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Maike Paul; Nils B. Kerpen. Erosion protection by winter state of salt marsh vegetation. Journal of Ecohydraulics 2021, 1 -10.
AMA StyleMaike Paul, Nils B. Kerpen. Erosion protection by winter state of salt marsh vegetation. Journal of Ecohydraulics. 2021; ():1-10.
Chicago/Turabian StyleMaike Paul; Nils B. Kerpen. 2021. "Erosion protection by winter state of salt marsh vegetation." Journal of Ecohydraulics , no. : 1-10.
Stepped revetments are effective in limiting wave overtopping. Small-scale studies provided insights in the design of crest-levels and step geometries of these structures. The validation of these insights at large scale, along with the analysis of individual overtopping volumes, is required to formulate recommendations for detail design. This paper investigates wave overtopping rates and individual overtopping volumes at stepped revetments by means of full-scale flume experiments. Two cross-sections, each with a slope of 1:3, were studied with uniform step heights of 0.17 m and 0.50 m. The revetments reduced wave overtopping rates in comparison to smooth dikes with influence factor for roughness (γf) between 0.43 and 0.73. An empirical formula for γf is proposed with which the wave overtopping rate at stepped revetments can be determined. Previous small-scale studies underestimate γf of this study by 2-31 %. Individual overtopping volumes were described by a Weibull distribution, revealing a higher median shape factor (b=1.63) for stepped revetments compared to breakwaters, smooth dikes or vertical walls.
Talia Schoonees; Nils B. Kerpen; Torsten Schlurmann. Full-scale experimental study on wave overtopping at stepped revetments. Coastal Engineering 2021, 167, 103887 .
AMA StyleTalia Schoonees, Nils B. Kerpen, Torsten Schlurmann. Full-scale experimental study on wave overtopping at stepped revetments. Coastal Engineering. 2021; 167 ():103887.
Chicago/Turabian StyleTalia Schoonees; Nils B. Kerpen; Torsten Schlurmann. 2021. "Full-scale experimental study on wave overtopping at stepped revetments." Coastal Engineering 167, no. : 103887.
In this study, the wave-induced distribution of 13 microplastic (MP) samples of different size, shape, and density was investigated in a wave flume with a sandy mobile beach bed profile. The particle parameter were chosen based on an occurrence probability investigated from the field. MP abundances were analyzed in cross-shore and vertical direction of the test area after over 40,000 regular waves. It was found, that MP particles accumulated in more shallow waters with increasing size and density. Particles with high density (ρs>1.25 g/cm3) have been partly confined into deeper layers of the sloping beach during the formation of the bed profile. Particles with a density lower than that of water used in the experiments floated constantly in the surf zone or deposited on the beach caused by wave run-up. A correlation was found between the settling velocity of the MP particles and the flow velocity at the accumulation point and a power function equation developed. The obtained results were critically discussed with findings from the field and further laboratory studies.
Nils B. Kerpen; Torsten Schlurmann; Alexander Schendel; Jannek Gundlach; Daniel Marquard; Markus Hüpgen. Wave-Induced Distribution of Microplastic in the Surf Zone. Frontiers in Marine Science 2020, 7, 1 .
AMA StyleNils B. Kerpen, Torsten Schlurmann, Alexander Schendel, Jannek Gundlach, Daniel Marquard, Markus Hüpgen. Wave-Induced Distribution of Microplastic in the Surf Zone. Frontiers in Marine Science. 2020; 7 ():1.
Chicago/Turabian StyleNils B. Kerpen; Torsten Schlurmann; Alexander Schendel; Jannek Gundlach; Daniel Marquard; Markus Hüpgen. 2020. "Wave-Induced Distribution of Microplastic in the Surf Zone." Frontiers in Marine Science 7, no. : 1.
