Recent evidence suggests that population declines of some avian species may be driven primarily by reduced quantity and diversity of early-successional habitat on the breeding grounds. Increasing intensity of forest management on private lands and decreased harvest rates on federal lands has resulted in a loss of the diverse early-successional...
Model studies of two-dimensional, time-dependent, wind-forced, stratified downwelling circulation on the continental shelf have shown that the near-bottom offshore flow can develop time- and space-dependent fluctuations involving spatially periodic separation and reattachment of the bottom boundary layer and accompanying recirculation cells. Based primarily on the observation that the potential vorticity...
Many miles of roads are built in the Pacific Northwest Forests to provide access for logging and fire protection. Logging roads often cross steep mountainous terrain. Logging roads and the associated cut and fill slopes represent a discontinuity in the natural stress state in the soil mantle. These conditions result...
Predictions of mechanical collisions between two bodies frequently cannot be completed by the impulse-momentum equation together with a complete description of the motion of the system at the initial contact. Additional account must be taken of the deformations and frictional interaction induced by the impulsive reaction force, where the bodies...
This report is one of a series issued in cooperation with the ANC-23 panel on composite construction for flight vehicles of the departments of the Air Force, Navy, and Commerce.
US forestlands are increasingly subject to disturbances including wildfire, insects and disease, and urban and exurban development. Devising strategies for addressing these "forest threats" depends on anticipating where individual disturbances are most likely and where they might occur in combination. However, many spatial data sets describing forest threats are produced...
Traditional risk-based analysis for levee planning focuses primarily on overtopping failure. Although many levees fail before overtopping, few planning studies explicitly include intermediate geotechnical failures in flood risk analysis. This study develops a risk-based model for two simplified levee failure modes: overtopping failure and overall intermediate geotechnical failure from through-seepage,...