Search

The maintenance of flood mitigation levees in the U.S. and elsewhere, has often found to be insufficient. Recent U.S. levee safety inspections have discovered substantial deficiencies in many federally monitored levees resulting in some of them being assigned an 'unacceptable' safety rating. Most levees in the U.S. were constructed using federal money but then were turned over to local government entities to maintain, thus socioeconomic characteristics of these communities may impact their ability to maintain their levee(s). We used dasymetric mapping to assign socioeconomic parameters to levee protected areas along the lower Illinois River to explore differences in these characteristics between communities with an unacceptable levee safety rating to those with an acceptable rating. Principal components analysis was used to determine which socioeconomic parameters explained the majority of variance between levee protected communities and the Mann-Whitney-Wilcoxon U-Test for significance testing. These analyses revealed that differences in total population , race, average per-capita income, and number of residential homes were influential indicators for explaining differences between comunities with levees with acceptable versus unacceptable ratings. These results suggest populations who inhabit levee systems with unacceptable safety ratings are white and relatively wealthier than communities located within levee systems with acceptable ratings. This finding is counter to research that shows that the poor and poorer minorities live in areas with higher flood risk. This is perhaps wealthier floodplain property owners inhabitating unacceptable levee systems may be foregoing necessary levee maintenance, inastead relying on other government programs to pay for flood damages. [ABSTRACT FROM AUTHOR]

Alluvial river landscapes of the lower Mississippi and Atchafalaya rivers in the south-central USA are flood prone and have shifted historically in position and form, resulting in interventions for flood reduction, navigation, and water supply. Fisk mapped these landscapes in the middle of the twentieth century as a series of artistic colourful map plates. Selected areas are revisited with modern data sets (LiDAR from 2003, hydrographic surveys from 2006 and 2007) including two sites along the Mississippi River (near the Old River juncture and near Morganza Floodway) and one in the middle Atchafalaya River. By using 2D and 3D geovisualization, we find that the extent, variety, and dimensions of anthropogenic landforms have grown in prominence since Fisk's mapping. The volumes of the highest positive landforms are quantified to provide some indication of direct and indirect anthropogenic activity in these landscapes. [ABSTRACT FROM AUTHOR]

The lowermost Mississippi River (LMR) is important to the environment and economy of continental United States. Although bathymetric data have been collected over many decades at numerous cross-sectional sounding points, there has been no consensus on appropriate interpolator for generating bathymetry. Such interpolation is critical to reliable assessments of channel morphology and channel change, which serve for dredging, engineering projects, and mapping of navigation hazards. This study aimed to identify an optimal spatial interpolation for mapping the river bathymetry from cross-sectional sounding measurements. We evaluated a variety of spatial interpolation methods including Inverse Distance Weighting (IDW), Ordinary Kriging (OK), Radial Basis Function (RBF), and Local Polynomial Interpolation (LPI). In addition, we also considered the anisotropic form of IDW (Elliptical IDW as EIDW), that of OK (OKA), and Universal Kriging (UK). Two reaches in the LMR, located between approximately RM (River Miles) 170–140 and RM 60–35, were chosen as the study area. Those interpolators were compared in terms of root-mean-square error (RMSE), mean absolute error (MAE), bias, and coefficient of determination (r2). Our results demonstrate that both of RBF and OKA performed the best in mapping the bathymetry of study reaches. Furthermore, our results also indicate that the addition of anisotropy can significantly reduce RMSE by 5–20%, as compared to isotropic methods. The findings better inform other researchers on selecting a proper interpolation technique for mapping river bathymetry, particularly for other reaches of the Mississippi River. [ABSTRACT FROM AUTHOR]

Due to increasing demands regarding student learning outcomes and accreditation, a capstone portfolio was added to assess critical thinking and communication skills of geography majors at a large public university in the USA. The portfolio guidelines were designed to be adaptable to a flexible curriculum where about half of the requirements within the major are structured. This paper discusses the portfolio requirements and assessment rubrics developed following multiple portfolio iterations, gives guidance to instructors, and synthesizes potential benefits for students, departments and employers. [ABSTRACT FROM PUBLISHER]

