2914 resultaten

  • Anaerobic degradation of a mixture of MtBE, EtBE, TBA, and benzene under different redox conditions

    Auteurs: Waals, M.J. van der; Pijls, C.; Sinke, A.J.C.; Langenhoff, A.A.M.; Smidt, H.; Gerritse, J. (2018)

    The increasing use of biobased fuels and fuel additives can potentially change the typical fuel-related contamination in soil and groundwater. Anaerobic biotransformation of the biofuel additive ethyl tert-butyl ether (EtBE), as well as of methyl tert-butyl ether (MtBE), benzene, and tert-butyl alcohol (TBA, a possible oxygenate metabolite), was studied at an industrially contaminated site and in the laboratory. Analysis of groundwater samples indicated that in the field MtBE was degraded, yielding TBA as major product. In batch microcosms, MtBE was degraded under different conditions: unamended control, with medium without added electron acceptors, or with ferrihydrite or sulfate (with or without medium) as electron acceptor, respectively. Degradation of EtBE was not observed under any of these conditions tested. TBAwas partially depleted in parallel with MtBE. Results of microcosm experiments withMtBE substrate analogues, i.e., syringate, vanillate, or ferulate, were in line with the hypothesis that the observed TBA degradation is a cometabolic process. Microcosms with ferulate, syringate, isopropanol, or diethyl ether showed EtBE depletion up to 86.5% of the initial concentration after 83 days. Benzene was degraded in the unamended controls, with medium without added electron acceptors and with ferrihydrite, sulfate, or chlorate as electron acceptor, respectively. In the presence of nitrate, benzene was only degraded after addition of an anaerobic benzene-degrading community. Nitrate and chlorate hindered MtBE, EtBE, and TBA degradation.

  • Below the surface : twenty-five years of seafloor litter monitoring in coastal seas of North West Europe (1992–2017)

    Auteurs: Maes, T.; Barry, J.; Leslie, H.A.; Vethaak, A.D.; Nicolaus, E.E.M.; Law, R.J.; Lyons, B.P.; Martinez, R.; Harley, B.; Thain, J.E. (2018)
    Gepubliceerd in: Science of the total environment, volume 630 (2018), pagina 790-798

    Marine litter presents a global problem, with increasing quantities documented in recent decades. The distribution and abundance of marine litter on the seafloor off the United Kingdom's (UK) coasts were quantified during 39 independent scientific surveys conducted between 1992 and 2017. Widespread distribution of litter items, especially plastics, were found on the seabed of the North Sea, English Channel, Celtic Sea and Irish Sea. High variation in abundance of litter items, ranging from 0 to 1835 pieces km−2 of seafloor, was observed. Plastic tems such as bags, bottles and fishing related debris were commonly observed across all areas. Over the entire 25-year period (1992–2017), 63% of the 2461 trawls contained at least one plastic litter item. There was no significant temporal trend in the percentage of trawls containing any or total plastic litter items across the long-term datasets. Statistically significant trends, however, were observed in specific plastic litter categories only. These trends were all positive except for a negative trend in plastic bags in the Greater North Sea - suggesting that behavioural and legislative changes could reduce the problem of marine litter within decades.

  • Advancing disaster risk reduction through the integration of science, design, and policy into eco-engineering and several global resource frames

    Auteurs: Whelchel, A.W.; Reguero, B.G.; Wesenbeeck, B.K. van; Renaud, F.G. (2018)

    By the later part of the 21st Century, our planet will be faced with compelling climatic circumstances requiring tradeoffs to maintain viable environmental conditions and standards of living. The prognosis for people near coastlines and waterways is particularly dire without decisive actions that capitalize on shared strengths such as ecosystems. One clear opportunity is the regenerative services and co-benefits of natural infrastructure that reduce the impacts of environmental disasters as magnified by climatic change. Certainly, nature-based solutions are increasingly being viewed as critical actions to reduce societal risk. However, to advance the use of natural infrastructure through eco-engineering, there is a need to clarify the science regarding risk reduction effectiveness, develop agreeable principles, standards, and designs, and grow a demonstration site network responsive to circumstances faced by communities around the globe. In addition, there is a need to consider the legal, policy, and regulatory obstacles and opportunities for natural infrastructure within local to national contexts (i.e., science-based building codes, architectural design criteria, incentive policies, etc.). Ultimately, the integration of science, designs, and policy coupled with installation within several globally recognized resource frames (IWRM, ICZM, etc.) will help establish eco-engineering standards. Supportive coastal, river, and urban examples from around the world are used to illustrate the current state of knowledge, model this integration of science, design, and policy, serve as initial “benchmark site”, and finally help define guiding principles for the emerging field of eco-engineering.

