| 1. |
- Arheimer, Berit, et al.
(författare)
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Climate change impact on riverine nutrient load and land-based remedial measures of the Baltic sea action plan.
- 2012
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Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 41:6, s. 600-612
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Tidskriftsartikel (refereegranskat)abstract
- To reduce eutrophication of the Baltic Sea, all nine surrounding countries have agreed upon reduction targets in the HELCOM Baltic Sea Action Plan (BSAP). Yet, monitoring sites and model concepts for decision support are few. To provide one more tool for analysis of water and nutrient fluxes in the Baltic Sea basin, the HYPE model has been applied to the region (called Balt-HYPE). It was used here for experimenting with land-based remedial measures and future climate projections to quantify the impacts of these on water and nutrient loads to the sea. The results suggest that there is a possibility to reach the BSAP nutrient reduction targets by 2100, and that climate change may both aggravate and help in some aspects. Uncertainties in the model results are large, mainly due to the spread of the climate model projections, but also due to the hydrological model.
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| 2. |
- Donnelly, Chantal, et al.
(författare)
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A numerical model of coastal overwash
- 2009
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Ingår i: Proceedings of the Institution of Civil Engineers. Maritime Engineering. - : Thomas Telford Ltd.. - 1741-7597 .- 1751-7737. ; 162:3, s. 105-114
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Tidskriftsartikel (refereegranskat)abstract
- Overwash, the flow of water and sediment over the crest of a beach, contributes to flooding and the deposition of sand landward of the beach crest. Washover, the sand deposited by overwash, contributes to the sediment budget and migration of barrier islands. The ability to predict the occurrence, location, and thickness of overwash deposits is important for coastal residents, coastal town planners, environmental planners, and engineers alike. In this study, a numerical model that simulates the sediment transport and one-dimensional barrier profile change caused by overwash was developed. The magnitude of overwash and the morphology of washovers are dependent on the overwash regime. New formulae are developed to estimate the sediment transport rate over the beach crest for both run-up overwash, using ballistics theory, and inundation overwash, treating flow over the crest as weir flow. Two-dimensional flow is described on the back barrier by considering the continuity of a block of water at steady state, taking into account lateral spreading, friction, and infiltration. The model is tested against 26 different beach profile sets from several different locations, and several different storms, exhibiting a variety of initial morphologies. The model is capable of reproducing varying overwash morphology responses including dune crest erosion, dune destruction, barrier rollback, the thinning of a washover deposit on the backbarrier, and overwash over a multiple dune system.
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| 3. |
- Donnelly, Chantal, et al.
(författare)
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Characterisation and modelling of washover fans
- 2007
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Ingår i: Coastal Sediments '07 - Proceedings of 6th International Symposium on Coastal Engineering and Science of Coastal Sediment Processes. - Reston, VA : American Society of Civil Engineers. - 9780784409268 ; , s. 2061-3073
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Konferensbidrag (refereegranskat)abstract
- Pre- and post-storm topography and aerial photography, collected in regions where new washover fans were formed, were studied to determine the extent of morphologic, vegetative and anthropogenic control on washover shape and extent. When overwash is funnelled through a gap in a dune ridge and then spreads laterally on the back barrier, decelerating and depositing sediment, it forms washover fans. Fans were shown to primarily occur at pre-existing gaps in the foredune. During overwash, these gaps, or overwash throats, widened and deepened. The shape and extent of the fan was shown to depend on not only the pre-storm topography, but also the existence of beach tracks, roads and other anthropogenic influences and vegetation. The cross-shore overwash profile change model by Larson et al. and Donnelly et al. was modified to include pre-storm throat widths and a lateral spreading angle estimated from the pre-storm topography as inputs and tested using cross-shore profiles through the fan centres. These new inputs make the model more generalised, such that the calibrated model is applicable to a wider range of cross-shore profiles. © 2007 ASCE.
