Effectiveness of Pocket Wave Absorbers in Vertical-Wall, Coastal Entrance Structures

preliminary information on the effectiveness of pocket wave absorbers (relative to wave conditions) in vertical steel sheet-pile coastal entrance structures. OVERVIEW: The U.S. Army Corps of Engineers is responsible for dozens of harbor entrances in the Great Lakes constructed with parallel jetties. These jetties, many in operation for more than 100 years, were typically constructed of rock-filled timber cribs. Over time, the wood cribbing has experienced significant deterioration, thus causing the jetty to be rather porous. Many of these structures have been rehabilitated. The typical rehabilitation approach has been to drive steel sheet pile around the existing structure and place a concrete cap on top, thereby encasing the original structure. After completion of the rehabilitation projects, the wave climate between the jetties appears to increase significantly causing navigational difficulties and damage to moored vessels within the harbor. This is apparently due to the fact that the timber crib jetties were rough, porous structures, especially in their deteriorated state, and were much more effective at dampening wave energy than the rehabilitated, sheet-pile encased jetties. The steel sheet-pile structures, being considerably more reflective than the deteriorating timber structures, are largely responsible for the increasingly energetic wave climate. To mitigate for the more energetic wave climate, the Corps has remove

Anthropogenic Impacts to the Sediment Budget of São Francisco River Navigation Channel using SWAT

The São Francisco River Basin, located in eastern Brazil, has undergone a significant amount of anthropogenic changes in the last several decades, such as agricultural expansion, irrigation activities, mining, and the construction of large dams. Together, these changes have altered the historic sediment budget and have led to an aggradation of sediments in the navigation channel, impacting the ability to efficiently ship agricultural commodities to regional ports. In an effort to aid decision makers in future waterway navigation planning, an international partnership between the Brazilian government agency CODEVASF and the US Army Corps of Engineers (USACE) was created. Through this partnership a SWAT model of the 630 000 km2 São Francisco River basin was developed to better understand both the historic and current sediment budget within the navigation channel. The SWAT model of the São Francisco River Basin was calibrated for hydrology and sediment loads. Monthly discharges were calibrated at 17 Agência Nacional de Águas (ANA) gages, with Nash-Sutcliffe efficiency (NSE) values ranging from 0.42 to 0.75 for an eleven year simulation. Sediment loads were calibrated to an ANA sediment gage located in the Middle São Francisco River Navigation Channel, with a PBIAS (Percent Bias) of 11.6. Based on model results, the aggradation rate of sediment in the São Francisco River and major tributaries has increased by approximately 20 Mt since Pre-European settlement of the basin (from approximately 7 Mt/a to 27 Mt/a). This increase has contributed to an impaired navigation channel due to shoaling of sandy sediments in the navigation channel