20 Mar 2023

Numerical Modeling of Supercritical Flow in the Los Angeles River: Part I: Adaptive Hydraulics Numerical Modeling of the 1943 Physical Model

Abstract: The Los Angeles District of the US Army Corps of Engineers is assisting the City of Los Angeles with restoration efforts on the Los Angeles River. The city wishes to restore portions of the channelized river to a more natural state with riparian/vegetative green spaces for both wildlife and public recreation usage. The Los Angeles River provides an important role for the City of Los Angeles from a flood-control perspective, and functionality needs to be preserved when contemplating system modifications. This report details the development of an Adaptive Hydraulics (AdH) numerical model capable of representing this complex system consisting of both subcritical and supercritical flow regimes. Due to limited hydraulic data in the study area, an extensive model validation to observed data was not possible. To bridge the data gap, a numerical model was developed from a previously completed physical model study with extensive quantitative measurements and qualitative reports of hydraulic conditions. This approach allowed engineers to evaluate the effectiveness of the AdH model in representing this complex hydraulic system along with determining the best methodology to accurately represent the existing conditions. This study determined appropriate model parameters that will be utilized in further numerical modeling efforts to evaluate system modifications associated with restoration efforts.

1 Oct 2020

Development of a General Anadromous Fish Habitat Model: Phase 2: Initial Model Quantification

Abstract: The General Anadromous Fish Habitat Model (now the General Salmonid Habitat Model) was developed to assist in the plan formulation process for ecosystem restoration and mitigation projects. The model generates relative differences in habitat quality between proposed alternative future scenarios. In order to provide model development transparency, this report presents the initial quantification phase of the model development process. The draft model depicted in this report is scalable, meaning various parameters may be measured at different landscape scales (for example, reach vs. watershed). The model can be applied (model domain) in watersheds that currently or previously supported salmonid fish species. Application outside of the model domain would need further evaluation to ensure appropriate sensitivity to the new system of interest. Although the model is being developed to explicitly capture changes in fish habitat in response to restoration actions, this model would be appropriate for use in any planning project focused on the restoration of streams, rivers and, estuaries (for example, dam removals, in-stream habitat enhancement), because the parameters are measures of ecosystem level structure, function, and process.

17 Jun 2020

PUBLICATION NOTICE: Development and Application of the CASM-SL to Support Nutrient Management in Potential Sangamon River Levee Setbacks

Abstract: Levee setbacks are defined by the intentional relocation of levees away from the river bank. This placement is often done to reduce flood risk, but it can also have environmental benefits. The Comprehensive Aquatic System Model (CASM) was used to look at the potential fate of nutrients and several environmental benefits for five potential management scenarios along the lower Sangamon River in Illinois. The model results showed that two scenarios were much more environmentally favorable relative to the outcomes considered here. One of the scenarios, where the existing gates were operated to allow the river access to the area behind the levee during extreme floods, was better at nitrogen and phosphorous accumulation. Removing the gates and creating a levee setback at this same site produced more aquatic plants, invertebrates, and fish but was not as effective at nutrient accumulation. This application of CASM demonstrates the potential of the model to provide objective rankings for the environmental benefits of levee setbacks.