Shoreline Protection Structures Research Articles

Urban oasis? Abundant dice snake (Natrix tessellata) populations along artificial lakeside habitats in urban landscapes

ContextHuman-induced landscape modification, such as urbanization, creates new environments that can have adverse effects on flora and fauna, posing threats to biodiversity. Understanding how reptiles respond to urbanization is crucial, especially in light of their ongoing population declines.ObjectivesWe examined the influence of landscape-scale and local-scale urbanization features on the abundance of an aquatic snake species. Our investigation focused on dice snakes (Natrix tessellata) inhabiting a lake with a heavily urbanized shoreline.MethodsWe conducted visual encounter surveys at 25 study sites during the activity period of dice snakes around Lake Balaton in Hungary. We measured both landscape-scale and local-scale variables, including urban land use cover, vegetation cover, road cover, distance of main roads and city size, emergent vegetation cover and the area of artificial rock and concrete shoreline protection structures. We analysed snake survey data using N-mixture models to estimate abundance and examine relationships with landscape-scale and local-scale variables.ResultsUrban land use cover, road cover, the proximity of main roads and the extent of artificial rock and concrete shoreline protection structures positively affected the abundance of snakes. These findings imply that urban habitats may offer new ecological opportunities for dice snakes.ConclusionsThe findings of this study indicate that both landscape-scale and local-scale human-induced landscape modifications may have a positive impact on the abundance of urban snakes. Taken together, our findings suggest that urbanization is a complex phenomenon, affecting species at different levels and with subtle effects.

Nature-Based Coastal Protection by Large Woody Debris as Compared to Seawalls: A Physical Model Study of Beach Morphology and Wave Reflection

Anchored Large Woody Debris (LWD) is increasingly being used as one of several nature-based coastal protection strategies along the north-western coasts of Canada and the US. As an alternative to conventional hard armoring (e.g., seawalls), its usage is widely considered to be less harmful to the coastal ecosystem while maintaining the ability to protect the beaches against wave attack and erosion. The effects of seawalls on beaches have been extensively studied; however, the performance and efficacy of LWD and its potential as a suitable alternative to seawalls (and other shoreline protection structures) are still understudied in current research. This paper presents and compares the effects of a conventional vertical seawall with two different LWD structures on beach morphology and wave reflection through large-scale physical modeling in a wave flume at a 1:5 scale. An assessment of techniques used to measure beach morphology and an assessment of model effects were included in the study. It was found that the wave reflection could be reduced by using a single log instead of a wall structure, while changes in the beach morphology response largely depended on the type of the LWD structure. A stacked log wall showed near-identical behavior as a conventional seawall. Visible model effects from the experiments, including the effect of the flume sidewalls on the beach morphology, were quantified and analyzed to inform future research.

Sediment transport simulation and design optimization of a novel marsh shoreline protection technology using computational fluid dynamics (CFD) modeling

Coastal Louisiana has the nation's most fragile and valuable wetlands, whose loss represents 80% of the total losses in the United States. The severely restricted mobility of conventional shoreline protection structures makes them impossible to be redeployed. The Wave Suppression and Sediment Collection (WSSC) system is a novel technology of high mobility and compatible with existing shoreline protection technologies. Previous laboratory studies on WSSC showed great potential for wave reduction and sediment collection. The current study aimed to optimize the design parameters of WSSC using a validated computational model. A computational fluid dynamics (CFD) model was developed and validated using experimental data from the previous laboratory study. Then, a parametric analysis was conducted with a focus on the performance optimization of wave reduction and sediment collection with respect to pipe diameter and face slope. Simulation results showed that the wave reduction efficiency decreased with increasing pipe diameter and face slope. In contrast, the sediment transport efficiency was enhanced by increasing pipe diameter but was not affected significantly by varying face slopes.

Physical model studies on damage and stability analysis of breakwaters armoured with geotextile sand containers

Harnessing the advantages of geotextile sand containers (GSCs), numerous submerged breakwaters and shoreline protection structures have been constructed worldwide. But an emerged breakwater structure with geotextile armour units, capable of replacing the conventional structures, is rarely discussed. A 1:30 scaled physical experimentation is chosen as a preliminary investigation to test the feasibility of using GSCs as breakwater armour units. Structural design is evolved based on a comprehensive literature survey. The paper focuses on the stability parameters and damage characteristics of the proposed structure. Four different configurations are subjected to waves, confining to Mangaluru's wave parameters. Effect of armour unit size and sand fill ratio on the stability of the structure is analysed and it is concluded that changing sand fill ratio from 80% to 100% shot up the structural stability to a maximum of 14%. Increasing bag size also resulted in the increased stability up to 8%. Experiments revealed that the best performing configuration could withstand wave heights up to 2.7 m. Stability curves for all tested configurations are discussed and can serve as an effective guideline for designing GSC breakwaters.

