Treesearch

Natural channels never stop changing their geomorphic characteristics. Natural alluvial streams are similar to living creatures because they generate water flow, develop point bars, alter bed profile, scour the bed, erode the bank, and cause other phenomena in the stream system. The geomorphic changes in a natural system lead to a wide array of research worldwide, because methods of predicting channel change are limited. Bank erosion due to meandering of the channel is a critical issue in modern river engineering. In the United States, the severity of the problem was recognized when...

Smoke from wildfires can expose individuals and populations to elevated levels of particulate matter (PM) and ozone (O3). Between 21 July and 26 August 2002, the McNally Fire burned over 150 000 acres (61 000 ha). The fire occurred in the Sequoia National Forest, in the southern Sierra Nevada of California. This study evaluated the effects of the McNally Fire on air quality, specifically particles

As with every natural process, river morphology incorporates a complex and nuanced set of processes that combine to produce an infinite set of possible outcomes. Natural laws that govern natural systems cause rivers to react to changes in the environment in order to maintain equilibrium. Changes in hydraulics, sediment transport, and habitat help keep natural systems in balance. Natural reactions can be predictable, such as seasonal variations in weather patterns, or quite unpredictable, such as major flooding events or tectonic activity. Human impact to the environment is rarely subtle...

The Elephant Butte Reach spans about 30 miles, beginning from the South Boundary of the Bosque del Apache National Wildlife Refuge (River Mile 73.9) to the "narrows" of the Elephant Butte Reservoir (River Mile 44.65), in central New Mexico. Sediment plugs occasionally form along the Middle Rio Grande, completely blocking the main channel of the river. In 1991, 1995, and 2005, the Tiffany Plug was initiated at the upstream end of the Elephant Butte Reach. In 2008, the Bosque del Apache Plug formed just upstream of the Elephant Butte Reach. Sediment plugs occur at the location of a constricti...

The hydraulic characteristics are determined for the June 11, 2010, flood on the Little Missouri River at the Albert Pike Recreation Area in Arkansas. These characteristics are then used to predict the high-water elevations for the 10-, 25-, 50-, and 100-year flood events in the Loop B, C, and D Campgrounds of the recreation area. The peak discharge and related roughness characteristics of the June 11, 2010, flood are determined using detailed field survey data and iterative slope-area modeling, while standard step modeling is used to assess the fit of computed to observed high-water...

Four watersheds with differing geology and land cover in eastern Puerto Rico have been studied on a long-term basis by the U.S. Geological Survey to evaluate water, energy, and biogeochemical budgets. These watersheds are typical of tropical, island-arc settings found in many parts of the world. Two watersheds are located on coarse-grained granitic rocks that weather to quartz- and clay-rich, sandy soils, and two are located on fine-grained volcanic rocks and volcaniclastic sedimentary rocks that weather to quartz-poor, fine-grained soils. For each bedrock type, one watershed is covered...

We measured soil chemical and microbial properties at a depth of 0–20 cm among mine tailings, abandoned mined land, contaminated cropland, and uncontaminated cropland around a magnesite mine near Haicheng City, Liaoning Province, China. The objective was to clarify the impact of Mg on the soils. We found that soluble Mg2+ concentration and pH were significantly higher in contaminated soils (266–345 mg kg-1 and 9.9-10.3, respectively) than in uncontaminated soils (140 mg kg-1 and 7.1, respectively). Soil nutrients (total N, total P, mineral N, available P and soluble Ca) and microbial...

The Middle Rio Grande is a 29-mi reach of the Rio Grande in central New Mexico extending from the downstream side of Cochiti Dam to Bernalillo, New Mexico. A map of the Middle Rio Grande reach is presented in Figure 1.1. In recent years, the Middle Rio Grande has been the focus of a variety of channel restoration techniques, including the use of native material and rock spur-dike structures in attempts to control bank erosion rates, channel migration rates, and habitat degradation (Darrow 2004).

Fluvial systems respond to changes in boundary conditions in order to sustain the flow and sediment supplied to the system. Local channel responses are typically difficult to predict due to possible affects from upstream, downstream, or local boundary conditions that cause changes in channel or planform geometry. Changes to the system can threaten riverside infrastructure and riparian zones, which may affect the local ecology. This research focuses on meandering channel patterns and the forces applied to their physical boundaries by the complex three-dimensional (3-D) flow found in...

Widespread outbreaks of mountain pine beetle in North America have drawn the attention of scientists, forest managers, and the public. There is strong evidence that climate change has contributed to the extent and severity of recent outbreaks. Scientists are interested in quantifying relationships between bark beetle population dynamics and trends in climate. Process models that simulate climate suitability for mountain pine beetle outbreaks have advanced our understanding of beetle population dynamics; however, there are few studies that have assessed their accuracy across multiple...