| 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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