Small Craft Harbour Design

Understanding Small Craft Harbour Design in Atlantic Canada

Small craft harbours serve as vital economic lifelines for coastal communities throughout Atlantic Canada, supporting commercial fishing operations, recreational boating, and marine tourism. In Nova Scotia alone, the Department of Fisheries and Oceans Canada (DFO) maintains over 180 small craft harbours, representing a significant portion of the national network that generates billions of dollars in economic activity annually. The design of these facilities requires a sophisticated understanding of marine engineering principles, local environmental conditions, and the specific operational needs of harbour users.

For engineering firms operating in the Maritime provinces, small craft harbour design presents unique challenges that demand expertise in coastal processes, structural engineering, and environmental stewardship. The harsh North Atlantic environment, characterized by significant tidal ranges, storm surge events, and ice loading conditions, requires robust design solutions that can withstand decades of service while remaining economically viable for the communities they serve.

Site Assessment and Feasibility Analysis

The foundation of any successful small craft harbour project begins with comprehensive site assessment and feasibility analysis. This critical phase establishes the technical and economic parameters that will guide all subsequent design decisions.

Bathymetric and Topographic Surveys

Accurate bathymetric data forms the cornerstone of harbour design. Modern multibeam sonar systems can achieve vertical accuracies of ±0.15 metres in typical harbour depths, providing the detailed seabed information necessary for dredging calculations, breakwater siting, and berth layout optimization. In Nova Scotia's Bay of Fundy region, where tidal ranges can exceed 12 metres, survey timing must account for the full tidal cycle to capture both navigation channel depths and intertidal zone characteristics.

Topographic surveys of the upland areas must integrate seamlessly with bathymetric data, typically referenced to the Canadian Geodetic Vertical Datum (CGVD2013). This integration is essential for designing wharves, boat ramps, and shore-side facilities that function effectively across all tide and weather conditions.

Geotechnical Investigations

Subsurface conditions along the Atlantic Canadian coastline vary dramatically, from the granite bedrock of the Atlantic coast to the softer sedimentary formations found in the Gulf of St. Lawrence region. A typical geotechnical investigation for small craft harbour design includes:

• Borehole drilling to depths of 15-30 metres below seabed level

• Standard Penetration Testing (SPT) at 1.5-metre intervals

• Undisturbed sampling for laboratory analysis of soil strength parameters

• Cone Penetration Testing (CPT) to characterize stratigraphic variations

• Laboratory testing for grain size distribution, Atterberg limits, and consolidation characteristics

In areas where glacial till or marine clay deposits are present, careful attention must be paid to settlement analysis and foundation design. The sensitive marine clays found in parts of Cape Breton and the Northumberland Strait region can exhibit significant long-term consolidation settlement under structural loads.

Metocean Data Collection

Understanding the wave climate, currents, and water level variations at a harbour site is essential for designing structures that will perform reliably throughout their design life. Wave data collection typically involves deployment of directional wave buoys for a minimum of one year, supplemented by hindcast modelling using historical wind records extending back 30-50 years.

For harbours along the Nova Scotia coast, design wave heights for 50-year return period events typically range from 3-6 metres in exposed locations, with corresponding wave periods of 8-12 seconds. These parameters drive the design of breakwater armour units, crest elevations, and structural loading calculations.

Breakwater and Coastal Protection Design

Breakwaters represent the most substantial engineering structures in small craft harbour development, providing the wave sheltering necessary for safe vessel operations and mooring. The selection of breakwater type depends on site-specific factors including water depth, wave climate, foundation conditions, and available construction materials.

