Levee Sites Research Articles

Assessing the impact of sample size and geology on earthen embankment design and construction

This technical paper investigates the influence of sample size and geologic characteristics on the geotechnical design of levee embankments. Sample quality plays a vital role in quantifying engineering properties for levee embankment projects, and numerous studies have highlighted the impact of sample disturbance on such engineering properties. Despite this evidence, conventional tube and piston samplers of different diameters continue to be widely used, potentially leading to underestimation of shear strength. The paper focuses on comparing 7.6 cm and 12.7 cm diameter undisturbed Shelby tube samples and CPT data collected from three levee sites in the Greater New Orleans Area, Louisiana, USA, which encompass diverse geologic histories. The study aims to assess the effect of industry used samples size and geology on levee construction costs. The findings provide valuable insights into optimizing sample collection methods and improving geotechnical design for earthen embankments.

Revisiting levees in southern Texas using Love-wave multichannel analysis of surface waves with the high-resolution linear Radon transform

Shear-wave velocities were estimated at a levee site by inverting Love waves using the multichannel analysis of surface waves (MASW) method augmented with the high-resolution linear Radon transform (HRLRT). The selected site was one of five levee sites in southern Texas chosen for the evaluation of several seismic data-analysis techniques readily available in 2004. The methods included P- and S-wave refraction tomography, Rayleigh- and Love-wave surface-wave analysis using MASW, and P- and S-wave cross-levee tomography. The results from the 2004 analysis revealed that although the P-wave methods provided reasonable and stable results, the S-wave methods produced surprisingly inconsistent shear-wave velocity [Formula: see text] estimates and trends compared with previous studies and borehole investigations. In addition, the Rayleigh-wave MASW method was nearly useless within the levee due to the sparsity of high frequencies in fundamental-mode surface waves and complexities associated with inverting higher modes. This prevented any reliable [Formula: see text] estimates for the levee core. Recent advances in methodology, such as the HRLRT for obtaining higher resolution dispersion-curve images with the MASW method and the use of Love-wave inversion routines specific to Love waves as part of the MASW method, provided the motivation to extend the 2004 original study by using horizontal-component seismic data for characterizing the geologic properties of levees. Contributions from the above-mentioned techniques were instrumental in obtaining [Formula: see text] estimates from within these levees that were very comparable with the measured borehole samples. A Love-wave approach can be a viable alternative to Rayleigh-wave MASW surveys at sites where complications associated with material or levee geometries inhibit reliable [Formula: see text] results from Rayleigh waves.

Study on Levee Visual Inspection Information System Building Using Mobile Technology

In this paper, we propose the mobile visual inspection information system using DGPS and portable range finder for levee safety inspection. Instead of existing visual inspection management method that is stored hand-written data, this system is designed to manage directly the visual inspection information using mobile devices in the field of levee. And through extracting accurate DGPS coordinates information about damage location of levee, this system is developed to ensure efficiency for the main task arising from the levee site such as inspection, maintenance and reinforcement. Furthermore, when damage has occurred at the point that inspector is not able to approach, this system can record the damage site data correctly, by converting data such as position, orientation and height of the damage point into the World Geodetic System coordinates. The position, orientation and height data was extracted automatically through the DGPS and portable range finder. And by applying the augmented reality method, this system was implemented for inspector to revisit the point of damage easily in order to perform the management, maintenance and reinforcement of the levee later.

