US Coastal Research Articles

Cover crop grazing length impacts on soil health and crop productivity in US Coastal Plain soils

AbstractIntroducing integrated crop‐livestock systems into row crop production promotes income diversification and potential soil health benefits through cover crop grazing on degraded soils of the southeastern United States, but effects of these practices on crop yields and soil health in Coastal Plain soils are not well established. A 4‐year study was performed to evaluate the effects of grazing a multi‐species winter cover crop on soil health and crop yields under mid‐February, mid‐March, and mid‐April cattle removal dates and a non‐grazed control within an annual cotton (Gossypium hirsutum L.) and peanut crop rotation (Arachis hypogaea L.). Chemical soil health indicators (soil organic carbon and permanganate oxidizable carbon), physical soil health indicators (water‐stable aggregates and penetration resistance), biological soil health indicators (microbial biomass carbon, soil respiration, and arbuscular mycorrhizal fungi colonization), crop yield, and cover crop biomass were evaluated. Cover crop biomass at termination was reduced by 3660, 5250, and 5610 kg ha−1 for the mid‐February, mid‐March, and mid‐April cattle removal treatments compared to the non‐grazed control. No grazing treatment effects were observed for biological soil properties. Soil organic carbon was higher in the non‐grazed treatment than the mid‐April grazing treatment across 0‐ to 30‐cm depth. Penetration resistance across 0‐ to 50‐cm depth and water‐stable aggregates at the 0‐ to 30‐cm depth were both negatively impacted by increased grazing period lengths. Results from this study suggest that longer cover crop grazing periods have little effect on biological and chemical soil health indicators in the short term but can negatively impact some physical soil health indicators.

Regional Sediment Management in US Coastal States: Historical Trends and Future Predictions

Sea level rise and natural disasters, such as hurricanes and tropical storms, are resulting in coastal erosion-related problems across the US. Beach nourishment is one of the most commonly adopted solutions for erosion mitigation. Borrow sources for nourishment are often from offshore or upland mines. However, in some areas, sediment availability from known borrow sources is becoming scarce. This suggests that sediment should be considered a non-renewable resource within the framework of long-term planning and coastal management decisions. Regional Sediment Management (RSM), or the beneficial use of dredge material (BUDM), targets inlets for borrowing material and can also be a more cost-efficient strategy that has widely been supported by the US Army Corps of Engineers as a system-based approach. However, not all states have embraced this approach, and a national-scale evaluation of these projects in coastal management and adaptation is needed. This study examines past RSM/BUDM projects in the top ten most highly nourished states in the US and compares those trends to a selection of minimally nourished states from different coasts. Based on the historical trends identified, the volume of sediment required for future RSM/BUDM projects in these areas over the next 50 years is predicted using Auto Regressive Integrated Moving Average (ARIMA) models. Although growth in the total number of RSM/BUDM projects was measured over time, there was a decline in the volume of sediment placed for these projects. Results of the forecasting model suggest that CA, NC, and the FL Gulf Coast could require the highest volume of sediments for RSM/BUDM activities over the next 50 years. Based solely on proximity to inlets for sediment resources, DE, FL Atlantic, and NJ coasts are potential beaches that can increase BUDM activities. This study aims to provide a framework to evaluate the suitability of future RSM/BUDM projects in efforts to mitigate coastal erosion.

Mobile Observations of Ozone and Aerosols in Alabama: Southeastern US Summer Pollution and Coastal Variability

AbstractWe present a detailed analysis of measurements of ozone (O3) and aerosols collected using multiple platforms and instruments during a 5‐day mini‐campaign in Alabama, for improving our understanding of the chemistry and air quality in the Southeastern United States. Our study features the first on‐road O3 lidar profiling on highways and the coordinated airborne observations that captured O3 and aerosol structures associated with synoptic weather conditions, stratospheric intrusions, wildfire smoke transport, and enhancements in urban areas. The Doppler wind lidar data suggest that the vertical structures and variability of O3 and aerosols at Dauphin Island, a coastal site in the Gulf of Mexico, were related to both the synoptic flow and local‐scale land‐sea breeze circulation. The onshore gulf breeze, which typically started in the afternoon, helped to quickly dilute air pollutants near the surface, resulting in large gradients toward inland areas. In contrast, gradients were much smaller on days without a gulf breeze. O3 and humidity were highly anti‐correlated in the lower free troposphere, but weakly anti‐correlated in the planetary boundary layer (PBL) suggesting more complicated emissions and sink of O3 in the PBL. Our on‐road and airborne measurement strategies to quantify the vertical and horizontal chemical gradients will be useful for future geostationary satellite validation.

