Anchor Damage Research Articles

Anchor Fault Identification Method for High-Voltage DC Submarine Cable Based on VMD-Volterra-SVM

This article introduces a new method for identifying anchor damage faults in fiber composite submarine cables. The method combines the Volterra model of Variation Mode Decomposition (VMD) with singular value entropy to improve the accuracy of fault identification. First, the submarine cable vibration signal is decomposed into various Intrinsic Mode Functions (IMFs) using VMD. Then, a Volterra adaptive prediction model is established by reconstructing the phase space of each IMF, and the model parameters are used to form an initial feature vector matrix. Next, the feature vector matrix is subjected to singular value decomposition to extract the singular value entropy that reflects the fault characteristics of the submarine cable. Finally, singular value entropy is used as a feature value to input into the Support Vector Machine (SVM) for classification. Compared with Empirical Mode Decomposition (EMD) and Ensemble Empirical Mode Decomposition (EEMD), the proposed method achieves a higher fault identification accuracy and effectively identifies anchor damage faults in submarine cables. The results of this study demonstrate the feasibility and practicality of the proposed method.

Setting sustainable limits on anchoring to improve the resilience of coral reefs

Boat anchoring is common at coral reefs that have high economic or social value, but anchoring has received relatively little attention in reef resilience studies. We developed an individual-based model of coral populations and simulated the effects of anchor damage over time. The model allowed us to estimate the carrying capacity of anchoring for four different coral assemblages and different starting levels of coral cover. The carrying capacity of small to medium-sized recreational vessels across these four assemblages was between 0 and 3.1 anchor strikes ha−1 day−1. In a case study of two Great Barrier Reef archipelagos, we modelled the benefits of anchoring mitigation under bleaching regimes expected for four climate scenarios. The partial mitigation of even a very mild anchoring incidence (1.17 strikes ha−1 day−1) resulted in median coral gains of 2.6–7.7 % absolute cover under RCP2.6, though benefits varied temporally and depended on the Atmosphere-Ocean General Circulation Model used.

Surface Mechanical Effects of Wildfires on Rocks in Climbing Areas

Wildfires are widely recognized as a cause of mechanical damage to rocks. Nevertheless, previous research has neglected how wildfires might impact sport climbing areas. In Spain, two large wildfires affected two climbing areas between 2020 and 2021. This paper addresses the rock mechanical effects of wildfires that could lead to safety issues, such as rock falls, climbing hold deterioration, and climbing anchor damage. In this study, the Non-Destructive Techniques (NDTs) of Ultrasonic Pulse Velocity (UPV) and Schmidt Hammer (SH) were used, and two types of measurements were carried out: randomized grid measurements and measurements along the climbing routes. Two phenomena were recognized: (a) thermal breakdown and (b) mineralogical changes. The results of using the SH show a relationship between the decrease in the rebound value and the observed mechanical damage. Field observations showed mechanical weathering, such as cracking, spalling, granular disaggregation, and thermochemical weathering with different temperature thresholds. Observed thermochemical reactions included reddening, CaCO3 calcination, rock decomposition, and quartz cracking. The set of changes involves a major rock outcrop transformation and an acceleration of fire-induced weathering processes. Both areas exhibited more effects at the bottom of the wall. Furthermore, in this paper, we explore how iconic climbing routes can be considered a form of cultural heritage and the consequences of their loss.

Long-Term Persistence of Propeller and Anchor Damage to Seagrass Canopy and Demersal Biodiversity in Puerto Rico

Long-Term Persistence of Propeller and Anchor Damage to Seagrass Canopy and Demersal Biodiversity in Puerto Rico

A Hybrid Model Integrating CNN–BiLSTM and CBAM for Anchor Damage Events Recognition of Submarine Cables

A Hybrid Model Integrating CNN–BiLSTM and CBAM for Anchor Damage Events Recognition of Submarine Cables

Research on anchor damage and protection of three-core composite submarine cable considering impact angle

Submarine cables are important equipment in many power engineering and communication engineering projects. However, power transmission and signal transmission is threatened by anchors hitting submarine cables. Due to the nature of the helical structure of the cable, different angles of impact have different effects on submarine cable damage. In this paper, a three-dimensional dynamic response analysis model, “ship anchor – three-core composite submarine cable – soil”, is developed based on ABAQUS to study how the impact angle of ship anchors influences the damage to submarine cables. It explores the damage to cables struck by anchors of different weights and at different speeds. The longitudinal compression rates of conductors and the optical fibre units of submarine cables at different burial depths are obtained and advice for the protection of cables is provided. The results show that anchor speed has a greater impact on cable damage than anchor mass. The impact angle on cable conductors and the optical fibre units decreases as the depth of burial increases. A burial depth greater than 1.9 times the cable diameter provides a protective effect on the submarine cable.

