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Hydrological drought and river disconnectivity worsen from dams and human activities. This research investigates how dam constructions exacerbate hydrological drought and river disconnectivity in Apalachicola River system. Data from two hydrological stations (1928-2022), a hydrographic survey, high-resolution LiDAR, and a triangular irregular network (TIN) were used to identify three connectivity flow (141.5 m3/s, 169.8 m3/s, and 226.4 m3/s) categories, each impacting floodplain differently. A relative elevation model (REM) was also developed for floodplain connectivity assessment. Findings show a significant increase in the frequency, duration, and magnitude of connectivity low flow events from pre-dam to post-dam periods, especially at the 169.8 m³/s connectivity flow threshold. A 20th percentile variable threshold shows increasing hydrological drought. Drought increases have led to decreased connectivity between tributaries and the main river system, and an increase in the moderately disconnected floodplain area from 37.1% to 46.0%. Adaptive management strategies are needed to address drought-induced floodplain disconnectivity [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.

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]

Floodplain characteristics contribute to the natural regeneration of vegetation and help facilitate their ecosystem recovery but vary within and between river systems and more so in a river system recovering from anthropogenic disturbances. Here, we explored the floodplain characteristics that contribute to the woody vegetation regeneration on point bars of the middle reach of the Apalachicola River in Florida, USA, which has been passively recovering for over two decades after dredging and disposal activities ended. Woody vegetation regeneration on point bars was analysed using 1999 and 2019 aerial imagery and divided into zones and sections. Data were extracted from a digitized geodatabase regarding several floodplain characteristics with potential to influence vegetation regenetation. Later, we analysed noncollinear floodplain characteristics using a random forest (RF) regression model. The top characteristics that contributed to the RF model include vegetation density, distance‐to‐seeding source and bend curvature. Findings suggest that high vegetation density contributes substantially to woody vegetation regeneration. The negative relationship between distance‐to‐seeding source and vegetation regeneration shows the importance of seeding availability. The bend curvature corresponds with the highest regeneration in the lowermost section of point bars. Our results signify the importance of maintaining healthy vegetated corridors as a buffer to reinforce the vegetation community and potential seed source for passive recovery. These findings regarding floodplain characteristics can be applied to future active restoration of anthropogenically disturbed floodplains. [ABSTRACT FROM AUTHOR]

Presents an overview of current geomorphic research in the southern United States. Conveys that the limited historical effort offers both challenges and opportunities for conducting geomorphic work in the region; much is unknown about these unique landscapes. States applied and theoretical geomorphology will benefit the society and future of the South. (CMK)

Describes and promotes topic synthesis, an approach where students rather than instructors summarize the key points of the previous lecture at the beginning of the next class. Benefits include improved oral presentation skills and reinforcement of key concepts. The method also provides an accurate assessment tool. (MJP)

Hydrological drought forecasting is essential for effective water resource management planning. Innovations in computer science and artificial intelligence (AI) have been incorporated into Earth science research domains to improve predictive performance for water resource planning and disaster management. Forecasting of future hydrological drought can assist with mitigation strategies for various stakeholders. This study uses the transformer deep learning model to forecast hydrological drought, with a benchmark comparison with the long short-term memory (LSTM) model. These models were applied to the Apalachicola River, Florida, with two gauging stations located at Chattahoochee and Blountstown. Daily stage-height data from the period 1928–2022 were collected from these two stations. The two deep learning models were used to predict stage data for five different time steps: 30, 60, 90, 120, and 180 days. A drought series was created from the forecasted values using a monthly fixed threshold of the 75th percentile (75Q). The transformer model outperformed the LSTM model for all of the timescales at both locations when considering the following averages: M S E = 0.11 , M A E = 0.21 , R S M E = 0.31 , and R 2 = 0.92 for the Chattahoochee station, and M S E = 0.06 , M A E = 0.19 , R S M E = 0.23 , and R 2 = 0.93 for the Blountstown station. The transformer model exhibited greater accuracy in generating the same drought series as the observed data after applying the 75Q threshold, with few exceptions. Considering the evaluation criteria, the transformer deep learning model accurately forecasts hydrological drought in the Apalachicola River, which could be helpful for drought planning and mitigation in this area of contested water resources, and likely has broad applicability elsewhere. [ABSTRACT FROM AUTHOR]

Lowland coastal plain rivers are important for navigation and ecosystems, having unique concerns regarding water and sediment management. The Apalachicola River in Florida, the lower end of the ACF (Apalachicola–Chattahoochee–Flint) system, had historical modifications beginning in the 1800s. Most impacts are attributable to the Apalachicola Navigation Project in the latter half of the 20th century, which included dredging, disposal, rock and snag removal, artificial cutoffs, and wing‐dike building. As one of few studies using paired hydrographic surveys over a long reach and time (170 km, 50 years), we defined four zones of bed elevation change between 1960 and 2010 based on the cumulative thalweg elevation plots. The river has four bed change zones: (1) uppermost, marked degradation from river mile (RM) 106 to 85 because of dam construction; (2) middle, minimal degradation from RM 85 to 34; (3) artificial cutoff zone, highest degradation, from RM 34 to 27; and (4) lowermost zone, aggradation from RM 27 to Apalachicola Bay because of upstream bed and bank sediment disturbances. Artificial cutoffs and lithology influence lateral migration, with rates being highest in cutoff zones and least in areas with some bedrock upstream and finer sediments downstream. Length changes from 1941 to 2019 are stable, except for the middle reach, which lengthened nearly 10%, and the lower non‐tidal reach, where length shortened with cutoffs then regained in subsequent decades. Minimizing disturbance has led to 18% of the sand bar area revegetating since a decade of dredging ended. This framework helps in understanding historic and ongoing human activities, notably upstream water consumption, connectivity changes, sediment inputs, and climate change, that will affect the water and sediment management of the river, its floodplain, and bay, thus varying approaches for restoration. [ABSTRACT FROM AUTHOR]