Introduction to the special issue on Sea Grant: Science serving America’s coastlines and people

The National Sea Grant College Program is thrilled to partner with Oceanography to publish a special issue focused on Sea Grant’s contributions to enhancing the use and conservation of US coastal, marine, and Great Lakes resources to create a strong and sustainable economy, healthy coastal ecosystems, and resilient and inclusive communities. This introduction presents an overview of the National Sea Grant College program and highlights articles in this special issue.

Rolling Easements as a Viable Tool to Address Rising Sea Levels in US Coastal Communities

Rolling Easements as a Viable Tool to Address Rising Sea Levels in US Coastal Communities

Decreasing Richness and Biomass During a Flood Pulse Observed in a Southeastern US Coastal Floodplain Following a Multi-Year, Supra-Seasonal Drought

Floodplains of the southeastern United States exhibit high biological abundance and diversity, maintained by periodic inundation from seasonal flooding. To examine the relationship between invertebrate community composition and seasonal flooding following periods of drought, we quantified aquatic macroinvertebrate communities monthly in an inundated floodplain during the annual flood pulse (December-April) in two years: one following a multi-year drought and one during a larger than average flood. We predicted that floodplain communities would differ in richness, biomass, and community composition between years and that differences would be driven by the annual flood pulse and organic matter availability. We collected macroinvertebrates from a floodplain of the Altamaha River, a free-flowing 6th order river in the Coastal Plain region of the southeastern US. With invertebrates identified to genus, we estimated richness, abundance, biomass, community composition, and proportions of functional feeding group abundance. Richness was generally higher in the drought year but decreased throughout the flood pulse, while during the flood year richness was lower and increased over time. Biomass decreased throughout the flood pulse following the drought year and increased during the flood year. There was high overlap in invertebrate community composition based on abundance data during both years of the study with collector gatherers being the most abundant functional feeding group. Our study provides insight to the response of aquatic communities to an extended drought and subsequent return to normal flow in a lower river wetland.

Removing federal subsidies from high‐hazard coastal areas slows development

The US federal government has implemented a variety of policies and subsidies that help coastal development remain viable, including investments in risk reduction measures, subsidized flood insurance, and post‐disaster assistance. In this study, we explored how the removal of federal subsidies impacts coastal development patterns by measuring the causal effect of the US Coastal Barrier Resources Act (CBRA) on building activity. Implemented in 1982, CBRA withdrew eligibility for federal funding for infrastructure, post‐disaster assistance, and subsidized flood insurance along designated sections of coastal barriers (“CBRA units”). Using a novel built‐structures dataset, we employed a spatial regression discontinuity design to compare development rates within and outside of CBRA units in 1980 and 2016. We found that enactment of the CBRA has resulted in significant reductions in development activity: indeed, development rates were reduced by more than 75% in CBRA areas as compared to non‐CBRA areas. Our findings suggest that policies like CBRA can be effective at slowing development in other sensitive or hazardous areas, and could help to preserve natural environments for habitat conservation and climate adaptation purposes.

Shifting Baselines May Undermine Shoreline Management Efforts in the United States

Rising sea levels, extreme weather events, and unsustainable coastal zone development pose serious threats to growing coastal communities. Human actions, such as shoreline development and hardening in at-risk areas, can damage nearshore ecosystems and exacerbate existing risks to coastal populations. A comprehensive understanding of shoreline changes in response to development, storm events, and sea-level rise is needed to effectively mitigate coastal hazards and promote adaptive and resilient coastlines. To determine whether human modification of shorelines can be accurately quantified and assessed over time, we evaluated past and present shoreline mapping and classification efforts in the United States. We coupled a review of available US shoreline data with a survey of coastal planners and managers involved with US state shoreline mapping programs. Using these data, we estimated the current extent of shoreline modification along the Atlantic, Pacific, and Gulf US coasts. However, we found that quantifying shoreline modifications over time nationally—or even within a single state—is currently infeasible due to changes in shoreline resolution associated with advances in shoreline mapping methodologies and a lack of regularly updated shoreline maps. State-level analysis from surveys revealed that 20 US coastal states have undertaken shoreline mapping projects, with sixteen tracking shoreline type and/or condition. However, of the 36 shoreline maps and databases identified, only half (18) were updated regularly or had planned updates. Lacking shoreline change data, coastal communities risk accepting increasingly degraded coastal zones and making poor management decisions based on shifted baselines. Thus, we recommend increasing the scale and funding for several ongoing innovative shoreline mapping efforts. These efforts are particularly focused on improving and standardizing shoreline mapping techniques, as well as establishing accurate baselines for shoreline conditions in the United States. Without accurate baselines and regular, consistent updates to shoreline data, managers cannot manage shorelines in a way that effectively mitigates coastal hazards while also promoting socio-ecological resilience in a changing climate.

