Geology topics

Dongxiao Yin

Publications and source records attributed to Dongxiao Yin.

6 recordsLinked to original sources

USGS2026

Spatial heterogeneity of salt marsh vulnerability to sea-level rise: Dual controls of hydrological setting and salinity regime

Salt marsh vulnerability to sea-level rise (SLR) is typically assessed using point measurements of vertical accretion, neglecting three-dimensionality of geomorphic evolution and spatial variability. Recent studies suggest links between vertical and horizontal vulnerability, with differences between oligohaline and polyhaline marshes, yet these relationships remain untested in estuary-marsh systems. Here we combine geospatial analysis with hydrodynamic modeling to evaluate how unvegetated/vegetated marsh ratio (UVVR), a metric of marsh degradation, relates to elevation across hydrological regions and salinity regimes in the Albemarle-Pamlico Estuarine System, the largest lagoonal estuary in U.S. We show that at given normalized elevation, UVVR decreases across hydrological regions and salinity regimes from offshore to inland. UVVR-elevation relationship varies systematically with both hydrological setting and salinity regime, with hydrology exerting stronger influence. These findings challenge the assumption of a universal marsh deterioration trajectory and underscore the need to account for spatial heterogeneity when predicting responses to SLR.

North Carolina↗

USGS2025

Wind pumping dominates landward salt transport in a weakly tidal estuary

In tidally energetic estuaries, salinity dynamics vary with tidal forcing as well as factors such as river discharge and bathymetry. However, in weakly tidal estuaries, mechanisms governing salt transport remain poorly understood. Here, we investigate salt transport processes in a weakly tidal estuary, Albemarle Sound on the U.S. East Coast, using a deterministic numerical model. In 2022, the volume averaged salinity of Albemarle Sound ranged from ∼2 to 10 psu. Although seasonal river discharge typically induces gradual salinity changes of less than 1 psu per month, four wind events caused sharp salinity increases of 1–2 psu within just a few days. We find that wind pumping, defined as the net salt transport due to temporal correlations between velocity and salinity associated with wind events, is the dominant mechanism contributing to these episodic increases in volume averaged salinity. In Albemarle Sound, wind pumping operates on timescales of several days, which is longer than the tidal timescale, and occurs intermittently throughout the year rather than following a regular repetitive pattern. Our analysis suggests that salt transport by wind pumping is typically an order of magnitude larger than by gravitational circulation and serves as the primary mechanism balancing salt loss from river flow. Isolating wind pumping requires averaging over variability of multiple days, longer than typical tidal averaging. Wind pumping likely also controls material exchange with coastal ocean, influencing biogeochemical processes in the estuary. This mechanism may be important in other systems with similar characteristics, particularly in coastal lagoons with multiple subembayments.

North Carolina↗

USGS2025

Numerical simulation of sound-side barrier-island inundation and breaching during Hurricane Dorian (2019)

Hurricane-induced morphological changes and associated community hazards along sandy, barrier-island coastlines have been studied primarily from the perspective of ocean-side attack by storm-driven ocean surge and large waves. Thus, our understanding of long-term barrier island morphological change focuses on beach erosion, overwash, and inlet formation. In contrast, outwash events with inundation from the sound side, such as one that occurred in Cape Lookout National Seashore, North Carolina, USA during Hurricane Dorian (September 2019), are understudied. Studying such events can improve understanding of barrier island response and stability for a broader range of conditions. Here, we model the hydrodynamics and morphological evolution of a barrier island using a coupled wave-current-sediment transport modeling system. Wind-driven surge in Pamlico Sound led to overtopping from the sound side, which eroded outwash channels and transported sediment seaward into the nearshore. Simulations reproduce the channel features observed with aerial imagery and provide information not available from the remote-sensing observations, including channel depths (>2 m) and the fate of the eroded sand. We found that >99% of the eroded sand was deposited in the nearshore, within 1,000 m of the shoreline in depths <10 m, suggesting that the deposited sediment remains available for littoral transport and beach recovery. Simulations with combinations of coarse or fine sediment and vegetated or unvegetated landcover indicate that channel position did not vary with grain size or vegetation, while volume of erosion and channel morphology were more responsive to variations in grain size and less responsive to presence of vegetation.

