Coastline and tidal rivers

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Coastline and tidal rivers

Colin Smale

That old chestnut again...

There seems to be an open discussion about how far up a river the natural=coastline should go. The wiki suggests the coastline should be the high water line going up to the tidal limit (often a lock or a wier) but this can be a substantial distance inland. This is AIUI the general scientific approach.

There has been some discussion in the past about letting the coastline cut across the river at some convenient point, possibly because it "looks better" or "seems more natural" or "is less work."

I looked at a few rivers along the south coast to see how they had been tagged and it seems most have the coastline up to the tidal limit. However the coastline around the mouth of the Dart has recently been modified to cut across the mouth, and Salcombe Harbour is also mapped this way.

Is there a consensus for a particular definition of "coastline" in tidal estuaries? Should we try to keep a consistent paradigm, or doesn't it matter?



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Re: Coastline and tidal rivers

TonyS

I'm with Colin on this.

My experience of sailing and reading Admiralty charts is that the coastline is the High Water line.  Yes it looks inconvenient or unnatural - but tidal area as implied by coastline is so important to small boat users. The River Dart

Way: 194211894 waterway= riverbank

is a really arbitrary line across the river from Dartmouth Castle, this offends my view of what a coastline is.

Another relevant concept is salinity - tidal coastline is saline and does affect plant and marine life . Which leads us into a conundrum - things such as salt marsh and mangrove swamps which are all inter-tidal; where should the coastline be?

We should also be aware that an incoming tide blocks the natural flow of the river and causes the river to form a type of lake which reduces as the tide ebbs. This effect can cause people to think a river is tidal in that area when it is not.

In my local area the River Ribble estuary in OSM changes from riverbank to coastline near Warton airfield, but wikipedia describes "The Normal Tidal Limit (NTL) of the river is at Fishwick Bottoms, between Preston and Walton-le-Dale, 11 miles (18 km) from the sea"

so where should the boundary of coastline to  riverbank be? I suggest where the inter-tidal range or zonal area is small - range < 1 foot, line of zone perpendicular to the boundary is < 1 yard (or metric equivalent).
A heuristic could be where it becomes long and thin? Ribble is almost acceptable - Dart is not as I write this.

But really I prefer the existing guidance.

Regards
TonyS999


On 28/08/2018 08:49, Colin Smale wrote:

That old chestnut again...

There seems to be an open discussion about how far up a river the natural=coastline should go. The wiki suggests the coastline should be the high water line going up to the tidal limit (often a lock or a wier) but this can be a substantial distance inland. This is AIUI the general scientific approach.

There has been some discussion in the past about letting the coastline cut across the river at some convenient point, possibly because it "looks better" or "seems more natural" or "is less work."

I looked at a few rivers along the south coast to see how they had been tagged and it seems most have the coastline up to the tidal limit. However the coastline around the mouth of the Dart has recently been modified to cut across the mouth, and Salcombe Harbour is also mapped this way.

Is there a consensus for a particular definition of "coastline" in tidal estuaries? Should we try to keep a consistent paradigm, or doesn't it matter?




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Re: Coastline and tidal rivers

David Groom
In reply to this post by Colin Smale
There is no consensus.

Personally I'm not in favour of the view that any body of water which is tidal should be bounded by a way tagged as coastline. 

Reasons for this

1) Ask any one who lives in say central London "do you live on the coast" or do you live beside a river", most would I'm sure say beside a river, so surely our data should reflect that.  I think this probably is what you mean by "seems more natural"

2)  In part because the converse is not true, we bound large non tidal water areas as coastline

3) If knowledge that a body of water is tidal is important it can be tagged "tidal = yes"


David




------ Original Message ------
From: "Colin Smale" <[hidden email]>
To: "Talk-GB" <[hidden email]>
Sent: 28/08/2018 08:49:01
Subject: [Talk-GB] Coastline and tidal rivers

That old chestnut again...

There seems to be an open discussion about how far up a river the natural=coastline should go. The wiki suggests the coastline should be the high water line going up to the tidal limit (often a lock or a wier) but this can be a substantial distance inland. This is AIUI the general scientific approach.

