In the context of ‘green’ approaches to coastal engineering, the term 'eco-engineering' has emerged in recent years to describe the incorporation of ecological concepts (including ‘artificially water-filled depressions and surface textured tiles on seawalls and drilled holes in sea structures) into the conventional design process for marine infrastructures . Limited studies have evaluated the potential increase in wave energy dissipation resulting from the increased hydraulic roughness of ecologically modified sea defences which could reduce wave overtopping and consequent coastal flood risks, while increasing biodiversity. This paper presents results of small-scale laboratory investigations of wave overtopping on artificially roughened seawalls. Impulsive and non-impulsive wave conditions with two deep-water wave steepness values (= 0.015 and 0.06) are evaluated to simulate both swell and storm conditions in a two-dimensional wave flume, with an impermeable 1:20 foreshore slope. Measurements from a plain vertical seawall are taken as the reference case. The seawall was subsequently modified to include 10 further test configurations where hydraulic effects, reflective of ‘eco-engineering’ interventions, were simulated by progressively increasing seawall roughness with surface protrusions across three length scales and three surface densities. Measurements at plain a vertical seawall (reference condition) compared favorably to empirical predictions from the EurOtop II Design Manual and served as a validation of the experimental approach. Results from physical model experiments showed that increasing the length and/ or density of surface protrusions reduced overtopping on seawalls. Benchmarking of test results from experiments with modified seawalls to reference conditions showed that the mean overtopping rate was reduced by up to 100% (test case where protrusion length and density were maximum) under impulsive wave conditions. Results of this study highlight the potential for eco-engineering interventions on seawalls to mitigate extreme wave overtopping hazards by dissipating additional wave energy through increased surface roughness on the structure.

中文翻译：

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防波堤的生态工程–地形复杂性增强带来的增强气候适应能力的机会

在沿海工程的“绿色”方法背景下，近年来出现了“生态工程”一词，用以描述生态学概念的结合（包括“人工充水的凹陷和海堤上的表面有纹理的瓷砖以及海底钻孔”结构）纳入常规的海洋基础设施设计流程。有限的研究评估了由于生态改造的海上防御系统的水力粗糙度增加而导致的波浪能量消散的潜在增加，这可以减少波浪超顶和随之而来的沿海洪灾风险，同时增加生物多样性。本文介绍了在人工粗糙的海堤上进行波浪超顶的小规模实验室研究的结果。具有两个深水波陡度值（= 0的脉冲和非脉冲波条件）015和0.06）进行了评估，以模拟二维波状水槽中的涨潮和暴风雨条件，前坡为不可渗透的1:20。参考平直海堤的测量结果。随后对海堤进行了修改，使其包含10个其他测试配置，其中通过逐步增加海堤粗糙度并在三个长度范围和三个表面密度范围内增加表面凸起来模拟反映“生态工程”干预的水力效应。在平原垂直海堤（参考条件）下的测量结果优于EurOtop II设计手册的经验预测，并作为实验方法的验证。物理模型实验的结果表明，增加表面突起的长度和/或密度可以减少海堤的过度覆盖。修改后的海堤实验的参考结果的基准测试结果表明，在脉冲波条件下，平均超载率降低了100％（突出长度和密度最大的测试案例）。这项研究的结果突显了通过对海堤进行生态工程干预，通过增加结构表面的粗糙度来消散额外的波浪能量，从而减轻极端波浪过顶危害的潜力。