The wave overtopping discharge at coastal defense structures is directly linked to the freeboard height. By means of physical modelling, experiments on wave overtopping volumes at sloped coastal structures are customarily determined for constant water levels and static wave steepness conditions (e.g., specific wave spectrum). These experiments are the basis for the formulation of empirically derived and widely acknowledged wave overtopping estimations for practical design purposes. By analysis and laboratory reproduction of typical features from exemplarily regarded real storm surge time series in German coastal waters, the role of non-stationary water level and wave steepness were analyzed and adjusted in experiments. The robustness of wave overtopping estimation formulae (i.e., the capabilities and limitations of such a static projection of dynamic boundary conditions) are outlined. Therefore, the classic static approach is contrasted with data stemming from tests in which both water level and wave steepness were dynamically altered in representative arrangements. The analysis reveals that mean overtopping discharges for simple sloping structures in an almost deep water environment could be robustly estimated for dynamic water level changes by means of the present design formulae. In contrast, the role of dynamic changes of the wave steepness led to a substantial discrepancy of overtopping volumes by a factor of two. This finding opens new discussion on methodology and criteria design of coastal protection infrastructure under dynamic exposure to storm surges and in lieu of alterations stemming from projected sea level rise.
Nils B. Kerpen; Karl-Friedrich Daemrich; Oliver Lojek; Torsten Schlurmann. Effect of Variations in Water Level and Wave Steepness on the Robustness of Wave Overtopping Estimation. Journal of Marine Science and Engineering 2020, 8, 63 .
AMA StyleNils B. Kerpen, Karl-Friedrich Daemrich, Oliver Lojek, Torsten Schlurmann. Effect of Variations in Water Level and Wave Steepness on the Robustness of Wave Overtopping Estimation. Journal of Marine Science and Engineering. 2020; 8 (2):63.
Chicago/Turabian StyleNils B. Kerpen; Karl-Friedrich Daemrich; Oliver Lojek; Torsten Schlurmann. 2020. "Effect of Variations in Water Level and Wave Steepness on the Robustness of Wave Overtopping Estimation." Journal of Marine Science and Engineering 8, no. 2: 63.
A set of scale-model tests carried out to enlarge the range of wave steepness values analysed in run-up, overtopping and armour layer stability studies, focusing on oblique extreme wave conditions and on their effects on a gentler slope breakwater’s trunk armour and roundhead, is presented in this paper. A stretch of a rubble mound breakwater (head and part of the adjoining trunk, with a slope of 1(V):2(H)) was built in a wave basin at the Leibniz University Hannover to assess, under extreme wave conditions (wave steepness of 0.055) with different incident wave angles (from 40º to 90º), the structure behaviour in what concerns wave run-up, wave overtopping and damage progression of the armour layer. Two types of armour elements (rock and Antifer cubes) were tested. Non-intrusive methodologies including a new application of laser scanning technique for the assessment of both armour layer damage and wave run-up and overtopping were used. It is expected that such work will contribute also with data to improve empirical formulas as well as to validate complex numerical model for wave-structure interaction.
João Alfredo Santos; Francisco Pedro; Mário Coimbra; Andrés Figuero; Conceição Fortes; José Sande; Moritz Körner; Rute Lemos; Antje Bornschein; Julius Weimper; Jeroen Van Den Bos; Bastian Dost; Bas Hofland; Rita Carvalho; Alberto Alvarellos; Enrique Peña; Reinhard Pohl; Nils Kerpen; Maria Teresa Reis. 3-D Scale Model Study of Wave Run-Up, Overtopping and Damage in a Rubble-Mound Breakwater Subject to Oblique Extreme Wave Conditions. Defect and Diffusion Forum 2019, 396, 32 -41.
AMA StyleJoão Alfredo Santos, Francisco Pedro, Mário Coimbra, Andrés Figuero, Conceição Fortes, José Sande, Moritz Körner, Rute Lemos, Antje Bornschein, Julius Weimper, Jeroen Van Den Bos, Bastian Dost, Bas Hofland, Rita Carvalho, Alberto Alvarellos, Enrique Peña, Reinhard Pohl, Nils Kerpen, Maria Teresa Reis. 3-D Scale Model Study of Wave Run-Up, Overtopping and Damage in a Rubble-Mound Breakwater Subject to Oblique Extreme Wave Conditions. Defect and Diffusion Forum. 2019; 396 ():32-41.
Chicago/Turabian StyleJoão Alfredo Santos; Francisco Pedro; Mário Coimbra; Andrés Figuero; Conceição Fortes; José Sande; Moritz Körner; Rute Lemos; Antje Bornschein; Julius Weimper; Jeroen Van Den Bos; Bastian Dost; Bas Hofland; Rita Carvalho; Alberto Alvarellos; Enrique Peña; Reinhard Pohl; Nils Kerpen; Maria Teresa Reis. 2019. "3-D Scale Model Study of Wave Run-Up, Overtopping and Damage in a Rubble-Mound Breakwater Subject to Oblique Extreme Wave Conditions." Defect and Diffusion Forum 396, no. : 32-41.
