10 Jun 2024

Post-wildfire Curve Number Estimates for the Southern Rocky Mountains in Colorado, USA

Abstract: The curve number method first developed by the USDA Soil Conservation Service (now the Natural Resources Conservation Service) is often used for post-wildfire runoff assessments. These assessments are critical for land and emergency managers making decisions on life and property risks following a wildfire event. Three approaches (i.e., historical event observations, linear regression model, and regression tree model) were used to help estimate a post-wildfire curve number from watershed and wildfire parameters. For the first method, we used runoff events from 102 burned watersheds in Colorado, southern Wyoming, northern New Mexico, and eastern Utah to quantify changes in curve number values from pre- to post-wildfire conditions. The curve number changes from the measured runoff events vary substantially between positive and negative values. The measured curve number changes were then associated with watershed characteristics (e.g., slope, elevation, northness, and eastness) and land cover type to develop prediction models that provide estimates of post-wildfire curve number changes. Finally, we used a regression tree method to demonstrate that accurate predications can be developed using the measured curve number changes from our study domain. These models can be used for future post-wildfire assessments within the region.

10 Jun 2024

Lock and Dam 25, Upper Mississippi River Navigation Study: Ship-Simulation Results

Abstract: The US Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory (CHL), used the Ship/Tow Simulator to evaluate navigational conditions for the US Army Corps of Engineers, St. Louis District (MVS), proposed 1,200 feet (ft) lock chamber at Lock and Dam 25 in a tow simulation study. The study considers the impacts to navigation throughout construction sequences of the proposed 1,200 ft lock chamber and the final completed project. Testing occurred at CHL in October–November 2022 with five industry tow pilots. A total of 47 unique test conditions for a total of 187 ship-simulation exercises were evaluated. All final project simulations indicated that the design is feasible. When testing the construction scenarios of the design, it was evident that a tug assist boat would be necessary for entering the 600 ft lock for both approaches. Results found that the intermediate wall construction should begin at the existing structure and progress downstream. Entering the 600 ft lock from the pool side was additionally completed successfully; however, modifications are needed for entering from the tailwater side. Ultimately, the results of this study will aid MVS in the design plan and decision-making regarding the proposed lock.

10 Jun 2024

Getting Started with FUNWAVE-TVD: Troubleshooting Guidance and Recommendations

Abstract: This technical note reviews some common initialization errors when first getting started with the numerical wave model, FUNWAVE-TVD (Fully Nonlinear Wave model–Total Variation Diminishing), and provides guidance for correcting these errors. Recommendations for troubleshooting the source or cause of instabilities in an application of the model as well as recognizing the difference between physical and numerical instabilities are also outlined and discussed. In addition, a quick start troubleshooting guide is provided in the Appendix. This guidance is particularly useful for novice to intermediate users of FUNWAVE-TVD who are less familiar with the workflow of setting up the model and interpreting error output statements.

31 May 2024

Hydraulic Load Definitions for Use in Load and Resistance Factor Design (LRFD) Analysis, Including Probabilistic Load Characterization, of 10 Hydraulic Steel Structures: Report Number 1

Abstract: In the past, allowable stress design (ASD) was used to design steel structures. The allowable stresses used were determined from previous practice, with limited understanding of the reliability and risk performance provided by the structure. Engineering methods based on Load and Resistance Factor Design (LRFD) provide more accurate lifetime models of structures by providing risk-based load factors. Besides improved safety, cost savings can be provided through improved performance and, in some cases, by delaying rehabilitation. This research project develops LRFD-based engineering procedures for the evaluation and design of hydraulic steel structures (HSS). Hydraulic loads are a key element to the LRFD analysis. This report identifies the primary hydraulic loads and describes procedures that can be used to determine these hydraulic loads. Existing design guidance for HSS is described and presented in the individual chapters. The appendixes to the report provide examples of the procedures used to compute the hydrostatic, wave, and hydrodynamic loads. A new approach for determining wind-induced wave loads was developed. Design guidance for computing the hydrodynamic load was limited for many of the HSS. Additional research is recommended to improve capabilities for computing hydraulic loads. Details on these recommendations can be found in this report.

