepare. Here we analyze the likelihood of exceedances above mean higher high water and the corresponding property value exposure for minor, major, and extreme coastal floods. Our results suggest that, in response to sea level rise, nuisance flooding (NF) could generate property value exposure comparable to, or larger than, extreme events. Determining whether (and when) low cost, nuisance incidents aggregate into high cost impacts and deciding when to invest in preventive measures are among the most difficult decisions for policymakers. It would be unfortunate if efforts to protect societies from extreme events (e.g., 0.01 annual probability) left them exposed to a cumulative hazard with enormous costs. We propose a Cumulative Hazard Index (CHI) as a tool for framing the future cumulative impact of low cost incidents relative to infrequent extreme events. CHI suggests that in New York, NY, Washington, DC, Miami, FL, San Francisco, CA, and Seattle, WA, a careful consideration of socioeconomic impacts of NF for prioritization is crucial for sustainable coastal flood risk management.

City Blueprints: 24 Indicators to Assess the Sustainability of the Urban Water Cycle

Abstract: Climate change, population growth and increased consumption, coupled with urbanization, are all placing increased pressure on water management. This global challenge can often best be addressed at the local level, e.g. in cities by optimizing the role of civil society. Although there are approaches for assessing the sustainability of countries and cities, there is no dedicated framework for the assessment of the sustainability of urban water management. We have therefore compiled a comprehensive list of indicators (the city blueprint) for this. The city blueprint is proposed as a first step towards gaining a better understanding and addressing the challenges of integrated urban water management (IUWM). City blueprints will enable the IUWM of cities to be compared, and stimulate the exchange of success stories (good practices) between cities to address the enormous IUWM challenges which lie ahead. The city blueprint provides a quick scan and baseline assessment. It comprises elements from a variety of methodologies, such as water footprint, urban metabolism and ecosystem services. The indicators have been subdivided into eight broad categories, i.e. (1) water security following the water footprint approach developed by Hoekstra and Chapagain (2007), (2) water quality, which includes surface water and groundwater, (3) drinking water, (4) sanitation, (5) infrastructure, (6) climate robustness, (7) biodiversity and attractiveness and (8) governance. Experience using city blueprints for the cities of Rotterdam, Maastricht and Venlo (in the Netherlands) have been included as practical examples. It was concluded that simplicity (ease of calculation and data availability), transparency and ease of communication makes the blueprint a valuable tool for policy makers, decision makers and resource managers as a first step in the process of understanding, envisioning, developing and implementing measures to transform the water management of cities. The best results are obtained when all the stakeholders are involved and connected right from the start.