North Carolina↗

USGS2024

Modeled coastal-ocean pathways of land-sourced contaminants in the aftermath of Hurricane Florence

Extreme precipitation during Hurricane Florence, which made landfall in North Carolina in September 2018, led to breaches of hog waste lagoons, coal ash pits, and wastewater facilities. In the weeks following the storm, freshwater discharge carried pollutants, sediment, organic matter, and debris to the coastal ocean, contributing to beach closures, algae blooms, hypoxia, and other ecosystem impacts. Here, the ocean pathways of land-sourced contaminants following Hurricane Florence are investigated using the Regional Ocean Modeling System (ROMS) with a river point source with fixed water properties from a hydrologic model (WRF-Hydro) of the Cape Fear River Basin, North Carolina's largest watershed. Patterns of contaminant transport in the coastal ocean are quantified with a finite duration tracer release based on observed flooding of agricultural and industrial facilities. A suite of synthetic events also was simulated to investigate the sensitivity of the river plume transport pathways to river discharge and wind direction. The simulated Hurricane Florence discharge event led to westward (downcoast) transport of contaminants in a coastal current, along with intermittent storage and release of material in an offshore (bulge) or eastward (upcoast) region near the river mouth, modulated by alternating upwelling and downwelling winds. The river plume patterns led to a delayed onset and long duration of contaminants affecting beaches 100 km to the west, days to weeks after the storm. Maps of the onset and duration of hypothetical water quality hazards for a range of weather conditions may provide guidance to managers on the timing of swimming/shellfishing advisories and water quality sampling.

Journal of Geophysical Research: Oceans↗

USGS2022

Understanding the role of initial soil moisture and precipitation magnitude in flood forecast using a hydrometeorological modelling system

We adapted the WRF-Hydro modelling system to Hurricane Florence (2018) and performed a series of diagnostic experiments to assess the influence of initial soil moisture and precipitation magnitude on flood simulation over the Cape Fear River basin in the United States. Model results suggest that: (1) The modulation effect of initial soil moisture on the flood peak is non-linear and weakens as precipitation magnitude increases. There is a threshold value of the soil saturation, below and above which the sensitivity of flood peak to the soil moisture differentiates substantially; (2) For model spin-up, streamflow needs longer time to reach the ‘practical’ equilibrium (10%) than the soil moisture and latent heat flux. The model uncertainty from spin-up can propagate through the hydrometeorological modelling chain and get amplified into the flood peak; (3) For ensemble flood modelling with a hydrometeorological system, modelling uncertainty is dominated by the precipitation forecast. Spin-up induced uncertainty can be minimized once the model reaches the ‘practical’ equilibrium.

North Carolina↗

USGS2021

Hydrometeorology and hydrology of flooding in Cape Fear River basin during Hurricane Florence in 2018

Hurricanes are the major flood generating mechanism dominating the upper tail of the peak discharge distribution over the Cape Fear River Basin (CFRB). In 2018, Hurricane Florence swamped CFRB as the ninth-most-destructive hurricane ever hit the United States and set new records of peak discharges over the main river channel and three out of five of its major tributaries. In this study, we examined the hydrometeorology and hydrology of this flood via combined observation and numerical experiment analyses. Our results suggest that the slow-motion in combination to the “L-shaped” path was the most distinctive feature of the hurricane that incurred catastrophic and widespread rainfall and flooding over CFRB. The total rainfall from the storm played a controlling role in the magnitude and spatial distribution of the flood peaks at basin scale. Above that, the spatial heterogeneities of rainfall distribution and hydrologic characteristics was responsible for the distinctive flood responses within the basin. The bi-peak shape of the flood hydrograph for the Deep River was due to the combined effects of rainfall distribution, land cover, and topographic gradient. The exceptional unit peak discharge over the Black River basin was associated with its drainage network structure, topographic gradient and rainfall distribution. The floodplain downstream of the Cape Fear River temporarily stored flood water and attenuated both the riverine floods from upstream and the compound flood over the coastal area. Furthermore, numerical analyses found that re-infiltration accounted for 76% of the total infiltration on average. Re-infiltration was superior to local infiltration over CFRB during Hurricane Florence.

North Carolina↗