# Navigational Risk Assessment in Offshore Wind Farms Using Spatial Ship Domain Models
###### Abstract
Evaluating how hazards ahead of the ship's bow, astern of the ship's aft and on the port and starboard sides, along with under-keel and over-head clearance requirements, influence the determination of safe navigation within Offshore Wind Farms (OWFs) areas by: 1. Determining the navigational risk numeric indicators (R\({}_{\text{NLF}}\), R\({}_{\text{NLA}}\), R\({}_{\text{NWP}}\), and R\({}_{\text{NWS}}\)) with respect to maintaining the required safe distance ahead of the ship's bow, behind its stern, and on the ship's port and starboard sides. This is carried out using the PIANC guidelines and the 2D ship domain model by [PERSON] [20] and [PERSON] [23; 24]. This includes consideration of the stopping maneuveres by reversing the engine from Full Ahead to Full Astem (FSAH-FAS), and from Half Ahead to Full Astem (HAH-FAS), as well as the turning circle maneuver at FSAH with a rudder angle of 35\({}^{\circ}\) starboard. 2. Determining the numeric indicators of navigational risk (R\({}_{\text{NND}}\) and R\({}_{\text{NH}}\)) related to maintaining the required under-keel and over-head clearance to ensure the safety of vessel traffic lanes for representative ship types navigating within OWF areas. This is based on the 3D ship domain model by [PERSON] [8; 23; 25]. 2. Identifying vessels that may pose specific risks to OWF operations, and determining vessel types that are considered safe and could be permitted to navigate or fish in or around OWF zones. 3. Comparing the domain parameters for the selected vessels based on the PIANC guidelines, [PERSON]'s 2D model, and [PERSON]'s 3D model, across the OX, OY, and OZ planes. To enhance clarity, Table 1 summarizes the abbreviations used throughout this manuscript to support the reader's understanding of the technical terminology related to navigational risk assessment and offshore wind farm operations. Figure 1: Illustrative drawing of the simplified and composite three-dimensional (3D) ship domain model by [PERSON], based on [8]. The model dimensions include \(SD_{L}\)—the domain’s length; \(SD_{W}\)—its width; \(SD_{D}\)—its depth; and \(SD_{H}\)—its height. Figure 2: A graphical representation of navigational risk indicators (\(R_{N}\)) based on ship domain parameters (\(SD_{LF}\), \(SD_{LA}\), \(SD_{WP}\), \(SD_{WS}\)) and the proximity to the closest navigational obstruction (\(\mathrm{d}_{N}\)). \begin{table}
\begin{tabular}{c l} \hline \hline
**Abbreviation** & \multicolumn{1}{c}{**Full Term**} \\ \hline ADT & Ship’s Air Draft (\(\mathrm{H}_{\mathrm{N}}\)), the vertical height of the ship’s highest point above the waterline \\ COLREG & International Regulations for Preventing Collisions at Sea \\ \(\mathrm{d}_{\mathrm{N}}\) & Distance to the nearest navigational danger (hazard) \\ ECDIS & Electronic Chart Display and Information System \\ EEZ & Exclusive Economic Zone \\ FAS & Full Astern \\ FSAH & Full Speed Ahead \\ HAH & Half Ahead \\ IMO & International Maritime Organization \\ OHC & Over-Head Clearance \\ OWF & Offshore Wind Farm \\ OWT & Offshore Wind Turbine \\ PIANC & World Association for Waterborne Transport Infrastructure \\ RL & Risk Level \\ RND & Vertical component of the navigational risk indicator (\(R_{N}\)) that concerns keeping an adequate \\ RNH & Vertical component of the navigational risk indicator (\(R_{N}\)) that concerns keeping an adequate \\ RNH & required over-head clearance (OHC) or air draft clearance \\ RNLF & Horizontal component of the navigational risk indicator (\(R_{N}\)) that concerns keeping an adequate \\ \end{tabular}
\end{table} 
Table 1: List of abbreviations used in the manuscript.