Scientific & Engineering Analyses, Evaluations, & Studies

Scientific Analyses, Studies & Evaluations
Work	Description
Chloride distribution	An evaluation of the distribution of chloride concentration within the Lower Savannah River is being conducted, including field data gathering, model development, and calibration, and modeling simulation. The goal is to determine the potential for increases in salinity intrusion to cause an associated increase in the chloride concentrations at the City’s raw water intake.
Dissolved oxygen distribution	A dissolved oxygen model will be utilized to define the impact of the proposed deepening on the spatial and temporal concentrations of dissolved oxygen within the primary study area. Project effects on dissolved oxygen levels will be evaluated under critical conditions to determine the impact to aquatic species.
Salinity distribution	Evaluation of the salinity distribution has four goals. The first is to refine the hydrodynamic model to include a relationship between surface water and interstitial salinity. The second goal is to update the hydrodynamic model to include the projection of the temporal and spatial nature of temperature throughout the system. The third goal is to re-evaluate the 1997 calibration using the revised grid structure and optimized based upon convergence testing. The fourth goal is to provide verification of the calibrated hydrodynamic model using the in-stream data collected in the summer of 1999.
Freshwater marsh succession	The reliability of vegetation maps produced through remote sensing methods is contingent upon the results of a formal accuracy assessment. Such an accuracy assessment is conducted by field inspection and examination of detailed aerial photography of randomly selected locations that represent the variability of vegetation signatures within the marsh. USFWS identified this work as necessary for them to compare to Dr. Kitchen's earlier work to the Tier I findings and verify the overall study.
Marsh salinity field data collection	The goal of this work is to provide sufficient data to allow for determination of the relationship between interstitial salinity in the marshes and salinity within the adjacent river channels.
Marsh vegetative survey	The goals of this work are to (1) update and expand the existing information regarding the distribution of plant species within the tidal fresh water and brackish marshes of the Savannah National Wildlife Refuge, and (2) continue to define the environmental factors that determine the plant distributions.
Marsh vegetation survey by USFWS	This work will establish 6 additional study sites comprised of 6 transects and an array of 24 shallow wells for monitoring of interstitial salinity. Salinity monitoring and vegetation sampling will be conducted. Digital videography work will be collected to provide baseline data on the feasibility of using this technique to conduct routine monitoring of vegetation study sites. USFWS researchers will participate in formal accuracy assessment and sediment/marsh variability reconnaissance efforts with ATM researchers.
SNWR freshwater marsh continued vegetation monitoring	This work will provide for continued monitoring of all established vegetation study plots, including the 10 FWS transect areas (seven marsh sites, as per methods of Latham, 1991 and the three tidal forest sites using point-centered quarter transect techniques.) This work will provide for continued monitoring of the 10 quadrats established by ATM during the 1997 study, as well as collection of data on additional Rapid Assessment Plots (RAP). Quadrat data will be collected during both the early and late growing season.
SNWR freshwater marsh water level study	This work will provide detailed data on hydrologic regimes within the specific vegetation associations identified through vegetation monitoring and mapping. Water level monitoring instrumentation will be installed at chosen locations to determine hydrologic regimes within distinct vegetation association. In addition, the instrumentation will be used to determine to what extent the floating vegetation mats rise and fall with the tide. The instrumentation will be moved to various locations for the duration of the project to cover the range of vegetation associations found within the project area. For subsequent use in the marsh succession model, the water level data will be related to marsh surface elevations as determined by GPS survey.
SNWR freshwater marsh topography survey	A key component of the spatial aspect of the marsh succession model will be marsh topography. Survey grade elevations will be made at each of the 10 FWS vegetation monitoring sites along the floodplain. These marsh elevations will be tied to the results of the water level study to define hydrologic signatures. The topographic survey will be conducted using GPS survey equipment.