28 May 2024

Statistical Analysis of Storm Surge and Seiche Hazards for Lake Erie

Abstract: Storm surge and seiche events are generally forced by severe storms, initially resulting in a wind-driven super elevation of water level on one or more sides of a lake (surge) followed by a rebound and periodic oscillation of water levels between opposing sides of the lake (seiche). These events have caused flooding along Lake Erie and significant damages to coastal communities and infrastructure. This study builds upon statistical analysis methods initially developed for the 2012 federal interagency Great Lakes Coastal Flood Study. Using the Coastal Hazards System's stochastic Storm Simulation (StormSim) suite of tools, including the Probabilistic Simulation Technique (PST), and regional frequency model, historical extreme events were assessed in a local frequency analysis and a regional frequency analysis to quantify the annual exceedance frequency (AEF) of WLD events specific to Lake Erie. The objective of this study was to quantify AEFs of storm surge and seiche hazards to provide a better understanding of these events to aid flood mitigation and risk reduction for lakeside properties.

21 May 2024

Low Sill Control Structure: Physical Modeling Investigation of Riprap Stability Downstream of End Sill

The model investigation reported herein describes the process to model and analyze the stability of scaled riprap in the existing 1:55 Froude-scaled Low Sill Control Structure physical model. The existing model is a fixed-bed model, so modifications were made to create a testing section for the scaled stone. Three separate gradations of scaled riprap were tested at varying boundary conditions (discharge, head and tailwater elevations, and gate openings). Each test was surveyed using lidar for pre to posttest comparisons. It was found that Gradation B remained stable throughout the tests in the physical model.

21 May 2024

Site Selection and Conceptual Designs for Beneficial Use of Dredged Material Sites for Habitat Creation in the Lower Columbia River

Abstract: Channel maintenance in most major rivers throughout the United States requires ongoing dredging to maintain navigability. The US Army Corps of Engineers explores several options for placement based on sediment characteristics, material quantity, cost, operational constraints, and minimization of potential adverse effects to existing resources and habitat. It is a priority to beneficially reuse dredged sediments to create habitat and retain sediments within the river system whenever possible. Nonetheless, there can be discrepancies among state and federal resource agencies, landowners, tribes, and various other stakeholders about what constitutes a benefit and how those benefits are ultimately weighed against short- and long-term tradeoffs. This work leveraged prior Regional Sediment Management efforts building consensus among stakeholders on a suite of viable strategies for in-water placement in the lower Columbia River. The goal was to identify suitable locations for applying the various strategies to maximize habitat benefits and minimize potential adverse effects. A multistep site-selection matrix was developed with criteria accounting for existing site conditions, overall placement capacity, tradeoffs, long-term maintenance, cost, stakeholder concerns, and landscape principles in the context of other habitat restoration projects implemented in the lower river. Three highly ranked sites were selected for conceptual design and exemplify results of collaborative beneficial use implementation.

15 May 2024

Vessel Impacted by Structure on the Ohio River: Louisville District

Abstract: This Dredging Operations Technical Support (DOTS) Program technical note presents the results of a study undertaken by the Navigation Branch, US Army Engineer Research and Development Center (ERDC), Coastal and Hydraulics Laboratory (CHL), at the request from the Louisville District (LRL) to examine an incident involving a single vessel and structure in a high-water condition. The vessel-position data used in this request were broadcast from an onboard Automatic Identification System (AIS) transceiver and received by US Army Corps of Engineers (USACE)–owned Lock Operations Management Application (LOMA) tower sites located along the Ohio River.

14 May 2024

Snow-Impacted National Inventory of Dams by GAGESII Watershed

Abstract: This Engineering Research and Development Center (ERDC) Technical Note describes the development of a set of locations within the contiguous United States (CONUS) where snowmelt is a component of the annual streamflow. The locations are selected from the US Geological Survey (USGS) Geospatial Attributes of Gages for Evaluating Streamflow II (GAGESII) and National Inventory of Dams (NID) data sets. The 30-year normal snow regimes were used to identify all GAGESII watersheds that have any of the basin delineated as transitional (rain/snow), snow dominated, or perennial snow zones. NID dams that are within snow affected GAGESII watersheds are included in the data set. The purpose of this ERDC Technical Note is to describe the development of a comprehensive data set of CONUS GAGESII and dam infrastructure affected by snow changing regimes.

14 May 2024

Low Sill Control Structure: Physical Modeling Investigation of Velocities Downstream of the End Sill

Abstract: The model investigation reported herein describes the process to measure velocities at various locations downstream of the Low Sill Control Structure using an existing 1:55 Froude-scaled physical model. To collect these measurements, an acoustic-Doppler velocimeter was deployed downstream of the structure at varying locations and depths. A total of 79 velocity measurements were taken across nine flow conditions (discharge, head and tailwater elevations, and gate openings) provided by the US Army Corps of Engineers, New Orleans District.