  • Qualitative flood risk assessment for the Western Province of Sri Lanka

    Auteurs: Weerasinghe, K.M.; Gehrels, H.; Arambepola, N.M.S.I.; Vajja, H.P.; Herath, J.M.K.; Atapattu, K.B. (2018)
    Gepubliceerd in: Procedia engineering, volume 212 (2018), pagina 503-510

    The Western Province of Sri Lanka, is comprised of the 03 most densely populated districts, and is home to the administrative and business capital of the country. The Province contributes the highest share, around 41.2%, to the GDP. The mega scale development projects implemented in this province are often challenged by urban flooding, which is caused by heavy rainfall coupled up with urban expansion, deficiencies in the drainage systems, insufficient retention capacity etc., and there is a prioritized need to reduce the impact of floods. This paper presents the results of a qualitative flood risk assessment at the scale of Grama Niladhari (GN) Division, which is the lowest administrative unit in the country. The essence of the method applied for delineating the combined flood risk levels is a statistical expression of hazard, exposure and vulnerability. Three types of vulnerabilities, namely, social, economic, and physical (housing), have been considered. The results influence to conclude that the flood risk of population is more sensitive to economic vulnerability than to social vulnerability; also that the type of housing units is a reasonable indicator for assessing the risk of housing. The application of risk information in the decision making process reduces the future flood risk as it allows integration of flood mitigation options during development planning, reduce the vulnerability of population and allocate sufficient funding for relief and rehabilitation.

  • Compound simulation of fluvial floods and storm surges in a global coupled rivercoast flood model : model development and its application to 2007 Cyclone Sidr in Bangladesh

    Auteurs: Ikeuchi, H.; Hirabayashi, Y.; Yamazaki, D.; Muis, S.; Ward, P.J.; Winsemius, H.C.; Verlaan, M.; Kanae, S. (2017)

    Water-related disasters, such as fluvial floods and cyclonic storm surges, are a major concern in the world's mega-delta regions. Furthermore, the simultaneous occurrence of extreme discharges from rivers and storm surges could exacerbate flood risk, compared to when they occur separately. Hence, it is of great importance to assess the compound risks of fluvial and coastal floods at a large scale, including mega-deltas. However, most studies on compound fluvial and coastal flooding have been limited to relatively small scales, and global-scale or large-scale studies have not yet addressed both of them. The objectives of this study are twofold: to develop a global coupled river-coast flood model, and to conduct a simulation of compound fluvial flooding and storm surges in Asian mega-delta regions. A state-of-the-art global river routing model was modified to represent the influence of dynamic sea surface levels on river discharges and water levels. We conducted the experiments by coupling a river model with a global tide and surge reanalysis data set. Results show that water levels in deltas and estuaries are greatly affected by the interaction between river discharge, ocean tides and storm surges. The effects of storm surges on fluvial flooding are further examined from a regional perspective, focusing on the case of Cyclone Sidr in the Ganges-Brahmaputra-Meghna Delta in 2007. Modeled results demonstrate that a >3 m storm surge propagated more than 200 km inland along rivers. We show that the performance of global river routing models can be improved by including sea level dynamics.

  • Development of damage functions for flood risk assessment in the city of Colombo (Sri Lanka)

    Auteurs: Dias, P.; Arambepola, N.M.S.I.; Weerasinghe, K.; Weerasinghe, K.D.N.; Wagenaar, D.J.; Bouwer, L.M.; Gehrels, H. (2018)
    Gepubliceerd in: Procedia engineering, volume 212 (2018), pagina 332-339

