3D modelling of beach topography changes caused by the tombolo phenomenon using terrestrial laser scanning (TLS) and unm
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ORIGINAL
3D modelling of beach topography changes caused by the tombolo phenomenon using terrestrial laser scanning (TLS) and unmanned aerial vehicle (UAV) photogrammetry on the example of the city of Sopot Cezary Specht 1
&
Pawel S. Dabrowski 1
&
Mariusz Specht 2
Received: 22 April 2020 / Accepted: 8 June 2020 # The Author(s) 2020
Abstract In 2011, a yacht marina was built in Sopot (the largest holiday resort in Poland), which initiated the formation of a local shallowing of the bottom related to the tombolo effect. The building of the marina led to disturbances in the transmission of bottom deposits along the coast, which resulted from waves and the shift of the beach coastline by approx. 50 m towards the sea. Its effects include progressive morphological changes in the shore and the sea bottom, which will lead to the formation of a peninsula between the shore and the marina in the future. This paper presents the results of a comparative analysis of the accuracy of 3D modelling of the tombolo phenomenon in the onshore part of the beach using both point clouds obtained by terrestrial laser scanning methods and photogrammetric methods based on unmanned aerial vehicle photographs. The methods subjected to assessment include both those for land modelling and for determining the coastline course and its changes. The analysis results prove the existence of sub-metre differences in the imaged relief and the coastline course, which were demonstrated using an analysis of land cross-sections. The possibilities and limitations of both methods are demonstrated as well.
Introduction Sopot is one of the major Polish holiday and spa resorts situated on the coast of the Baltic Sea. The city has the longest wooden pier in Europe, which is regularly damaged by storms. In October 2009, a violent storm completely destroyed the wooden structure of the pier groyne. The only economically viable method for protecting the pier was to build two breakwaters from the eastern and southern side (Fig. 1). The basin bordered between these breakwaters and the pier groyne
* Pawel S. Dabrowski [email protected] Cezary Specht [email protected] Mariusz Specht [email protected] 1
Department of Geodesy and Oceanography, Gdynia Maritime University, Gdynia, Poland
2
Department of Transport and Logistics, Gdynia Maritime University, Gdynia, Poland
and head has become the natural marina (Mayor of the City of Sopot n.d.). Expert discussions and their opinions resulted in a decision to build a yacht marina in Sopot (3 basins, a maximum of 103 vessels: 40 large ones, up to 14 m in length, and 63 boats up to 10 m in length) for PLN 72 million. The seemingly undoubted decision is currently becoming a serious problem for the city, as the building of the marina led to the local inhibition of the transport of debris (sand) along the coast, which resulted in its accumulation between the marina and the shore and the shift of the coastline towards the sea (approx. − 50 m), and initiated the process of inevitable formation of a peninsul
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