Rubble Mound Breakwaters

Rubble mound breakwaters remain the most common choice for small craft harbours in Atlantic Canada, owing to their flexibility in construction, ability to accommodate settlement, and relative ease of repair. A typical cross-section includes:

• Core material: Quarry run stone, typically 1-500 kg

• Filter layer: 500-2,000 kg stone to prevent core material migration

• Armour layer: Primary protection using 5-15 tonne stone or concrete armour units

• Crest structure: Cast-in-place concrete cap for access and overtopping control

Armour stone sizing follows the Hudson formula or Van der Meer equations, with stability coefficients adjusted for the specific stone shape and placement method. For exposed Atlantic coast locations, armour stone requirements of 10-15 tonnes are common, necessitating careful sourcing from regional quarries capable of producing such large, angular stones.

Vertical Wall Structures

In locations where space is limited or deep water extends close to shore, vertical wall breakwaters may offer advantages over rubble mound alternatives. Concrete caisson structures, typically founded on prepared stone beds, can provide both wave protection and berthing functions. However, the higher reflected wave energy and more demanding foundation requirements make these structures less common in Nova Scotia's variable coastal geology.

Ice Loading Considerations

Small craft harbour structures in Atlantic Canada must be designed to resist ice forces that can reach 500-1,500 kN per metre of structure width depending on location and ice conditions. The Northumberland Strait and Gulf of St. Lawrence regions experience the most severe ice conditions, with consolidated ice thicknesses reaching 0.6-1.0 metres in typical winters. Design approaches include:

• Sloped faces on breakwater heads to promote ice ride-up rather than crushing failure

• Ice deflector cones on vertical pile structures

• Increased structural reinforcement in the ice impact zone

• Sacrificial fender systems to absorb ice contact forces

Wharf and Berthing Facility Design

Wharves and berthing facilities must accommodate the operational needs of harbour users while withstanding the combined effects of vessel loads, environmental forces, and the corrosive marine environment. Design life expectations of 50-75 years require careful attention to materials selection and durability provisions.

Structural Systems

Common wharf structural systems for Atlantic Canadian small craft harbours include:

Timber crib wharves: Traditional construction method using interlocking timber cribs filled with stone ballast. While increasingly replaced by modern alternatives, timber cribs remain cost-effective for certain applications and can achieve service lives of 30-50 years with proper maintenance.

Steel pipe pile structures: Hollow steel pipe piles driven to refusal in bedrock or dense till, supporting precast or cast-in-place concrete deck systems. Typical pile diameters range from 400-600 mm with wall thicknesses of 12-20 mm. Corrosion protection through coating systems and sacrificial steel allowances extends service life in the aggressive marine environment.

Concrete sheet pile bulkheads: Prestressed concrete sheet piles driven in interlocking configuration provide both earth retention and berthing face functions. This system works well in softer soil conditions where driving to depth is practical.

Deck Elevations and Freeboards

Establishing appropriate wharf deck elevations requires balancing operational convenience against flood and wave overtopping risks. In the Bay of Fundy region, where extreme high water levels can exceed 8 metres above chart datum, deck elevations of 9-10 metres above chart datum are common. This provides adequate freeboard for vessel loading operations while maintaining reasonable distances for cargo handling.

Climate change projections for sea level rise in Atlantic Canada range from 0.3-1.0 metres by 2100, depending on emission scenarios. Current best practice incorporates these projections into design elevations, often through provisions for future deck raising or acceptance of increased overtopping frequency in later years of the structure's service life.

Fendering and Mooring Systems

Fender systems must absorb the kinetic energy of berthing vessels while limiting reaction forces transmitted to the wharf structure. For small craft harbours accommodating vessels up to 20 metres in length, typical fender designs include:

• Rubber cylindrical fenders, 200-400 mm diameter

• Composite plastic lumber fender piles

• Extruded rubber D-type or arch fenders for heavier vessels

Mooring hardware must accommodate the full range of vessels using the facility, with bollard capacities typically ranging from 50-200 kN for small craft applications. Bollard spacing of 10-15 metres along wharf faces provides flexibility for various vessel lengths.

Dredging and Navigation Channel Design

Maintaining adequate water depths for vessel access often requires initial capital dredging and ongoing maintenance dredging programs. Channel design must balance the needs of harbour users against the environmental impacts and costs associated with dredging operations.

