On and Off-Trail Hiking Impacts on Soil Infiltration Rate: A Case Study from UCR Botanical Garden

Over the past century, the number of outdoor recreationists has steadily increased, reflected in official visitation records and the growth of outdoor infrastructure and tourism economies.
Although outdoor recreation is a healthy and low-cost pastime, the increased frequency of pedestrian use can have negative consequences. Leave No Trace principles practiced by backcountry adventurers are increasingly more critical in the front country as recreation areas see more and more visitors. Traveling on durable surfaces (or the official trail) is an intrinsic component of Leave No Trace since deviations from officially designated trails to reduce vegetation and compress soils. Repetitive trampling deteriorates underfoot vegetation and forms a path that widens and deepens, exposing the soil surface to other erosive forces such as raindrop splash, wind, and overland flow. Pressure from footsteps compacts the soil surface, reducing soil porosity and structure. The reduction of surficial pores inhibits infiltration rates, reduces capacity, and results in ponding in flat and low relief areas. This study evaluates the effect of on and off-trail hiking on soil infiltration rates. Using SATURO (Dual Head Infiltrometer), we measured saturated hydraulic conductivity at six different sites, representing a diversity of location, vegetative composition, trail difficulty, slopes, and elevations within the University of California Riverside Botanical Garden. Each site included sampling points from undisturbed areas (unimpacted vegetation), disturbed (unofficial trails), and official trails. The results showed that deviating from the official trail reduced saturated hydraulic conductivity with an average percent difference of 70.35±27.96% between undisturbed areas and official trails and 61.08±34.27% between undisturbed areas and unofficial trails.