Mitchell E. Brown

The Coastal Modeling System Flow Model (CMS-Flow): Past and Present

Abstract CMS-Flow is a coupled time-dependent circulation, sediment transport and morphodynamic model based on the numerical solution of the mass, momentum and transport equations on a Cartesian (quad-tree) grid network with both explicit and implicit solvers. It has been developed and is currently supported under the Coastal Inlets Research Program (CIRP) conducted at the U.S. Army Engineer Research and Development Center (ERDC), Coastal and Hydraulics Laboratory (CHL). The models primary function is to support multi-disciplinary research teams and conduct practical projects at coastal inlets. CMS-Flow has been designed with a relatively simple code structure which allows for rapid development and inclusion of new sediment transport algorithms, while always being accessible to the general modeling community, including both USACE and commercial users. Today, CMS-Flow is an integral component of the CIRP, providing technology for simulating hydrodynamics, waves, sediment transport and morphology for short and long timeframes in coastal inlets, adjacent beaches, navigation channels and bays.

LONG-TERM MORPHOLOGICAL MODELING AT COASTAL INLETS

Abstract : The U.S. Army Corps of Engineers Coastal Modeling System (CMS) is used to simulate the long-term morphodynamics of coastal barrier-inlet systems.The CMS consists of an integrated numerical modeling system for simulating wave, current, water levels, sediment transport and morphology change. In order to quantify the physical effects of long-term, regional climactic changes in the environment, numerical morphodynamic models must be able to reproduce the known generic characteristics that drive barrier inlet processes, including equilibrium inlet dimensions and sediment budget for the tidal shoals. In this study, model results are presented for a 10-year simulation of an idealized inlet and bay system with dimensions similar to that of Humboldt Bay, CA. The model reproduces reasonably well several geomorphic and hydrodynamic features of the inlet at Humboldt Bay. The model results demonstrate the feasibility of applying the CMS for simulating long-term morphology at coastal inlets for practical applications.

Long-Term Morphology Modeling for Barrier Island Tidal Inlets

The U.S. Army Corps of Engineers, Coastal Inlets Research Program, conducted at the U.S. Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory, has developed the Coastal Modeling System (CMS) as a coupled wave, hydrodynamic, and sediment transport numerical modeling system. The primary focus of this study is to validate CMS for long-term applications through simulations of tidal inlet evolution and verify the results against established theoretical and empirical formulations that describe the stability and equilibrium conditions of tidal inlets. A wide range of conditions are chosen to test the breadth of model applicability including varying waves, tide and inlet geomorphic characteristics. The model is run for 100 years and the resulting morphological state is gauged in terms of inlet stability theory. Overall, CMS compares well to theoretically and empirically predicted inlet cross-sectional areas with some noted deviations due in part to the artificial nature of the idealized inlet geometry. The sharp spatial transition at either end of the inlet throat leads to artificially large gradients that may increase erosion and associated cross-sectional area. The results suggest that CMS can efficiently and accurately, to the degree of available empirical information, quantify long-term evolution of barrier island tidal inlet systems. DISCLAIMER: The contents of this report 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 commercial products. All product names and trademarks cited are the property of their respective owners. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents. DESTROY THIS REPORT WHEN NO LONGER NEEDED. DO NOT RETURN IT TO THE ORIGINATOR. ERDC/CHL TR-18-12 iii

Merrimack Estuary and Newburyport Harbor sediment management studies

This report documents a numerical modeling study investigating sediment transport and morphology change adjacent to Merrimack Inlet, Newburyport, and nearshore in the vicinity of Salisbury Beach and Plum Island, Massachusetts. Concerns at the site include beach erosion, shoreline retreat on Plum Island downdrift of and within the inlet, and reduced navigability of the inlet. The numerical modeling evaluation consists of two phases. The Phase I study was conducted with the damaged and partially rehabilitated South Jetty between 2012 and 2014, and the Phase II study was conducted with the fully rehabilitated South Jetty between 2015 and 2016. Historical hydrodynamic and sediment data in the study area were assembled, and a field data collection program was carried out. The datasets were used to develop a coastal wave, hydrodynamic, and sediment transport model. Different alternatives were developed to evaluate sediment management strategy and structure modification, and the calculated bed sediment volume changes of each alternative were compared with the results under base (existing) condition. Alternative simulations demonstrated the Coastal Modeling System capability in evaluating beach erosion, structure performance, sediment transport, and morphology change in the inlet and estuarine system. DISCLAIMER: The contents of this report 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 commercial products. All product names and trademarks cited are the property of their respective owners. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents. DESTROY THIS REPORT WHEN NO LONGER NEEDED. DO NOT RETURN IT TO THE ORIGINATOR. ERDC/CHL TR-18-7 iii

An Optimized Combined Wave and Current Bottom Boundary Layer Model for Arbitrary Bed Roughness

Abstract : A robust method for computing the bed shear stress in unstratified combined wave and current flows is presented. The present approach follows from existing theories describing the nonlinear wave and current interaction in the benthic boundary layer but is designed for arbitrary wave, current, and roughness conditions, including the limiting case of pure waves or pure currents. The stress model is intended as a stand-alone application or for coupling to three-dimensional shelf circulation models, where a broad range of flow conditions are encountered. High-quality data for combined flows and pure waves are used with the present stress formulation to better refine empirical model closure constants in the fully rough turbulent regime. Introducing a first-order correction to the definition of the wave boundary layer thickness produces accurate estimates of both the measured friction factor and wave boundary layer height. A speed of convergence test indicates that the present model is more efficient than previous models that use the same turbulent closure scheme. This is primarily due to an improved solution algorithm that avoids the nested iterations common to established combined wave and current bottom boundary layer models.