Coastal Plain Rivers Research Articles

Evolution of an incised valley coastal plain estuary under low sediment supply: a ‘give‐up’ estuary

AbstractThe literature on incised river valley sedimentology is dominated by studies of sediment‐rich systems in which the valley has been filled during and/or shortly after drowning. In contrast, the Holocene evolution of the Kosi Lagoon, South Africa (an incised coastal plain river valley) took place under very low sedimentation rates which have produced a distinctive stratigraphy and contemporary sedimentary environments. The findings are based on a synthesis of the results of studies of seismic stratigraphy, sediment distribution, morphodynamics and geomorphology. Barrier migration was prevented by a high pre‐Holocene dune barrier against which Holocene coastal deposits accumulated in an aggradational sequence. Holocene evolution of the back barrier involved: (i) drowning of the incised valley; (ii) wave‐induced modification of the back‐barrier shoreline leading to segmentation during the highstand; and (iii) marine sedimentation adjacent to the tidal inlet. Segmentation has divided the estuary into a series of geochemically and sedimentologically distinctive basins connected by channels in the estuarine barriers. The seismic stratigraphy of the back barrier essentially lacks a transgressive systems tract, shoreline modification and deposition having been accomplished during the highstand. The lack of historical geomorphological change suggests that the system has achieved morphological equilibrium with ambient energy conditions and low sediment supply. This study presents a classification for estuarine incised valley fills based on the balance between sea‐level rise and sedimentation in which Kosi represents a ‘give‐up’ estuary where much of the relict incised channel form is drowned and preserved. It exhibits a fundamentally different set of evolutionary processes and stratigraphic sequences to those of the better known incised valley systems in which sedimentation either keeps pace with sea‐level (‘keep‐up’ estuaries) or occurs after initial drowning (‘catch‐up’ estuaries).

SEDIMENT DYNAMICS IN THE RESTORED REACH OF THE KISSIMMEE RIVER BASIN, FLORIDA: A VAST SUBTROPICAL RIPARIAN WETLAND

ABSTRACTHistorically, the Kissimmee River Basin consisted of a broad nearly annually inundated riparian wetland similar in character to tropical Southern Hemisphere large rivers. The river was channelized in the 1960s and 1970s, draining the wetland. The river is currently being restored with over 10 000 hectares of wetlands being reconnected to 70 river km of naturalized channel. We monitored riparian wetland sediment dynamics between 2007 and 2010 at 87 sites in the restored reach and 14 sites in an unrestored reference reach. Discharge and sediment transport were measured at the downstream end of the restored reach. There were three flooding events during the study, two as annual flood events and a third as a greater than a 5‐year flood event. Restoration has returned periodic flood flow to the riparian wetland and provides a mean sedimentation rate of 11.3 mm per year over the study period in the restored reach compared with 1.7 mm per year in an unrestored channelized reach. Sedimentation from the two annual floods was within the normal range for alluvial Coastal Plain rivers. Sediment deposits consisted of over 20% organics, similar to eastern blackwater rivers. The Kissimmee River is unique in North America for its hybrid alluvial/blackwater nature. Fluvial suspended‐sediment measurements for the three flood events indicate that a majority of the sediment (70%) was sand, which is important for natural levee construction. Of the total suspended sediment load for the three flood events, 3%–16% was organic and important in floodplain deposition. Sediment yield is similar to low‐gradient rivers draining to the Chesapeake Bay and alluvial rivers of the southeastern USA. Continued monitoring should determine whether observed sediment transport and floodplain deposition rates are normal for this river and determine the relationship between historic vegetation community restoration, hydroperiod restoration, and sedimentation. Published in 2011 by John Wiley & Sons, Ltd.

