12 May 2021

Automated Characterization of Ridge-Swale Patterns Along the Mississippi River

Abstract: The orientation of constructed levee embankments relative to alluvial swales is a useful measure for identifying regions susceptible to backward erosion piping (BEP). This research was conducted to create an automated, efficient process to classify patterns and orientations of swales within the Lower Mississippi Valley (LMV) to support levee risk assessments. Two machine learning algorithms are used to train the classification models: a convolutional neural network and a U-net. The resulting workflow can identify linear topographic features but is unable to reliably differentiate swales from other features, such as the levee structure and riverbanks. Further tuning of training data or manual identification of regions of interest could yield significantly better results. The workflow also provides an orientation to each linear feature to support subsequent analyses of position relative to levee alignments. While the individual models fall short of immediate applicability, the procedure provides a feasible, automated scheme to assist in swale classification and characterization within mature alluvial valley systems similar to LMV.

30 Apr 2021

Sustainment Management System, Water Control Structures: Inventory and Inspection Template

Abstract: Department of Defense (DoD) military services own and maintain a portfolio of dams, dikes, and levees including over 800 assets with a total replacement value of over $2 Billion. The Inspector General has previously found that the DoD requires an inspection policy for dams, to prevent failures. The Office of the Secretary of Defense (OSD) directed the U.S. Army Engineer Research and Development Center, Construction Engineering Laboratory (ERDC-CERL), to create an inspection method and integrate that method with the Enterprise Sustainment Management System, with aims to provide OSD a consistent description of all DoD real property and facilitate calculation of the Facility Condition Index (FCI) for each asset. This report builds upon ERDC-CERL TR-18-9 to propose a method for both inventory and inspection rating for DoD dams, levees, and dikes. A new real property classification system for DoD water control structures is proposed. To better fulfil the OSD requirement for consistent condition and FCI reporting, it is proposed that DoD reevaluate the replacement values and sustainment cost factors for its water retaining structures. A draft guide for linear segmentation for levees is proposed. Future work will allow CERL to develop an Initial Operating Capability for a module within the Enterprise Sustainment Management System to support the OSD requirement.

1 Oct 2020

Laboratory Evaluation of Aquablok™ Erosion Resistance: Implications for Geotechnical Applications

Abstract: AquaBlok™ (AB) is a commercial product traditionally used as an alternative material for contaminated sediment capping applications. Previous studies of AB capping performance have reported enhanced stabilization through increased erosion resistance. Subsequently, AB has been considered for use as an alternative levee repair material due to its cohesive properties. Through a series of laboratory experiments, this study investigated the erosion behavior of new AquaBlok formulations (10%, 20%, and 30% clay by weight) under increased shear stresses previously unachievable in the previous tests. The new AquaBlok formulations were tested in non-compacted and compacted states to simulate the physical properties in capping and levee repair applications. In the non-compacted state, excess hydration of the clay matrix extended approximately 5 cm below the bed surface, which greatly reduced erosion resistance and was independent of clay percentage. Below this horizon, critical shear stress increased, and erosion rates decreased, with clay percentage, respectively. However, this does not consider a continuous change in hydration state when exposed to free water. In the compacted state, erosion rates were greatly arrested, with measureable erosion only possible under the maximum applied shear stress (24 Pa). The results are discussed in the context of capping and levee applications.

24 Sep 2020

Study of Sand Boil Development at Kaskaskia Island, IL, Middle Mississippi River Valley

Abstract: Mississippi River flooding in 2013 and 2016 caused severe underseepage and development of several medium to large high-energy sand boils behind the landside levee toe at Kaskaskia Island, IL. This levee system is located between St. Louis and Cape Girardeau, MO, and is part of the Kaskaskia Island Drainage and Levee District on the Middle Mississippi River. Flooding on the Mississippi River in 2013 and 2016 was below the design flowline for this levee. This report documents a case history study into the causes of seepage, piping, and sand boil development at a levee reach at Kaskaskia. Site-specific geotechnical data were collected and evaluated to determine the causes for poor performance at the studied levee reach locations. Data collected involved design documents, geologic and geotechnical borings, closely spaced cone-penetrometer tests (CPTs), electrical resistivity surveys, laboratory soil testing of sand boil ejecta, CPT samples from targeted stratigraphic horizons in the subsurface, and both piezometer and river-stage data. These data indicate sand boils present within this levee reach involved a chronic seepage condition that became progressively worse through time. This condition was directly related to the underlying site geology, namely the top stratum thickness and the depositional environment in this levee reach.