Wetland landscape dynamics, Swifterbant land use systems, and the Mesolithic–Neolithic transition in the southern North Sea basin

Over the last decade, excavations in the lower Scheldt river basin (NW Belgium) have identified the first presence of the transitional Mesolithic–Neolithic Swifterbant culture, previously only known from the Netherlands and one site in northwest Germany. These excavations have also yielded the first evidence for the presence of Early Neolithic Linearbandkeramik, Limbourg, Blicquy and Epi-Rössen cultural remains in these wetland landscapes. High quality organic preservation at these sites offered the opportunity to reliably place the Swifterbant within the absolute chronology of the Mesolithic–Neolithic transition in this region, as well as the reconstruction of Swifterbant subsistence practices, most notably the incorporation of cattle husbandry into a traditional hunting-fishing-gathering economy. Two different site types could be identified between the six excavated sites – dune and natural levee sites – which had contemporaneous periods of occupation, but different occupation histories. The integration of the dates from these different site types with the palaeoenvironmental dates provides an initial model of the Swifterbant settlement system in the area and its role in the specific tempo and trajectories of cultural and economic change that occurred during the neolithisation of the Scheldt basin. This model consists of relatively specialized and temporarily inhabited cattle and hunting-fishing camps on the dunes and larger, more continuously occupied levee camps along the river valleys. Bayesian statistical modeling suggests that Swifterbant occupation of the dune sites occurred during a brackish water flooding period and that occupation of the levee sites was more continuous.

Effects of Woody Vegetation on Seepage-Induced Deformation and Related Limit State Analysis of Levees

AbstractWork in this paper investigates the effects of woody vegetation on soil hydraulic conductivity and the related probability of exceeding deformation-based performance limit states. A summary of results obtained from laboratory and field hydraulic conductivity tests for four levee sites is presented. Limit states, as defined based on the framework of critical state soil mechanics, are developed and simple probability analyses are used to quantify the probability of exceedance under hydraulic loading. A case study of Elkhorn Levee near Sacramento, California, is presented to demonstrate the applicability of the limit states concept. The field and laboratory hydraulic conductivity data obtained from the four levee test sites show no clear trend to support the notion that woody vegetation leads to either high or low values of hydraulic conductivity; site-specific testing is needed to discern such an effect. Even though the levee case used in this study (Elkhorn) was in a marginal condition of stability...

Simplified Methodology for Consideration of Two-Dimensional Dynamic Response of Levees in Liquefaction-Triggering Evaluation

AbstractLevees are very challenging engineering structures to study, in part because they are not typically well-engineered structures. Unfortunately, there is little to no guidance as to how to evaluate the seismic vulnerability of levees. This study focuses on systematically studying the dynamic response of levees using a wide range of input ground motions and developing a simplified procedure for the liquefaction triggering evaluation of earthen levees, accounting for the dynamic response of the levee. The study was based on three levee sites representative of three select California Central Valley regions; however, because floodplains tend to generally have similar depositional environments, the study can be extended to other regions as long as some of the principal characteristics are still applicable. A wide range of input ground motions was used to capture and assess the variability in response and performance because of multiple possible earthquake scenarios. Two aspects of the dynamic response an...

Site Response and Basin Waves in the Sacramento–San Joaquin Delta, California

The Sacramento–San Joaquin Delta is an inland delta at the western extent of the Central Valley. Levees were built around swampy islands starting after the Civil War to reclaim these lands for farming. Various studies show that these levees could fail in concert from shaking from a major local or regional earthquake resulting in salty water from the San Francisco Bay contaminating the water in the Delta. We installed seismographs around the Delta and on levees to assess the contribution of site response to the seismic hazard of the levees. Cone penetrometer testing shows that the upper 10 s of meters of soil in the Delta have shear‐wave velocities of about 200 m/s, which would give a strong site response. Seismographs were sited following two strategies: pairs of stations to compare the response of the levees to nearby sites, and a more regional deployment in the Delta. Site response was determined in two different ways: a traditional spectral ratio (TSR) approach of S waves using station BDM of the Berkeley Digital Seismic Net as a reference site, and using SH / SV ratios of noise (or Nakamura’s method). Both estimates usually agree in spectral character for stations whose response is dominated by a resonant peak, but the most obvious peaks in the SH / SV ratios usually are about two‐thirds as large as the main peaks in the TSRs. Levee sites typically have large narrow resonances in the site response function compared to sites in the farmland of the Delta. These resonances, at a frequency of about 1–3 Hz, have amplitudes of about 15 with TSR and 10–12 with Nakamura’s method. Sites on farmland in the Delta also have amplifications, but these are typically broader and not as resonant in appearance. Late (slow) Rayleigh waves were recorded at stations in the Delta, have a dominant period of about one second, and are highly monochromatic. Results from a three‐station array at the Holland Marina suggest that they have a phase velocity of about 600 m/s and arrive at about the same azimuth as the straight‐line back azimuth to the source. A dispersion curve determined for the basin or valley waves yields a shallow velocity profile that increases from about 350 m/s in the upper 0.2 km to about 1.1 km/s at a depth of about 2 km.

