Rip currents in the non-tidal surf zone with sandbars: numerical analysis versus field measurements

Aleksandra Dudkowska , Aleksandra Boruń , Jakub Malicki , Jan Schönhofer , Gabriela Gic-Grusza

Abstract

Rip currents, which are local seaward-directed jets with their mean velocity exceeding 0.5 m/s, have been a subject of many studies since the 1940s. They are an important part of the nearshore current system and in specific hydro- and litomorphological conditions can cause changes in the local bathymetry. Thus, a detailed analysis of the characteristics of this phenomenon is crucial both to public safety and hydroengineering. The main purpose of this research is to determine the wave conditions of a multi-bar non-tidal coastal zone environment in which rip currents can occur. In this study, we focus on a multi-bar non-tidal coastal zone environment located in the Southern Baltic Sea, where rip current driving forces are mostly reduced to the wind and wind-induced waves. This is one of very few comprehensive approaches to exploring the possibility of rip currents occurrence in such environmental conditions. During two field expeditions, there were carried out in situ measurements exploiting two GPS drifters. The results indicate the formation of irregular non-longshore flows (related to rip currents) in the studied area. To answer the question under what conditions the formation of rip currents takes place, an extended modelling experiment was performed. Deep-water wave conditions typical of the studied area were chosen due to bouy measurements. The total of 589 combinations of the significant wave height, the mean period and wave direction values were examined as test cases. The coastal flow in the area and tracks of virtual drifters were simulated by XBeach numerical model for all test cases. As a result, 589 nearshore currents fields were generated and two scenarios were indicated: a regular circulation (dominated by the longshore current) which is typical of this area (547 cases), and flows with rip current features (42 cases). This reflects the results of the field measurements carried out. It can be concluded that the wave direction is a dominating factor in the formation of rip currents. Namely the flows of this type may occur in the area of interest when the direction of a deep water wave is almost perpendicular to the shore. Such situations occur rarely. They cover about 7% of the days of the year. Thus, rip currents do not appear to be a significant factor in the reconstruction of the sea bottom in the studied area.
Publication typeIn press (online first, early view)
Author Aleksandra Dudkowska (FOG/IO/DPO)
Aleksandra Dudkowska,,
- Division of Physical Oceanography
, Aleksandra Boruń (FOG/IO)
Aleksandra Boruń,,
- Institute of Oceanography
, Jakub Malicki
Jakub Malicki,,
-
, Jan Schönhofer
Jan Schönhofer,,
-
, Gabriela Gic-Grusza (FOG/IO/DPO)
Gabriela Gic-Grusza,,
- Division of Physical Oceanography
Journal seriesOceanologia, ISSN 0078-3234, e-ISSN 2300-7370, (N/A 70 pkt)
Issue year2020
Noonline first
Pages1-18
Publication size in sheets0.85
Keywords in Englishrip current,coastal zone, coastal flows, wind-wave conditions
ASJC Classification1104 Aquatic Science; 1902 Atmospheric Science; 1910 Oceanography; 2212 Ocean Engineering
DOIDOI:10.1016/j.oceano.2020.02.001
URL https://doi.org/10.1016/j.oceano.2020.02.001
Languageen angielski
LicenseJournal (articles only); published final; Uznanie Autorstwa - Użycie Niekomercyjne - Bez utworów zależnych (CC-BY-NC-ND); with publication
Score (nominal)70
Score sourcejournalList
ScoreMinisterial score = 70.0, 27-03-2020, ArticleFromJournal
Publication indicators Scopus SNIP (Source Normalised Impact per Paper): 2017 = 1.157; WoS Impact Factor: 2018 = 1.988 (2) - 2018=2.112 (5)
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