Due to climatic change and the increased usage of coastal areas, there is an increasing risk of dike failures along the coasts worldwide. Wave run-up plays a key role in the planning and design of a coastal structure. Coastal engineers use empirical equations for the determination of wave run-up. These formulae generally include the influence of various hydraulic, geometrical and structural parameters, but neglect the effect of the curvature of coastal dikes on wave run-up and overtopping. The scope of this research is to find the effects of the dike curvature on wave run-up for regular wave attack by employing numerical model studies for various dike-opening angles and comparing it with physical model test results. A numerical simulation is carried out using DualSPHysics, a mesh-less model and OpenFOAM, a mesh-based model. A new influence factor is introduced to determine the influence of curvature along a dike line. For convexly curved dikes (αd = 210° to 270°) under perpendicular wave attack, a higher wave run-up was observed for larger opening angles at the center of curvature whereas for concavely curved dikes (αd = 90° to 150°) under perpendicular wave attack, wave run-up increases at the center of curvature as the opening angle decreases. This research aims to contribute a more precise analysis and understanding the influence of the curvature in a dike line and thus ensuring a higher level of protection in the future development of coastal structures.
Suba Periyal Subramaniam; Babette Scheres; Malte Schilling; Sven Liebisch; Nils B. Kerpen; Torsten Schlurmann; Corrado Altomare; Holger Schüttrumpf. Influence of Convex and Concave Curvatures in a Coastal Dike Line on Wave Run-up. Water 2019, 11, 1333 .
AMA StyleSuba Periyal Subramaniam, Babette Scheres, Malte Schilling, Sven Liebisch, Nils B. Kerpen, Torsten Schlurmann, Corrado Altomare, Holger Schüttrumpf. Influence of Convex and Concave Curvatures in a Coastal Dike Line on Wave Run-up. Water. 2019; 11 (7):1333.
Chicago/Turabian StyleSuba Periyal Subramaniam; Babette Scheres; Malte Schilling; Sven Liebisch; Nils B. Kerpen; Torsten Schlurmann; Corrado Altomare; Holger Schüttrumpf. 2019. "Influence of Convex and Concave Curvatures in a Coastal Dike Line on Wave Run-up." Water 11, no. 7: 1333.
Wave overtopping—i.e., excess of water over the crest of a coastal protection infrastructure due to wave run-up—of a smooth slope can be reduced by introducing slope roughness. A stepped revetment ideally constitutes a slope with uniform roughness and can reduce overtopping volumes of breaking waves up to 60% compared to a smooth slope. The effectiveness of the overtopping reduction decreases with increasing Iribarren number. However, to date a unique approach applicable for a wide range of boundary conditions is still missing. The present paper: (i) critically reviews and analyzes previous findings; (ii) contributes new results from extensive model tests addressing present knowledge gaps; and (iii) proposes a novel empirical formulation for robust prediction of wave overtopping of stepped revetments for breaking and non-breaking waves. The developed approach contrasts a critical assessment based on parameter ranges disclosed beforehand between a smooth slope on the one hand and a plain vertical wall on the other. The derived roughness reduction coefficient is developed and adjusted for a direct incorporation into the present design guidelines. Underlying uncertainties due to scatter of the results are addressed and quantified. Scale effects are highlighted.
Nils B. Kerpen; Talia Schoonees; Torsten Schlurmann. Wave Overtopping of Stepped Revetments. Water 2019, 11, 1035 .
AMA StyleNils B. Kerpen, Talia Schoonees, Torsten Schlurmann. Wave Overtopping of Stepped Revetments. Water. 2019; 11 (5):1035.
Chicago/Turabian StyleNils B. Kerpen; Talia Schoonees; Torsten Schlurmann. 2019. "Wave Overtopping of Stepped Revetments." Water 11, no. 5: 1035.