Mapping of benthic ecosystems: Key to improving the management and sustainability of anchoring practices for ocean-going vessels

A global fleet of more than 48,000 vessels conveys >80% of world trade by volume. Anchor damage to benthic habitats by these vessels, along with the burgeoning cruise ship industry, represents a key threat to benthic biodiversity and ecosystem function. Here, we use vessel positional information (Automated Identification System (AIS) data) to map anchoring activity. We then focus on the important role that high resolution habitat mapping will play in understanding the distribution of habitat types which may be impacted by anchoring activities. Many international ports have high-intensity anchor areas that remain unmapped and thus risks to benthic biodiversity are poorly understood and inadequately managed. We use case studies from an anchorage in south-eastern Australia, major trade routes in the Middle East and the anchoring of cruise vessels in the Caribbean to highlight the important role of habitat mapping in reducing anchoring impacts. We contend that mapping represents an important safeguard against anchoring impacts from unexpected events such as the COVID-related redirection of cruise vessels to anchorages and the blocking of the Suez Canal by the Ever Given grounding. With increasing maritime trade expected over coming decades there is a need to transition toward sustainable anchorage management practices and provide public confidence in stewardship of marine ecosystems by the maritime industry into the future.

On-line status monitoring and surrounding environment perception of an underwater cable based on the phase-locked Φ-OTDR sensing system.

A newly designed phase-locked (PL) Φ-OTDR system was proposed and instrumented. Field tests of water impact, anchor damage towing and tide diagnosing were carried out in a natural freshwater lake as well as the East China Sea. Personnel movement trajectory monitoring and ship flow monitoring were carried out by a buried cable along the floodplain of the Yangtze River. It proved that the proposed system can monitor the real-time status and sense the surrounding environment of existing underwater communication cables, which could be helpful for the maintenance of the cable itself as well as underwater information collection.

Seagrass restoration trials in tropical seagrass meadows of Kenya

The degradation of seagrasses is becoming prevalent in the Western Indian Ocean (WIO) region due to anchor damage, sea urchin herbivory, extreme events such as cyclones and floods and anthropogenic factors such as pollution and sediment inflows. Consequently, there have been numerous efforts to advance the restoration of degraded seagrass beds in several countries in the region. In Kenya, experimental restoration efforts were started in 2007 in response to seagrass habitat degradation due to sea urchin herbivory. Although the initial efforts experienced challenges, there were lessons learned which provided insights into subsequent restoration work using different techniques. In this paper, insights are provided into three types of restoration techniques; the sod technique, the seagrass mimic technique, and the Hessian bag technique. In the case of the sod technique, Thalassodendron ciliatum showed a decline from 20 ± 1.7 shoots sod-1 in the first three weeks to 7 ± 4.4 shoots sod-1 at the end of the experimental period of the study, while Thalassia hemprichii sods showed an increase from 28 ± 3.4 shoots sod-1 to 32 ± 2.7 shoots sod-1 over the same period. For the Hessian bag method, the expectation was that the pilot site would be filled with the transplanted seagrass species, Thalassia hemprichii, but the findings showed that different species including Halodule uninervis, Syringodium isoetifolium, Halophila stipulacea, Cymodocea rotundata, and Cymodocea serrulata colonized the area. This indicated that it was not possible to restore the area to its original status, but that the area could be rehabilitated. The costs of restoration have also been assessed as well as community participation in such initiatives. These findings provide insights for restoration efforts in Kenya and provide a baseline for future work.

Reconnecting reef recovery in a world of coral bleaching

AbstractCoral bleaching can have widespread impacts on reefs leaving many areas in need of coral recovery. While the long‐term mitigation of bleaching requires transitioning to a low carbon economy, local management has focused on approaches that seek refugia from or tolerance to bleaching stressors, reduce additional stressors, or facilitate coral recovery. Here, we describe a tactical response to coral bleaching events that seeks to identify the most important reefs for driving imminent recovery. A bleaching recovery algorithm is described that identifies those reefs that provide the most important sources of coral larvae that supply many reefs in the early stages of post‐bleaching recovery (i.e., reefs in need of coral larval supply). We describe the algorithm with a simple toy example and then apply it to the Great Barrier Reef, which has experienced three mass bleaching events in the last 5 yr. Once such reefs have been identified it makes practical sense to undertake a vulnerability assessment and if necessary reduce manageable stressors, such as outbreaks of crown‐of‐thorns starfish or anchor damage, so that critical sources of coral recovery are not depleted further. In short, algorithms like this can help managers target finite management resources, including restoration, to where they might be most effective in facilitating natural processes of recovery.