Laboratory study and mathematical modeling of a novel marsh shoreline protection technology for sand collection

Erosion along shorelines is a major cause in the conversion of shoreline wetlands to open water bodies. Conventional shoreline protection structures are expensive to construct and may impede environmental exchanges essential for connectivity and functionality. A novel marsh shoreline protection technology, the Wave Suppressor and Sediment Collection (WSSC) system, addresses these issues. Laboratory studies were conducted on three WSSC units to determine the governing parameters of sediment collection efficiency of this technology. The three units had varying open areas and pipe sizes which enabled those parameters to be directly compared. Two types of sands with median particle diameters (d50) of 0.43 and 0.34 mm were used to evaluate the effects of particle size on the collection efficiency of the units. A new mathematical model was developed to predict the sediment collection efficiency using Van Rijn’s equation for particle fall velocity, and Ribberink and Al-Salem’s equation for sand concentration distribution in a water column. Results showed that the Unit 1, Unit 2 and Unit 3 are capable of collecting sand at 0.30, 0.21 and 0.21 (kg/h) for sand 1, and at 0.39, 0.29, 0.39 (kg/h) for sand 2 respectively. The mathematical model fit the experimental data well and from the model, mass accumulation coefficient (α) alpha was calculated. Mass accumulation coefficients (α) for sand 1 and sand 2 were- 0.94 and 0.97 for Unit 1, 0.63 and 0.70 for Unit 2 and 0.32 and 0.22 for Unit 3 respectively. A sensitivity study of the mathematical model was also performed to determine the governing factors behind the sand collection. The sensitivity study found that water depth, wave height and particle diameter affected the sand collection efficiency the most. The amount of open area on the units, frequency and wavelength were also found to have some effect on collection efficiency.

Performance characterization of a novel marsh shoreline protection technology: The Wave Suppression and Sediment Collection (WSSC) system

Minimizing coastal wetland loss is a high priority in coastal areas worldwide. Typical shoreline protection consists of hard structures placed near areas affected by wave action. These commonly used protection methods are costly, and may have negative impacts on the surrounding areas. The Wave Suppression and Sediment Collection (WSSC) system, made of multiple Wave Robber® units, is an alternative shoreline protection structure. The primary goal of this study is to determine the performance characteristics of the technology in terms of energy coefficients. Experiments were performed on three scaled units within a laboratory wave tank. Performance characterization showed that the units have wave energy reflections of 0.47–0.83, transmission ranging from 0.10 to 0.42, and wave energy dissipation between 0.49 and 0.88, depending upon unit geometry and wave conditions. Performance data were also compared to other studies on shoreline protection structures. WSSC units reflect more wave energy and transmit less energy compared to other breakwater systems. These units could be utilized in coastal marshes with a large fetch, to reduce wave-induced erosion.

Increasing microhabitat complexity on seawalls can reduce fish predation on native oysters

Increasingly, urbanised coastlines are being armoured by shoreline protection structures, such as seawalls. Seawalls typically lack the complex microhabitats and protective spaces of natural shorelines and consequently organisms that settle on them may be particularly susceptible to predation. We tested whether the addition of complex microhabitats to seawalls enhances the survivorship of oysters, key habitat-forming species on intertidal shores, by reducing the intensity of predation. At two sites in Sydney Harbour, we compared the magnitude and sources of mortality of juvenile oysters among (1) flat tiles, without crevices or ridges; (2) complex tiles, with 2.5cm high ridges, separated by crevices; and (3) complex tiles, with 5cm high ridges, separated by crevices. We also compared predatory fish visitation and feeding among sites and treatments using GoPro® cameras. The abundance and feeding of predatory fish was much greater at one of the study sites than the other, but at neither site differed among treatments. At the site with greater predatory fish abundances, survivorship of juvenile oysters was 50% greater on the 5cm complex tiles than flat tiles, and on complex tiles approximately 300% greater in crevices than on ridges. Of the dead oysters, almost all were cracked, indicative of fish predation. In contrast, at the site with fewer predatory fish, there were no detectable differences in oyster survivorship between treatments. These results suggest that the addition of complex habitat to seawalls could be an effective strategy in reducing fish predation pressure on juvenile oysters at sites with abundant predatory fish. A greater understanding of the site-specific pressures is required to enhance the abundances of desirable species and functions on seawalls.

