Shortcut Trails at Fossil Ridge: Measuring and Fixing Erosion

The Trouble with Shortcuts

1Ms. Yolanda Restrepo's sixth graders spent a day at Fossil Ridge State Park on a geology field trip. Visitors may collect loose fossil shells from a gravel bed at the bottom of the ridge, where the shells have weathered out of old limestone layers. A gravel trail zigzags from the parking lot at the top of the hill down to the fossil bed. Many visitors skip the zigzags and walk straight down the steep slope instead. Their footsteps have worn several bare shortcut paths into the hillside.

2Ranger Dmitri Volkov showed the class what happens next. Where feet crush the plants, rain runs straight down the bare paths and carries soil with it. Small gullies form, and mud washes over the fossil bed and into Ridge Creek below. To monitor the problem, the ranger pushed steel erosion pins into the ground at four places on the same slope last April. When each pin was set, its top stood 5.0 cm above the soil. As soil washes away, more of the pin shows. At each pin, the ranger also recorded plant cover: the percent of a 1 m by 1 m frame that plants covered. All four places got the same rain from April to October.

3This year, the park tested three fixes on three shortcut paths that were about equally steep and equally busy. All three paths are on the same ridge and got the same rain. Path A got no fix. Path B got "Please stay on the trail" signs at the top and bottom. Path C got a sign, a row of logs across its top, and young native plants set into the bare soil. A trail camera counted hikers on each path, and new erosion pins measured the soil lost from May to October.

4The park has set its goals for all six shortcut paths on the ridge. Each path should lose less than 1 cm of soil from May to October, and visitors must still be able to reach the fossil bed by the zigzag trail. The project can spend no more than $11,000 in all.