Anchor penetration depth in sandy soils and its implications for cable burial

Modern society is dependent on offshore cables and consequently cable faults lead to major disruption and economic loss. The most effective way to protect offshore cables from anchor damage is to bury them in the seabed, but current guidance is ambiguous. This paper attempts to produce more rational design guidance for anchor penetration in sand based on centrifuge modelling, allowing suitable burial depths for cables to be calculated based on the more useful metrics of anchor or ship size.A miniature anchor was dragged through sand of different densities within a centrifuge with maximum anchor penetration being measured. The most significant factor that influences anchor penetration depth is the size of the anchor, investigated by completing centrifuge tests at different g-levels. A linear relationship was recorded between anchor size and penetration depth which was used to develop new guidelines for cable burial. The new chart is clear and easy to use, with the cable burial depths given in relation to anchor size, anchor mass and ship mass. Use of this chart will enable the safe and economic burial of cables, and lead to a decrease in the impact of anchor damage to offshore cables.

The influence of boat moorings on anchoring and potential anchor damage to coral reefs

Recreational boating is increasingly popular and provides social and economic benefits, but can also have ecological impacts, including damage from anchoring on sensitive seabed habitats like coral reefs. Mooring buoys are commonly used to manage anchoring activity, and I tested whether they moderated anchoring on coral reefs in the British Virgin Islands. A spatial survey revealed that overall boat use (moored plus anchored) was 3.6 times higher at sites with moorings than those without. The density of boats anchored on coral reef was, however, reduced by roughly half at sites with moorings. A survey of two sites before and after moorings were installed confirmed that the addition of moorings increased the total number of boats at a site, but reduced the rate of anchoring on reef. At any given site, the rate of anchoring on reef increased as the total number of boats present increased, but the effect of crowding was diminished at sites with moorings. Moorings can thus be an effective management tool for mitigating anchor damage to sensitive habitats, and because boat densities continue to rise worldwide, these findings focus attention on discovering why moorings reduce the tendency of boats to anchor on reef as sites become more crowded.

Assessing behavioural and social responses to an eco-mooring trial for Zostera marina conservation management in Torbay, Southwest England

Seagrass beds are critically important habitats delivering a range of ecosystem service benefits that support human wellbeing. They are, however, declining globally at an unprecedented rate. The damaging effects on Zostera marina (Common Eelgrass) seagrass beds in UK waters from mechanical recreational boating activities, namely anchoring and traditional swing mooring scour, suggest that measures of implementing management to mitigate human impacts need prioritising. Eco-moorings, a design that reduces the abrasion pressure of anchoring and mooring on the seabed, are such a mitigation method. In the UK, limited test sites and a lack of social acceptance of the technology compounds the limited uptake of eco-moorings to date. To advance the evidence base, this study focusses on a bespoke eco-mooring design deployed in 2017 to protect seagrass beds within a popular anchorage in Southwest England. We assess the behavioural and social responses of recreational boaters to the trial eco-mooring through 1) mapping of boating activity pre- and post-deployment and 2) structured questionnaires both on-site and online to local and national audiences respectively. Results of mapped boating activity demonstrated a shoreward distribution shift of anchoring away from the deployed eco-mooring, with 45.4% of all anchoring vessels directly within or within a range of potential influence of the seagrass bed. Through the deployment of the eco-mooring (where no mooring previously existed), an estimated additional 20% of anchoring pressure was alleviated from the seagrass bed. A total of 89.6% of on-site respondents reacted positively to the prospect of further eco-moorings being deployed locally. When questioned, 74.6% of on-site and 82.8% of online respondents demonstrated a preference for the physical action of mooring a vessel over anchoring. This suggests that implementation of eco-moorings in seagrass-dense regions could successfully alleviate anchor damage, especially where over half of respondents indicated an awareness of seagrass presence prior to anchoring their vessel and/or hesitance to cease visiting preferential anchoring sites (sheltered bays). This study recommends targeting conservation guidance at the powerboat community, the dominant group anchoring/mooring in the study area and identified as not currently engaged in seagrass education campaigns. It is proposed that management introduce incentives such as free of charge eco-moorings and/or anchoring charges in Marine Protected Areas/Voluntary No Anchor Zones to conserve and recover seagrass and other sensitive seabed habitats nationally.