Stepped revetments are multi-functional coastal structures o ering protection against flooding. Despite the fact that these structures have been implemented for more than 60 years, comprehensive design guidance is lacking. Previous research studied overtopping of stepped revetments with slopes ranging between 1:1 to 1:4. To address the knowledge gap of predicting overtopping of stepped revetments with gentler slopes, this paper presents results of physical model tests for a 1:6 sloped stepped revetment with step heights of 0.05 m. The tests were conducted in a 110 m long, 2.2 m wide and 2.0 m deep wave flume. A fit through the overtopping results is compared with the reference curve for a smooth slope of EurOtop (2016), which allows the determination of the influence factor for roughness ( gamma_f ) of the stepped revetment. A value of gamma_f = 0.74 (r^2 of 0.94) is proposed to be used in combination with the overtopping prediction formula of EurOtop (2016) for slopes under breaking wave conditions. The results of the study indicate a high slope dependency for gamma_f .
Talia B. Schoonees; Nils Kerpen; Sven Liebisch; Torsten Schlurmann. WAVE OVERTOPPING PREDICTION OF A GENTLE SLOPED STEPPED REVETMENT. Coastal Engineering Proceedings 2018, 1, 99 .
AMA StyleTalia B. Schoonees, Nils Kerpen, Sven Liebisch, Torsten Schlurmann. WAVE OVERTOPPING PREDICTION OF A GENTLE SLOPED STEPPED REVETMENT. Coastal Engineering Proceedings. 2018; 1 (36):99.
Chicago/Turabian StyleTalia B. Schoonees; Nils Kerpen; Sven Liebisch; Torsten Schlurmann. 2018. "WAVE OVERTOPPING PREDICTION OF A GENTLE SLOPED STEPPED REVETMENT." Coastal Engineering Proceedings 1, no. 36: 99.
The wave impacts on horizontal and vertical step fronts of stepped revetments is investigated by means of hydraulic model tests conducted with wave spectra in a wave flume. Wave impacts on revetments with relative step heights of 0.3 < Hm0/Sh < 3.5 and a constant slope of 1:2 are analyzed with respect to (1) the probability distribution of the impacts, (2) the time evolution of impacts including a classification of load cases, and (3) a special distribution of the position of the maximum impact. The validity of the approved log-normal probability distribution for the largest wave impacts is experimentally verified for stepped revetments. The wave impact properties for stepped revetments are compared with those of vertical seawalls, showing that their impact rising times are within the same range. The impact duration for stepped revetments is shorter and decreases with increasing step height. Maximum horizontal wave impact loads are about two times larger than the corresponding maximum vertical wave impact loads. Horizontal and vertical impact loads increase with a decreasing step height. Data are compared with findings from literature for stepped revetments and vertical walls. A prediction formula is provided to calculate the maximum horizontal wave impact at stepped revetments along its vertical axis.
Nils B. Kerpen; Talia Schoonees; Torsten Schlurmann. Wave Impact Pressures on Stepped Revetments. Journal of Marine Science and Engineering 2018, 6, 156 .
AMA StyleNils B. Kerpen, Talia Schoonees, Torsten Schlurmann. Wave Impact Pressures on Stepped Revetments. Journal of Marine Science and Engineering. 2018; 6 (4):156.
Chicago/Turabian StyleNils B. Kerpen; Talia Schoonees; Torsten Schlurmann. 2018. "Wave Impact Pressures on Stepped Revetments." Journal of Marine Science and Engineering 6, no. 4: 156.
To understand the processes and energy dissipation performance caused by turbulence during the wave run-up over a stepped revetment, hydraulic model tests with steady flow conditions are conducted and correlated with unsteady flow conditions of the wave run-up within a short time frame. Under irregular waves, the run-up reduction over a stepped revetment is dependent on the Iribarren number and decreases for decreasing Iribarren numbers. Velocity gradients are found to be similar in a steady and unsteady flow regime near the pseudo-bottom.
Nils B. Kerpen; Daniel B. Bung; Daniel Valero; Torsten Schlurmann. Energy dissipation within the wave run-up at stepped revetments. Journal of Ocean University of China 2017, 16, 649 -654.
AMA StyleNils B. Kerpen, Daniel B. Bung, Daniel Valero, Torsten Schlurmann. Energy dissipation within the wave run-up at stepped revetments. Journal of Ocean University of China. 2017; 16 (4):649-654.
