This report details the process of developing and validating a multidimensional hydrodynamic, salinity, sediment transport, and coastal wetland morphology model of the Lower Mississippi River Delta. This model has been developed to run various sediment diversion scenarios. The results of these scenario analyses are documented in this report.The morphologic modeling results for the diversion scenario analyses show net land gain in the near vicinity of the diversion outlets and net land loss farther away from the outlets. The areas of land gain roughly correspond with the zones of sand deposition whereas the areas of largest land loss correspond with areas where there is diversion-induced inundation but not significant deposition of sediment from the diversion. The modeling results indicate that diversion-induced inundation results in a reduction in plant productivity, which induces an acceleration of land loss.Significant uncertainty exists with respect to the response of the existing wetland vegetation to diversion-induced inundation. The magnitude of this uncertainty can only be narrowed with further consensus building within wetland science.With respect to salinity, the receiving waters tend to freshen significantly during diversion operations. However, when operations cease, the recovery of salinity is almost entirely determined by prevailing offshore and/or riverine conditions.

The purpose of this Coastal and Hydraulics Engineering Technical Note (CHETN) is to document and demonstrate the Rapid Operational Access and Maneuver Support (ROAMS) v2.0 computational scripting/application program interface (API) platform. ROAMS provides improved knowledge of potential lines of communication and vessel routes through hydrodynamic modeling and path optimization under a variety of environmental conditions and input-information qualities/sources. Primary focus of this document is given to the implementation of penalty barrierbased path optimization to provide guidance for subsequent work. The platform additionally provides object-oriented, script-based interaction with principal U.S. Army Corps of Engineers (USACE) hydrodynamic models. BACKGROUND: Military undertakings in waterborne environments can be broadly classified into two types of activities: logistics and operational. Logistics activities are concerned with the establishment of lines of communication (LOC) to efficiently move equipment, personnel, and provisions from an offshore intermediate staging base (ISB) to a Sea Port of Debarkation (SPOD). The SPOD may be but is not limited to a world-class port, an unimproved beach at the coastline, or an upstream site in an estuary. Locations are typically chosen through a combination of expert judgment, analyses of nautical charts, and scenario planning to avoid known environmental austere obstacles such as shoals, reefs, and wreckage. The qualitative nature of the military logistics planning process causes direct comparison of LOC to be challenging; furthermore, qualitative methods do not guarantee the selection of an optimal site that maximizes total throughput and uptime percentage. The military has some logistics tools that facilitate planning of this type such as the Analysis of Mobility Platform (AMP) (Mckinzie and Barnes 2004). Other systems to conduct environmental measurements, such as Joint-Logistics-Over-The-Shore (JLOTS) Environmental Monitoring System (JEMS), typically lack the capability to translate those measurements into applicable decisions (U.S. Transportation Command 2016). Military operational activities constitute any other type of actions that do not principally involve military logistics (Defense Technical Information Center 2011). These activities often require routes to be revised during the operation as environmental and mission conditions evolve. Operational activities are more likely to encounter obstacles including enemy combatants, manmade impediments such as mines, scuttled vessels, or environmental obstructions like reefs and shoals. An initial route for such operations is selected much like the military logistics case. Subsequent adjustments to routes may be done on an ad hoc basis at the discretion of the commanding officer using the improved information about the mission state.

The U.S. Army Engineer Research and Development Center (ERDC) solves the nation's toughest engineering and environmental challenges. ERDC develops innovative solutions in civil and military engineering, geospatial sciences, water resources, and environmental sciences for the Army, the Department of Defense, civilian agencies, and our nation's public good. Find out more at www.erdc.usace.army.mil. To search for other technical reports published by ERDC, visit the ERDC online library at http://acwc.sdp.sirsi.net/client/default.

Building environmental simulation workflows is typically a slow process involving multiple proprietary desktop tools that do not interoperate well. In this work, we demonstrate building flexible, lightweight workflows entirely in Jupyter notebooks. We demonstrate these capabilities through examples in hydrology and hydrodynamics using the AdH (Adaptive Hydraulics) and GSSHA (Gridded Surface Subsurface Hydrologic Analysis) simulators. The goal of this work is to provide a set of tools that work well together and with the existing scientific python ecosystem, that can be used in browser based environments and that can easily be reconfigured and repurposed as needed to rapidly solve specific emerging issues such as hurricanes or dam failures. As part of this work, extensive improvements were made to several generalpurpose open source packages, including support for annotating and editing plots and maps in Bokeh and HoloViews, rendering large triangular meshes and regridding large raster data in HoloViews, GeoViews, and Datashader, and widget libraries for Param. In addition, two new open source projects are being released, one for triangular mesh generation (Filigree) and one for environmental data access (Quest).

A water diversion designed to channel sediment-rich water from the Mississippi River into Breton Sound marsh was evaluated through application of a numerical model. The model was validated to data collected from April to December 2010. After model validation was complete, simulations to understand the effects of the proposed diversion on hydrodynamics, salinity, sedimentation, and land building were conducted. Model salinity results indicate that the proposed diversion will rapidly freshen most of Breton Sound and maintain fresh water conditions in the Sound until the diversion is closed. After closure, the time of recovery of salinity in Breton Sound is a function of the prevailing winddriven currents and Mississippi River discharges through the eastern passes. With respect to the land building potential, model results indicate that the diversion has the capability to create land, but that the diversion cannot operate at full capacity for the full life cycle of the project. Deposition of sand at the diversion channel mouth creates a backwater effect that causes the water surface elevation in the outfall channel to exceed prescribed design constraints. The outfall channel mouth will therefore need to be periodically dredged and placed to form new land elsewhere in the marsh.