Vegetative recovery of military vehicle impacts at Fort Lewis, WA

by 1979- Simmons, Katie Jean

Vehicles driven off-road damage the soil and vegetation on the terrain, which can cause soil erosion and degradation of the landscape. This type of damage occurs on military installations due to training. Military training lands must be managed in an attempt to minimize the overall impacts of training on the terrain. The Army Training and Testing Area Carrying Capacity (ATTACC) is a model used by the U.S. Army to manage their training lands. Methods of determining the impacts produced by a vehicle and subsequent vegetative recovery have been used at Fort Lewis, WA for the Light Armored Vehicle (LAV). The LAV is an eight-wheeled vehicle with a maximum curb weight of approximately 14,000 kg. In June of 2003, the vehicle was operated in spiral patterns (five high-speed and five low-speed), and the impacts of the vehicle were assessed at this time. Measurements were taken at 13-20 points along each of the 10 spirals. The impact measurements taken at each point were disturbed width and impact severity. The impacts were reassessed after six months and one year to determine recovery from the initial damage. Different types of impacts (imprint, scrape, combination, and pile) were determined based on the characteristics of the damage produced. The recovery of these different impact types was also assessed. The study site at Fort Lewis was found to have an overall vegetative recovery of 43% after one year, but the different impact types varied in the amount of recovery. Imprint impact types had an almost complete recovery of 74%, while the scrape and combination showed little recovery (11% and 22%, respectively) after one year. The pile also showed a high recovery of 54%. Areas where the vehicle was operated at low iv speeds showed high recovery (78%). Recovery was much lower (29%) for areas where the vehicle was operated at high speeds. The damage produced was higher and recovery lower when the vehicle was turning sharply. The data produced by this study will be useful in managing the training with LAVs at Fort Lewis by implementation into the ATTACC model. Further study must be done to determine when these impacts would be fully recovered from the damage. The results found in this study are only applicable to the LAV and Fort Lewis. Other vehicles produce different impacts, and other locations have different climates, soils, and vegetation types that would respond differently to vehicle impacts. The methods used in this study can be utilized at other locations and with different vehicles to provide applications to more sites and a wider variety of vehicles. v