Old River is one of the most important river junctures in North America. It connects three large, navigable rivers the Mississippi, Atchafalaya and Red which support economies and environments critical to United States of America. Starting in the 1800s, the Atchafalaya River began receiving more flow through this juncture, and by the mid-1900s, an avulsion was likely so the Old River Control Project was authorized to prevent diversion of the Mississippi River to the Atchafalaya. This paper examines the historical changes of Lower Old River, the main juncture prior to 1963 before the flow became controlled by structures, including its flow changes, human modifications, and whether and how it was changing as the Atchafalaya received more flow. In contrast to some reports that suggest that bidirectional flow in Old River was just a few years in duration, occasional flow from the Red River is documented: starting in the 1880s and persisting for several decades through 1945. This paper identifies three transitions in the transformation from bidirectional to unidirectional flow, the first of unknown cause in the late 1910s, the second likely instigated by the flood of record in 1927, and the third immediately following a local artificial cut-off in 1944-1945. Also, changes in flow and geometry in Lower Old River are related to changes in the adjacent Mississippi and Atchafalaya Rivers. [ABSTRACT FROM AUTHOR]

Change in fluvial systems has interested geomorphologists for several decades, but awareness of change dates back much further to the ancient Greeks. This paper introduces seven articles that focus on aspects of temporal and/or spatial change in rivers in the central and southeastern United States of America. Timescales examined span from the late Pleistocene through historical and into modem times. Spatial scales investigated range from small watersheds to the juncture between two of the larger rivers in North America. Natural drivers of change discussed include sea-level rise which followed the last glacial maxima and influenced drainage connections, avulsions, and lateral migration which influenced channel position and caused stream capture; and transitions across geomorphic provinces with differing bedrock and structure. Human-induced drivers of change include land use alterations such as settlement and logging which influenced sediment input and channel form, artificial cut-offs, removal of log rafts, dredging, and artificial channels and floodways which changed flow, sedimentation, and geometry, and the introduction of contaminants which influenced sediment quality. Collectively, these papers fill voids in the literature on topics and places where there has been little prior investigation. [ABSTRACT FROM AUTHOR]

Floodplain mining creates a vulnerable landscape comprised of pits, bare land and stock piles with minimal vegetation. During floods, when stages can exceed bank- full by several meters, all or part of the channel may divert into a pit, re-routing the flow and transforming the planform and profile of alluvial landscapes. Using geospatial data from the mined Tangipahoa River floodplain for 1980 to 2004, the objectives of this study are to (1) assess if pit characteristics such as proximity to channel and size affect the potential for diversion; and (2) interpret relationships between pit diversions, channel changes, and floods. Of the 56 pits mapped in the floodplain in 1980, six had been captured by 2004. Captured pits were closer to the main channel than those which were not captured, but the areas of captured and noncaptured pits were not significantly different. However, avulsions into large pits caused more channel planform change than those into smaller pits. Other findings are that point bar areas increased 72% overall, more so in the mined reach, and that degradation exceeded 6 m in the mined reach, in contrast with aggradation of 1 m roughly 20 valley km downstream. Results will be useful in understanding landscape vul- nerability and can be applied to river management and restoration. [ABSTRACT FROM AUTHOR]

This study uses oxbow lakes to ascertain the extent and nature of change in a river's form, focusing on the effects of post-1950s floodplain gravel extraction on the geomorphology of the Leaf River in southeastern Mississippi, USA. The river and oxbow lakes of a 5 km reach were examined for the effects of local and upstream floodplain and in-channel gravel mining. Data from 12 cross-sections suggests that the present-day river is 35% wider and 12% shallower than the cross-sectional geometry in cutoffs that pre-date 1955. Field measurements reveal that the Leaf River was relatively stable from at least 1911 to the early 1940s, but has since undergone an average of 2.65 m of degradation in the study reach. Survey data from a nearby USGS stream gage show that degradation began abruptly in the mid 1970s, most likely as a result of in-stream mining and pit avulsions on a major tributary that deprived downstream areas of bed load and created profile adjustments. [ABSTRACT FROM AUTHOR]

Discusses topic synthesis as a vehicle for improving oral communication skills, comprehension and retention in higher education. Topic synthesis as approach where students summarize the key points of the previous lecture at the start of the class; Mechanics of implementing topic synthesis; Benefits; Evaluation of topic synthesis by students.

Discusses the motivation, implementation and impressions of involving students in written and oral field guide contributions in geography classes. Quality of an exclusively instructor-generated product; Advantages of written and oral communication opportunities; Acquisition of self-esteem.

Until recently a neglected region, renown for limited exposures, the southern United States is becoming an area of geomorphic discovery. This article presents an overview of current geomorphic research in this region, suggesting that despite past problems, academic geographers have made significant contributions to the geomorphology of the South in recent years. Research topics published on the region are highly varied, with some spatial bias as well as topical bias toward fluvial systems. Yet because of the limited historical work, much is unknown about these unique landscapes and their susceptibility to natural and human disturbances, and much benefit is to be gained from both applied and theoretical study of them. [ABSTRACT FROM PUBLISHER]