Designing, And Constructing Seaplane Base Facilities Chapter 2



a. Demand. Aeronautical demand is the number of seaplanes and/or seaplane operations a community has and an estimate of how many it will have in the future.

b. Use. Factors in addition to typical aviation activity which may justify a seaplane base are:

(1) geographical isolation;
(2) lack of land airports;
(3) special flight activities; and
(4) recreational access.

c. Potential. When urban populations abut suitable water operating areas, potential exists for a community seaplane base. The community need and proximity to the suitable water operating area influence the size of a seaplane base. Resident pilot operations plus fixed base operator activities will constitute the primary use. Fixed base operators may use seaplanes to provide charter, student training, aerial photography, and air cargo services. In emergencies, seaplanes can evacuate people and deliver food and medical supplies. The combination of these activities constitutes the need for a seaplane facility.


A forecast of the number of seaplanes to be based at a seaplane facility, currently and within five years, is suggested. The five year forecasted need will assist in identifying the appropriate size and support requirements for the seaplane base.


a. Size. The size of the water operating area depends on: the performance characteristics of the seaplanes using the site, existing or potential obstructions in the surrounding area, water currents, and wave action.

b. Location. The location of the water operating area and related shore development is influenced by:

(1) number aircraft expected to use the site;
(2) proximity of airports and other seaplane bases;
(3) accessibility to shore support;
(4) character of development of the surrounding area;
(5) atmospheric and meteorological conditions, such as fog, wind, and smoke;
(6) river geography, shifting channels, swells;
(7) ship and boating activity; and
(8) local regulations, and noise considerations.

c. Coordinated Use. Although each community and site is different, a relationship does exist, and operational use of seaplanes must be coordinated with other users and interested parties in the area. Ample maneuvering and turning areas should be provided with considerations made for shipping, pleasure boats, prevailing winds, and currents.


a. Populated Areas. The approach and departure paths should be clear of established shipping or boating lanes. An overwater approach is preferable to an approach/departure path over populated areas, beaches, and shore developments. Where surrounding development mitigates against straight-in approach and/or straight-out departure paths, an overwater climbing turn or letdown procedure may be possible.

b. Operational Limitations. The approach and departure paths should be clear of hazards. If an obstruction to air navigation, determined to be a hazard, cannot be altered or removed, the FAA will impose aircraft operational limitations, such as, limit the type of aircraft operations, to mitigate the hazard. Lighting, or marking obstructions to air navigation is frequently sufficient to preclude an object being a hazard and avoid the need for operational limitations.


When selecting a site, it is necessary to choose one that has adequate length, width, and depth dimensions, as well as an unobstructed approach and departure path for the type of seaplanes to be accommodated.

a. Current Flow. Landing and takeoff areas should be located where the currents are less than 3.5 mph (5.5 km/h). Where currents exceed this recommendation, provisions should be made to allow space to accommodate handling difficulties particularly in the slow taxiing mode used to approach a floating dock or in beaching operations. It is preferable to have the current flow away from the dock or float. Prevailing winds may negate some adverse effect of currents. The following locations should be avoided:

(1) currents that exceed 7 mph (12 km/h);

(2) a location where water turbulence is caused by a sharp bend in the river, the confluence of two currents, or a locations where rip tides are prevalent; and

(3) river rapids.

b. Water Level. As a general rule, if the change in water level exceeds 18 - 24 inches (45 - 60 cm), floating structures or moderately inclined beaching facilities may be necessary to accommodate aircraft at the shoreline or waterfront area. Where water level variations exceed 6 feet (2 m), special or expanded development may be required to dock the aircraft, such as, a dredged channel, an extended pier, or special hoisting equipment.


a. Wave Height. The most desirable conditions exist where the surface of the water is moderately disturbed. Locations where large swells occur, or are frequently created by deep draft vessels and/or tugboats, should be avoided.

b. Floating Debris. Areas subject to excessive debris or debris over extended periods of time should be avoided. Logs are not only a hazard to aircraft, but also to docking facilities constructed in the river. A floating log moving at river speed has considerable momentum and the potential for destruction when it impacts a fixed object.


A sheltered mooring or anchorage area, protected from winds and currents, is recommended. A cove, small bay, or other protected area is ideal and can normally be expanded to include docking facilities and on-shore parking areas.


a. Operational Flexibility. An unmarked sea lane or water operating area is normally the choice of seaplane pilots. This allows the pilot to take advantage of the entire water area in order to adjust landing and takeoff operations for current, wind, and waves.

b. Prevailing Winds. If a sea lane is designated, it should be aligned to provide maximum wind coverage. It may be desirable to limit wind analyses to wind data taken during daylight hours since seaplane operations are almost nil after dark,

c. Wind Data. Recorded wind observations taken in the immediate vicinity of the site over an extended period of time are the most desirable. When local observations are not available, data from a nearby locality or airport can be used. Wind data should be validated by comparing observed wind conditions at the proposed water operating area with winds reported at the nearby location. These comparisons should be made under conditions of high and low wind velocity, from all quadrants, on both clear and cloudy days, and at substantially different temperatures.


a. Type. Soil type and bottom conditions can influence construction of fixed and floating dock structures, as well as affect taxi operations from the water operating area to the shoreline facility. Mud bottoms ordinarily present little or no difficulty. A hard bottom, such as shale or solid rock, can make construction of fixed and off-shore structures difficult and costly. Anchors tend to drag over this type of bottom unless specially designed mooring anchors are used.

b. Conditions. Artificial bodies of water such as reservoirs often contain trees or stumps not completely grubbed before flooding. Debris from the former vegetation can be hazardous to aircraft floats and hulls as it rises to the surface or remains partially submerged. Objects that project from the bottom and constitute a water hazard should be removed. If this is impractical, then the objects should be conspicuously marked to alert users to their presence.


The location of bird sanctuaries or areas that attract flocks of birds should be considered when orienting water operating areas. Waterways historically used by large flocks of birds should be avoided.


In seeking approval for establishment of a seaplane base, the permitting authority may require an environmental analysis. This evaluation should include an analysis of the proposals impact on water quality, wildlife, existing and proposed land use, noise, and historical/archeological factors. The design of fueling facilities and storage areas should comply with local regulations and accepted measures for pollution prevention. Order 5050.4, Airport Environmental Handbook, should be followed for an environmental study if Federal financial aid is involved. State Environment Policy Act (SEPA) may also apply to the development of a seaplane base.


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