Predicting shallow surficial failures in the Mississippi River levee system using airborne hyperspectral imagery

Shallow surficial failures or levee slides in the Mississippi River levee system are very common. There is currently no system to identify or predict the location of these slides before they occur. Studies of slide occurrence mechanisms suggest that probable slide-affected areas are characterized by anomalous vegetation. Compact Airborne Spectrographic Imager II (CASI II) imagery was analysed for selected levee sites in association with slide inventory data and field observations. Normalized Difference Vegetation Index (NDVI), Red edge Vegetation Stress Index (RVSI) and Red Edge Position Index (REP) were calculated from the acquired CASI II imagery. The vegetation indices were used to locate the stressed or anomalous vegetation and predict levee slides. The statistical significance of the predictors was determined by logistic regression. All predictors were found statistically significant for developing a slide prediction model. The slide prediction model was developed by combining the single predictors, categorized vegetation indices, into a model based on all three predictors. Percentage of Search Area Reduction (PSAR) and Failure Index (FI) were used to evaluate the performance of the slide prediction model. Evaluation of the model performance shows that it achieves a maximum FI of 0.43 and PSAR of 99.5.

Evaluating levee failure susceptibility on the Mississippi River using logistic regression analysis

The goal of this investigation was to test the relative importance of geologic, geomorphic, and other physical factors that have led to levee failures through the past century along much of the Mississippi River. Logistic regression analysis assessed site characteristics at levee-failure locations identified in a database of historical levee failures along 685 km of the Middle and Lower Mississippi River (MMR and LMR). Levee site parameters were evaluated using geologic maps, soil survey maps, digital elevation models (DEMs), historic river maps, dredging reports, and field evaluations. Two statistical models were created for each river reach, one with a conservative ≥ 95% significance threshold, and another with a relaxed significance threshold (≥ 80% for the MMR, and ≥ 90% for the LMR). The conservative MMR model identified the presence/absence of channel fills as a significant and primary predictor of levee failures. The liberal MMR model identified several additional significant controls: location on a meander bend, channel width, land-cover type, and intensity of dredging. The conservative LMR model identified location of failure on a meander bend, land-cover type, channel constriction factor, and sinuosity of the channel as significant, while the liberal LMR model added: the presence of borrow pits, channel width, vegetative buffer width, and presence/absence of bank revetment. The results presented here could potentially assist engineers and decision-makers in choosing appropriate locations and designs for levees in the future.

Investigating Neolithic land use in Swifterbant (NL) using micromorphological techniques