Groins along the Northern Yucatán Coast

ABSTRACT Tereszkiewicz, P.; McKinney, N., and Meyer-Arendt, K.J., 2018. Groins along the northern Yucatan coast. Coastal erosion is a global issue, putting increasing physical and socioeconomic stresses on coastal communities. While shoreline protection structures are typically seen as potential solutions, negative environmental impacts often result. Groins, a shore-normal type of structure, can successfully impound sediment; however, improper design can lead to downdrift erosion and create hazardous rip currents. Widespread construction of groins on the northern coast of the Yucatan Peninsula is thought to have caused significant morphologic change to the shoreline, raising questions as to their effectiveness. The objective of this regional survey was to collect geodata on shoreline position and existing shoreline protection structures. Methods included (1) GPS mapping of the shoreline and groin structures along a 13-km stretch of coastline; (2) developing a classification for groin construction, conditi...

Coastal defences versus coastal ecosystems: A regional appraisal

Societal concern (both real and imagined) over coastal erosion and flooding, often results in construction of sea defences to protect property. Sea defences are, however, damaging to the natural ecosystems that provide quantifiable ecosystem services to the human population. Protection of property is, however, the most common driving force behind construction of sea defences and the basis of any associated economic appraisals. Protection of the coastal ecosystem (sedimentary, biological and chemical) while commonly implied in strategic documents (e.g. Habitats Directive 92/43/EEC, Water Framework Directive 2000/60/EC, OSPAR Convention), remain largely aspirational notions that currently have a much lower priority, or none at all, in sea defence decision-making. Under this anthropic view of coastal protection it is not surprising that defence structures proliferate. In many instances, shoreline armouring is considered on a case by case basis with little regard to the cumulative effects. This is true whether or not there is a strategic approach to coastal protection. In this paper the Northern Ireland coast is used as a case study to document the nature and extent of shoreline protection structures associated with sandy beaches. The nature and extent of sea defence structures were documented from a low-level oblique helicopter-based photographic survey and mapped in a GIS. The implications for the coastal ecosystem are considered. A sustainable approach to shoreline management demands a balance between protection of property and preservation of coastal ecosystem services.

Artificial substrates enhance non-native macroalga and N2 production

The introduction of non-native species occurs within a context of other anthropogenic impacts: thus a holistic approach is needed to understand interactive effects. Installation of shoreline protection structures is increasing in response to rising sea levels and increasing frequency of intense storms. Shoreline hardening structures can facilitate establishment of non-native species with multiple potential consequences. We measured abundances of both native and non-native Codium, a green macroalga, on natural hard substrates (oyster reefs) and artificial substrates (bulkheads and revetments) in two estuaries and assessed the effects of each Codium species on nitrogen fixation and net N2 fluxes. Native C. decorticatum was the most abundant (86 %) Codium on oyster reefs, while exotic C. fragile dominated (99 %) artificial substrates. N2 production via denitrification was greater than nitrogen fixation for both species and the net N2 production associated with non-native C. fragile was greater than with native C. decorticatum. Comparing our results with surveys conducted in the 1940s before C. fragile had invaded, indicates that non-native Codium has outcompeted native Codium on artificial substrates, but that natural substrate provided by oyster reefs remains a refuge for native Codium. Although shoreline hardening with artificial structures can reduce ecosystem services provided by coastal marsh and other habitats, an unexpected beneficial consequence was the N2 production associated with the non-native Codium, which has the potential to mitigate anthropogenic nutrient loading. Our results illustrate that the interaction between multiple anthropogenic impacts can be positive, and indicate that non-ephemeral macroalgae could be an overlooked component in nitrogen removal from marine ecosystems by enhancing denitrification.

Geological Causes of Local Variation in Coastal Bluff Recession Rates, Northeast Ohio Shoreline of Lake Erie

The Lake Erie shoreline at Painesville-on-the-Lake has receded 180 m since 1876, yet during the past decade rates have varied locally by 0–5 m/yr. The study area is a portion (0.5 km in length) of a continuous section of coastal bluffs 17 m tall. The section was selected to minimize variation in physical parameters, including shoreline orientation and exposure, offshore bathymetry and sediment, beach width, minimal shoreline protection structures, and generally homogeneous bluff materials. In spite of these similarities, some portions of the bluff recede episodically by block-fall and other portions continuously by slumping.