Agricultural Stakeholders’ Perceptions of Occupational Health and Safety in the Southeastern US Coastal States

This publication aims to answer four questions regarding perceptions of occupational health and safety in the southeastern coastal states. Written by Tracy Irani, Beatrice Fenelon Pierre, and Tyler S. Nesbit, and published by the UF/IFAS Department of Family, Youth and Community Sciences, October 2021.

Examining factors influencing plan integration for community resilience in six US coastal cities using Hierarchical Linear Modeling

Flooding poses a grave threat to property and the safety of human communities. Urban planning efforts and guidance can have an important influence on the vulnerability of development in hazardous areas. This study is the first to use Hierarchical Linear Modeling (HLM) to investigate the influence of local planning capacity and other contextual factors on the integration of hazard mitigation policies and building of resilience across community 'networks of plans' in six US coastal cities. Findings indicate significant variation across cities regarding plan integration to enhance resilience. Communities with larger proportions of renters and lower socioeconomic status are shown to be less likely to incorporate hazard mitigation policies in local plans, controlling for community planning capacity. We also find evidence that communities with prior hazard experience are more likely to have resilience-focused plans, even in physically vulnerable neighborhoods which, in the absence of recent hazards, are actually less likely to receive positive policy attention. The study concludes by discussing the results and offering recommendations to inform more effective approaches as practitioners reevaluate their plans and work to foster more coordinated mitigation efforts across local networks of plans.

Changing ecological and agricultural expectations for US Coastal Plain managed grasslands

Across the US Coastal Plain, native grasses and legumes may provide viable alternatives to monoculture pastures of introduced sod‐forming grasses, which require recurring costly inputs. Some available cultivars of native grasses, mostly from neighboring regions, have potential to combine forage production for grazing livestock with enhanced habitat, especially for grassland birds. A few native legume species have potential to enhance ecosystem service provisioning of existing grass pastures. Such pastures with native grasses and legumes could complement restoration plantings to increase connectivity and scale of ecosystem function; however, coordination of pasture and restoration plantings would be needed to optimize benefits.

Reproductive Phenology and the Larval Period of the Western Dwarf Salamander (Eurycea paludicola) in Southeastern Louisiana

Cryptic species are often lacking in basic natural history data, which makes it difficult to effectively manage and conserve populations of these taxa. Eurycea paludicola (Western Dwarf Salamander) is a newly designated cryptic species that is endemic to the southeastern US Coastal Plain. Despite the ubiquity of this salamander in many mesic habitats, descriptions of the natural history of this species are lacking compared to other taxa within the Dwarf Salamander complex. Here we describe the reproductive phenology, habitat, and developmental period of a population of Western Dwarf Salamanders in southeastern Louisiana. We include descriptions of the color and pattern of larvae and metamorphs based on our observations of 192 individuals and provide comments on sampling strategies for plethodontid larvae in microhabitats that can be difficult to survey. Reproductively active adults of the Western Dwarf Salamander were found from mid-November through late December and larvae were present at least from mid-March to mid-May. Individuals complete metamorphosis in the summer, and recent metamorphs can be found along wetland margins from late April through early June. This is the first study to highlight the reproductive and developmental timing of the Western Dwarf Salamander, and our results indicate that these salamanders exhibit similar life-history traits to other members of the Dwarf Salamander complex.

Combined Modeling of US Fluvial, Pluvial, and Coastal Flood Hazard Under Current and Future Climates

AbstractThis study reports a new and significantly enhanced analysis of US flood hazard at 30 m spatial resolution. Specific improvements include updated hydrography data, new methods to determine channel depth, more rigorous flood frequency analysis, output downscaling to property tract level, and inclusion of the impact of local interventions in the flooding system. For the first time, we consider pluvial, fluvial, and coastal flood hazards within the same framework and provide projections for both current (rather than historic average) conditions and for future time periods centered on 2035 and 2050 under the RCP4.5 emissions pathway. Validation against high‐quality local models and the entire catalog of FEMA 1% annual probability flood maps yielded Critical Success Index values in the range 0.69–0.82. Significant improvements over a previous pluvial/fluvial model version are shown for high‐frequency events and coastal zones, along with minor improvements in areas where model performance was already good. The result is the first comprehensive and consistent national‐scale analysis of flood hazard for the conterminous US for both current and future conditions. Even though we consider a stabilization emissions scenario and a near‐future time horizon, we project clear patterns of changing flood hazard (3σ changes in 100 years inundated area of −3.8 to +16% at 1° scale), that are significant when considered as a proportion of the land area where human use is possible or in terms of the currently protected land area where the standard of flood defense protection may become compromised by this time.