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| 4. |
- Donnelly, Chantal
(författare)
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Coastal Overwash: Processes and Modelling
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Overwash is the flow of water and sediment over the crest of a beach system when the runup level of waves or the water level, often enhanced by storm surge, exceeds the local beach or dune crest height. The impacts of overwash on coastal barriers or low lying mainland coasts are striking. Overwash may cause deposition of sand on and landward of the beach crest, large fan shaped deposits on back barriers, large sheet like deposits over an entire barrier, sand deposition into back barrier waterways, or may even lead to breaching of coastal barriers. It would therefore be highly useful to be able to predict the occurrence of overwash events and the magnitude and shape of the washover deposited during them. Although a number of studies describing overwash and washover deposits have been published, there remains a large scope to describe overwash processes, overwash hydrodynamics and to develop models for predicting the magnitude and shape of washover deposits on the back barrier. The objective of this study was to improve the capability to predict sediment transport caused by overwash, and hence the resulting topographic changes. The sediment transported by overwash is a function of the overwash hydrodynamics, and the overwash hydrodynamics are affected by a number of different, interacting processes. One of the main tasks for this study was therefore to identify and describe both the forcing and back barrier processes that affect overwashing flow. Overwash was shown to occur due to both wave runup overtopping the beach crest and surge levels exceeding the beach crest height. On the back barrier, overwash hydrodynamics and sediment transport were shown to be affected by the back barrier water level, friction, infiltration, lateral spreading and anthropogenic influences. New, mid-scale laboratory experiments of runup overwash were conducted to gain an understanding of back barrier flow hydrodynamics. The laboratory data were supplemented with field data to derive relationships to estimate overtopping depths and wave front velocities on the beach crest and back barrier. Additionally, three different types of overwash model were developed. The first, a parametric model, uses simple, readily available data to predict the type of cross-shore morphodynamic change expected for a given incipient barrier profile and maximum storm characteristics. Secondly, an analytical model was derived to calculate order-of-magnitude beach face retreat and overwash volumes for schematised incipient beach profiles. Finally, a numerical model was developed to calculate in more detail the barrier profile change resulting from an overwash event. This model uses incipient beach profiles and a time-series of storm characteristics to calculate the beach profile change. All three models were calibrated, validated and verified against a large, new data set of pre- and post-storm beach profiles measured where overwash had occurred and show promising results for predicting beach profile change.
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| 5. |
- Donnelly, Chantal, et al.
(författare)
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Environmental impact of undular tidal bores in tropical rivers
- 2005
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Ingår i: Environmental Fluid Mechanics. - : Springer Science and Business Media LLC. - 1573-1510 .- 1567-7419. ; 5:5, s. 481-494
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Tidskriftsartikel (refereegranskat)abstract
- A tidal bore impacts significantly on the estuarine ecosystem, although little is known on the flow field, mixing and sediment motion beneath tidal bores. In the absence of detailed systematic field measurements, a quasi-steady flow analogy was applied to investigate undular tidal bores with inflow Froude numbers between 1.25 and 1.6. Experimental results indicated that rapid flow redistributions occur beneath the free-surface undulations, with significant variations in bed shear stress between wave crests and troughs. Dynamic similarity was used to predict detailed flow characteristics of undular tidal bores. The effects of periodic loading on river sediments, scour of river bed and flow mixing behind the bore are discussed. A better understanding of these processes will contribute to better management practices in tidal bore affected rivers, including the Styx and Daly rivers in tropical Australia.
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| 6. |
- Donnelly, Chantal
(författare)
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Morphologic Change by Overwash: Establishing and Evaluating Predictors
- 2007
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Ingår i: Journal of Coastal Research. - 0749-0208. ; :SI 50 (special issue), s. 520-526
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Tidskriftsartikel (refereegranskat)abstract
- The ability to predict cross-shore profile response to coastal overwash is important for both understanding how barrier islands respond to overwash and for disaster management on developed coastlines. This study establishes morphologic and hydrodynamic parameters for predicting the type of cross-shore profile response following overwash for given pre-storm profile and storm conditions. More than 50 data sets were categorised into 7 different types of cross-shore profile response to overwash. These responses are: 1) crest accumulation 2) landward translation of dunes/berms 3) dune lowering 4) dune destruction 5) barrier accretion 6) barrier rollover (short-term),and 7) barrier disintegration. Dimensionless parameters describing the pre-storm morphology and storm characteristics for these data sets were then plotted in two-dimensional space and trends for the different response types identified. For some responses it was possible to define criteria for their occurrence and for the others an approximate trend could be identified. Maximum surge level, maximum run-up level, storm overtopping duration, beach crest height, dune width and dune volume proved some of the most important parameters to distinguish responses. The criteria that are established and trends identified should allow the user to qualitatively predict the overwash response of a given cross-shore beach profile to a given set of storm conditions, using readily available data.
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| 7. |
- Donnelly, Chantal, et al.
