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How wide is a road? The association of roads and mass-wasting disturbance in a forested montane environment


Matthew C. Larsen and John E. Parks

U.S. Geological Survey, GSA Center, Suite 400-15, 651 Federal Drive, Guaynabo, Puerto Rico, 00965-5703, USA


Abstract

A spatial data base of 1,609 landslides was analysed using a geographic information system to determine landslide frequency in relation to highways. A 126 km long transportation network in a 201 km² area of humid-tropical, mountainous, forested terrain in Puerto Rico was used in conjunction with a series of 20 buffer (disturbance) zones varying from 5 to 400 m in length, measured perpendicular to the highways. Average landslide frequency in the study area at distances greater than 85 m from roads was about 6 landslides per km². At distances of 85 m or less on either side of a highway, landslide frequency was about 30 landslides per km². On average, this elevated disturbance rate affected 330 m2 km-2 y-1 within the 170 m swath. The mass-wasting rate outside of the disturbance zone affected 40 m2 km-2 y-1. These results indicate that the rate of mass-wasting disturbance is increased from 5 to 8 times in a 170 m wide swath along road corridors. The lateral extent of the environmental impact of roads in the study area is greater than is commonly perceived. The approach described herein demonstrates a simple method to assess the spatial association of mass wasting with highways.


Larsen, M.C. and Parks, J.E., 1997, How wide is a road? The association of roads and mass-wasting disturbance in a forested montane environment: Earth Surface Processes and Landforms, vol. 22, p. 835-848.

 
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