River impoundment and sunfish growth

AbstractImpoundment of rivers by dams is widespread and one of the most devastating anthropogenic impacts to freshwater environments. Linking theoretical and applied research on river impoundment requires an improved capacity for predicting how varying degrees of impoundment affects a range of species. Here, growth of 14 North American sunfish species resilient to river impoundment was compared in rivers versus impoundments. Growth response to river impoundment varied widely, but consistently among taxa: five species (shadow bass, rock bass, flier, redbreast sunfish and green sunfish) showed significantly higher growth in riverine ecosystems, four species (largemouth bass, smallmouth bass, spotted bass and longear sunfish) showed significantly higher growth in impounded ecosystems, and five species (bluegill, black crappie, white crappie, redear sunfish and warmouth) displayed no difference in growth between rivers and impoundments. Furthermore, significant linear models were developed for predicting growth of two species (largemouth bass, R2 = 0.75 and warmouth, R2 = 0.44) based on a physiographically specific index of reservoir retention time. For another species (white crappie), growth could not be predicted by the retention time index in Central Lowlands rivers (R2 = 0.001), but was strongly predicted by this factor in southeastern Coastal Plain rivers (R2 = 0.76) showing how impacts of impoundment, and prediction of its consequences, can vary across river landscape types. Further analysis of fish growth in response to river impoundment, regulation and fragmentation could greatly enhance conservation biology, restoration ecology and basic land use decisions in riverine landscapes. Copyright © 2010 John Wiley & Sons, Ltd.

Livingstonia (Thalassiosirales, Bacillariophyta), a new genus of fultoportulate centric diatoms from an Atlantic coastal plain river in Florida, southeastern United States

Prasad A.K.S.K and Nienow J.A. 2011. Livingstonia (Thalassiosirales, Bacillariophyta), a new genus of fultoportulate centric diatoms from an Atlantic coastal plain river in Florida, southeastern United States. Phycologia 50: 264–280. DOI: 10.2216/09-89.1A morphological and taxonomic account of Livingstonia palatkaensis, a new genus and species of centric diatoms belonging to the order Thalassiosirales Glezer & Makarova, is provided. Descriptions are based on material collected from the St. Johns River, a major, highly colored blackwater river in the Atlantic coastal plain in the southeastern United States. Scanning electron microscopic observations clearly show that although the valve structure in Livingstonia shares broad similarities with the genera Thalassiosira and Skeletonema, the types of the two fultoportulate families Thalassiosiraceae and Skeletonemataceae, respectively, it is sufficiently dissimilar to warrant the description of a new genus. Livingstonia is characterized by the presence of compound marginal processes, each formed from the external extension of a fultoportula and a semielliptical hyaline hood or cover. The areolae have semicontinuous internal cribra. A single rimoportula is present near the valve center. No fultoportulae are found at or near the center of the valve face. Furthermore, Livingstonia lacks connecting threads of marginal fultoportulae and an external extension of the rimoportula on the valve face, a combination of features that is unusual in the genus Skeletonema. Livingstonia is also distinguished from two recently described freshwater genera in the Thalassiosiraceae from the southeastern United States, Cyclotubicoalitus and Spicaticribra, in having a rimoportula away from the margin but close to the center of the valve and in other key characteristics. A note on another freshwater, co-occurring, more frequent and widespread, chain-forming, closely related diatom, Skeletonema potamas, is also included. Livingstonia is tentatively placed in the family Thalassiosiraceae.

Historical morphogenesis of the Turia River coastal flood plain in the Mediterranean littoral of Spain

Abstract The cross-referencing of sedimentological, stratigraphic, geoarchaeological and radiocarbon data enables us to establish the geomorphologic evolution of the Late Holocene coastal flood plain of the Turia River. The Holocene marine transgression formed a coastal barrier lagoon environment in the coastal plain. During the Late Holocene, increased sediments supplied to the low reach of the river promoted: (a): the progradation of deltaic coastal sandy ridges on the coastline and (b): the aggradation of the floodplain on top of the sedimentary sequence. Four phases are clearly recognised in the geoarchaeological record of the flood plain. (1): High magnitude flooding events (2800 BP to 3rd century BC). (2): Slow riverbed aggradation and progressive levee formation (low energy flood regime) in Roman times (2nd century BC to 5th century AD). (3): Swampy environmental processes (6th to 9th centuries). (4): Second high-magnitude flooding phase (11th century). The navigable channel of the Roman and early Islamic periods became a wide and shallow braided channel in Medieval times. These phases are correlated with others detected by researchers in many areas of the Mediterranean region and with global Holocene climate events.