Chicago/Turabian StyleNils B. Kerpen; Daniel B. Bung; Daniel Valero; Torsten Schlurmann. 2017. "Energy dissipation within the wave run-up at stepped revetments." Journal of Ocean University of China 16, no. 4: 649-654.
Lokesha; N.B. Kerpen; S.A. Sannasiraj; V. Sundar; Torsten Schlurmann. Experimental Investigations on Wave Transmission at Submerged Breakwater with Smooth and Stepped Slopes. Procedia Engineering 2015, 116, 713 -719.
AMA StyleLokesha, N.B. Kerpen, S.A. Sannasiraj, V. Sundar, Torsten Schlurmann. Experimental Investigations on Wave Transmission at Submerged Breakwater with Smooth and Stepped Slopes. Procedia Engineering. 2015; 116 ():713-719.
Chicago/Turabian StyleLokesha; N.B. Kerpen; S.A. Sannasiraj; V. Sundar; Torsten Schlurmann. 2015. "Experimental Investigations on Wave Transmission at Submerged Breakwater with Smooth and Stepped Slopes." Procedia Engineering 116, no. : 713-719.
Nannina Horstmann; Nils Kerpen; Nils Goseberg; Torsten Schlurmann. INVESTIGATION ON THE EVOLUTION AND PROPAGATION OF WAVES IN HIGHLY CONCENTRATED FLUID. Coastal Engineering Proceedings 2014, 1, 24 .
AMA StyleNannina Horstmann, Nils Kerpen, Nils Goseberg, Torsten Schlurmann. INVESTIGATION ON THE EVOLUTION AND PROPAGATION OF WAVES IN HIGHLY CONCENTRATED FLUID. Coastal Engineering Proceedings. 2014; 1 (34):24.
Chicago/Turabian StyleNannina Horstmann; Nils Kerpen; Nils Goseberg; Torsten Schlurmann. 2014. "INVESTIGATION ON THE EVOLUTION AND PROPAGATION OF WAVES IN HIGHLY CONCENTRATED FLUID." Coastal Engineering Proceedings 1, no. 34: 24.
Hydraulic model tests at a scale of 1:10 are carried out in a 40 m x 25 m wave basin with a state-of-the-art 3D wave generator in order to collect wave overtopping data at vertical walls and dykes with topped vertical walls. Wave conditions in the near field of the structures, velocities under waves and the mean overtopping discharge are measured. The experiments have been commissioned by the Lower Saxony Water Management, Coastal Defense and Nature Conservation Agency (NLWKN) with the purpose to deliver essential overtopping data for validation of numerical models. Two main geometries are analyzed – each for two specific wave spectra. Overtopping rates are investigated with respect to the remaining freeboard height Rc and the influence of oblique wave attack β{0°, 10°, 30°, 40°, 50°, 60°}. Results are compared with existing analytical approaches. As expected for this special geometrical coastal protection structure, it is examined that overtopping discharges increase with decreasing remaining freeboard. Intensity of the reduction is more dependent on the wave spectra than on the dyke geometry. Mean wave overtopping rate increases with decreasing relative water depth Hm0/d directly in front of the vertical wall. Furthermore, the mean wave overtopping rates decrease with an increasing angle of wave attack β. The correlation between mean wave overtopping rate and freeboard height is given in four newly adapted design formulas, describing the overtopping performance of the two discussed dyke geometries with topped vertical walls.
Nils B. Kerpen; Torsten Schlurmann. WAVE OVERTOPPING AT DYKES WITH TOPPED VERTICAL WALL - IMPACTS OF OBLIQUE WAVE ATTACK. Coastal Engineering Proceedings 2012, 1, 1 .
AMA StyleNils B. Kerpen, Torsten Schlurmann. WAVE OVERTOPPING AT DYKES WITH TOPPED VERTICAL WALL - IMPACTS OF OBLIQUE WAVE ATTACK. Coastal Engineering Proceedings. 2012; 1 (33):1.
Chicago/Turabian StyleNils B. Kerpen; Torsten Schlurmann. 2012. "WAVE OVERTOPPING AT DYKES WITH TOPPED VERTICAL WALL - IMPACTS OF OBLIQUE WAVE ATTACK." Coastal Engineering Proceedings 1, no. 33: 1.