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| Titel |
The role of beach morphodynamic state on infragravity swash on beaches: field observations. |
| VerfasserIn |
Paula Gomes da Silva, Mauricio González, Raul Medina |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250151858
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| Publikation (Nr.) |
 EGU/EGU2017-16623.pdf |
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| Zusammenfassung |
| The runup generated by waves can be defined as the maximum height above sea water level
on the coastline and is an important criterion for costal structures/nourishment design and
erosion/flooding risk analysis. Given the complexity of nonlinear processes involved in the
runup generation, its prediction is commonly made by means of empirical formulations that
relate wave and beach parameters. The most accepted parametrization presented till the
moment was proposed by Stockdon et al. (2006), in which the runup exceeded by 2 percent
of the waves (R2) is described in terms of setup (η - the steady superelevation of the mean
water level caused by breaking waves) and incident and infragravity swash (Sinc and Sig-
time-varying fluctuations around the setup caused by non-breaking waves). Such formulation
has been widely accepted and its efficiency was appraised in many works. Nevertheless,
although empirical parametrization of infragravity swash using incident wave’s
parameters shows reasonable skill, the correlation can still present considerable
scatter.
The amount of infragravity energy on swash is directly related to the morphodynamic
beach state, in a way that beach profiles classified as reflective (low wave energy, coarse
sediment and higher beach slope) tend to show lower Sig values than dissipative ones (high
wave energy, fine sediment and lower beach slope). However, since Stockdon’s formula for
predicting infragravity swash consider only wave parameters, its use implies that beaches
receiving the same wave energy but with different grain size and beach slope would present
the same Sig values.
This work assumed the hypothesis that the scatter verified on the predictions of the
infragravity swash is mainly related to the lack of information about the beach state in
Stockdon formula. Based on that, a field campaign was designed and carried out in Somo-El
Puntal beach, north Spain, with the aim of generating data to be analyzed in terms of
infragravity swash. An important aspect about this field site is that, given the gradient of wave
energy that reaches each part of the beach, it can present many morphodynamic states
simultaneously, allowing a high range of measurements in a single beach. Thus, wave,
currents, sediment and runup data were measured in three different profiles, as well as the
whole beach topography, bathymetry and video camera images. These data, summed to those
available from Stockdon study, were used to verify the validity of the hypothesis and to
propose a new approach for empirically determining infragravity swash on beaches. |
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