Flood Hydrology and Methylmercury Availability in Coastal Plain Rivers

Mercury (Hg) burdens in top-predator fish differ substantially between adjacent South Carolina Coastal Plain river basins with similar wetlands coverage. In the Congaree River, floodwaters frequently originate in the Blue Ridge and Piedmont regions, where wetlands coverage and surface water dissolved methylmercury (MeHg) concentrations are low. Piedmont-driven flood events can lead to downward hydraulic gradients in the Coastal Plain riparian wetland margins, inhibiting MeHg transport from wetland sediments, and decreasing MeHg availability in the Congaree River habitat. In the adjacent Edisto River basin, floodwaters originate only within Coastal Plain sediments, maintaining upward hydraulic gradients even during flood events, promoting MeHg transport to the water column, and enhancing MeHg availability in the Edisto River habitat. These results indicate that flood hydrodynamics contribute to the variability in Hg vulnerability between Coastal Plain rivers and that comprehensive regional assessment of the relationship between flood hydrodynamics and Hg risk in Coastal Plain streams is warranted.

Geological controls and effects of floodplain asymmetry on river–groundwater interactions in the southeastern Coastal Plain, USA

Channel sediment and alluvial aquifer hydraulic properties exert a major control on river–groundwater interactions. Channels and floodplains are often asymmetrical, resulting in differences in sediment hydraulic properties across the river. Floodplain asymmetry is common along Coastal Plain rivers in South Carolina and North Carolina, USA. The Tar River, North Carolina, has an asymmetrical valley. The study objective was to characterize the effects of floodplain asymmetry and geological controls on river–groundwater interactions. Floodplain and river channel sediments adjacent to the river were characterized with split spoon cores and hand auger samples along a 22-km reach. Hydrogeology was characterized with 38 piezometers and water level recorders in and adjacent to the river. Ground penetrating radar was used to define the shallow stratigraphy. Channel sediments were significantly different between the north and south sides of the river. Hydraulic conductivity and groundwater inputs were greater on the side of the river (north) that contained more permeable fluvial deposits. Groundwater chemistry (δ18O, specific conductance) data also suggested greater exchange between surface water and groundwater on the north side of the river channel. A conceptual hydrogeological model illustrates that groundwater movement and contaminant transport to the river differs across the channel due to asymmetrical geology.

Controls on sediment delivery in coastal plain rivers

Rivers crossing coastal plains are often inefficient conveyors of sediment, so that changes in upstream sediment dynamics are not evident at the river mouth. Extensive accommodation space and low stream power often result in extensive alluvial storage upstream of estuaries and correspondingly low sediment loads at the river mouth. However, gaging stations with sediment records are typically well upstream of the coast, and thus tend to overestimate sediment yields by under-representing the lower coastal plain and because there is often a net loss of sediment in lower coastal plain reaches. Studies of alluvial sediment storage have generally focused on accommodation space, but, using examples from Texas, we show that low transport capacity controlled largely by slope is a crucial factor.

Lateral channel migration effects on riparian forest structure and composition, Congaree River, South Carolina, USA

Lateral channel migration initiates complex and dynamic biogeomorphic responses that are fundamental to the creation and maintenance of riparian habitats along low-gradient, coastal plain rivers. This study examines the effects of lateral migration rates on the structure and composition of riparian forests along the Congaree River, Congaree National Park, in the Atlantic Coastal Plain, South Carolina. Lateral channel migration rates were measured in a GIS using aerial photos from 1938–2006. Forest variables were measured from a stratified-random sample of 25 paired edge-interior plots, and analyzed using Mann-Whitney tests, Spearman’s correlations, multi-response permutation procedures (MRPP), and non-metric multi-dimensional scaling (NMS) ordinations. Lateral channel migration produced a significant directional control on riparian forests. Pointbar forests exhibited classic forward succession dependent on spatial and temporal controls related to elevation, flood frequency, and lateral migration rates. Cutbank forests responded positively to exposure along the edge and increased in structural complexity with increasing proximity to the river; density, basal area, and richness varied inversely with lateral migration rates. Cutbank edges with low lateral migration allowed longer time for trees to colonize and they contained greater density, basal area, and richness. Cutbanks with high lateral migration contained lower tree density, basal area, and richness.