SNWR freshwater marsh sediment characterization/mapping	The data to date strongly indicate that vegetation distribution is heavily influenced by sediment characteristics. Two primary sediment characteristics will be investigated in this work: (1) the locations of sediments that support floating vegetation mats, and (2) the locations of sediments that support the production of hydrogen sulfide gas or methane gas. Some investigators hypothesize that floating vegetation mats are able to support relatively high plant diversities because, since they float, they are flooded less often than plants that are rted into a firm substrate. The marshes of highest plant diversity within the study area exist as floating vegetation mats. This work will map the areas of floating mats for incorporation into the marsh succession model. Field mapping will be conducted in conjunction with collection of Rapid Assessment Plot data and other ongoing fieldwork. Ground penetrating radar (GPR) may be used to assist in mapping substrate types in selected locations. GPR data will be augmented and verified by extraction of sediment cores. In addition, production of hydrogen sulfide or methane gas may be a very sensitive indicator of areas that are receiving inputs of saline water during incoming tides. This work will also provide for collection of sediment samples at various locations throughout the study area. These samples will be analyzed in the lab for their potential for producing either hydrogen sulfide or methane gas and assessed for their contribution to production of floating mats.
SNWR freshwater marsh transplanting experiments	This work is intended to translocate and transplant intact cores of plant/substrate units in such a fashion as to cross transplant within, between, and among tidal marsh types (fresh, intermediate and brackish) while documenting subsequent vegetation responses, if any over time. In addition to confirming or clarifying correlational results of the other field studies, this technique was found to be extremely valuable to previous studies (Pearlstine et al. 1990) for providing time-lines for vegetation responses as well as indications of ecological community structural changes due to hydrologic alterations.
SNWR freshwater marsh continued salinity monitoring	Except for the salinity monitoring conducted during the summer of 1999, there has been an absence of any long-term salinity monitoring subsequent to the removal of the time gate. However, even the summer 1999 monitoring did not capture seasonal or annual salinity dynamics in the marshes. Data regarding these dynamics are critical to defining the ecological functioning of the marsh. This work will continue the marsh salinity monitoring initiated during the summer of 1999 by permanently installing a YSI 6000 XLM salinity meter or comparable salinity meter in each of the 10 permanent study plots.
SNWR freshwater marsh salinity spatial synoptic sampling	Salinity in the marsh substrates is one of the principal community structuring factors the tidal wetlands of the Savannah River. Meters in ten transect sites provide ideal information on the temporal dynamics of salinities at specific sites. To maximize the value of this information it is necessary to complement this long-term spatially limited information (10 sites) with short-term, spatially intense synoptic sampling (approximately 100 sites) to resolve spatial distribution of salinity across and up and down the floodplain gradient. This sampling would be conducted by grabbing samples at pre-selected grid-point locations across the wetland complex from a roving airboat outfitted with GPS navigation. It would be scheduled to co-incident with the 2 major wetland plant samplings that correspond to the early and late growth season time points.
SNWR freshwater marsh tree gap analysis	The tree community structure at various sites within the floodplain is a reflection of past and historic hydrologic conditions. A tree “gap” study will be conducted within the tidal forested transect sites previously established and monitored for breeding bird surveys. The intent is to document the relationship between tree canopy species and the sapling/seedlings in the various regeneration layers. This analysis will distinguish how present hydrologic regimes may compare to the previous conditions under which the canopy trees were established. These sites are unlikely to occur on the transects proper and will require finding tree fall sites in the immediate vicinity of the transects or as proximal as feasible.
SNWR freshwater marsh sediment characterization/Mapping (Spatial synoptic analysis)	In addition to the sediment sampling initiated previously at each of the 10 FWS permanent study sites, a synoptic series of regularly grid-spaced sites will be sampled in conjunction with seasonal (early and late growing season) vegetation sampling along the upstream/downstream gradient. These data will be used to create a substrate characterization set of GIS layers to define transition and breakpoint regions representing the spatial boundaries of marsh zones from fresh to sub saline conditions. This work is essential to developing a spatial characterization of marsh substrate types across the various gradients of hydro periods, salinities, riverine inputs, and tidal influences (tidal subsidies). This information is essential to the implementation of spatially based vegetation succession modeling.