    Depth vs. damage curves were developed for a flood risk assessment carried out in Colombo, Sri Lanka. The major elements of the damage assessment comprised building fabrics, building contents, distributed infrastructure and vehicles. Current approaches to damage function development were improved on by separating damage to building fabric and contents; using actual building footprints rather than assigning building functions to city zones; assessing infrastructure damage accurately; and incorporating damage to vehicles. Information sources included infrastructure agencies, bills of quantities for buildings, expert consultations, household surveys and insurance agencies. The building fabric was assigned three categories, namely semi-permanent, single storey and two storey. The building contents were classified into 7 types based on function as warehouse/storage, industrial, shops, offices, residential, educational and health. The proportion of contents asset values to that of the fabric ranged from 1.67 for warehouse/storage to 0.20for educational. Both ‘what-if’ analyses and historic data were used to generate the curves. Data were obtained as losses per unit area or unit length; or as point losses.For the 140 square km urban area, the generated flood damages ranged from USD 37 to 549 million for return periods from 5 to 100 years, with average inundation depths ranging from 0.48 m to 1.28 m (and outliers up to 5.8 m). The total non-residential to residential building damage increased with return period (and together accounted for 75-85% of damage). The residential contents to fabric damage ratio was generally around 1.5. The percentage damage to infrastructure was not very significant, although that to vehicles was, especially at lower return periods.

  • Skin effect of fresh water measured using distributed temperature sensing

    Auteurs: Solcerova, A.; Emmerik, T. van; Ven, F.H.M. van de; Selker, J.; Giesen, N.C. van de ()
    Gepubliceerd in: Water, volume 10 nummer 2, pagina 1-12

    A phenomenon known as the skin effect (a layer of surface water that is colder than the water beneath it) was previously described in oceanography and verified in lab measurements. Only a few measurements have been done on the skin effect in field conditions, and therefore this phenomenon is relatively unknown. This paper presents measurements of the skin effect for three fresh water bodies in the Netherlands, Israel and Ghana. Using Distributed Temperature Sensing, high temporal and spatial resolution measurements were made below, at and above the air–water surface. Measurements presented in this study suggest that the skin effect of fresh water bodies is predominantly a daytime phenomenon and only occurs during low to zero wind speeds. The thickness of the skin effect was measured to be an order of magnitude larger than the previously assumed less than 1 mm.

  • Installatiehandleiding RWsOS-Noordzee_final (najaarsrelease 2016)

    Auteurs: Sumihar, J.; Bogaard, T. (2016)

  • Delft Dashboard : a MATLAB-based rapid tool for setting up coastal and estuarine models : tool description and model verification

    Auteurs: Nederhoff, K.; Dongeren, A.R. van; Ormondt, M. van (2016)

    Delft Dashboard (DDS) is a tool for rapid setup of coastal and estuarine hydrodynamic and basic morphological numerical models. The quality of numerical models created with Delft Dashboard in comparison to observations and/or other well-calibrated models in reproducing water levels is assessed in this report. It is concluded that numerical models created with Delft Dashboard have a good skill in the reproduction of the tidal propagation in the ocean and on the continental shelf. Reproduction of in-situ observations, which are usually obtained near the coast, is, however, more difficult.

  • Modellering alternatieve loswal locaties

    Auteurs: Hendriks, E.; Schuurman, F. (2017)

    Dit rapport bespreekt resultaten van berekeningen van de retourstroming van baggerspecie vanaf de loswal naar de Maasmond als functie van loswallocatie en hydrodynamische omstandigheden. Deze resultaten geven inzicht in de dynamiek van het slibtransport in de kustzone rondom de Maasmond en bieden een essentieel kwantitatief kader voor de keuze van een alternatieve loswallocatie. Het verband tussen de afstand van de loswallocatie tot de Maasmond en de retourstroming van baggerspecie blijkt sterk te zijn en goed kwantificeerbaar. Het berekende retourpercentage voor de huidige loswal (op 8 km van de monding) is 36% voor het referentiejaar 2007. Een vergroting van deze afstand tot 17 km leidt tot een afname van het retourpercentage tot 20%. Het retourpercentage varieert slechts beperkt van jaar tot jaar (+/- 3%), terwijl de aanslibbing sterker varieert (+/- 20%). De retourstroming en het baggerbezwaar zijn gevoelig voor de zoetwaterafvoer door de Nieuwe Waterweg. Een afname van de afvoer van 25% leidt tot 25% minder aanslibbing en 5% minder retourstroming. Een toename van de afvoer van 25% leidt tot 28% meer aanslibbing en 4% meer retourstroming.

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