Decadal Change in the Population of Dendrogyra cylindrus (Scleractinia: Meandrinidae) in Old Providence and St. Catalina Islands, Colombian Caribbean

The IUCN considers the stony coral Dendrogyra cylindrus as vulnerable. However, there is insufficient information on its population structure and dynamics, conservation status, or extinction risk and population decreases have been inferred from observations of habitat degradation. In 2002 and 2012, surveys using manta tows, circular plots and satellite images were performed in Old Providence and Santa Catalina Islands (Seaflower Biosphere Reserve) to determine changes in the condition and structure of a local population of D. cylindrus and its habitat. Size-frequency histograms were asymmetric and leptokurtic, showing positive distribution induced by colony fragmentation, which is indicative of reef degradation. Signs of degradation were more evident in 2012, when partial mortality of living tissue in the parent colony yielded 96.6% of the asexually produced fragments. Most of the fragments were from larger colonies (≥115cm), which exhibited the highest partial and total mortality (˃50%). Three of the four benthic habitats used by the species in 2002 were seen in 2012, but with reduced areas. The results suggest that the reduction of living tissue, the dominance of colonies produced asexually, and reduced size of fragments limit population growth and species viability in an unfavorable and changing habitat within this marine protected area (MPA) of the southwestern Caribbean. In the west of the reef complex of Old Providence, a synergy of multiple stressors could cause the habitat degradation and the fragmentation of colonies, limiting the potential recovery of the species and therefore the ability to create a healthy, genetically diverse and resilient population. Thus, these stressors must be minimized to prevent local extinction. Monitoring the population trends and recording sexual recruitment continues to be vital to understand the larvae’s habitat selection and determine whether these habitats are suitable for the survival of coral recruits. Other stressors to be monitored include anchor damage, diseases and bleaching. We recommend the MPA management program to include specific plans of conservation, recovery and restoration for coral reef builders species like D. cylindrus.

On-line monitoring system of 35 kV 3-core submarine power cable based on φ-OTDR

Submarine power cables are important in power transmission for islands, sea platform and wind plant. They are lying under the sea and endure the threatening of anchor while there is no effective method to find the anchor damage in time. In order to solve the problem, the anchor damage detection of submarine power cable based on φ-OTDR is proposed. The frequency measurement range of φ-OTDR has been tested as 0–800 Hz which can satisfy the requirement of optical fiber vibration sensing in submarine power cable. An optical fiber vibration monitor system is realized and put into service in a 35 kV three-core submarine power cable laid between two islands in China. The anchor drop and anchor drag incidents have been simulated. The vibration data of calm sea, anchor drop and anchor drag have been obtained and analyzed. Analysis results indicate that there are differences between calm sea, anchor drop and anchor drag in energy and amplitude distribution, the faults can be identified according to the differences. The anchor damage detection method proposed in this paper provides a feasible scheme for the on-line monitoring of the submarine power cable, which can early warn and alarm the anchor damage to submarine power cables.

Coral reef health and management on the verge of a tourism boom: A case study from Miches, Dominican Republic

The Miches Municipality lies in the second poorest province in the Dominican Republic, and its inhabitants rely heavily on nearby coral reefs for food and livelihoods. With the sudden influx of tourism from the completion of a new highway, now is a crucial time to ensure that future tourist development in this region is locally driven and environmentally responsible. As coral reefs are a foundation of Miches' identity, economy, and natural wealth, they play an integral role in the realization of this goal. This study employed global reef monitoring protocols to conduct the first-ever quantitative health assessment of Miches' reefs in order to guide future management practices. Surveys of multi-taxa indicator species were conducted alongside assessments of coral bleaching, disease prevalence, and evidence of anthropogenic impacts. Key findings include extremely low abundances of fishery-targeted species, high prevalence of diseased coral, anchor damage at nearly every site, and high abundances of indicator species for nutrient-based pollution such as fertilizers and raw sewage. Deeper, offshore reefs exhibited better health than shallow, inshore reefs, though they were still more degraded than comparable reefs in Dominican marine protected areas. Overall, Miches reefs are highly threatened by four main factors: overfishing, land-based pollution, human-related structural damage, and coral bleaching. To improve the well-being of the region's coral reefs and the communities that depend on them, an adaptive management plan is recommended that encompasses strong fisheries regulations, basic yet consistent monitoring efforts, and the integration of land-based and marine management practices.