Toward an Integrative Geological and Geophysical View of Cascadia Subduction Zone Earthquakes

The Cascadia subduction zone (CSZ) is an exceptional geologic environment for recording evidence of land-level changes, tsunamis, and ground motion that reveals at least 19 great megathrust earthquakes over the past 10 kyr. Such earthquakes are among the most impactful natural hazards on Earth, transcend national boundaries, and can have global impact.Reducing the societal impacts of future events in the US Pacific Northwest and coastal British Columbia, Canada, requires improved scientific understanding of megathrust earthquake rupture, recurrence, and corresponding hazards. Despite substantial knowledge gained from decades of research, large uncertainties remain about the characteristics and frequencies of past CSZ earthquakes. In this review, we summarize geological, geophysical, and instrumental evidence relevant to understanding megathrust earthquakes along the CSZ and associated uncertainties. We discuss how the evidence constrains various models of great megathrust earthquake recurrence in Cascadia and identify potential paths forward for the earthquake science community. ▪ Despite outstanding geologic records of past megathrust events, large uncertainty of the magnitude and frequency of CSZ earthquakes remains. ▪ This review outlines current knowledge and promising future directions to address outstanding questions on CSZ rupture characteristics and recurrence. ▪ Integration of diverse data sets with attention to the geologic processes that create different records has potential to lead to major progress.

Flue gas desulfurization gypsum and grass buffer strip influence on runoff and nutrient loss from inorganically and organically fertilized corn on a US Coastal Plain soil

Broiler litter (BL) and flue gas desulfurization gypsum (FGDG), both readily available in the US Southeast, can potentially ameliorate soil constraints adversely affecting agricultural productivity and environmental quality in the region. However, benefits and risks must be evaluated prior to making recommendations to producers. The effectiveness of a combination of FGDG and grass buffer strips (GBS) to reduce edge-of-field nutrient losses from corn (Zea mays L.) production under inorganic (NPK) or organic (BL) fertilization was evaluated on Coastal Plain soils near Tifton, Georgia, from April of 2014 through January of 2017. Nine treatments were randomly established in each of three replications on plots instrumented to collect runoff. This was the first phase of a three-phase study. Treatments consisted of combinations of three fertilizer treatments (NPK, BL, and BL+FGDG) and three GBS treatments (no GBS [–GBS], GBS without FGDG [GBS−FGDG], and GBS with FGDG [GBS+FGDG]). A tenth treatment of NPK+FGDG without GBS was also included. Annual rates for BL and FGDG were 13.45 Mg ha−1 each. The BL rate was based on a high nitrogen (N) demand of corn and would represent a risky scenario for nutrient loss. Runoff and concentrations and loads of nitrate-nitrogen (NO3-N), ammonium-nitrogen (NH4-N), total Kjeldahl nitrogen (TKN), dissolved reactive phosphorus (DRP), and total P (TP) were determined in runoff from 29 storms from May of 2015, through January of 2017. Rainfall partitioned into runoff (percentage runoff) decreased by 50% to 70% under –GBS with BL or BL+FGDG compared with NPK fertilization, and under GBS–FGDG or GBS+FGDG compared with –GBS for NPK and BL fertilization. Under –GBS, concentration of DRP and TP increased by ~160% from BL compared with NPK fertilization, and by 150% for DRP and by 115% for TP from BL+FGDG compared with NPK fertilization. On the other hand, the combined BL+FGDG and GBS+FGDG treatment reduced nutrient concentration by 65% to 80% compared with BL with –GBS (a standard practice), and nutrient load by 40% to 70% compared with NPK with –GBS (another standard practice) or BL with –GBS. Results indicate the potential for FGDG to improve edge-of-field runoff water quality when applied to fields with BL and to edge-of-field GBS. In planned follow-up articles, results will be compared with phase-2 when BL and FGDG rates were reduced by a third and phase-3 when BL application was discontinued.

Hurricane Freshwater Flood Risk Assessment Model for Residential Buildings in Southeast US Coastal States Considering Climate Change

AbstractA significant amount of hurricane losses are caused by rainfall-induced freshwater flooding, and hurricane precipitation is expected to increase in the warming climate. However, the climate...

Does removal of federal subsidies discourage urban development? An evaluation of the US Coastal Barrier Resources Act.

