The results illustrate the impact of shallowing on hydrosedimentary processes. The estuary is strongly dominated by spring—neap variability and shallowing, with increasing tidal distortion in the landward direction and a turbidity maximum zone created by sediment resuspension. The maximum flooding and ebbing velocity were stronger and tidal velocity distortion was more pronounced than in The salinity intrusion moved farther landward during low discharge in than in , but not during average and high discharge.
Other hydrosedimentary processes remained consistent with the previous study. This study also illustrates potential problems that can occur when attempting to use historical analyses. Li, J. Spatiotemporal change patterns of coastlines in Xiangshan Harbor Zhejiang, China during the past 40 years. As special and important landscape bodies, tidal inlets possess many coastal resources.
Consideration of the maintenance and protection of coastline resources and the environment is a challenging research topic, i. In this study, multitemporal Landsat images were used to explore and quantify relationships between the intensity of human activities and coastline changes. Specifically, 1 the spatial location, length, and tortuosity of coastlines in Xiangshan Harbor XH; Zhejiang Province, China tidal inlets, from to , were extracted from satellite images; 2 the coastline change indices and the intensity of human activities in the tidal inlet areas of XH were calculated and assessed; and 3 the relationships between coastline change characteristics and human activities during the past 40 years were explored and analyzed.
The results demonstrated that, during the past four decades, as human activities have intensified, the natural coastlines in XH continuously shrank, whereas artificial coastlines increased and then gradually became stable. Various human activities have changed the morphology of local coastlines in XH, and the overall coastline tortuosity has been continuously reduced. The intensity of human activities increased from to , and the intensity slowed after However, the impacts of human activities are extensive and almost cover the entire coastlines of the harbor.
The correlations between the intensity of human activities and the overall length and tortuosity of the coastlines were significantly negative, which means that, as human activities intensified, the length and tortuosity of the coastlines decreased. Kowalski, J. A comparison of salinity effects from hurricanes Dolly and Alex in a Texas lagoon system.
Hurricanes are not uncommon along the Gulf of Mexico coast, but there are few studies of the effects they have on coastal embayments. Surveys were performed to assess poststorm water quality after landfall of both storms at up to 18 sample stations. The main difference between storm effects was salinity reduction because of stormwater input from the watershed.
Effects from Hurricane Dolly were of short duration and small magnitude, whereas the effects from Hurricane Alex were extensive and lasted more than a month. Differences in spatial patterns in salinity were significantly more pronounced across the LLM than were temporal differences. Storm-related effects on water-column physiochemistry were persistently lowest near freshwater drains Arroyo Colorado.
Salinity remained less than 5 for more than 2 months during the Alex freshet. Freshwater input from Hurricane Dolly was relatively minor because the storm precipitation was largely restricted to the small Arroyo Colorado watershed. The greatest impact from that freshwater disturbance was the loss of seagrasses after prolonged exposure to hyposalinity.
Hurricanes Dolly and Alex both affected the LLM but with contrasting impacts that reflected spatial and meteorological differences between the two storms. Long, A. Nutrient exchange between sediments and overlying waters in the Modaomen estuary China over a complete semidiurnal tide cycle: Implications of saltwater intrusion. Spatial and temporal variations of inorganic nutrients , , , , and and some relevant environmental parameters, including temperature, salinity, pH, Eh, dissolved oxygen DO , in surface sediments and overlying waters were investigated during the cruise held on 16 to 19 April over a complete tidal cycle a spring and neap tide together in the Modaomen estuary, Pearl River, China.
It was found that the dominant component of dissolved inorganic nitrogen DIN, expressed as sum of , , and was in sediment interstitial waters and in overlying waters. Overlying waters contained higher concentration of and lower concentrations of and than interstitial waters.
University of Zadar | Department of Geography, Center for Karst and Coastal Research - muscsurplongmade.cf
The exchange flux of inorganic nutrients between sediments and overlying waters was calculated using the Fick diffusion equation. Exchange flux calculations revealed that sediments were the sources of , , and but the sink of and. However, nutrimental exchange flux variations were not obvious during the present tidal cycle.
Results of correlation analysis of single factor and principal component analysis revealed that nutrimental exchange fluxes mainly depend on the nutrient concentration gradient and overlying water chemical environment due to high stratification of waters, obvious homogeneity of sediments, and relative weakness of bioturbation in the Modaomen estuary. Choi, J. Observing the laboratory interaction of undertow and nonlinear wave motion over barred and nonbarred beaches to determine beach profile evolution in the surf zone. A vertically two-dimensional laboratory experiment was performed with a movable bed to investigate the interaction of undertow and sawtooth-shaped nonlinear wave motion over the cross-shore evolution of barred storm and nonbarred normal beach profiles.