(författare)
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Morphologic Classification of Coastal Overwash
- 2006
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Ingår i: [Host publication title missing]. - : World Scientific Publishing Company. ; , s. 2805-2817
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Konferensbidrag (refereegranskat)abstract
- A set of pre- and post-storm beach profile data was assembled and the profiles classified into seven different cross-shore morphology change types resulting from overwash. These were crest accumulation, dune/berm translation, dune lowering, dune destruction, barrier accretion, short-term barrier rollover, and barrier destruction. Pre- and post-storm barrier profile sets from recent laboratory experiments also fell into the new classification system. Forcing mechanisms for the different categories are suggested. Understanding of the mechanisms leading to different types of cross-shore morphologic change is useful in developing cross-shore profile numerical modelling capabilities.
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| 8. |
- Donnelly, Chantal, et al.
(författare)
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Numerical Modelling of Beach Profile Change caused by Overwash
- 2006
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Ingår i: Proceedings Coastal Dynamics’05.
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Konferensbidrag (refereegranskat)abstract
- Beach profile change due to overwash has a major impact on both developed and undeveloped coasts following storms. The ability to predict such profile change has been further developed within a numerical beach profile change model, taking into account lateral spreading and infiltration on the back slope of the beach, and overwash where the beach crest becomes inundated. These new capabilities were tested for overwash of a low flat barrier and where dunes are present, reproducing well both the volume and shape of the overwash deposits.
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| 9. |
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| 10. |
- Donnelly, Chantal, et al.
(författare)
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One-line modelling of complex beach conditions: An application to coastal erosion at Hai Hau beach in the Red River Delta, Vietnam
- 2005
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Ingår i: Coastal Engineering. - : World Scientific Publishing Company. - 0378-3839. ; 1-4, s. 2449-2461
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Konferensbidrag (refereegranskat)abstract
- The long-term shoreline evolution at Hai Hau Beach in the Red River Delta, Vietnam was simulated using the one-line model GENESIS (Hanson, 1989). Dikes were modelled as seawalls and the sediment continuity equation in GENESIS was modified to take into account the offshore transport of fine-grained sediment. The model performed well, reproducing the magnitude and trend of the long-term shoreline change. Additionally, a net shoreline transport to the southwest was calculated which is in agreement with observations and the estimates of local engineers.
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| 11. |
- Donnelly, Chantal, et al.
(författare)
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State of knowledge on measurement and modeling of coastal overwash
- 2006
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Ingår i: Journal of Coastal Research. - : Coastal Education and Research Foundation. - 0749-0208 .- 1551-5036. ; 22:4, s. 965-991
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Tidskriftsartikel (refereegranskat)abstract
- A critical review is presented on the state of knowledge and calculation capability for coastal overwash. Overwash and overwash deposits (washover) accompanying hurricanes and severe storms can devastate coastal communities and habitat, but in many areas these processes are essential for maintaining the integrity of barrier islands while creating new habitat. This review covers general studies of overwash processes, studies from a geological perspective, physical modeling, field studies including measurements of washovers and related hydraulics, and the state of numerical modeling capability to predict overwash. Although significant literature exists describing individual overwash events and locations experiencing frequent overwash, complete hydrodynamic and morphologic documentation of an overwash event is lacking. A limited number of algorithms or models exist to quantify overwash occurrence, deposited sand volume, and upper beach profile evolution. Existing models of overwash occurrence and one-dimensional beach profile evolution have been shown to perform successfully against available data, and areas of improvement are identified. Models must be made capable of simulating the various washover morphologies that have been produced by different hydrodynamics, overwash spreading based on dune topography, friction and percolation, and interaction between swash bores. Comprehensive laboratory and field data sets to achieve these aims are still lacking.
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| 12. |
- Larson, Magnus, et al.
(författare)
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Analytical model of beach erosion and overwash during storms
- 2009
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Ingår i: Proceedings of the Institution of Civil Engineers. Maritime Engineering. - : Thomas Telford Ltd.. - 1741-7597 .- 1751-7737. ; 162:3, s. 115-125
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Tidskriftsartikel (refereegranskat)abstract
- During severe storms high waves and water levels may greatly impact the sub-aerial portion of the beach inducing significant morphological change at elevations that the waves can not reach under normal conditions. Morphological formations such as dunes and barrier islands may suffer from direct wave impact and erode. Overwash occurs if the wave run-up and/or the mean water level are sufficiently high allowing for water and sediment to pass over the beach crest, which in turn causes flooding and deposition of sediment shoreward of the crest. An analytical model of sub-aerial beach response to storms was developed based on impact theory, including overwash, and the evolution of schematised dunes was investigated. Furthermore, the analytical model was applied to the case of schematised barrier islands exposed to extensive overwash. After validation using field data, the analytical model was employed at two coastal sites, namely Ocean City on the United States east coast and the Ebro Delta on the Spanish Mediterranean coast, in order to calculate quantities for assessing the storm impact on beaches, such as eroded volume, overwash volume, beach crest reduction, and contour-line retreat. These quantities were subsequently analysed to derive empirical probability distribution functions to be utilised in different types of risk assessment concerning flooding and erosion in coastal areas.
