Annual prediction of shoreline erosion and subsequent recovery

publisher: Elsevier articletitle: Annual prediction of shoreline erosion and subsequent recovery journaltitle: Coastal Engineering articlelink: http://dx.doi.org/10.1016/j.coastaleng.2017.09.008 content_type: article copyright: Crown Copyright © 2017 Published by Elsevier B.V. All rights reserved

Coastal embayment rotation; morphological response to bi-directional wave climates and atmospheric forcing

Work from Chapter 2 is published in: Wiggins, M.; Scott, T.; Masselink, G.; Russell, P.; McCarroll, R.J., 2019, Coastal embayment rotation: Response to extreme events and climate control, using full embayment surveys. Geomorphology, 327, 385–403. DOI: https://doi.org/10.1016/j.geomorph.2018.11.014 Work from Chapter 3 is published in: Wiggins, M.; Scott, T.; Masselink, G.; Russell, P., Valiente N. G., 2019, Regionally-Coherent Embayment Rotation: Behavioural Response to Bi-Directional Waves and Atmospheric Forcing. Journal of Marine Science and Engineering, 7(4), 116. DOI: https://doi.org/10.3390/jmse7040116 Work from Chapter 4 is published in: Wiggins, M., Scott, T., Masselink, G., McCarroll, R. J., Russell, P., 2020, Predicting beach rotation using multiple atmospheric indices, Marine Geology, 426, 106207. DOI: https://doi.org/10.1016/j.margeo.2020.106207Beach rotation through longshore sediment transport can alter shoreline orientation, increasing erosional risks for coastal communities at short-term (storm events) and decadal to centurial time scales (long-term evolution). Identifying, predicting and planning for embayed beach rotation requires understanding of the morphological response to changes in directional wave climates driven by atmospheric forcing. Through assessment of annual to centurial datasets, this thesis aims to improve understanding of beach rotation at local (embayment) to regional (coastline) extents. The multi-annual rotational response of a 12-km, longshore-dominated gravel embayment (Start Bay, Devon, UK) to a set of extreme and contrasting bi-directional winter wave conditions was assessed using multi-method topo-bathymetric surveys. Previously, the limited extent of intertidal measurements constrained insights into sediment pathways during rotational events; however, this study found that accounting for measurement uncertainty was critical in the calculation of robust total sediment budgets (sub-aerial to sub-tidal), allowing identification of full-embayment rotation. Application of this new methodology revealed that under extreme directional wave energy (>1:50 year southerly winter season), full-embayment rotation (6.5 x 105 m3 transport) is possible through headland bypassing (50% of total) and sub-tidal change (33% of total), providing new insights into sediment transport pathways for gravel beaches. Retrieval of beach volumes after rotational events requires sustained or equal extreme wave energy from opposing directions; however, only sub-embayment rotation was observed (under opposing easterly conditions), proposing that headland bypassing is asymmetrical, extending previously understood timescales of recovery. Analysis of hindcast modelled wave data and a 10-year record of 36 intertidal beach profiles located across the full embayment of Start Bay, revealed that interannual to decadal scale beach rotation may be predicted by a new index of the normalized wave power directional balance (WDI), suggesting that subtle variations in bi-directional wave climate drive sustained changes in beach planform, increasing erosional risk at embayment extremities. Assessment of the modelled wave climate (1980 - 2018) highlighted that the two dominant wave directions (southerly and easterly) are correlated with winter averages of two key climate indices, the North Atlantic Oscillation (NAO) and West Europe Pressure Anomaly (WEPA). This is the first robust demonstration of the relationship between negative NAO and easterly wave power, indicating that atmospheric variability significantly explains the WDI and beach rotation at this location. Spatial expansion of this analysis revealed that bi-directional wave climates are regionally comparable, extending throughout the length of the South coast of England. Similar correlations with both climate indices were exhibited, showing other rotational sites are controlled by the atmospheric influence of bi-directional wave climates. Examination of 10-15 years of intertidal beach profiles at 22 embayed South coast locations identified 11 sites exhibiting significant rotational responses, with regionally coherent common factors, including oblique shoreline orientation to bi-directional wave approach, steep slopes and coarser sediment. Beach rotation was shown to be correlated with the WDI for most sites, and significant direct correlations between beach rotation and WEPA at a number of locations, indicates the future potential skilful forecasts of atmospheric indices may have in predicting seasonal rotation at regional to basin-wide scales. To explore the significance of recent (10-year) beach rotational behaviour in Start Bay within centurial timescales, a stepwise multi-linear regression model was developed to hindcast the WDI using long-term (1906-present) sea-level pressure records of the NAO and WEPA. It was found that combining the two indices vastly improved the predictive skill of the regression model when compared to using individual indices (R2 of 0.66 between model data and index predicted values of the WDI). Qualitative validation of beach rotation in response to the >100-yr hindcast WDI timeseries was achieved from proxy records of oblique photography and topographic maps, finding that low frequency (~60 years) phases of clockwise/anticlockwise beach rotation followed positive/negative phases of the detrended cumulative hindcast WDI record, over the period 1906 to 2018. This variability reflects observed multi-decadal fluctuations in phases of NAO (~60-80 year) and WEPA (~50-60 year), demonstrating atmospheric control of directional wave climate and beach rotation over centurial timescales, explaining historical accounts of coastal settlement relocation. When examined in the context of millennial-scale proxy NAO reconstructions, the recent centurial-scale analysis does not capture the much greater magnitude and duration of past detrended cumulative variability observed over the last 3000 years, indicating that previously inferred phases of extreme coastal realignment may recur in the future, presenting a significant long-term issue for locations affected by beach rotation. This work contributes new insights into embayment rotation at different spatial and temporal scales. Application of a new total sediment budget approach improves knowledge of full embayment rotation and recovery, whilst bi-directional waves are shown to predict beach rotation, driven by atmospheric forcing at medium to longer timescales. This thesis directly contributes towards new understanding of the past and future timescales of beach rotation, as well as proposing a mechanism for season ahead forecasting based on atmospheric variability

