Area "H" encompasses the northern portion of the Harold Ireland Trail and a section of the Sunset Loop Trail. Erosion features 23 and 26 are related to the lack of water bars and non-maintained water bars, respectively. Erosion features 24 and 25 are related to stream water flowing across the trail. The Harold Ireland Trail was constructed across two small stream channels with no provision made for stream water to safely cross the trail. In the winter during high stream flows, the trail fill prevents the stream from flowing down the channel and diverts the water onto the trail. The result of this process has been the formation of large rills and gullies. One of these rills transports water from erosion feature 24, off the Harold Ireland Trail, through the brush, onto the Sunset Loop Trail, ultimately causing the rill erosion at feature 22.

Areas "I" and "J" (Figure 1) are located in the redwood forest in the southern portion of the park. The Big Trees Trail traverses through Areas "I" and "J" and is less compacted than other trails in the park. The trail is cut into extremely soft soils and has redwood tree roots exposed on many sections. There are numerous "bootleg" trails between the Sequoia Bayview and Big Trees Trails. Based on trampled vegetation and step holds many of these trails have been created by hikers walking off the trail (see understory vegetation below), although in other places narrow grooves and skids indicate that some of these trails have been created by bicyclists riding off the trail. Erosion features 20A and 20B, in the vicinity of Area "J", are two grooves that appear to be related to bicyclists slowing down or braking on a sharp corner.

Area "K" encompasses the Upper Palos Colorados Trail located between the Sequoia Bayview Trail and Sunset Trail. The Upper Palos Colorados Trail traverses a steep northeast facing hillslope that drains into Palo Seco Creek. The trail has similar soil, width, and compaction characteristics to the Big Trees Trail. Surface water flowing down the trail in Area "K" has eroded soil in between the exposed roots. Erosion feature 21, located at the upper entrance to the trail, is the result of surface water flowing down the trail. Recreational land use may be causing the two rills to expand.

Surface water runoff was determined to be the dominant erosion mechanism acting on the park trails. Erosion generated by horses, bicycles, and hikers was determined to be a minor erosion mechanism on established park trails. However, recreational use was determined to be major source of soil erosion on "bootleg" trails. We noted many off trail hiking and biking tracks throughout the park. Hiking tracks were identified based on trampled plants, footprints, and the presence of step holds. Bicycle tracks were identified based on skid tracks through soft soils and narrow grooves. We observed that these "bootleg" trails often break through the soil O horizons exposing the erodible A horizons. With continued use, bicycle tracks begin to remove A horizon material, forming a groove that becomes progressively deeper. Hiking tracks expose and compact the A horizons and trample vegetation, making it difficult or impossible for the trail tread to naturally recover. Because the most fertile layer has been stripped, roots may have difficulty penetrating the compacted soil, and the trail may be eroding too rapidly for new plants to become established. Many of these trails, both hiking and bicycle, are oriented directly downhill, facilitating the rapid flow of water that deepens the tracks. One particularly bad "bootleg" trail begins near the DAR monument on the Big Trees Trail and ends near the junction of Fern Trail and the Sequoia Bayview Trail. Bicycle traffic on this trail has eroded a deep rill in the soft redwood soil.