Portable controlled field experiments to resolve human impacts in geomorphology

Abstract

Geomorphologists have long been challenged by the need to separate the impact of human activities from change that would have occurred without human interference. One research strategy is to utilize portable, controlled field experiments in which the magnitude of driving forces (e.g., rain or wind) can be set and where it is possible to sample the landscape according to the variety in natural variables and human effects. This paper reviews the use of portable field rainfall simulators and portable field wind tunnels, with two case studies explored in detail. The first case study involves a portable field rainfall simulator that was used to examine magnitude and persistence of erosional impacts from wildfires in the Greater Yellowstone Ecosystem. The second case study involves a portable field wind tunnel that was used to examine impacts on rates of sand transport from military maneuvers on the Fort Bliss Military Reservation in southern New Mexico. Both pieces of equipment satisfied the guidelines posed by previous studies, proved ideal for hypothesis testing, and yielded results that could not have been easily achieved by other research strategies. The rainfall simulation experiments revealed that post-fire soil loss was controlled by the percent litter cover, the logging history before the fires, and the percent silt content of soils. The wind tunnel experiments revealed the effect of tanks increasing sand transport through destroying the soil crust, churning the soils and crushing the vegetation.