4 May 2022

Calculation of Levee-Breach Widening Rates

Abstract: Inundation modeling is often conducted for levee systems to understand current flood risks. The extent of inundation caused by a breach in the levee is highly influenced by the widening rate of the levee breach. This study presents an approach for calculating levee-breach widening rates based on average flow velocity through the breach, embankment height, and erosion characteristics of the soil. Estimates of soil erodibility are derived through an analysis of the measurements of soil erodibility presented in the National Cooperative Highway Research Program (NCHRP) Report 915 database. Levee-breach widening rate curves are calculated based on these erosion properties to demonstrate the approach, and default curves are presented for typical levees built from coarse-grained soils and fine-grained soils. While the most accurate approach for a site is to calculate site-specific widening rate curves based on estimates of local soil erodibility, the default curves presented provide a suitable starting point for initial inundation modeling.

6 Dec 2021

Development of a Sand Boil Testing Laboratory and Preliminary Results

Purpose: To document the purpose, use, and preliminary results of a full-scale sand boil generator developed at the Geotechnical and Structures Laboratory.

13 Oct 2021

Engineering With Nature®: Supporting Mission Resilience and Infrastructure Value at Department of Defense Installations

Abstract: This book illustrates some of the current challenges and hazards experienced by military installations, and the content highlights activities at seven military installations to achieve increased resilience through natural infrastructure.

29 Sep 2021

Backward Erosion Testing: Magnolia Levee

Abstract: Using a confined flume device, an experimental study investigated the critical horizontal gradient of soils obtained from a site identified as potentially vulnerable to backward erosion piping (BEP). Tests were conducted on glacial outwash material obtained from a sand and gravel quarry in the vicinity of Magnolia Levee in the community of Magnolia, OH. The two bulk samples collected from the quarry had similar grain-size distributions, grain roundness, and depositional environments as the foundation materials beneath the levee. Samples were prepared at various densities and subjected to gradual increases of flow in a wooden flume with an acrylic top until BEP was observed. The critical average horizontal gradient ranged from 0.21 to 0.30 for a bulk sample with a coefficient of uniformity of 1.6, while tests conducted on a bulk sample with a coefficient of uniformity of 2.5 yielded critical average horizontal gradients of 0.31 to 0.36. The critical average gradients measured during these tests compared favorably to values in the literature after applying adjustments according to Schmertmann’s method.

29 Jan 2021

Mississippi River Adaptive Hydraulics Model Development and Evaluation, Commerce to New Madrid, Missouri, Reach

Abstract: A numerical, two-dimensional hydrodynamic model of the Mississippi River, from Thebes, IL, to Tiptonville, TN (128 miles/206 km), was developed using the Adaptive Hydraulics model. The study objective assessed current patterns and flow distributions and their possible impacts on navigation due to Birds Point New Madrid Floodway (BPNMF) operations and the Len Small (LS) levee break. The model was calibrated to stage, discharge, and velocity data for the 2011, 2015–2016, and 2017 floods. The calibrated model was used to run four scenarios, with the BPNMF and the LS breach alternately active/open and inactive/closed. Effects from the LS breach being open are increased river velocities upstream of the breach, decreased velocities from the breach to Thompson Landing, no effects on velocity below the confluence, and cross-current velocities greater than 3.28 ft/s (1.0 m/s) within 1186.8 ft (60 m) of the bankline revetment. Effects from BPNMF operation are increased river velocities above the confluence, decreased velocities from the BPNMF upper inflow crevasse (Upper Fuseplug) to New Madrid, cross-current velocities greater than 1.5 ft/s (0.5 m/s) only near the right bank where flow re-enters the river from the BPNMF lower inflow/outflow crevasse Number 2 (Lower Fuseplug) and St. Johns Bayou.

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.