Application of ecosystem‐scale fate and bioaccumulation models to predict fish mercury response times to changes in atmospheric deposition

Management strategies for controlling anthropogenic mercury emissions require understanding how ecosystems will respond to changes in atmospheric mercury deposition. Process-based mathematical models are valuable tools for informing such decisions, because measurement data often are sparse and cannot be extrapolated to investigate the environmental impacts of different policy options. Here, we bring together previously developed and evaluated modeling frameworks for watersheds, water bodies, and food web bioaccumulation of mercury. We use these models to investigate the timescales required for mercury levels in predatory fish to change in response to altered mercury inputs. We model declines in water, sediment, and fish mercury concentrations across five ecosystems spanning a range of physical and biological conditions, including a farm pond, a seepage lake, a stratified lake, a drainage lake, and a coastal plain river. Results illustrate that temporal lags are longest for watershed-dominated systems (like the coastal plain river) and shortest for shallow water bodies (like the seepage lake) that receive most of their mercury from deposition directly to the water surface. All ecosystems showed responses in two phases: A relatively rapid initial decline in mercury concentrations (20-60% of steady-state values) over one to three decades, followed by a slower descent lasting for decades to centuries. Response times are variable across ecosystem types and are highly affected by sediment burial rates and active layer depths in systems not dominated by watershed inputs. Additional research concerning watershed processes driving mercury dynamics and empirical data regarding sediment dynamics in freshwater bodies are critical for improving the predictive capability of process-based mercury models used to inform regulatory decisions.

Landscape evolution space and the relative importance of geomorphic processes and controls

The concept of landscape evolution space (LES) is introduced as a tool for assessing landscapes and geomorphic systems, intended to be a systematic means for assessing the various factors that contribute to the potential for change in geomorphic systems. The LES conceptual model is based on the energy and mass available to drive and accommodate landscape evolution. An n-dimensional landscape evolution space is defined not only by spatial coordinates, but also by the availability of mass and energy. The LES is thus a space or hypervolume representing the resources available for geomorphic evolution and landscape change. An expression for LES is derived based on elevation, material density, surface area, and inputs of solar, meteoric, and biological energy and mass. Though primarily an heuristic device, the LES model can be used to address concrete problems. Two examples are given. In one, increased surface area due to topographic roughening and dissection of an incised plateau is found to only slightly offset erosional removals of mass in terms of the magnitude of the LES. In the other, sensitivity of coastal plain rivers to several impacts of sea level and climate change is explored. The LES model also leads to the concept of a geomorphological niche, representing the resources available to drive or support a specific process or suite of processes. Considerations of landscape evolution have traditionally focused on the interplay of endogenic vs. exogenic processes, uplift vs. denudation, or soil formation vs. erosion. The LES model explicitly broadens the conceptual framework of landscape evolution beyond the traditional dialectics.

Floodplain geomorphic processes and environmental impacts of human alteration along Coastal Plain rivers, USA

Human alterations along stream channels and within catchments have affected fluvial geomorphic processes worldwide. Typically these alterations reduce the ecosystem services that functioning floodplains provide; in this paper we are concerned with the sediment and associated material trapping service. Similarly, these alterations may negatively impact the natural ecology of floodplains through reductions in suitable habitats, biodiversity, and nutrient cycling. Dams, stream channelization, and levee/canal construction are common human alterations along Coastal Plain fluvial systems. We use three case studies to illustrate these alterations and their impacts on floodplain geomorphic and ecological processes. They include: 1) dams along the lower Roanoke River, North Carolina, 2) stream channelization in west Tennessee, and 3) multiple impacts including canal and artificial levee construction in the central Atchafalaya Basin, Louisiana. Human alterations typically shift affected streams away from natural dynamic equilibrium where net sediment deposition is, approximately, in balance with net erosion. Identification and understanding of critical fluvial parameters (e.g., stream gradient, grain-size, and hydrography) and spatial and temporal sediment deposition/erosion process trajectories should facilitate management efforts to retain and/or regain important ecosystem services.

