Influence of a dam on fine-sediment storage in a canyon river

Glen Canyon Dam has caused a fundamental change in the distribution of fine sediment storage in the 99-km reach of the Colorado River in Marble Canyon, Grand Canyon National Park, Arizona. The two major storage sites for fine sediment (i.e., sand and finer material) in this canyon river are lateral recirculation eddies and the main-channel bed. We use a combination of methods, including direct measurement of sediment storage change, measurements of sediment flux, and comparison of the grain size of sediment found in different storage sites relative to the supply and that in transport, in order to evaluate the change in both the volume and location of sediment storage. The analysis shows that the bed of the main channel was an important storage environment for fine sediment in the predam era. In years of large seasonal accumulation, approximately 50% of the fine sediment supplied to the reach from upstream sources was stored on the main-channel bed. In contrast, sediment budgets constructed for two short-duration, high experimental releases from Glen Canyon Dam indicate that approximately 90% of the sediment discharge from the reach during each release was derived from eddy storage, rather than from sandy deposits on the main-channel bed. These results indicate that the majority of the fine sediment in Marble Canyon is now stored in eddies, even though they occupy a small percentage ( similar to 17%) of the total river area. Because of a 95% reduction in the supply of fine sediment to Marble Canyon, future high releases without significant input of tributary sediment will potentially erode sediment from long-term eddy storage, resulting in continued degradation in Marble Canyon

Avaliação de desempenho do processo de orçamento: estudo de caso em uma obra de construção civil

O presente trabalho tem como objetivo propor um modelo para avaliar o processo de orçamentação na construção civil. Trata-se de uma pesquisa de caráter exploratório, baseada em um estudo de caso realizado em uma construtora brasileira. Como instrumento de intervenção foi utilizada a Metodologia Multicritério de Apoio à Decisão Construtivista (MCDA-C), a qual permitiu identificar, organizar, mensurar e integrar os fatores necessários e suficientes, quando da avaliação de um orçamento, segundo a percepção do decisor em questão. O trabalho faz uma revisão de literatura sobre avaliação de desempenho e o gerenciamento de projetos no contexto de obras de construção civil. É apresentado o desenvolvimento do modelo construído para apoio à decisão, o qual permitiu ao gerente de engenharia avaliar o desempenho de um orçamento, identificando os fatores que causam desvios, a fim de eliminar ou minimizar suas causas, além de servir de base para propostas de melhorias no processo de orçamentação

Label-free, multiplexed detection of bacterial tmrna using silicon photonic microring resonators

A label-free biosensing method for the sensitive detection and identification of bacterial transfer-messenger RNA (tmRNA) is presented employing arrays of silicon photonic microring resonators. Species specific tmRNA molecules are targeted by complementary DNA capture probes that are covalently attached to the sensor surface. Specific hybridization is monitored in near real-time by observing the resonance wavelength shift of each individual microring. The sensitivity of the biosensing platform allowed for detection down to 53 fmol of Streptococcus pneumoniae tmRNA, equivalent to approximately 3.16 × 10(7) CFU of bacteria. The simplicity and scalability of this biosensing approach makes it a promising tool for the rapid, PCR-free identification of different bacteria via tmRNA profiling

Gully monitoring at two locations in the Grand Canyon National Park

For more information on the USGS-the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment-visit http://www.usgs.gov or call 1-888-ASK-USGS For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprod To order this and other USGS information products, visit http://store.usgs.gov Suggested citation: Schott, N.D., Hazel, J.E., Jr., Fairley, H.C., Kaplinski, M., and Parnell, R.A., 2014, Gully monitoring at two locations in the Grand Canyon National Park, Arizona, 1996Arizona, -2010, with emphasis on documenting effects of the March 2008 highflow experiment: U.S. Geological Survey Open-File Report 2014-1211. ISSN 2331ISSN -1258 Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted material contained within this report. Datums Vertical and horizontal coordinate information is referenced to the 2007 realization of the National Spatial Reference System, North American Datum of 1983, NAD83 (NSRS2007), in meters. Elevation, as used in this report, refers to GPS derived ellipsoid height above the GRS80 ellipse, in meters, and not NAVD88 orthometric height. Abstract Many archeological sites in the Grand Canyon are being impacted by gully incision. In March 2008, a high-flow experiment (2008 HFE) was conducted with the intention of redistributing fine sediment (sand, silt, and clay) from the bed of the Colorado River to higher elevations along the channel margin. Deposition of fine sediment in gully mouths has been hypothesized to slow gully erosion rates and lessen impacts to archeological sites. The effects of the 2008 HFE on gullies were evaluated by comparing the topographic changes of three gullies at two study sites before and after the 2008 HFE. Comparison results indicated that sediment was deposited in gully mouths during the 2008 HFE, and that the inundated areas nearest to the river can be extensively altered by mainstream flow during high-flow events. Additionally, the history of gully evolution at the two study sites was examined between 1996 and 2010 and indicated that gullies have been subjected to thalweg incision and gully widening processes over a decadal timescale. Although the small sample size precludes extrapolating the results to other gullies, the findings contribute to the understanding of gully erosion in archeologically significant areas and have implications for future monitoring of gully erosion and evaluating the effectiveness of check dams intended to mitigate that erosion at archaeological sites in the Grand Canyon National Park