The approach to the design of a bridge is intimately tied to the environment and is dictated by the circumstances under which the bridge is to be constructed or to function. Each site is topographically different and the availability of materials and labour varies. Hence each bridge is unique, requires a unique solution, and an original approach from the designer.

The demands which Australia has placed upon its bridge builders are mixed. The early settlements were isolated communities on the flat coastal plain of a relatively flat continent, and neither community requirements nor extreme topography challenged bridge builders to extend existing technology, such as was exerted on the great suspension bridge builders in America. But the settlements were, on the other hand, literally at the end of the earth, being separated by enormous distances and time from Europe, which was the source of new design and development in bridges. In addition the modern materials of the time, such as cast iron, had to be transported vast distances to this country and hence Australian bridge builders needed to rely on their own resourcefulness, bred of isolation, distance and a unique environment.

One manifestation of this unique environment is the behaviour of the rivers in Australia, which is unlike anything experienced in Europe or, indeed, in most other countries of the world. These rivers, like the climate itself, reflect harsh extremes, so that a river channel may be dry for many months of the year, but in flood may carry more water than the Nile in flood (to quote the example of the Ord River). With no records of floods to guide them, the early settlers had to grapple with this strange phenomenon, and even today, when dry river beds can be driven across for much of the year the economic cost of a community isolated by flood waters is a factor against which the provision of a flood-proof and expensive bridge has to be equated.

In solving these problems, Australia has embraced the innovations produced by others and adapted them successfully to the unique situations presented. We have examples of some very fine 19th century bridge engineering provided for the railway expansion, conceived mainly by British engineers working in the then isolation of the Australian hinterland, and we have well developed examples of many of the newer European techniques such as cable-stayed bridges.

The development of bridge technology in Australia began with the rudimentary road systems which were established in the infant European settlements to enable movement around the settlements and, later, the hinterland. Initially the settlements were confined to small coastal or riverine locations and relied heavily on water transport for supplies and communication. As the settlements became more established it was necessary to move further afield to establish farms, gather raw materials and so on. In the early years bridge technology was limited very much to the 18th century European technology of masonry arches and cast iron, the latter still in its infancy and not produced to any great extent in Australia. The demand was for cheap, rapid construction, using readily accessible materials and utilising the abundant availability of convict labour. This, of course, led to simple tree trunk bridges but, as the Colony gained stability, the government looked towards more permanent structures and, as the skills for quarrying and stone dressing became available, masonry bridges began to be designed and built. As all metal materials had to be imported, iron bridges were rarely appropriate and were in any case still too novel for colonial application.

Australian Academy of Technological Sciences and Engineering