Observations of the velocity structure at the Kilo Nalu Observatory on the south shore of Oahu, Hawaii show that thermally driven baroclinic exchange is a dominant mechanism for cross-shore transport for this tropical forereef environment. Estimates of the exchange and net volume fluxes are comparable and show that the average residence time for the zone shoreward of the 12 m isobath is generally much less than 1 day. Although cross-shore wind stress influences the diurnal cross-shore exchange, surface heat flux is identified as the primary forcing mechanism from the phase relationships and from analysis of momentum and buoyancy balances for the record-averaged diurnal structure. Dynamic flow regimes are characterized based on a two-dimensional theoretical framework and the observations of the thermal structure at Kilo Nalu are shown to be in the unsteady temperature regime. Diurnal phasing and the cross-shore momentum balance suggest that turbulent stress divergence is an important driver of the baroclinic exchange. While the thermally driven exchange has a robust diurnal profile in the long term, there is high temporal variability on shorter time scales. Ensemble-averaged diurnal profiles indicate that the exchange is strongly modulated by surface heat flux, wind speed/direction, and alongshore velocity direction. The latter highlights the role of alongshore variability in the thermally driven exchange. Analysis of the thermal balance in the nearshore region indicates that the cross-shore exchange accounts for roughly 38% of the advective heat transport on a daily basis.

This Regional Sediment Management Technical Note (RSM-TN) describes studies of sediment related problems for the Utulei Beach region on the Island of Tutuila as part of the American Samoa Regional Sediment Management (RSM) Program. This document discusses (1) the existing shoreline conditions, (2) the oceanographic characteristics, and (3) the U. S. Army Engineer Research and Development Center (ERDC) Coastal Modeling System (CMS) numerical modeling conducted to identify sediment pathways in the region. The results of these investigations will be used to inform future decisions about potential RSM projects for the region. This study investigates sediment-related problems and opportunities in the village of Pago Pago in the Utulei Beach region on the Island of Tutuila, American Samoa. BACKGROUND: RSM refers to the effective and regionally comprehensive use of littoral, estuarine, and riverine sediment resources in an environmentally sensitive and economically efficient manner. RSM was officially implemented at the U.S. Army Corps of Engineers (USACE), Honolulu District (POH), in February 2004. While POH has investigated RSM opportunities along several regions in Hawaii, this project is the first in the U.S. Territory of American Samoa. NOTE:The contents of this technical note are not to be used for advertising, publication, or promotional purposes.Citation of trade names does not constitute an official endorsement or approval of the use of such products.

This study was conducted as a conceptual effort, at an island scale as opposed to the extensive watershed scale within the continental United States, to apply the Coastal Modeling System (CMS) and the Particle Tracing Model (PTM) numerical models to investigate the transport and fate of inland sediment inputs to the nearshore littoral environment. In tropical islands with high elevations, terrestrial runoff can pose a severe threat to the health of surrounding coral reefs (Pinniak 2004). Because inland sediment input to the nearshore littoral environment is a coral reef stressor, the CMS and PTM were applied to better understand the circulation patterns along the coast that influence the transport and fate of the Honokowai stream sediment inputs within the nearshore littoral environment of the West Maui, HI, region. Further comprehensive three-dimensional (3D) modeling of the region is recommended to quantify cohesive sediment transport, temperature and salinity effects, and pre-and post-storm sedimentation data at coral reefs. BACKGROUND: Regional Sediment Management (RSM) refers to the effective use of littoral, estuarine, and riverine sediment resources in an environmentally sensitive and economically efficient manner. RSM was officially implemented at the U.S. Army Corps of Engineers (USACE), Honolulu District (POH), in February 2004. The POH overall RSM strategy is to investigate RSM opportunities along all regions in Hawaii and the U.S. Pacific Territories. Conceptual regional sediment budgets have been developed in various regions throughout the islands to gain a general understanding of the control that morphology and coastal processes have on sediment pathways and transport volumes.

is working toward beneficial reuse of suitable quality dredged sediment rather than disposing of it upland or offshore, as is typically done. For that purpose, this RSM-TN reviews previous work in the region including maintenance dredging and sediment budgets, evaluates sediment quality data, and projects future sediment volumes and shoaling rates. Additionally, this RSM-TN identifies environmental coordination requirements and permits and documents discussions with the non-federal sponsors and other stakeholders to identify stockpile, beneficial reuse, and disposal options. The non-federal sponsors of this RSM initiative are the State of Hawaii Department of Land and Natural Resources (DLNR), Office of Conservation and Coastal Lands (OCCL), and the Division of Boating and Ocean Recreation (DBOR). The City and County of Honolulu (C&C) is one of several project stakeholders.

PURPOSE: This U.S. Army Corps of Engineers (USACE) Regional Sediment Management Technical Note (RSM-TN) reviews the initial sand bypassing effort conducted by the State of Hawaii, Division of Boating and Ocean Recreation (DOBOR), at Kikiaola Light Draft Harbor (KLDH). DOBOR, as the harbor's non-federal sponsor, implemented a sand bypass project in 2014 to help address the issues of sediment accretion up-drift of the harbor and erosion of the down-drift beaches. This RSM-TN reviews the results of the bypassing effort by performing a shoreline change analysis, reviewing beach profile monitoring reports, and quantifying recent harbor shoaling. The intent is to pave the way for beneficial use of dredged material at KLDH. Recommendations are made with respect to future sand bypass efforts and potential remediation for Kikiaola Gulch, which discharges fine grained terrestrial sediments into the harbor basin. The non-federal sponsor of this RSM study is the State of Hawaii, Department of Land and Natural Resources, Office of Conservation and Coastal Lands.BACKGROUND: RSM refers to the effective use of littoral, estuarine, and riverine sediment resources in an environmentally sensitive and economically efficient manner. RSM changes the focus of engineering activities from the local or project-specific scale to a broader scale that is defined by natural sediment processes. A prime motivator for the implementation of RSM principles and practices is the potential for reducing construction, maintenance, and operation costs of federally authorized projects.