This study began as an attempt to develop a statewide thematic approach to surveying the ditches and canals which are a commonly encountered, but previously little studied, property type in California. In the past, canals were not always recognized as a type of cultural resource that might need study, and furthermore, although highways and other transportation facilities often intersect artificial waterways, projects that merely cross linear resources typically have little potential to affect them. As a result, structures such as canals, railroads, or roads that were bridged by a transportation project were rarely included in cultural resource studies.
Now there is increased awareness that canals and other water conveyance facilities can be historically significant, and that when projects do have the potential to affect them, they need to be studied systematically. However, important water conveyance systems are frequently extensive and sometimes quite complex, while transportation project effects on them are typically limited to a small segment of the entire property. Under these circumstances, developing a basic historical context would allow researchers to work from a baseline of existing knowledge, thus helping to achieve a suitable balance between the need for adequate information and expenditure of a reasonable level of effort.
Because of California’s unique combination of natural resources, climate, topography, history, and development patterns, the state has a variety and number of water conveyance systems possessed by few if any other states. Consequently, little guidance has been developed at a national or regional level, leaving California to develop its own statewide historic context and methodology. Sufficient research has now been conducted on California’s water conveyance systems to provide this historic context and survey methodology for the appropriate consideration of water conveyance systems, especially the frequently encountered canals and ditches, in order to take into account the effect of transportation projects on historic water conveyance facilities.