Urban development relies on many factors to remain viable, including infrastructure, services, and government provisions and subsidies. However, in situations involving federal or state level policy, development responds not just to one regulatory signal, but also to multiple signals from overlapping and competing jurisdictions. The 1982 U.S. Coastal Barrier Resources Act (CoBRA) offers an opportunity to study when and how development restrictions and economic disincentives protect natural resources by stopping or slowing urban development in management regimes with distributed authority and responsibility. CoBRA prohibits federal financial assistance for infrastructure, post-storm disaster relief, and flood insurance in designated sections (CoBRA units) of coastal barriers. How has CoBRA’s removal of these subsidies affected rates and types of urban development? Using building footprint and real estate data (n = 1,385,552 parcels), we compare density of built structures, land use types, residential house size, and land values within and outside of CoBRA units in eight Southeast and Gulf Coast states. We show that CoBRA is associated with reduced development rates in designated coastal barriers. We also demonstrate how local responses may counteract withdrawal of federal subsidies. As attention increases towards improving urban resilience in high hazard areas, this work contributes to understanding how limitations on infrastructure and insurance subsidies can affect outcomes where overlapping jurisdictions have competing goals.

Hurricane Risk Assessment for Residential Buildings in the Southeastern US Coastal Region in Changing Climate Conditions Using Artificial Neural Networks

AbstractHurricanes cause severe damage along US coastal regions, which may be aggravated in changing climate conditions. This paper investigates the impact of climate change on the hurricane risk f...

Using CMECS to Create Benthic Habitat Maps for Pleasant Bay, Cape Cod, Massachusetts

Benthic habitat maps are an important part of ecosystem-based management as they document biotic and abiotic resources. Integrating multiple ecosystem and environmental components is challenging, and the ability to do this is highly dependent on the methodology employed. The US Coastal and Marine Ecological Classification Standard (CMECS) uses a standardized set of classifications in a hierarchal structure to create benthic habitat maps. This study used acoustic surveys and benthic samples from Pleasant Bay, Cape Cod, MA, to develop benthic habitat maps and test relationships between biotic and abiotic variables. The collected data comprise a critical baseline record of biological and physical characteristics and will inform future management decisions as well as guide future studies of coastal resources in Pleasant Bay.

National Atlases – an atlas type reconsidered

Abstract. The publication of the first National Atlas in 1899 marked the emergence of an atlas category that thrived over the upcoming century. The "Atlas de Finlande", successfully presented at the Paris World Exhibition in 1900, used to coin this title and being published in Paris by the National Geographic Society of Finland, had a true nation-building function.In the same year, following the US victory in the Spanish-American War, the Atlas of the Philippine Islands (Atlas de Filipinas) was published by the US Coastal and Geodetic Survey, containing two front pages, one in English indicating the USC&GS as publisher, the other in Spanish mentioning the supervision of the project by Father J. Algue, the director of the Manila Observatory. Never referred to as a national atlas, it comprises a series of maps on the Islands and a bilingual abstract on map conventions, a bilingual gazetteer and a thorough introduction into places, places names and their pronunciation. For these atlases, the publication circumstances remain somehow heterogeneous and cannot be compared with modern national atlases and even atlases published in the same period seem to have different hallmarks.Why considering the Atlas de Finlande a national atlas but define the 1878 Statistical Atlas of the United States only a statistical Atlas? Because of the title? What atlases are more nationally defined than school atlases? Is an atlas published by a non-governmental executing agency a national atlas? Is governmental support and approval needed?How national atlases fit into different approaches to thoroughly define them (e.g. Salischew 1967) has been subject to academic cartographic self-conception that ignored technological, institutional, economic and user-related developments over time. In addition, these approaches to categorise atlases solely focused structural elements, such as the number and topics of maps and their temporal and spatial sequence. The question of how atlases have been characterised by their publishers and have been perceived in closely following reviews is a possible approach to either situate national atlases as a strict category or a politically induced perception.The article introduces a post-structuralist approach focussing the textual analysis of both, self-perception verbalized through introductions and prefaces in respective atlases and reviews, contemporarily published in the following years. Introducing common definitions and juxtapose the historical perception of national atlases tries to operationalize Harley's critical approach, that situates maps in their respective historical context. By regarding an atlas not only as a bound collection of maps but as a carefully organised selection of spatial information unveils the power of atlases, which maybe exceeds those of single maps. To analyse atlases in their historic context by including their self-definition and contemporary perception will identify so far unattended aspects and to alternative views on national atlases and their editing and production frameworks. Thus retrograde definitions can be reconsidered.