Managing lakeshore erosion: Impacts of bank protection on Loch Lomond, Scotland

The shoreline of Loch Lomond is currently undergoing erosion not only because of passive natural changes but also because of active changes produced by the interaction of shoreline protection structures and natural processes. In order to assess the influence of protection structures on different types of loch shore, the shores were classified and their total extent, including the extent of artificial shore, was quantified. The effect of structures is often felt on adjacent shores as well as on those that the structure is designed to protect. In order to assess the extent of impact of structures, sediment cells were identified along the loch shore within which the effects of a structure may produce compensatory effects but beyond which they will not. A management strategy is presented that is aimed at minimising the detrimental effects of any future intervention in the shore system.

Development of Great Lakes shoreline management plans by Ontario conservation authorities

The Great Lakes shoreline in Ontario is subject to severe flooding and erosion due to frequent high water level periods and storm events leading to wind and wave action. After extensive property damages in 1985 and 1986, the province established a shoreline management program to be administered by the Ontario Ministry of Natural Resources. A key component of this program is the development of Great Lakes shoreline management plans by Ontario conservation authorities. A review of three such plans reveals a focus on understanding the range and frequency of shoreline flooding and erosion, and the use of land use regulations and shoreline protection structures to reduce the impact from these hazards. Limited attention and responses are provided for the range of issues and concerns that occur in these shoreline areas such as ecosystem management, species and habitat protection, and water quality. A lack of consistency, enforcement, monitoring and coordination occurs in the provincial program which has also recently been affected by related land use and environmental planning initiatives and government financial restraints.

Long-term shoreline changes and the concentration of heavy minerals in beach sands of the Nile Delta, Egypt

Analyses have been undertaken of shoreline positions established from beach profile surveys at 65 positions along the coastline of the Nile Delta spanning the years 1971 to 1990. The analyses identify long-term linear trends as well as any cycles in the horizontal movement of shoreline positions. The results reveal longshore patterns wherein erosion along a stretch of coast gives way to accretion in an adjacent stretch, defining a subcell within the overall littoral system of the delta. The rate of shoreline retreat has been greatest along the Rosetta promontory (− 106 m/yr) and Damietta promontory (− 10.4 m/yr). Significant erosion has also occurred along the central bulge of the delta coast, but at a lesser rate (− 6.5 m/yr). Areas of accretion exist within the saddles or embayments between the promontories, with the maximum shoreline advance averaging about 13 m/yr. The identified patterns of erosion versus accretion along the delta reflect the natural processes of wave-induced longshore currents and sediment transport. Associated with this longshore sediment movement is a selective transport of different minerals according to their densities and grain sizes, with the light minerals (quartz and feldspar) having the highest advection rates and the dense opaque minerals the lowest rates, tending to remain behind as a lag within the erosion areas. As a result of this longshore grain sorting paralleling the patterns of shoreline erosion versus accretion, there are correlations between the rates of shoreline change and the heavy-mineral contents and mean grain sizes of the beach sediments. These large scale delta-wide patterns are affected somewhat by local shoreline changes and mineral variations induced by the construction of jetties or shoreline protection structures.

Changes in climate and levels of lake Michigan: shoreline impacts at Chicago

This study concerns effects along the Illinois shoreline resulting from the record-low levels of Lake Michigan during 1964–65, and the potential impacts of future low water levels at Chicago resulting from potential climate changes. The low lake levels of the 1960s did not cause major impacts at Chicago when they occurred. The two major impacts discerned (damage to shoreline protection structures and the encroachment of structures onto areas too close to the lake) resulted from a sequence of low-water levels followed by high-water levels a few years later. Climate scenarios, derived from general circulation models (GCMs) and extreme historical precipitation values, were used in a basin hydrologic model to determine potential future lake levels. Possible impacts were then estimated by 29 lakeshore experts. If the average lake level were reduced ⩽ 1.0 m during the next 50 yr, shoreline impacts would not be severe and cost about $ 100 million. Many of the adjustment costs could be offset by normal maintenance and replacement costs. If the average lake level was reduced more than 1.5 m during the next 50 yr, very sizable economic impacts would occur, costing between $3 and $35 billion (1988 dollars). Some of the adjustment cost could be offset by normal replacement costs, particularly if a master plan for changing affected facilities were implemented in advance. The type of climate change and degree of lakelevel change will greatly affect the severity of the effects at Chicago.