SNWR freshwater marsh vegetation change analysis	This work will continue a study already initiated by the USFWS based on other sources of funding. The work will be based on analysis of aerial photography and satellite imagery to determine changes in vegetation signatures over time. A primary aspect of the analysis will focus on the changes in the shrub swamp located in the transition zone between the tidal forest and the tidal freshwater marsh. Some field observations have indicated that the shrub cover has been increasing in this area. Comparisons between historical imagery and current imagery will be made to confirm and quantitate this trend.
Marsh succession modeling	The goals of this work are to integrate data collected under the field data collection works into wetland impact prediction model. This model will be a geographic information system (GIS)-based spatial model that will predict changes in wetland vegetation distribution caused by salinity and water level changes associated with harbor deepening. A further goal of the model will be to study potential long-term (50-year) changes in vegetation distribution resulting from sea level rise.
SNWR freshwater marsh nekton study	In order to determine the nektonic usage of the various marsh types, replicate flume net traps (as per McIvor et al. 1989) will be placed in critical tidal exchange points between the dredged channel networks and the adjacent expansive intertidal marshes. The net traps will be set on the marsh surface-proper, situated transverse to specific topographic depressions where tidal flows tend to be confined and collected between the marshes and adjacent channels. The sides of the mouth of the traps will extend to the lower tidal elevation limit of the emergent vegetation to the upper limit of the high tide water surface elevation. Cod-end pieces will be attached variously to the ends of the trap to collect nekton entrained through the flume on the rise and fall of the tides. Flume traps will be established at selected points, as described above, in each of the three marsh types along the salinity gradient. These sites should occur in the proximity of established vegetative sampling transects. Data obtained from the traps will be coordinated with other investigators sampling fish communities in the river and sub tidal reaches of the canal network to determine what portion of the fish species pool occupy and use the marsh surface.
SNWR freshwater marsh migratory bird study	Avian use of the four major tidal wetland types within the Savannah National Wildlife Refuge will be assessed seasonally. These types include tidal swamp forests, fresh-, intermediate-, and brackish- marshes. Study design, to be completed in March 2000, is intended to document avian use by fall and spring migrants, and selected over-wintering birds. The design will focus on both spatial and temporal use, incorporating replicate surveys to ensure statistical validity. Sampling will begin in the fall of 2000 and run through the spring of 2001. Sampling methods will include point counts, mist netting and response to call recordings. Only birds using the habitats examined will be recorded, flyovers will not be included in the survey results. Sampling times will be centered on peak migration times, the last week of September for fall migration and the first week of May for spring migration. Winter sampling will be from December through March.
SNWR freshwater marsh seed production study	Study sites will be set up in major vegetative communities in each of the 3 marsh types (fresh, intermediate, and brackish). Within each site, key edible seed producing species will be monitored for seasonal phenological development. Individual plants of each of the selected species will be tagged and carefully monitored through the season for flowering event timing and intensity. Seeds will be carefully counted on the flowering heads of each individually tagged stem. The intent is to monitor numbers and biomass of ripe seeds cumulatively produced over the season for each tagged stem. This is turn will be translated into aerial production within the species stands and communities by using percent cover occupied by the key species in each type. This study proved impractical to implement. At the suggestion of the US Fish and Wildlife Service, the funding was shifted to the migratory bird study.
Beach erosion study	This work will: � Develop computer models to describe the waves and currents in the study area. � Qualitatively and (to the practical extent) quantitatively define the historical bathymetry and shoreline changes that have occurred in the study area including the development of the federal navigation project and the construction of the jetties at the mouth of the Savannah River. � Qualitatively assess changes in mechanisms that control shoreline accretion/erosion: incident wave energy, currents, sediment supply, and shoreline hardening (e.g., seawalls, groin fields, etc.). � Use computer modeling to describe the existing conditions that influence sediment transport in the area, including incident wave energy and currents. Use the modeling results and historic change analysis to develop a sediment budget for the study area. � Use computer modeling to determine effects to the local wave and current conditions caused by the proposed channel deepening. Utilizing the projected effects to the wave and current conditions, quantify the potential impact of the proposed channel deepening. Any effects of the proposed deepening on the nearshore and inlet sediment budget will also be identified.