In the Swifterbant area in The Netherlands, a complete Neolithic landscape is preserved, buried in a wetland environment. A dozen sites (dating from ca. 4300-4000 cal. BC) on levees of a former creek system are characterized by a black layer containing large amounts of carbonized plant remains, burnt bone, flint and pottery. These sites are usually interpreted as occupation sites with accumulated refuse of a society in transition from a Mesolithic to a Neolithic lifestyle (hunting and herding), in an area that was too wet for crops. In the context of a new research campaign in the area, we investigated the site- and land-use on two locations (S2 and S4) using micromorphological techniques. On S2, the soil matrix in the archaeological horizon has a heterogeneous, non-sedimentary appearance due to the ubiquitous presence of rounded and subrounded aggregates. These aggregates indicate that the sediment was disturbed after deposition, but it is unclear by what human activity. This disturbance is not restricted to the archaeological site horizon, but extends also into the under- and overlying layers. On S4, three layers can be distinguished. Only the lower and central parts are usually regarded as archaeological layers. The lower layer shows thorough mixing of the (partly decalcified) groundmass and the incorporation of anthropogenic materials (carbonized plant remains, burnt bone, etc.). Most probably, the thorough mixing is a result of tillage. The central layer consists of thinly laminated phytoliths and carbonized plant remains with ample fragments of (burnt) bone, angular sediment clods and some dog coprolites. Mineral sediments are absent. Apparently, the layer was formed by human activities that resulted in a massive accumulation of burnt organic materials and anthropogenic debris. The preservation of the microlayering formed by phytoliths and carbonized is remarkable, since trampling would have deformed or disturbed the layering. The surprising conclusion therefore has to be that this location was not the main settlement area-as was implicitly thought until now. Rather, the area should be interpreted as a location where specific activities resulted in the accumulation of burnt plant material, e.g. a waste dump. The upper layer again has indications of anthropogenic soil disturbance. Samples from the basin adjacent to the levee site show sediments that are deformed by trampling. The transition of the site to the channel shows no signs of trampling, but rather interfingering of site layers with channel sediments. Lack of trampling in the central zone of S4 and the adjacent channel shore is at odds with the classical interpretation that the site represents a settlement area. The black layers that up till now were thought to encompass a complete settlement, could very well be a very prominent part of larger sites with remains of human activities during the Neolithic. (C) 2009 Elsevier B.V. All rights reserved.

Dynamic Properties of Highly Organic Soils from Montezuma Slough and Clifton Court

The nonlinear dynamic properties of highly organic soils from two levee sites in the Sacramento-San Joaquin Delta in California are described. Cyclic triaxial, resonant column and torsional shear tests were performed on thin-walled tube samples obtained from beneath levee crests, beneath adjacent berms, and in the free field such that the in situ vertical effective stresses ( σ vo ′ ) ranged from about 16 to 67 kPa . These highly organic soils had considerably different organic characteristics from those used in previous studies of dynamic properties. The tested samples had organic contents of 14 to 61%, initial water contents ( wo ) of 88 to 496%, shear wave velocities ( Vs ) of 20 to 130 m∕s , and organic components that ranged from highly fibrous to highly decomposed and amorphous. Secant shear modulus (G) , normalized secant shear modulus (G∕ Gmax ) , and equivalent damping ratio (ξ) versus cyclic shear strain amplitude ( γc ) relations are presented, and their dependence on variables such as consolid...

How the Olmec used bitumen in ancient Mesoamerica

Bitumen, found in abundance in Mesoamerica’s southern Gulf Coast region in natural seeps and in many archeological contexts, is an important economic resource and exchange item that has received little consideration in Mesoamerica. Analyses of archeological, ethnoarcheological, and experimental data provide insights on the organization of bitumen processing activities, and the end product (archeological bitumen), which the Olmec (1200–400 BC) used in the production of many items. Archeological data are derived from investigations at El Remolino and Paso los Ortices— two Early Formative period levee sites in the San Lorenzo Olmec region. Our findings suggest that among the Olmec, bitumen processing was organized as a specialized activity, involving multiple production stages, but not necessarily elite involvement or control.