Regimes Contributory to Progressive Loss of Alabama Coastal Shoreline and Wetlands: ABSTRACT

ABSTRACT Coastal survey data from the 1700's to the present indicate progressive loss of Alabama coastal shoreline and wetlands. Alabama coastal shoreline/wetland environments include those of bays, estuaries, Mississippi Sound, lagoons, lakes, fluvial deltas and Gulf barrier. Areas showing the highest rates of loss include Mississippi Sound north shoreline and islands, Mobile Bay west shoreline, Gulf shoreline of Dauphin Island, and north shoreline of Morgan Peninsula. Other areas showing progressive substantial loss are Mobile Bay east shoreline, Perdido Bay, and Perdido estuary. The relationship between erosional loss and accretionary gain of Gulf barrier shoreline in Baldwin County (from Mobile Point to Alabama Point) is complex but this shoreline appears to be generally stable with isolated short segments of erosional as well as accretionary beach. Negative economic results of shoreline/wetland loss include shoreline property devaluation, costs associated with erosion protection, and loss of wetlands supportive of fishery species reproduction. Accretionary gain of land areas appears to be negligible. Although no new wetlands appear to be developing along Mississippi Sound shoreline exposed to erosional affects of waves and currents, it is postulated that subsidence and drowning of terrane adjacent to Mississippi Sound is resulting in some new upland swamp and bayou areas. The balance between loss and gain of wetlands has not been estimated. General descriptions are given for the unique combinations of factors postulated as contributory to loss of specific shoreline/wetland. Primary factors associated with shoreline loss are wave, current and tidal parameters, local subsidence, sea level rise, position and character of natural barriers, position and nature of shoreline protection structures, anthropogenic affects, local bathymetry, shoreline orientation, local sediment budgets, and morphological and physical character of shoreline/wetland.

The Effects of Coastal Protection Structures on Beaches Along Northern Monterey Bay, California

As a result of the severe coastal wave damage experienced over the past decade along the California coast, a large number of shoreline protection structures have either been built or proposed. As the numbers of structures and their coastal frontage has increased, concern with the effects of the structures on the adjacent beaches has arisen. A one-year study along the central California coast was carried out in an effort to resolve some of the critical questions regarding the impact of these structures on beaches. Based on precise, biweekly, wading-depth surveys in the vicinity of four protective structures, a number of consistent seasonal beach changes were observed: (1). With the arrival of winter waves, the summer berm in front of the four seawalls was eroded before the berm in front of the adjacent unprotected beaches. (2). Where a sloping permeable revetment is adjacent to an impermeable vertical seawall, the berm in front of the vertical seawall was eroded sooner. (3). Once the berm on the unprotected beach retreated landward beyond the seawall, beach face profiles in front of the seawall and adjacent beach were usually indistinguishable. (4). Accelerated erosion occurred at the downdrift ends of the seawalls and extended as far as 150 m downcoast. This excess scour is believed to result from a combination of wave reflection and sand impoundment upcoast. (5) Rebuilding of the nearshore beach profile occurred in a uniform manner with no obvious differences between seawall-backed and adjacent unprotected beaches.

Engineering Group of the Geological Society, 1983–84

12-15 September 1983. The engineering geology of tidal rivers . Held at the University of Hull. Local secretary, Dr P. Young. 12 September. The impact of construction on tidal river systems: An overview. Published in Q. J. eng. Geol. London, 17, 193–8. Impact of engineering structures on tidal flow and sediment distribution in the Thames. Published in Q. J. eng Geol London, 17, 207–18. Thames tidal flood risk—the need for the Barrier. Published in Q. J. eng. Geol. London, 17, 199–206. Deep foundations—the River Hull Tidal Surge Barrier. Published in Q. J. eng. Geol. London, 17, 291–300. Engineering solutions to geological problems in the design and construction of the Humber Bridge. Published in Q. J. eng. Geol. London, 17, 301–6. A buried valley in the Orwell Estuary. Published in Q. J. eng. Geol London, 17, 283–88. Engineering geological and geophysical investigation of the Barking Creek Tidal Barrier Site. Published in Q. J. eng. Geol. London, 17, 259–68. A geophysical survey of the Crouch/Roach river system with special reference to buried channels, Published in Q. J. eng. Geol. London. 17, 269–82. Sediment transport at inlets and the formation of subtidal in let deltas. E. H. Owens. The paper reviews the state of knowledge of inlet sediment dynamics for river systems with a tidal range greater than 2 m. The primary implications for engineering or structural activities in the vicinity of an inlet are related to shoreline protection structures at inlet margins, and dredging activities within the inlet area as a whole. Hydraulic/soil