The main problem with fords and stepping-stones is how to cross the stream during high water. Although advice on alternative routes can be provided, if flooding occurs frequently and the trail is popular it is better to have bridges. Where people with disabilities are encouraged to use the trail, bridges are a necessity.
Apart from the simplest, shortest spans, bridges are complex structures requiring engineering skills for their design, construction and maintenance. In a recreation context, their design also provides opportunities to enhance the enjoyment of visitors. To this end, consideration should be given to using multidisciplinary teams of engineers, architects and landscape
architects as well as artists for the design and siting of bridges.
There are five main types that might be used in the outdoors, some more appropriate in some places than others:
– simple beam bridges, in which single or multiple beams are supported at both sides of the stream to be crossed;
– trussed beams, in which a larger structure is constructed from small sections joined together for strength;
– cantilever beams, in which the beams are supported at one side only, and they rely on their anchoring and inherent stiffness to support the load;
– arch bridges, in which the construction technique forms an inherently strong structure;
– suspension bridges, in which the walking surface is suspended from tensioned cables fixed to supports on both sides of the stream.