IMPACTS OF VEHICLES ON NATURAL TERRAIN AT SEVEN SITES IN THE SAN FRANCISCO BAY AREA

The impacts of off-road vehicles on vegetation and soil were investigated at seven representative sites in the San Francisco Bay area. Plant cover of grass and chaparral (with shrubs to 4 m tall) have been stripped by the two- and four-wheel vehicles in use. Impacts on loamy soils include increased surface strength (as much as 275 bars), increased bulk density (averaging 18%) to depths of 90 cm or more, reduction of soil moisture by an average 43% to 30 cm depths, greatly reduced infiltration, extension of the diurnal temperature range by as much as 12 degree C, and reduction of organic carbon by an average 33% in exposed soils. Very sandy soils respond similarly to vehicular use except that moisture is increased and surface strength of beach sand is decreased. These physical and chemical impacts reduce the land's capability of restoring its vegetative cover, which in turn adversely affects animal populations. Both the loss of plant cover and the physical changes caused by vehicles promote erosion. Neither the increased sediment yield nor the increased runoff is accommodated on the sites of use, and both are causing adverse effects to neighboring properties.

  • Corporate Authors:

    Springer Verlag

    175 5th Avenue
    New York, NY  USA  10010
  • Authors:
    • Wilshire, H G
    • Nakata, J K
    • Shipley, S
    • Prestegaard, K
  • Publication Date: 1978

Media Info

  • Features: References;
  • Pagination: p. 295-319
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00195247
  • Record Type: Publication
  • Source Agency: Engineering Index
  • Files: TRIS
  • Created Date: Aug 28 1979 12:00AM