[Tagging] Coastline for rivers, estuaries and mangroves?

Graeme Fitzpatrick graemefitz1 at gmail.com
Mon Sep 3 21:58:35 UTC 2018

This has recently been discussed on the Australian list, with reference
being made to
which is based on the UN Convention on the Law of the Sea

For our discussion now:
"Territorial Sea Baseline

The term Territorial Sea Baseline (TSB) refers to the line from which the
seaward limits of Australia's Maritime Zones are measured. These include
the breadth of the territorial sea; the seaward limits of the contiguous
zone, the exclusive economic zone and, in some cases, the continental shelf.

The territorial sea baseline may be of various types depending upon the
shape of the coastline in any given locality:

   - The Normal baseline corresponds with the low water line along the
   coast, including the coasts of islands. Under the Convention, normal
   baseline can be drawn around low tide elevations which are defined as
   naturally formed areas of land surrounded by and above water at low tide
   but submerged at high tide, provided they are wholly or partly within 12
   nautical miles of the coast. For Australian purposes, normal baseline
   corresponds to the level of Lowest Astronomical Tide (LAT)
   - Straight baselines are a system of straight lines joining specified or
   discrete points on the low-water line, usually known as straight baseline
   end points. These may be used in localities where the coastline is deeply
   indented and cut into, or where there is a fringe of islands along the
   coast in its immediate vicinity.
   - Bay or river closing lines are straight lines drawn between the
   respective low-water marks of the natural entrance points of bays or rivers.

Waters on the landward side of the baseline are internal waters for the
purposes of international law."

& NB that they say that the Normal baseline is the low water line!

The UN's definitions:

Straight baselines

1. In localities where the coastline is deeply indented and cut into, or if
there is a fringe of islands along the coast in its immediate vicinity, the
method of straight baselines joining appropriate points may be employed in
drawing the baseline from which the breadth of the territorial sea is

2. Where because of the presence of a delta and other natural conditions
the coastline is highly unstable, the appropriate points may be selected
along the furthest seaward extent of the low-water line and,
notwithstanding subsequent regression of the low-water line, the straight
baselines shall remain effective until changed by the coastal State in
accordance with this Convention.

3. The drawing of straight baselines must not depart to any appreciable
extent from the general direction of the coast, and the sea areas lying
within the lines must be sufficiently closely linked to the land domain to
be subject to the regime of internal waters.

4. Straight baselines shall not be drawn to and from low-tide elevations,
unless lighthouses or similar installations which are permanently above sea
level have been built on them or except in instances where the drawing of
baselines to and from such elevations has received general international

5. Where the method of straight baselines is applicable under paragraph 1,
account may be taken, in determining particular baselines, of economic
interests peculiar to the region concerned, the reality and the importance
of which are clearly evidenced by long usage.

6. The system of straight baselines may not be applied by a State in such a
manner as to cut off the territorial sea of another State from the high
seas or an exclusive economic zone.


Mouths of rivers

If a river flows directly into the sea, the baseline shall be a straight
line across the mouth of the river between points on the low-water line of
its banks.
So, unless any of us want to argue with the UN, or suggest that they change
their definitions to suit OSM! :-), I think that they could be counted as
the final word?


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