Shortnose sturgeon distribution field study	The goal of this study is to develop: � a baseline estimate of shortnose sturgeon abundance; � abundance and age distribution of juveniles; � verification of recruitment; � use of telemetry to establish the behavior of adults and juveniles within the impacted areas; and, � water quality monitoring to accompany samples and the use of such water quality data for evaluating potential impact of salinity increases and dissolved oxygen (D.O.) decreases on adult and juvenile shortnose sturgeon within the lower Savannah River.
Striped bass modeling	This work will collect data on velocities and depths in critical habitat areas of the Back River and identify offshore tidal forcing conditions for the baseline (1960-1970) 3-D hydrodynamic model runs. It will also prepare a baseline model grid that will reflect conditions that existed prior to the installation of the tide gate structure. Then it will provide preliminary velocity and depth data on pre-tidegate conditions in the Back River using the Tier I version of the model for use by the GA DNR and USACE, Savannah District Back River Restoration Project.
Assessment study of spawning sites and reproductive status of striped bass	Egg monitoring studies in the SRE began in the late 1970’s and have continued through 1999. Typically, these studies of egg abundance were limited to comparing relative changes in the spatial and temporal densities of eggs. Until Spring 1999, data on gear detection thresholds and efficiency of egg collection methods were non-existent and estimates of the actual number of eggs at large were unobtainable. This technique in combination with egg monitoring, will provide the necessary data to assess the importance of the Front River in sustaining the striped bass population. Salinity conditions suitable for striped bass spawning appear to have been remedied; however, the current maturational status and fecundity of this population is limited Whether low egg densities are related to the maturational status of the population or to a lack of suitable spawning conditions is unknown. Assessing striped bass maturity requires a sample of ovarian tissue, but fecundity estimates require examination of the entire ovary. The uncertainty about the number of adult female spawners makes sacrificing fish to obtain fecundity estimates undesirable. During Spring 1999, ultrasonic imaging, a simple and non-lethal technique, was used to examine the ovaries of striped bass. Additionally a sample of ovarian tissue from each female was obtained. These samples were used to enumerate eggs and estimate maturational status. The ultrasound images were used to develop a model that predicts ovary volume, which combined with the ovarian tissue sample, was used to predict striped bass total fecundity and maturational status. Though successful, use of this technique was preliminary, and continued ultrasound imaging could provide a three-fold advantage. First, data on the maturation and fecundity estimates of female striped bass can be obtained without sacrificing any additional fish because the model has been validated and additional data will strengthen maturation and fecundity estimates. Secondly, maturation and fecundity estimates from years 1999 and 2000 can be compared to provide insights into temporal trends in the maturational status and fecundity estimates of the adult female striped bass population. Thirdly, the maturity and fecundity estimates can be used to decipher the egg production estimates from the egg monitoring studies. The data from the egg monitoring study can result in estimates of the total number of eggs released in the estuary, but the maturational status and fecundity estimates can help determine the number of eggs released by female striped bass of a given length and weight. If these data indicate that low egg abundances are a result of large number of small females, then restoration of the striped bass population is only a few years away (i.e., total egg production should increase as female striped bass become larger and able to contribute significantly more eggs). However, if the data indicate that egg abundances are a result of small number of various size class spawners, then additional questions arise regarding recruitment of adult female striped bass and the suitability of available spawning and rearing habitats in the Savannah River Estuary.
Temporal and spatial distribution study	The purpose of this study is to document the spatial, seasonal, and inter-annual use of nursery habitats by estuarine dependent species within the Savannah River estuary. Additionally, an important focus of this study is to obtain information on habitat vital to species for which Fishery Management Plans have been developed as mandated by the Magnuson - Stevenson Act. Through a collaborative effort between the Georgia Cooperative Fish and Wildlife Research Unit and the South Carolina Department of Natural Resources, various methods will be used to collect this information over a wide range of habitats.
