There are many aspects of trail design that combine to create a smooth-flowing, appealing, and sustainable trail, and where implemented successfully, these should result in minimum impact. Trail design techniques for minimising soil loss are addressed in this resource sheet.
Soil loss on trails is greatly influenced by the grade, soil characteristics and slope alignment angle of the trail, as well as tread (trail path) drainage and amount of rock in the surface material to a lesser extent. These issues can be managed to allow for a high level of trail usage whilst maintaining trail condition.
Soil type varies greatly even within trail networks and individual locations, as does their ability to retain or drain water, the susceptibility to compaction and erosion, and stability. The texture of a soil is important in predicting the behaviour of trail tread; loamy soils are usually best to maintain soil cohesion whist allowing for drainage. For the South West conditions, sites with well-graded soils (including a range of particle sizes), are most suitable, particularly for curves which receive a high level of lateral force from MTBs.
Prevention of major soil displacement can be achieved using berms, smooth trail flow, and tread armouring. The flow of trails can be designed to influence the speed of the riders, such as by maintaining a consistent flow to reduce the need for braking and skidding. Avoiding abrupt changes and sharp corners can prevent trail widening and reduce soil displacement, see image below.
Tread armouring hardens the trail surface (e.g. with imported rocks, gravel, boardwalks), effectively reducing the rider-caused erosion, and used in instances of wet or soft areas where the trail needs to be raised.