Pathways for Nutrient Loss to Water; Slurry and Fertilizer Spreading

End of project reportThere are almost 150,000 farms in Ireland and these contribute substantial quantities of N and P to inland and coastal waters. Some of these nutrients are carried from wet soils by overland flow and by leaching from dry soils. Farm practice can reduce the loss from farms by judicious management of nutrients. Improvements are required to diminish export of nutrients without impairing operations on the farm. Literature regarding nutrient loss from agriculture was reviewed in this project and maps were prepared to predict best slurry spreading times around Ireland. Two further maps were prepared to show slurry storage requirement on farms

Relationship between frontal dust storms and transient eddy activity in the northern hemisphere of Mars as observed by Mars Global Surveyor

We have compiled a catalog of frontal dust storms in the northern hemisphere using Mars Orbiter Camera daily global maps spanning ~2.3 Martian years of Mars Global Surveyor (MGS) observations (from 1999 to 2003). The most vigorous frontal storms that flush dust to the low latitudes occur in early-mid fall and mid-late winter, away from the northern winter solstice. While many streaks are observed in the polar hood during the winter solstice period, no frontal dust storms are observed in the vicinity of the north polar region. We have also analyzed simultaneous MGS Thermal Emission Spectrometer (TES) temperature data and found statistically significant negative temperature anomalies associated with frontal storms. In the lowest scale height of the atmosphere, the geographical and seasonal distributions of temperature standard deviations associated with transient variations agree well with the distributions of frontal storms. The correlation deteriorates with increasing altitude, suggesting that lower-level temperature waves are associated with the frontal dust storms. Specifically, eastward traveling m = 3 waves with periods of 2–3 sols appear to be closely related to the development of flushing frontal storms

Patterns and potential solutions to coastal geohazards at Golovin, Alaska

Thesis (M.S.) University of Alaska Fairbanks, 2014The objective of this research is to measure the localized potential for shoreline change and flooding on the Golovin spit, Alaska. Long-term trends of shoreline change have been measured using multi-temporal aerial photography and satellite imagery from 1972-2013, while seasonal and annual changes in shoreline geometry have been measured by re-surveying the beach in July 2012, July 2013, and October 2013. The local bathymetry was updated with data derived from the WorldView-2 satellite to increase the spatial resolution of nearshore topography. These inputs were then integrated to establish an XBeach 1-dimensional numerical model connecting offshore storm water elevations to nearshore dynamics. The spit was found to experience episodic erosion of beach sediments, followed by sediment accretion. This resulted in a dynamic position of the shoreline, with no long-term trend in either the offshore or landward directions. Modeled storms resulted in inundation of low elevations of the spit at a 5- year return interval, with inundation of infrastructure on a 25-year return interval. The modeled results suggest overwash of the entire spit at the 50-100-year return interval. All models were based on the best available forcing data from hindcast modeling. Reinforcing and increasing the elevation of a temporary berm and/or a permanent levee structure, using a 25-year return interval as a design parameter, would help to reduce localized flooding on the spit, and may be considered in the future

Propagation of uncertainty across modeling chains to evaluate hydraulic vulnerability in coastal areas

The aim of the thesis is to investigate the propagation of the uncertainties from meteorological to coastal forecasts, in order to obtain a better understanding of the uncertainties associated to the numerical modeling systems. The first phases focused on the parameter settings of the morphological model XBeach, as source of uncertainties within the model itself. This was done by means of a sensitivity analysis of the model that allowed to characterize how the model responds to changes in input, with an emphasis on finding the input parameters to which outputs are the most sensitive. Moreover, an estimate of how the uncertainties propagate within the numerical modeling chain was made by means of the ensemble technique. Moving from a single-deterministic to probabilistic forecasts, it is possible to give some useful indication of the forecast reliability. Therefore, the meteorological Limited Area Ensemble Prediction System COSMO-LEPS was used to generate 16 different meteorological forecasts that were used to force the wave\oceanographic models SWAN and ROMS and finally the morphological model XBeach. The study focused on two different storm events both occurred in the autumn 2015-winter 2016 on the Emilia-Romagna coasts.The results showed that, in both cases, the uncertainties of the wind and pressure fields clearly propagated through to the oceanographic models up to influence the coastal forecasts. The accuracy of the forecasts of the oceanographic and morphological models is largely dependent on the quality in wind data. However, extension of the ensemble approach to the coastal areas showed encouraging results and suggested, as a future development, the possible optimization of the system by using a meteorological ensemble built in such a way as to optimize the spread in terms of the surface variables used to drive the marine-coastal model components

Forecasting of ionospheric characteristics during quiet and disturbed conditions

An autocovariance forecasting procedure for single location ionospheric characteristics is presented. Its accuracy is illustrated as a function of the amount of time extrapolation for selected European stations under quiet and disturbed conditions