11 Dec 2024

Numerical Modeling of Supercritical Flow in the Los Angeles River: Part II: Existing Conditions Adaptive Hydraulics Numerical Model Study

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 green spaces for both wildlife and public recreation usage. The Los Angeles River provides an important role from a flood-control perspective, and functionality needs to be preserved when contemplating system modifications. This report details the development of an Adaptive Hydraulics numerical model capable of modeling this complex system consisting of both subcritical and supercritical flow regimes. The model geometry was developed to represent the existing conditions system for future usage in quantifying the impact associated with proposed restoration alternatives. Due to limited hydraulic data in the study area, an extensive model validation to observed data was not possible. A model was developed and simulated using the most appropriate input parameters. Given the lack of measured data for model validation, an extensive number of sensitivity simulations were completed to identify the most impactful parameters and quantify a reasonable level of confidence in the model results based on the uncertainty in the model inputs.

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.