scholarly journals Characterization of Overtopping Waves on Sea Dikes with Gentle and Shallow Foreshores

2020 ◽  
Vol 8 (10) ◽  
pp. 752 ◽  
Author(s):  
Tomohiro Suzuki ◽  
Corrado Altomare ◽  
Tomohiro Yasuda ◽  
Toon Verwaest
Keyword(s):  
Climate Change ◽  
Flow Velocity ◽  
Flow Model ◽  
Vertical Wall ◽  
Time Dependent ◽  
Physical Model Test ◽  
Wave Flow ◽  
Flow Depth ◽  
Sea Dikes

Due to ongoing climate change, overtopping risk is increasing. In order to have effective countermeasures, it is useful to understand overtopping processes in details. In this study overtopping flow on a dike with gentle and shallow foreshores are investigated using a non-hydrostatic wave-flow model, SWASH (an acronym of Simulating WAves till SHore). The SWASH model in 2DV (i.e., flume like configuration) is first validated using the data of long crested wave cases with second order wave generation in the physical model test conducted. After that it is used to produce overtopping flow in different wave conditions and bathymetries. The results indicated that the overtopping risk is better characterized by the time dependent h (overtopping flow depth) and u (overtopping flow velocity) instead of hmax (maximum overtopping flow depth) and umax (maximum overtopping flow velocity), which led to overestimation of the risk. The time dependent u and h are strongly influenced by the dike configuration, namely by the promenade width and the existence of a vertical wall on the promenade: the simulation shows that the vertical wall induces seaward velocity on the dike which might be an extra risk during extreme events.

scholarly journals Overtopping Metrics and Coastal Safety: A Case of Study from the Catalan Coast

2020 ◽  
Author(s):  
Corrado Altomare ◽  
Xavi Gironella ◽  
Tomohiro Suzuki ◽  
Giacomo Viccione ◽  
Alessandra Saponieri
Keyword(s):  
Flow Characteristics ◽  
Flow Depth ◽  
Detailed Characterization ◽  
Wave Overtopping ◽  
Experimental Campaign ◽  
Catalan Coast ◽  
The Relationship ◽  
Hazard Levels ◽  
Sea Dikes

Design criteria for coastal defenses exposed to wave overtopping are usually assessed by mean overtopping discharges and maximum individual overtopping volumes. However, it is often difficult to give clear and precise limits of tolerable overtopping for all kind of layouts. A few studies analyzed the relationship between wave overtopping flows and hazard levels for people on sea dikes, confirming that one single value of admissible mean discharge or individual overtopping volume is not a sufficient indicator of the hazard, but detailed characterization of flow velocities and depths is required. This work presents the results of an experimental campaign aiming at characterizing the flow characteristics associated to maximum individual overtopping volumes for an urbanized stretch of a town along the Catalan coast, where a walking and bike path and a railway run along the coastline are exposed to significant overtopping events every stormy season. The work compares different safety criteria for pedestrian. Results prove that safety of pedestrian on a sea dike can be still guaranteed even for overtopping volumes larger than 1000 l/m. Pedestrian hazard is rather proved to be linked to the combination of overtopping flow velocity and flow depth.

scholarly journals Enhancing the Ecological Value of Sea Dikes

Water ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1617 ◽  
Author(s):  
Scheres ◽  
Schüttrumpf
Keyword(s):  
Climate Change ◽  
Climate Change Adaptation ◽  
Interdisciplinary Collaboration ◽  
Ecological Value ◽  
Protection Measures ◽  
Surface Protection ◽  
Societal Needs ◽  
Ecological Aspects ◽  
The World ◽  
Sea Dikes

Sea dikes protect low-lying hinterlands along many coasts all around the world. Commonly, they are designed as embankments with grass covers or grey revetments accounting for the prevailing hydraulic loads. So far, incorporation of ecological aspects in the dike design is limited. With regard to increasing environmental awareness and climate change adaptation needs, the present study reviews methods for ecological enhancement of sea dikes and discusses limitations and challenges related to these methods. In doing so, one key aspect is to maintain dike safety while increasing the ecological value. Potential for ecological enhancement of sea dikes has been found regarding natural or nature-based solutions in the foreshore, dike surface protection measures (vegetated dike covers, hard revetments and dike roads) and the dike geometry. While natural and nature-based solutions in the foreland are investigated thoroughly, so far only few experiences with ecological enhancements of the dike structure itself were gained resulting in uncertainties and knowledge gaps concerning the implementation and efficiency. Additional to technical uncertainties, engineers and ecologists meet the challenge of interdisciplinary collaboration under consideration of societal needs and expectations.

scholarly journals On the characterization of glacier response by a single time-scale

2001 ◽  
Vol 47 (159) ◽  
pp. 659-664 ◽  
Author(s):  
W. D. Harrison ◽  
D. H. Elsberg ◽  
K. A. Echelmeyer ◽  
R. M. Krimmel
Keyword(s):  
Climate Change ◽  
Mass Balance ◽  
Time Constant ◽  
Time Scale ◽  
Response Models ◽  
Single Time ◽  
Glacier Changes ◽  
Major Increase ◽  
Effect Of Surface

AbstractGlacier response to climate can be characterized by a single time-scale when the glacier changes sufficiently slowly. Then the derivative of volume with respect to area defines a thickness scale similar to that of Jóhannesson and others, and the time-scale follows from it. Our version of the time-scale is different from theirs because it explicitly includes the effect of surface elevation on mass-balance rate, which can cause a major increase in the time-scale or even lead to unstable response. The time constant has a dual role, controlling both the rate and magnitude of response to a given climate change. Data from South Cascade Glacier, Washington, U.S.A., illustrate the ideas, some of the difficulty in obtaining accurate values for the thickness and time-scales, and the susceptibility of all response models to potentially large errors.

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