Title

Relevance of historical nautical charts in sediment dynamic assessments on a high energy temperate shelf

Publication Name

Continental Shelf Research

Abstract

Shipping has been of critical importance for European colonisation and development in many parts of the world. These required the charting of safe shipping approaches, which gradually evolved into our modern nautical charts. Colonial charts provide an unique historical perspective and are of global scientific relevance for understanding the sedimentary dynamics and quantifying human alterations in the coastal zone. In areas where significant changes occurred, volumetric differences can be calculated providing a relative degree of certainty, whereas in broader areas the uncertainties are greater than the volumetric changes. In this study we looked at bathymetric and shoreline change since the mid 19th century based on information available on historical charts. We compared lead line soundings to contemporary Multibeam Echosounding (MBES) bathymetry and Light Detection and Ranging (LiDAR) data at four locations along the swell-dominated west coast of Victoria, Australia. Shorelines extracted from these charts were also used in conjunction with aerial photography and satellite imagery to show how changes following the construction of coastal infrastructure has affected natural processes of sediment transport and had long-term impacts on the adjacent coastline. We demonstrate how the construction of the port of Portland breakwaters trapped approximately 1,450,000 ± 550,000 m3 of sand, an equivalent amount of material eroded from the downdrift coastline; the closing of the southwest passage and the construction of the training walls of Port Fairy reduced the availability of sand to East Beach; the viaduct and breakwater construction at Warrnambool created a sand trap that accumulated 1,028,181 ± 575,613 m3 of sand, which made the shoreline prograde fast and reduced the harbour depth; and the dredging required to maintain the port of Apollo Bay created new land with the deposition of 291,712 ± 265,203 m3 of sand adjacent to the disposal area but caused erosion further downdrift.

Open Access Status

This publication is not available as open access

Volume

230

Article Number

104555

Funding Sponsor

Department of Environment, Land, Water and Planning, State Government of Victoria

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Link to publisher version (DOI)

http://dx.doi.org/10.1016/j.csr.2021.104555