Channel Geometry

Navigation channel dimensions follow guidelines established in PIANC (World Association for Waterborne Transport Infrastructure) publications, with modifications for local conditions. For small craft harbours, typical design parameters include:

• Channel width: 3-5 times the beam of the design vessel for one-way traffic

• Channel depth: Design vessel draught plus 0.6-1.5 metres underkeel clearance

• Turning basin diameter: 2-3 times the length of the largest vessel to be accommodated

In areas with significant tidal ranges, designers must decide whether to provide full-tide access or limit operations to specific tidal windows. Economic analysis comparing deeper dredging costs against operational restrictions typically guides this decision.

Sediment Transport and Maintenance Requirements

Understanding sediment transport patterns is crucial for predicting maintenance dredging requirements and designing harbour layouts that minimize sediment accumulation. Coastal sediment transport along Nova Scotia's shorelines can exceed 10,000-50,000 cubic metres per year in active littoral zones.

Harbour entrance orientation relative to predominant wave directions significantly affects shoaling rates. Where possible, entrance channels should be aligned perpendicular to the dominant wave direction to minimize wave-driven sediment transport into the protected basin.

Environmental Considerations and Regulatory Compliance

Small craft harbour projects in Canada must satisfy requirements under the Fisheries Act, Canadian Environmental Assessment Act, and various provincial regulations. Early engagement with regulatory authorities, including DFO, Environment and Climate Change Canada, and Nova Scotia Environment and Climate Change, is essential for project success.

Fish Habitat Protection

The Fisheries Act prohibits harmful alteration, disruption, or destruction of fish habitat without appropriate authorizations. Harbour projects typically require detailed fish habitat assessments documenting existing conditions and proposed mitigation measures. Common mitigation approaches include:

• Construction timing windows that avoid sensitive spawning periods

• Sediment control measures during dredging and construction

• Habitat compensation through restoration or enhancement projects

• Marine mammal monitoring programs during pile driving operations

Species at Risk Considerations

Atlantic Canadian waters support several species at risk, including North Atlantic Right Whales, Atlantic Salmon, and various marine bird species. Project planning must assess potential interactions with these species and incorporate appropriate protective measures.

Project Delivery and Construction Considerations

Successful small craft harbour projects require careful coordination of marine construction activities, often within constrained working seasons and challenging weather windows. Construction typically proceeds during the calmer summer months, with marine work limited to periods of favourable wave and current conditions.

Local construction expertise in Atlantic Canada has developed specialized capabilities for marine work, including experience with difficult foundation conditions, ice-affected structures, and remote site logistics. Engaging experienced marine contractors early in the project development process helps identify constructability issues and optimize designs for efficient construction.

Partner with Sangster Engineering Ltd. for Your Harbour Project

Small craft harbour design demands a comprehensive understanding of marine engineering principles combined with intimate knowledge of local conditions throughout Atlantic Canada. From initial feasibility studies through detailed design and construction administration, every project phase requires careful attention to technical requirements, regulatory compliance, and stakeholder needs.

Sangster Engineering Ltd. brings decades of experience in coastal and marine engineering to small craft harbour projects across Nova Scotia and the Maritime provinces. Our team understands the unique challenges of designing for the North Atlantic environment and maintains strong relationships with regulatory agencies and construction contractors throughout the region.

Whether you are planning a new harbour development, upgrading existing facilities, or addressing maintenance and rehabilitation needs, contact Sangster Engineering Ltd. in Amherst, Nova Scotia, to discuss how our expertise can support your project's success. Our commitment to technical excellence and practical, cost-effective solutions makes us the trusted engineering partner for marine infrastructure projects throughout Atlantic Canada.

Partner with Sangster Engineering

At Sangster Engineering Ltd. in Amherst, Nova Scotia, we bring decades of engineering experience to every project. Serving clients across Atlantic Canada and beyond.

Contact us today to discuss your engineering needs.