Submarine cables play an integral role in international data transmission and are crucial to the growth of the offshore renewable sector. It is imperative to ensure the adequate protection of submarine cables so that they remain safe from threats such as fishing gear, dredging, anchor strikes, and other dropped objects. The objective of this study is to develop a cable burial risk assessment tool for submarine cable routes. This tool would be used to investigate potential external threats (hazards) that may require additional protection for the cables, and to determine the threatline for each hazard. This paper will provide the methodology used to develop the cable burial risk assessment tool. This tool would be also applicable to telecommunication cable, or subsea power cable to energize an island or for oil and gas offshore field development.
In this paper we introduce an Excel workbook developed for cable burial risk assessments. There are two main factors to address in a cable burial risk assessment. First, what are the risks to the cable? Second, how can this risk be mitigated? The Cable Burial Risk Assessment (CBRA) tool was developed to help answer these questions. This tool focuses on anchor strikes, but it also includes functionality for considering fishing gear and military activity. The workbook also has functions to aid in the development of classification zones based on several different criteria, such as vessel traffic levels, soil types, and fishing intensity.
The risk assessment model evaluates the risk of anchor strike resulting from anchoring outside of designated areas. When a vessel deploys an anchor, the anchor could be dragged along the seabed for some distance before its depth is sufficient to hold the vessel. Therefore, the cable is not only in danger from a direct anchor strike, but also indirect strikes from the dragging of an anchor. The model used in this tool includes specific calculations for anchor drag distance, which is a function of vessel size, vessel speed, anchor type, and soil composition.
The anchor penetration model is an important aspect of cable burial risk assessment. There are several variables that influence the penetration depth of an anchor, including the soil type and the characteristics of the anchor (mass, fluke length, and fluke angle). This tool uses a single model to cover different vessel types, and the factors in the model account for differences in anchor size.