Documenting 12,000 Years of Coastal Occupation on the Osmore Littoral, Peru

The history of coastal settlement in Peru beginning ca. 12,000 years ago provides insight into maritime adaptations and regional specialization. We document the Late Paleoindian to Archaic occupational history along the Osmore River coastal plain near Ilo with 95 radiocarbon dates from eight sites. Site distribution suggests that settlement shifted linearly along the coast, possibly in relation to the productivity of coastal springs. Marine foods, raw materials, and freshwater were sufficient to sustain coastal foragers for over 12 millennia. Despite climatic changes at the end of the Pleistocene and during the Middle Holocene, we found no evidence for a hiatus in coastal occupation, in contrast to parts of highland northern Chile and areas of coastal Peru for the same time period. Coastal abandonment was a localized phenomenon rather than one that occurred across vast areas of the South Central Andean littoral. Our finds suggest that regional adaptation to specific habitats began with initial colonization and endured through time.

Direct connectivity between upstream and downstream promotes rapid response of lower coastal-plain rivers to land-use change

Direct connectivity between upstream and downstream promotes rapid response of lower coastal-plain rivers to land-use change

Wetland influences on mercury transport and bioaccumulation in South Carolina

There are three distinct geological provinces in South Carolina (SC), with the blue ridge/piedmont regions in the west/central portion of the state and the coastal plain region in the central/eastern region of the state. Samples were collected along this gradient to identify potential factors contributing to the concentrations of total Hg and total organic carbon (TOC) throughout the state. Overall, there is a gradient across the state, with water column concentrations of total Hg (9–53 pM) and TOC (80–2721 μM) increasing as one moves from the blue ridge/piedmont region to the coastal floodplain region. Total Hg at all sites in SC is significantly ( R 2 = 0.78; P < 0.001) correlated with TOC in the water samples. This correlation explains 78% of the variance in the data and suggests that mercury is associated with organic matter in water bodies throughout the state. A study of mercury speciation within the coastal plain Waccamaw River indicates that concentrations of total Hg range from 10–68 pM and methyl Hg concentrations range from 1–7 pM. Watershed transport efficiencies for coastal floodplain rivers sampled in this study range from 32–72% for total Hg and 78–477% for methyl Hg. The coastal plain sites are located in watersheds that contain a significantly ( P < 0.001) higher percentage of wetlands (16.3 ± 5%) than the blue ridge/piedmont region (1.14 ± 1.6%), suggesting that drainage through wetlands contributes to the increased concentrations of TOC and total Hg found in SC coastal plain rivers. There is a significant correlation between mean fish Hg concentrations in largemouth bass from each watershed and percent wetland area in each watershed ( R 2 = 0.66; P = 0.003). This correlation explains 66% of the variance in the data and suggests that increasing percentages of wetland area contribute to fish Hg concentrations in SC coastal plain rivers.

A conceptual and numerical model for groundwater management: a case study on a coastal aquifer in southern Tuscany, Italy

Ongoing hydrogeological research aims to develop a correct management model for the Plio-Pleistocene multi-aquifer system of the Albegna River coastal plain (southern Tuscany, Italy); overexploitation of this aquifer for irrigation and tourism has caused seawater intrusion. The conceptual model is based on field and laboratory data collected during the 1995–2003 period. Meteoric infiltration and flows from the adjoining carbonate aquifer recharge the aquifer. Natural outflow occurs through a diffuse flow into the sea and river; artificial outflow occurs through intensive extraction of groundwater from wells. Water exchanges in the aquifer occur naturally (leakage, closing of aquitard) and artificially (multiscreened wells). The aquifer was represented by a three-dimensional finite element model using the FEFLOW numerical code. The model was calibrated for steady-state and transient conditions by matching computed and measured piezometric levels (February 1995–February 1996). The model helped establish that seawater intrusion is essentially due to withdrawals near the coast during the irrigation season and that it occurs above all in the Osa-Albegna sector, as well as along the river that at times feeds the aquifer. The effects of hypothetical aquifer exploitation were assessed in terms of water budget and hydraulic head evolution.