The bottom elevations, free-surface motion, and flow velocity were measured under regular wave conditions, excluding infragravity waves, over a movable bed. The observations were conducted in the surf zone during alternate repeats of the two wave conditions until each quasiequilibrium state was reached. From the net sediment transport of the observation area, it was shown that the storm case was in an erosion state and that the normal case was in an accretion state.
The measurements confirmed that the strong undertow, which is a dominant factor in the offshore migration mechanism, was developed in the erosion state but that the undertow in the accretion state was weaker. The measurements also showed that in the shoaling zone, the symmetry of wave motion of the storm-erosion case was larger than that of the normal-accretion case; however, in the surf zone, the symmetry of wave motion of the normal-accretion case was larger than that of the storm-erosion case.
In addition, the asymmetry of wave motion of the storm-erosion case was larger than that of the normal-accretion case in both regions.
Coastline Changes of the Baltic Sea from South to East
The onshore migration effect of the sawtooth-shaped nonlinear wave motion, which was relatively weak in the accretion state, was more significant than that in the erosion state, because the undertow was not enough strong in the accretion state. Wernette, P. Defining dunes: Evaluating how dune feature definitions affect dune interpretations from remote sensing.
Coastal resiliency is the ability of a beach—dune system to recover to a previous state after a storm, and this resiliency is affected by prestorm beach and dune morphology and storm climate i.
Improvements in remote sensing technology such as LIDAR and structure from motion have enabled rapid collection and production of digital elevation models used to assess storm impact and recovery. Although rapid poststorm assessment requires a consistent approach for extracting dune morphology, relatively little attention has focused on defining the different parts of a dune.
Lace, Michael J.
The goals of this paper are to examine how the definition of a dune feature drives the methodology used to extract dunes and to synthesize a comprehensive definition of dune features. An analysis of existing approaches for extracting beach and dune morphology demonstrates that there is considerable variation in how the beach—dune transition i. Many definitions are recursive or include ambiguous terminology, resulting in a dune toe or crest line position dependent on user interpretation of the definition.
Other definitions rely heavily on user interpretation of dune features at varying stages in the feature extraction process. Reliance on visual interpretation can result in substantially different feature locations across different interpreters. Given the impact of varying definitions on dune resiliency assessments and legal implications for dune features location, this study proposes a series of semantic models for dune features. Semantic modelling of coastal morphology is vital for consistently and accurately assessing coastal recovery and predicting future coastal assessments on the basis of a consistent set of criteria.
Mylroie, J. Superstorms: Comments on Bahamian fenestrae and boulder evidence from the Last Interglacial. Two hypotheses have been advanced to demonstrate an increase in storm intensity during MIS 5e. The first considers fenestrae in eolian calcarenites at elevations up to 43 m in the Bahama Archipelago to be evidence of superstorm washover.
Additional observations include rip-up clasts and loss of bedform and root structures as a result of wave scour. Such an event should produce a tempestite with a wide-ranging footprint, but none exists above 10 m. This paper argues that the fenestrae are rainfall slurries, rip-up clasts are weathering products of calcarenite protosol development, and bed-form and root structure absence or presence reflects transgressive-phase vs. In the second case, a 2-km section of the coast of Eleuthera Island contains boulders proposed to have been tossed upward onto the land by superstorm waves, creating an age inversion of older boulders lying on younger rock.
These boulders are now karrentisch and rest on pedestals produced by denudation. To emplace them would require extreme energies, but other interpretations such as fossil tower karst and boulders rolling downslope remain viable alternatives. The proposed chronology of boulder emplacement at the end of MIS 5e conflicts with the field evidence of a terra rossa paleosol separating the pedestals and the boulders. A recent paper has argued that normal hurricane activity could have emplaced the boulders.
WADING IN WASTE
Both of these interpretations fail to explain the lack of similar-sized boulders elsewhere in the Bahama Archipelago. The failure to account for past coastline configuration, cave development in the boulders, and post-MIS 5e boulder denudation makes both boulder analyses incorrect, as discussed herein. Lindner, B. Increasing risk perception and understanding of hurricane storm tides using an interactive, web-based visualization approach.