Effects of external nutrient sources and extreme weather events on the nutrient budget of a Southern European coastal lagoon

The seasonal and annual nitrogen (N), phosphorus (P), and carbon (C) budgets of the mesotidal Ria Formosa lagoon, southern Portugal, were estimated to reveal the main inputs and outputs, the seasonal patterns, and how they may influence the ecological functioning of the system. The effects of extreme weather events such as long-lasting strong winds causing upwelling and strong rainfall were assessed. External nutrient inputs were quantified; ocean exchange was assessed in 24-h sampling campaigns, and final calculations were made using a hydrodynamic model of the lagoon. Rain and stream inputs were the main freshwater sources to the lagoon. However, wastewater treatment plant and groundwater discharges dominated nutrient input, together accounting for 98, 96, and 88 % of total C, N, and P input, respectively. Organic matter and nutrients were continuously exported to the ocean. This pattern was reversed following extreme events, such as strong winds in early summer that caused upwelling and after a period of heavy rainfall in late autumn. A principal component analysis (PCA) revealed that ammonium and organic N and C exchange were positively associated with temperature as opposed to pH and nitrate. These variables reflected mostly the benthic lagoon metabolism, whereas particulate P exchange was correlated to Chl a, indicating that this was more related to phytoplankton dynamics. The increase of stochastic events, as expected in climate change scenarios, may have strong effects on the ecological functioning of coastal lagoons, altering the C and nutrient budgets.Portuguese Science and Technology Foundation (FCT) [POCI/MAR/58427/2004, PPCDT/MAR/58427/2004]; Portuguese Science and Technology Foundation (FCT

Functional Design of Control Structures for Oregon Inlet, North Carolina: Hydraulic Model Investigation

Source: https://erdc-library.erdc.dren.mil/jspui/Oregon Inlet, the northernmost inlet through North Carolina's barrier islands known as the "Outer Banks," is a natural channel conducting flow between the Atlantic Ocean and extensive open bay sounds. As is typical of many natural inlets, navigation through the inlet can be dangerous due to shallow shifting sand shoals. The necessity of continued maintenance dredging and the exposure of commercial and private craft to shoaling and breaking waves indicate that inlet stabilization by jetties is desirable and should be investigated. The design study for the Manteo (Shallowbag) Bay Project included construction and testing of a physical model of Oregon Inlet. Model scales were 1:300 horizontally and 1:60 vertically. The model reproduced 12 square miles of ocean area to the 60-ft-depth contour and 17 square miles of Pamlico Sound. Initially, the model was molded of concrete; however, during the latter phase of the study, the entrance channel and vicinity were removed and molded with crushed coal for a movable-bed study. An extensive set of field data was collected and analyzed for use in model verification. The verification process indicated that tidal velocities and elevations were in satisfactory agreement with the prototype and the model could be reliably used as a predictive tool to investigate the effect of various jetty lengths, alignments, and spacings on flow conditions through the inlet and on tidal variations within Pamlico Sound. Model testing included the study of jetty alignment, length, and spacing and the effects of the jetty structures on tidal exchange and on the flow through Bonner Bridge. Also, steady-state ebb and flood storm surges were reproduced and the effects of the jetties on these flows examined. Staged jetty construction tests aided in determining the best construction sequence to limit excessive scour velocities. Sediment tracer tests indicated the shape and size of fillet development adjacent to the jetties. The movable-bed tests provided information on the effects of jetties on channel alignment for both normal tides and during storm surge conditions. The effects of bottom protection at the Bonner Bridge and the placement of sills in Davis and Middle Sloughs also were evaluated. It was concluded that the plan 2 jetty alignment with 2,500-, 3,500-, or 5,000-ft spacing would not negatively impact the tidal exchange, storm surge flows, or flow through Bonner Bridge. However, the larger spacings may permit bifurcation of the entrance channel or a more curvilinear channel._x000D_ _x000D_ NOTE: This file is large. Allow your browser several minutes to download the file

Los Angeles and Long Beach Harbors Model Enhancement Program, Effects of Wind on Circulation in Los Angeles-Long Beach Harbors

Source: https://erdc-library.erdc.dren.mil/jspui/A previously calibrated numerical three-dimensional hydrodynamic model for Los Angeles-Long Beach Harbors, California, was applied to study the combined effects of tide and wind on circulation. The model was calibrated and verified successfully with field data for a summer wind condition. In this report the calibration is compared to a no-wind condition to understand the effects of typical wind conditions on circulation. Also, wind conditions for approaching (winds from the southeast) and passing (winds from the north) frontal systems, typical of fall-winter weather patterns, were simulated. Results indicated the effects of wind can be significant. NOTE: This file is large. Allow your browser several minutes to download the file