Episodic Disturbance from Boat Anchoring Is a Major Contributor to, but Does Not Alter the Trajectory of, Long-Term Coral Reef Decline.

Isolating the relative effects of episodic disturbances and chronic stressors on long-term community change is challenging. We assessed the impact of an episodic disturbance associated with human visitation (boat anchoring) relative to other drivers of long-term change on coral reefs. A one-time anchoring event at Crab Cove, British Virgin Islands, in 2004 caused rapid losses of coral and reef structural complexity that were equal to the cumulative decline over 23 years observed at an adjacent site. The abundance of small site-attached reef fishes dropped by approximately one quarter after the anchoring event, but this drop was not immediate and only fully apparent two years after the anchoring event. There was no obvious recovery from the impact, and no evidence that this episodic impact accelerated or retarded subsequent declines from other causes. This apparent lack of synergism between the effect of this episodic human impact and other chronic stressors is consistent with the few other long-term studies of episodic impacts, and suggests that action to mitigate anchor damage should yield predictable benefits.

Decreasing seagrass density negatively influences associated fauna.

Seagrass meadows globally are disappearing at a rapid rate with physical disturbances being one of the major drivers of this habitat loss. Disturbance of seagrass can lead to fragmentation, a reduction in shoot density, canopy height and coverage, and potentially permanent loss of habitat. Despite being such a widespread issue, knowledge of how such small scale change affects the spatial distribution and abundances of motile fauna remains limited. The present study investigated fish and macro faunal community response patterns to a range of habitat variables (shoot length, cover and density), including individual species habitat preferences within a disturbed and patchy intertidal seagrass meadow. Multivariate analysis showed a measurable effect of variable seagrass cover on the abundance and distribution of the fauna, with species specific preferences to both high and low seagrass cover seagrass. The faunal community composition varied significantly with increasing/decreasing cover. The faunal species composition of low cover seagrass was more similar to sandy control plots than to higher cover seagrass. Shannon Wiener Diversity (H′) and species richness was significantly higher in high cover seagrass than in low cover seagrass, indicating increasing habitat value as density increases. The results of this study underline how the impacts of small scale disturbances from factors such as anchor damage, boat moorings and intertidal vehicle use on seagrass meadows that reduce shoot density and cover can impact upon associated fauna. These impacts have negative consequences for the delivery of ecosystem services such as the provision of nursery habitat.

Distribution and spatial modelling of a soft coral habitat in the Port Stephens–Great Lakes Marine Park: implications for management

Habitat mapping is a useful method for understanding the complex spatial relationships that exist in the marine environment, and is used to evaluate the effectiveness of management strategies, particularly in regards to marine protected areas. This study explored the observed and predicted distribution of an uncommon soft coral species, Dendronephthya australis within the Port Stephens–Great Lakes Marine Park. Dendronephthya australis was mapped by video operated by a SCUBA diver towing a time synchronised GPS. A species distribution model was created to explore the possible occurrence of D. australis outside of the mapped area, using four environmental parameters: bathymetry, slope of seabed, velocity of tidal currents, and distance from estuary mouth. Dendronephthya australis colonies occurred along the southern shoreline in the Port Stephens estuary between Fly Point and Corlette Point, but no colonies were found within sanctuary (no-take) zones within the marine park. The model illustrated limited habitat suitability for D. australis within a larger section of the estuary, suggesting this species has specific environmental requirements survival. Owing to its current threats (anchor damage and fishing line entanglement), implications from these findings will assist future management and protection decisions, particularly in regard to its protection within a marine park.

The Research and Design of Monitoring System for Submarine Cables

SOFC laid in complicated Marine environment, are extremely vulnerable to all kinds of external factors, and anchor damage is the biggest threat to submarine cable communication. In order to overcome the limitations of existing SOFC monitoring technology, the double M-Z distributed optical fiber sensing technology is selected to apply in on-line monitoring of SOFC, and the monitoring system is designed both in software and hardware. The optimization scheme of being in conjunction with monitoring and control system of SOFC is put forward in anticipation of the possible problem of false alarm in the future application of the monitoring system.