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| 13. |
- Larson, Magnus, et al.
(författare)
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Analytical Modeling of Dune Response due to Wave Impact and Overwash
- 2005
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Ingår i: [Host publication title missing]. - Reston, VA : American Society of Civil Engineers.
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Konferensbidrag (refereegranskat)abstract
- Abstract in UndeterminedAn analytical model of dune erosion was developed based on impact theory, where the weight of eroded material is assumed proportional to the impact force from waves hitting the dune. The model was validated with data from several laboratory and field studies on dune erosion covering a wide range of hydrodynamic, sediment, and geometric conditions. Overwash was then included in the model and the evolution of a rectangular‐shaped dune subject to both wave impact and overwash was investigated. Finally, an analytical solution for the case of a schematized barrier islands exposed to overwash was developed. Analytical models are useful in the initial stage of a project when approximate estimates are required.
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| 14. |
- Le Xuan, Hoan, et al.
(författare)
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Modeling Shoreline Evolution at Hai Hau Beach, Vietnam
- 2010
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Ingår i: Journal of Coastal Research. - : Coastal Education and Research Foundation. - 0749-0208 .- 1551-5036. ; 26:1, s. 31-43
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Tidskriftsartikel (refereegranskat)abstract
- The coastline of Hai Hau District, located on the northeast coast of Vietnam with about 30 km of shoreline, is chronically eroding. Previous studies have tried to highlight the main causes of the erosion along this coastline, and several hypotheses exist. To examine the hypothesis that gradients in the longshore sediment transport rate and cross-shore fine sediment lost offshore are the main causes generating the serius erosion at Hai Hau Beach, a newly developed numerical model of shoreline change based on the one-line theory was applied and compared with data. Sea dike segments, reinforced by stones and mortar, were modeled using a seawall boundary condition, and the sediment continuity equation was modified to take into account the offshore transport of fine-grained sediment. The simulated shorelines agreed well with the measured shorelines, both for the calibration and validation periods. The calculated sediment budget shows that the net sediment transport is in the southward direction and that a large amount of fine-grained sediment is lost into deep water. These two sinks of sediment are believed to be the main causes of the serious erosion at Hai Hau Beach.
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| 15. |
- Meier, H. E. Markus, et al.
(författare)
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Ensemble Modeling of the Baltic Sea Ecosystem to Provide Scenarios for Management
- 2014
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Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 43:1, s. 37-48
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Tidskriftsartikel (refereegranskat)abstract
- We present a multi-model ensemble study for the Baltic Sea, and investigate the combined impact of changing climate, external nutrient supply, and fisheries on the marine ecosystem. The applied regional climate system model contains state-of-the-art component models for the atmosphere, sea ice, ocean, land surface, terrestrial and marine biogeochemistry, and marine food-web. Time-dependent scenario simulations for the period 1960-2100 are performed and uncertainties of future projections are estimated. In addition, reconstructions since 1850 are carried out to evaluate the models sensitivity to external stressors on long time scales. Information from scenario simulations are used to support decision-makers and stakeholders and to raise awareness of climate change, environmental problems, and possible abatement strategies among the general public using geovisualization. It is concluded that the study results are relevant for the Baltic Sea Action Plan of the Helsinki Commission.
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| 16. |
- Meier, Markus, et al.
(författare)
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Comparing reconstructed past variations and future projections of the Baltic sea ecosystem first results from multi model ensemble simulations
- 2012
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 7:3, s. 034005-
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Tidskriftsartikel (refereegranskat)abstract
- Multi-model ensemble simulations for the marine biogeochemistry and food web of the Baltic Sea were performed for the period 1850-2098, and projected changes in the future climate were compared with the past climate environment. For the past period 1850-2006, atmospheric, hydrological and nutrient forcings were reconstructed, based on historical measurements. For the future period 1961-2098, scenario simulations were driven by regionalized global general circulation model (GCM) data and forced by various future greenhouse gas emission and air-and riverborne nutrient load scenarios (ranging from a pessimistic 'business-as-usual' to the most optimistic case). To estimate uncertainties, different models for the various parts of the Earth system were applied. Assuming the IPCC greenhouse gas emission scenarios A1B or A2, we found that water temperatures at the end of this century may be higher and salinities and oxygen concentrations may be lower than ever measured since 1850. There is also a tendency of increased eutrophication in the future, depending on the nutrient load scenario. Although cod biomass is mainly controlled by fishing mortality, climate change together with eutrophication may result in a biomass decline during the latter part of this century, even when combined with lower fishing pressure. Despite considerable shortcomings of state-of-the-art models, this study suggests that the future Baltic Sea ecosystem may unprecedentedly change compared to the past 150 yr. As stakeholders today pay only little attention to adaptation and mitigation strategies, more information is needed to raise public awareness of the possible impacts of climate change on marine ecosystems.
