Bridges and other structures also protect riparian areas from the effects of trails and their use, such as mechanical disturbance and the gas and oil leaks from motorized vehicles that are devastating to aquatic environments. The other important step in developing a trail, in addition to the inventory, is to know the purpose. A well-planned trail is designed to accomplish the particular purpose. A family trail used a few times a year or a cross country ski trail used only in winter are very different, in terms of potential impact and design standards, from a public trail that will be used year-round by many people. Type of use, frequency of use, and seasons of use all need to be reflected in the design and construction of trails.
Foot traffic has different impacts than do motorized vehicles.
Soil erosion from poor trail design affects vegetation, water movement and habitat. We can come to thoughtful decisions, as individuals, groups and communities, about an ecological balance that includes humans. It takes time to know the land and make decisions about trail siting, design and use. Observation and inventory of the land takes place over an entire cycle of seasons. An area that is dry in August may be wet in April, with implications for trail siting and design.