Salt marsh pore water geochemistry does not correlate with microbial community structure

Spatial and temporal trends in pore water geochemistry and sediment microbial community structure are compared at three intertidal sites of a saltmarsh on Sapelo Island, GA. The sites include a heavily bioturbated, unvegetated creek bank, a levee with dense growth of Spartina alterniflora, and a more sparsely vegetated ponded marsh site. The redox chemistry of the pore waters ranges from sulfide-dominated at the ponded marsh site to suboxic at the creek bank site. At the three sites, the vertical redox stratification of the pore waters is more compressed in summer than in winter. The trends in redox chemistry reflect opposing effects of sediment respiration and pore water irrigation. Intense and deep burrowing activity by fiddler crabs at the creek bank site results in the efficient oxidation of reduced byproducts of microbial metabolism and, hence, the persistence of suboxic conditions to depths of 50 cm below the sediment surface. Increased supply of labile organic substrates at the vegetated sites promotes microbial degradation processes, leading to sharper redox gradients. At the levee site, this is partly offset by the higher density and deeper penetration of roots and macrofaunal burrows. Surprisingly, the microbial community structure shows little correlation with the variable vertical redox zonation of the pore waters across the saltmarsh. At the three sites, the highest population densities of aerobic microorganisms, iron- plus manganese-reducing bacteria, and sulfate reducers coexist within the upper 10 cm of sediment. The absence of a clear vertical separation of these microorganisms is ascribed to the high supply of labile organic matter and intense mixing of the topmost sediment via bioturbation.

Rates and controls of anaerobic microbial respiration across spatial and temporal gradients in saltmarsh sediments

This study was undertaken to determine the rates and controls ofanaerobic respiration reactions coupled to organic matter mineralization as afunction of space and time along a transect from a bioturbated creekbank to themidmarsh in Georgia saltmarsh sediments. Sulfate reduction rates (SRR) weremeasured at 3 sites during 5 sampling periods throughout the growth season. Thesites differed according to hydrologic regime and the abundance of dominantplants and macrofauna. SRR and pore water / solid phase geochemistry showedevidence of enhanced sediment oxidation at sites exposed to intensebioturbation. Iron(III) reduction rates (FeRR) were directly determined insaltmarsh sediments for the first time, and in agreement with measured SRR,higher rates were observed at the bioturbated, unvegetated creekbank (BUC) andbioturbated, vegetated levee (BVL) sites in comparison to a vegetated mid-marsh(MM) site. An unexpected result was the fact that SRR varied nearly as muchbetween sites (2–3 x) as it did with temperature or season (3–4 x).The BVL site, vegetated by the tall form of Spartinaalterniflora, always exhibited the highest SRR and carbon oxidationrates (> 4000 nmol cm−3 d−1) with high activity levels extending deep (≥ 50 cm)into the sediment, while the MM site, dominated by the short form ofSpartina, always exhibited the lowest SRR which werelocalized to the top 15 cm of sediment. SRR and FeRR at BUC wereintermediate between those measured at the BVL and MM. Acetate was the mostabundant microbial fermentation product (concentrations up to > 1mM) in marsh porewaters, and its distribution reflectedrespirationactivity. Chemical exchange, caused by bioturbation, appeared to be the primarycontrol explaining trends in rates of sulfate and Fe(III) reduction withmacrophytes and carbon source acting as secondary controls.

Soil‐atmosphere exchange of methane in adjacent cultivated and floodplain forest soils

The soil‐atmosphere exchange of methane was measured in adjacent cultivated (corn) and forest (upper floodplain, mixed hardwood) habitats of the southeastern U.S. piedmont for a period of 3 years using closed chambers. We have evaluated the effect of the following factors on soil‐atmosphere methane exchange: (1) interannual variability of climatic conditions, (2) landscape position (i.e., river levee versus terrace), and (3) disturbance ranging from intense (cultivation) through moderate (approximately annual flooding events that last from weeks to months) to subtle (approximately annual flooding of a few days duration). We found that mean methane consumption in the cultivated and forested terrace sites was <0.3 mg CH4 m−2 d−1, whereas the mean consumption rate in forested levee sites was about 1.4 mg CH4 m−2 d−1 over the course of the 3 years. Moisture levels in the upper soil (0–5 cm) appear to exert little control of methane exchange in any of the habitats. We observed little seasonal variation in methane flux in the levee sites, in contrast to results observed by others in higher‐latitude and tropical forests. Our results suggest that very subtle differences in landscape position and disturbance impact the strength of the soil methane sink. We cannot conclude that agricultural development destroyed the methane sink capacity of these floodplain terrace soils because it was probably already quite low due to periodic disturbance by flooding. Limited measurements of nitrogen cycling suggest that methane flux differences observed among the different habitats are not obviously related to differences in N mineralization or nitrification as in other ecosystems.