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| 17. |
- Olsson, Jonas, et al.
(författare)
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Hydrological climate change impact assessment at small and large scales: Key messages from recent progress in Sweden
- 2016
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Ingår i: Climate. - : MDPI. - 2225-1154. ; 4:3
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Forskningsöversikt (refereegranskat)abstract
- Hydrological climate change impact assessment is generally performed by following a sequence of steps from global and regional climate modelling, through data tailoring (bias-adjustment and downscaling) and hydrological modelling, to analysis and impact assessment. This "climate-hydrology-assessment chain" has been developed with a primary focus on applicability to a medium-sized rural basin, which has been and still is the main type of domain investigated in this context. However, impact assessment is to an increasing degree being performed at scales smaller or larger than the medium-sized rural basin. Small-scale assessment includes e.g., impacts on solute transport and urban hydrology and large-scale assessment includes e.g., climate teleconnections and continental modelling. In both cases, additional complexity is introduced in the process and additional demands are placed on all components involved, i.e., climate and hydrology models, tailoring methods, assessment principles, and tools. In this paper we provide an overview of recent progress with respect to small- and large-scale hydrological climate change impact assessment. In addition, we wish to highlight some key issues that emerged as a consequence of the scale and that need further attention from now on. While we mainly use examples from work performed in Europe for illustration, the progress generally reflects the overall state of the art and the issues considered are of a generic character.
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| 18. |
- Strömbäck, Lena, et al.
(författare)
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The Importance of Open Data and Software for Large Scale Hydrological Modelling
- 2013
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Ingår i: Open water Journal. - Provo, UT, United States : Brigham Young University. - 2472-0259. ; 2:1
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- An important goal for hydrological research at SMHI in Sweden is large scale hydrological modelling. The goal of this work is to simulate hydrological conditions over large geographical areas, such as Europe and the Arctic region. Our most important tool is the HYPE model, which is designed to enable simulation over large areas. However, another important prerequisite for these large scale models is the availability of open data, which enables us to collect the information required for the model setup. In this paper we will give an overview over the work and focus on the aspects that make large scale modelling possible. In particular we will describe the HYPE model, the use of open data sources for modelling, how data is adapted to the models and how we feed results back to the community. In the end of the paper we give an overview of future perspectives and make an overview of the new EU project SWITCH-ON.
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| 19. |
- van Vliet, Michelle T. H., et al.
(författare)
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European scale climate information services for water use sectors
- 2015
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Ingår i: Journal of Hydrology. - Amsterdam, Netherlands : Elsevier. - 0022-1694 .- 1879-2707. ; 528, s. 503-513
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Tidskriftsartikel (refereegranskat)abstract
- This study demonstrates a climate information service for pan-European water use sectors that are vulnerable to climate change induced hydrological changes, including risk and safety (disaster preparedness), agriculture, energy (hydropower and cooling water use for thermoelectric power) and environment (water quality). To study the climate change impacts we used two different hydrological models forced with an ensemble of bias-corrected general circulation model (GCM) output for both the lowest (2.6) and highest (8.5) representative concentration pathways (RCP). Selected indicators of water related vulnerability for each sector were then calculated from the hydrological model results. Our results show a distinct north-south divide in terms of climate change impacts; in the south the water availability will reduce while in the north water availability will increase. Across different climate models precipitation and streamflow increase in northern Europe and decrease in southern Europe, but the latitude at which this change occurs varies depending on the GCM. Hydrological extremes are increasing over large parts of Europe. The agricultural sector will be affected by reduced water availability (in the south) and increased drought. Both streamflow and soil moistures droughts are projected to increase in most parts of Europe except in northern Scandinavia and the Alps. The energy sector will be affected by lower hydropower potential in most European countries and reduced cooling water availability due to higher water temperatures and reduced summer river flows. Our results show that in particular in the Mediterranean the pressures are high because of increasing drought which will have large impacts on both the agriculture and energy sectors. In France and Italy this is combined with increased flood hazards. Our results show important impacts of climate change on European water use sectors indicating a clear need for adaptation. (C) 2015 Published by Elsevier B.V.
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