Maureen K. Corcoran

Geomorphic Investigation of the Great Bend Region, Red River

The U.S. Army Engineer District, Vicksburg, conducted feasibility studies to rehabilitate the levees along the Red River from Fulton, AR, to the Arkansas-Louisiana state line. In support of these studies, research was performed by the U.S. Army Engineer Research and Development Center to provide a geomorphic framework for cultural resources in the project area. This research had three specific objectives: (1) identify and map geomorphic features in the study area on 1:24,000 scale maps, (2) define geomorphic processes that are active in the study area, and (3) reconstruct the geomorphic development of the study area to understand the significance of geomorphic features in terms of both locating previously unknown archaeological sites and discovering buried sites. Field investigations and aerial photography were used to interpret the geomorphology. Approximately 6 percent of the known archeological sites are located above the floodplain on valley slopes or bluffs. The remaining 94 percent of the sites are associated with the floodplain of the various fluvial components that form the study area. Forty-six percent of floodplain sites are located adjacent to crevasse channels. Other known archaeological sites are primarily located on the natural levee or adjacent point bars. DISCLAIMER: The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. All product names and trademarks cited are the property of their respective owners. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents. DESTROY THIS REPORT WHEN NO LONGER NEEDED. DO NOT RETURN IT TO THE ORIGINATOR. ERDC/GSL TR-18-17 iii

Remote Sensing and Monitoring of Earthen Flood-Control Structures

Abstract : The purpose of this study was to identify and review technologies that are applicable in locating weaknesses and poor performance within flood-control structures from extreme loading events. The focus of this study was to assess current technologies and state-of-practice techniques involving remote sensing, testing, and real-time monitoring of earthen structures. Advancements in satellite and sensor technology combined with high-speed internet and telecommunication capabilities and smart decision-making software permits real-time monitoring of earthen flood-control structures such as dams and levees. Technologies evaluated included both active and passive sensing methods. These technologies included satellite, airborne, and ground-based sensor systems to identify surface and subsurface characteristics of the watershed, as well as point sensors typically embedded in hydraulic structures to monitor the health of the structure. Point sensors typically record water loading, soil pore pressures, soil movements, and other important properties to evaluate global stability of the water control structure. Geophysical-based methods are typically used in mapping, monitoring, and detection of subsurface stratigraphy, seepage, and any changes in subsurface conditions through time within flood-control structures and their foundations.

Geotechnical Evaluation of the Brownsville Levee Cracking and Partial Slope Failure

Abstract : The U.S. International Boundary and Water Commission (IBWC) discovered cracks and a partial slope failure on a newly refurbished levee section and adjacent floodplain along the Rio Grande River in Brownsville, TX. The partial failure followed a significant drop inwater level in early April 2014. A geotechnical investigation was performed by the U.S. Army Engineer Research and Development Center (ERDC) to determine the causes for the partial levee failure and provide remediation alternatives. A series of events, combined with the local geologic conditions, led to the partial slope failure. Events included the 2012 levee construction, fluctuation and rapid drawdown conditions in the Rio Grande, and a higher elevation of Lake Brown (an oxbow of the Rio Grande) relative to the river. Progressive or creep-type failure mode was identified as the probable mechanism to explain the deformation observed in the field, and this was confirmed by seepage and stability analyses. Based on this evaluation, recommendations for remediation include: (1) implementation of a vegetation control program, (2) short-term monitoring, (3) evaluation of other locations along the river with similar river geometry and groundwater conditions, (4) efforts to minimize sudden drawdown, (5) additional analyses using the design hydrograph, and (6) incorporating cost/benefit analyses for the different alternatives.

The legacy of the 1948 underseepage and crevasse maps, Lower Mississippi River levees

Abstract : Seepage and crevasse maps showing levee performance from the 1937 and 1945 floods in the LMV were compiled as part of the comprehensive study by USACE (1956) into levee underseepage and its control. This map folio was limited in distribution, never officially published as a technical memorandum/report, and was thought to have been lost. The map folio was discovered as part of ongoing research into sand boils in the LMV and consists of 40 15-min scale maps extending from Cairo, IL, to New Orleans, LA. The complete set of maps was scanned and is being presented herein for wider dissemination. This map folio identifies sand boil locations, historic crevasses, severity of seepage, and extent of seepage control measures that were present prior to 1945. A historic summary is presented for background information and importance to ongoing studies of seepage control and internal erosion of levees.

Geologic controls of sand boil formation at Buck Chute, Mississippi

Abstract : Sand boil formation due to underseepage is a potential failure mechanism for levees in the Lower Mississippi River Valley. Sand boils were identified in the Buck Chute study area in the 1990s during high-water events and during the 2009 Flood. The site is unique due to the presence of point bar and abandoned channel deposits. To understand the role of these alluvial deposits on sand boil formation at the site, a geologic investigation of the subsurface was conducted. Using shallow geophysics, cone penetrometer tests (CPT), borings, and a geographic information system (GIS), researchers concluded that the thin blanket associated with point bar deposits, abandoned channel deposits causing a blocked seepage path, and head differential changes caused by the Muddy Bayou Control Structure were the controls of sand boil formation at Buck Chute.