Riverbed changes are important to applications in engineering in the environment, such as navigation, salt‐water intrusion and habitat quality. This study employed decadal hydrographic data over the past 50 years (1963–2013), as well as daily water stages and discharges to outline the long‐term channel morphological changes and bed‐load sediments deposited by floods in the lowermost Mississippi River (LMR). To generate accurate bathymetric digital elevation models (DEMs), we interpolated the hydrographic survey in a channel‐centred coordinate system by employing ordinary kriging with anisotropy. Riverbed deformations were estimated by subtracting the elevations between DEMs at two different times to generate a series of DoDs (DEM of difference). The results from DoDs exhibit temporal riverbed change patterns and also reveal net degradation after the completion of the Old River Control Structure in 1963, except for the period 1992–2004. Spatially, over 32% of the total area experienced continuous erosion, with only 0.4% having continuous aggradation. Historical erosion over the past 50 years could be removing the alluvial veneer in sections of the river, and exposing more non‐alluvial sediments, particularly between river kilometre RK 230 and RK 40. Our analysis also shows that riverbed deformation patterns are mainly controlled by flood events, backwater effects, as well as the drawdown effect near the Bonnet Carré spillway. In this study, we also examine whether the LMR traps bed‐load sediment under flood conditions. The probability distribution estimated by Monte Carlo simulation suggests only low amounts of bed‐load sediments are deposited on the channel bed during floods. Spatially, the short‐term bed‐load erosion/deposition pattern roughly matches the decadal‐scale riverbed deformation estimated from DoDs. Moreover, this study finds that the trends between the thalweg changes and riverbed deformation are similar, suggesting that both of these patterns are controlled by the same factors. [ABSTRACT FROM AUTHOR]

Anthropogenic impacts in large rivers are widely studied, but studies of recovery once a disturbance has stopped are uncommon. This study examines the biogeomorphic recovery of a 40‐km river corridor on the mid‐Apalachicola River, Florida following the cessation of dredging, disposal, and snag removal in 2002. This failed navigation project resulted in vegetation losses (~166 ha between 1941 and 2004), river widening, and increased point bar areas. We used paired sets of imagery for a 10‐year period during the recovery process at two different flow levels to assess sand bar change, land cover change, and their spatial variations. Most large sand bars decreased significantly in area due to growth of pioneer species, typically from the bankside of the bar. Mean bar area shrank 0.17 and 0.20 ha for the 30th and 1st percentile flows, respectively. For the entire study area, both water‐level comparisons showed gains in vegetation (23.36 and 15.83 ha), compensated by losses in the extent of water (16.83 and 8.55 ha) and sand bar losses (6.53 and 7.28 ha). Overall, these gains during the 10‐year passive recovery period are equivalent to ~15% of the vegetation losses that resulted from the navigational dredging. As found in other studies, most of the pioneer vegetation grew approximately 2 m relative elevation above the low‐water surface. The initial length of the tree line and the area of herbaceous growth both had a significant and positive relationship with the area of new vegetation growth over the study interval. As parts of the river are healing, reduced channel capacity from narrowing and tree growth will benefit the floodplain. As elsewhere, understanding of a river's biogeomorphology, hydrology, and disturbance history can help in selecting appropriate recovery metrics to further advance the understanding and management of disturbed floodplains. © 2020 John Wiley & Sons, Ltd. [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]

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 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.

The lowermost Mississippi River (LMR) is one of the largest deltaic systems in North America and one of the heavily human-manipulated fluvial river systems. Historic hydrographic surveys from the mid-1900s to the early 2010s were used to document the thalweg morphology adjustments, as well as the riffle–pool sequences. Extensive aggradation was observed during 1950s to 1960s, as the Atchafalaya River was enlarging before the completion of the Old River Control Structure (ORCS). Following the completion of the ORCS, reductions in sediment input to the LMR resulted in net degradation of the thalweg profile patterns since the mid-1960s except for the 1992–2004 period. Different flood events that supplied sediment might be the cause of upstream aggradation from 1963–1975 and net aggradation along the entire reach from 1992–2004. Furthermore, the change pattern of thalweg profiles appear to be controlled by backwater effects, as well as the Bonnet Carré spillway opening. Results from riffle–pool sequences reveal that the averaging Ws ratios (length to channel width) are 6–7, similar to numerous previous studies. Temporal variations of the same riffles and pools reveal that aggradation and degradation might be heavily controlled by similar factors to the thalweg variations (i.e., sediment supply, backwater effects). In sum, this study examines decadal-scale geomorphic responses in a low-lying large river system subject to different human interventions, as well as natural flood events. Future management strategies of this and similar river systems should consider recent riverbed changes in dredging, sediment management, and river engineering. [ABSTRACT FROM AUTHOR]

Reconciling economic growth and energy supply with the reduction of greenhouse gas emissions and other goals for environmental protection is a major challenge for emerging economies such as Brazil. Establishing energy security standards consistent with realistic economic growth projections while considering climate change requires complex calculations and relies upon risky assumptions. Yet, such calculations and decisions must be made to avoid future energy shortages and economic crises. This paper discusses the current dilemma concerning planning and decision-making for the Brazilian electric sector considering the construction of hydroelectric power plants in the Amazon region, energy security requirements, projected economic growth and climate change feedbacks. [ABSTRACT FROM AUTHOR]