Spawning aggregation study	In Georgia and South Carolina, existing information indicates that spotted sea trout Cynoscion nebulosus, red drum Sciaenops ocellatus, and black drum Pogonias cromis spawn in geographically and temporally isolated aggregations located inshore of the mouths of rivers/bays. Establishing the locations, times, and conditions under which aggregations of these recreationally important species form in the Savannah River will provide the opportunity to conserve the stocks through avoidance or mitigation should the proposed harbor deepening proceed.
Floridan aquifer	A plan to conduct additional evaluation of the possible effects of deepening on the Floridan Aquifer has been developed by the Savannah District and may be viewed here.

Engineering Analyses, Evaluations, & Modeling
Work	Description of work
River hydraulic modeling	This work will adapt the hydrodynamic model developed for the salinity distribution evaluation to evaluate the changes in current vectors and flow rates in the Savannah River.
Sedimentation modeling	This work will adapt the hydrodynamic/salinity model with variations to allow for prediction of the sediment deposition pattern in the river. It will be used in the evaluation of advance maintenance features and the construction cost estimating.
Evaluation of bank erosion changes	This work will utilize the river hydraulic and sedimentation modeling results to evaluate possible changes in erosion resulting from the project.
Advance maintenance features evaluation	This work will determine the advance maintenance features that will be needed for effective and efficient maintenance of the Savannah Harbor Expansion Project.
Ship simulation modeling	This work will simulate the handling characteristics of ships transiting the river to determine the ability of pilots to safely maneuver the vessels.
Disposal area capacity analysis	This work will update the evaluation in the Tier I as a result of information developed during Tier II.
Bank stability analysis	This work is to conduct a thorough riverbank and channel bank slope stability analysis to determine intrusion into or effect on adjacent lands or structures.
Dredged material beneficial usage evaluation	This work, developed in consort with the Beach Erosion Committee of the SEG, will examine the factors affecting beneficial usage of the dredged material removed from the navigation channel during construction. It will determine the economic, financial, and other benefits and costs likely to be realized. Conclusions will be reached about the ability to utilize suitable material beneficially on Tybee Island, or elsewhere, as part of the construction of navigation features.
Dredged material beneficial usage environmental criteria determination	This work, developed in consort with the Beach Erosion Committee of the SEG, will determine the range of material qualities, amounts, and locations acceptable to the appropriate resource agencies for potential beneficial placement of dredged materials.
HTRW screening	The Tier I analysis evaluated new work sediments to be removed from within the channel for the presence of hazardous, toxic, or radioactive wastes. This evaluation will be continued in Tier II by including the new work berth sediments and sediments on the river banks and in bend wideners to be removed by the project for the presence of hazardous, toxic, or radioactive wastes.
Sediment quality analysis	This work will determine the chemical constituents of the new sediments to be removed from the channel during construction of the project and evaluate potential effects.
Real estate analysis	This work will determine the real estate requirements to construct the project.
Economic reevaluation	This work will update the Tier I analyses to reflect current conditions and additional information developed in cooperation with the Economic Working Group. Economic conclusions will be reevaluated based on the updated analyses.
Cost/Benefit ratio evaluation and NED plan selection	This work will determine the project alternative having the highest net benefit utilizing the benefit information developed during the economic reevaluation and the cost information developed in the construction cost estimate.
Cultural resources survey of undisturbed areas	This work will survey areas identified in the Tier I process for cultural or historical resources.
Cultural resources survey of newly identified areas	This work will survey areas newly identified in the Tier II process for cultural or historical resources.
Cultural resources survey of mitigation features areas	This work will survey areas identified by the mitigation plan in the Tier II process for cultural or historical resources.
CSS Georgia activities	This work will survey and investigate the CSS Georgia site for cultural or historical resources.