Association of Levee Vegetation to Rice Water Weevil (Coleoptera: Curculionidae) Infestation in California Rice

The association between levee vegetation and rice infestation level by the rice water weevil, Lissorhoptrus oryzophilus Kuschel, was evaluated in California’s Sacramento Valley. Fields with vegetated versus bare levees were compared for adult weevil infestation during the spring flight period. Lower infestations were associated with bare levees at 13 of 15 locations from 1990 to 1992. Weevil infestation remained below the recommended treatment level at 8 of 15 bare levee sites, but only 1 of 15 weedy levee sites.

An Appalachian-sourced deltaic sequence, northeastern Alabama, U.S.A.: biofacies-lithofacies relationships and interpreted community patterns

The thin sequence of Lowe Pennsylvania rocks along Sand Mountain, Plateau coal field, northeastern Alabama, U.S.A., records the deposition in a deltaic coastal-plain paleoenvironment along the ancient Appalachian seaway. The section is laterally continuous, well exposed, and preserves a rich macrobiota. Identified coexisting paleodepositional environments contain distinctive biofacies. Biofacies in deltaic sites are characterized by the presence of various macrofloral assemblages. Alluvial-plain swamps, identified lithologically by homogeneous mudstone and siltstone, preserve bedded-plant litter as coalified compressions and impressions. Deep-swamp biofacies are comprised either of monotypic lycophyte canopy assemblages ( Lepidophloios) or their subterranean axial systems ( Stigmaria). Alluvial swamps and proximal levee sites contain canopy detritus of a mixed flora. This is reflected in the reduced domination of Lepidophloios, the increased importance of the lycophytes Sigillaria and Lepidodendron, and an abundance of gymnosperms, pteridosperms, pteridophytes, and Calamites. Macro-invertebrates occur almost exclusively as behavioral trackways of xiphosurid arthropods and epifauna attached to fragmentary plant parts. The peat-accumulating swamp biofacies is identified from palynological preparations. Palynofloras parallel macrofloral clastic swamp diversity and contain an abundance of palynomorphs with affinities to ferns and lyginopterid pteridosperms. Channel-form sandstone represent distributary and crevasse channel deposits in the lower part of the section, and uncomformable bedload-dominated, laterally migrating, braided-river channel deposits at the top of the sequence. Oriented sandstone cast and compressed logs (lycophytes and Calamites) occur with bedload features in distributary and braided channels. Crevasse sanstones preserve a higher proportion of calamitean axes, as well as trunks and rachises of medullosan pteridosperms. Macro-invertebrates and ichnofaunas have not been identified in these paleoenvironments. Bayfill sequences contain several in situ macro-invertebrate communities in addition to allochthonous plant detritus. This plant biofacies is characterized by calamitean and pteridospermous vegetation, that originated from levee sites. The macrofaunal biofacies is characterized by a molluscan assemblage, with community replacement relative to physical parameters of the water. The initial bayfill phase contains an inarticulate brachiopod community of Orbiculoidea and Lingula. The transition to the molluscan-dominated biofacies is signaled by infaunal colonization by Pteronites and Planolites (burrows). Biotic changes are reflected by the increasing abundance of brachiopods and other invertebrates usually considered to represent more open-marine conditions. Insights into Late Carboniferous open-marine communities can be discerned from lag accumulations of marine epifauna in storm-generated sandstones.