Antecedent alluvial morphology and sea‐level controls on form‐process transition zones in the lower Trinity river, Texas

AbstractAn important aspect of river science and management is the identification of key boundaries, transition zones and hinge points. Such critical areas are likely to be important foci or indicators of the effects of environmental change on river systems. While geological controls on such features are widely recognized in upland streams, inherited or antecedent forms may also be important controls of key transitional points or reaches in alluvial coastal plain rivers. The critical zone of the lower Trinity River, Texas marks an important transition in river channel and valley forms, dominant processes and resulting geomorphological, hydrological and ecological characteristics. Its location is not a transient result of upstream or downstream propagation of effects. Rather, the location marks the contemporary upstream extent of the effects of Holocene sea‐level rise, which in turn coincides with the point at which the Pleistocene upper Deweyville alluvial terrace surface is encountered. A more rapid rate of change and relatively sudden upstream displacement of this zone is likely when the upper Deweyville surface is flooded. Antecedent fluvial and alluvial topography inherited from previous aggradation, degradation and lateral migration episodes is likely to be an important control over modern fluvial forms and processes in other alluvial coastal plain rivers as well. Identification and mapping of such features may be extremely useful in pinpointing critical transition zones for water resource managers. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Estimating Relevance of Organic Carbon, Nitrogen, and Phosphorus Loads to a Blackwater River Estuary1

Abstract: In blackwater river estuaries, a large portion of external carbon, nitrogen, and phosphorus load are combined in complex organic molecules of varying recalcitrance. Determining their lability is essential to establishing the relationship between anthropogenic loads and eutrophication. A method is proposed in which organic C, N, and P are partitioned into labile and refractory forms, based upon first‐order decay estimated by biochemical oxygen demand relative to total organic carbon, and C:N and C:P ratios as a function of organic carbon lability. The technique was applied in developing total maximum daily loads for the lower St. Johns, a blackwater Atlantic coastal plain river estuary in Northeast Florida. Point source organic nutrients were determined to be largely labile. Urban runoff was found to have the highest relative labile organic N and P content, followed by agricultural runoff. Natural forest and silviculture runoff were high in refractory organic N and P. Upstream labile C, N, and P loads were controlled by autochthonous production, with 34‐50% of summer total labile carbon imported as algal biomass. Differentiation of labile and refractory organic forms suggests that while anthropogenic nutrient enrichment has tripled the total nitrogen load, it has resulted in a 6.7‐fold increase in total labile nitrogen load.

A 5,600-year-old wooden well in Zhejiang Province, China

In 1973, traces of China’s early Neolithic Hemudu culture (7,000–5,000 BP) were discovered in the village of Hemudu in Yuyao County, Zhejiang Province, in the lower Yangtze River coastal plain. The site has yielded animal and plant remains in large quantities and large numbers of logs secured with tenon and mortise joints, commonly used in wooden buildings and other wooden structures. For hydrogeologists, the most interesting structure is an ancient wooden well. The well is believed to be about 5,600 years old, which makes it the oldest wooden well yet found in China. The well site contains over 200 wooden components and can be divided into inner and outer parts. The outer part consists of 28 piles around a pond. The inner part, the wooden well itself, lies in the middle of the pond. The walls of the well were lined with close-set timber piles reinforced by a square wooden frame. The 28 piles in the outer part of the site may have been part of a shelter for the well, suggesting that the people of the Hemudu culture were already concerned with water hygiene and protection of their water source.

Characteristics of the introduced fish fauna of Israel

Fishes have been introduced worldwide with deleterious effects on various native ecosystems. To gain insight into this phenomenon in Israel, we studied the introduced ichthyofauna. There are 27 species of introduced fishes in the freshwater habitats of Israel, a large number for a nation this size. Ten of these species reproduce in the wild. Most of these fishes were introduced for aquaculture; some are constantly restocked. The proportion of restocked versus established species in Israel is high compared to other regions. New fish introductions continue in recent decades, unlike the global trend. In Israel these species are found in the Jordan Basin, Lake Kinneret (Sea of Galilee), and the coastal plain rivers. A few species are widespread, and most are found in Lake Kinneret. Harmful effects of introduced fishes have been suspected and in several cases demonstrated. We encourage further caution when new introductions are contemplated; in some regions eradication should be attempted.