There has been some discussion in the past about letting the coastline cut across the river at some convenient point, possibly because it "looks better" or "seems more natural" or "is less work."

I looked at a few rivers along the south coast to see how they had been tagged and it seems most have the coastline up to the tidal limit. However the coastline around the mouth of the Dart has recently been modified to cut across the mouth, and Salcombe Harbour is also mapped this way.

Is there a consensus for a particular definition of "coastline" in tidal estuaries? Should we try to keep a consistent paradigm, or doesn't it matter?


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Re: Coastline and tidal rivers

Colin Smale

David, do you consider that it would be advantageous to have consensus on this matter, and a consistent tagging paradigm in OSM? I am not prejudging what that consensus position might be, just sounding out if there is any point in having the discussion in the first place.

 


On 2018-08-28 13:09, David Groom wrote:

There is no consensus.
 
Personally I'm not in favour of the view that any body of water which is tidal should be bounded by a way tagged as coastline. 
 
Reasons for this
 
1) Ask any one who lives in say central London "do you live on the coast" or do you live beside a river", most would I'm sure say beside a river, so surely our data should reflect that.  I think this probably is what you mean by "seems more natural"
 
2)  In part because the converse is not true, we bound large non tidal water areas as coastline
 
3) If knowledge that a body of water is tidal is important it can be tagged "tidal = yes"
 
 
David
 
 
 
 
------ Original Message ------
From: "Colin Smale" <[hidden email]>
To: "Talk-GB" <[hidden email]>
Sent: 28/08/2018 08:49:01
Subject: [Talk-GB] Coastline and tidal rivers
 

That old chestnut again...

There seems to be an open discussion about how far up a river the natural=coastline should go. The wiki suggests the coastline should be the high water line going up to the tidal limit (often a lock or a wier) but this can be a substantial distance inland. This is AIUI the general scientific approach.

There has been some discussion in the past about letting the coastline cut across the river at some convenient point, possibly because it "looks better" or "seems more natural" or "is less work."

I looked at a few rivers along the south coast to see how they had been tagged and it seems most have the coastline up to the tidal limit. However the coastline around the mouth of the Dart has recently been modified to cut across the mouth, and Salcombe Harbour is also mapped this way.

Is there a consensus for a particular definition of "coastline" in tidal estuaries? Should we try to keep a consistent paradigm, or doesn't it matter?


 

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Re: Coastline and tidal rivers

David Groom

Colin

whilst in theory I'd say yes, in practice I'd say consensus is hard to achieve.

David



------ Original Message ------
From: "Colin Smale" <[hidden email]>
Sent: 28/08/2018 12:23:33
Subject: Re: [Talk-GB] Coastline and tidal rivers

David, do you consider that it would be advantageous to have consensus on this matter, and a consistent tagging paradigm in OSM? I am not prejudging what that consensus position might be, just sounding out if there is any point in having the discussion in the first place.

 


On 2018-08-28 13:09, David Groom wrote:

There is no consensus.
 
Personally I'm not in favour of the view that any body of water which is tidal should be bounded by a way tagged as coastline. 
 
Reasons for this
 
1) Ask any one who lives in say central London "do you live on the coast" or do you live beside a river", most would I'm sure say beside a river, so surely our data should reflect that.  I think this probably is what you mean by "seems more natural"
 
2)  In part because the converse is not true, we bound large non tidal water areas as coastline
 
3) If knowledge that a body of water is tidal is important it can be tagged "tidal = yes"
 
 
David
 
 
 
 
------ Original Message ------
From: "Colin Smale" <[hidden email]>
To: "Talk-GB" <[hidden email]>
Sent: 28/08/2018 08:49:01
Subject: [Talk-GB] Coastline and tidal rivers
 

That old chestnut again...

There seems to be an open discussion about how far up a river the natural=coastline should go. The wiki suggests the coastline should be the high water line going up to the tidal limit (often a lock or a wier) but this can be a substantial distance inland. This is AIUI the general scientific approach.

There has been some discussion in the past about letting the coastline cut across the river at some convenient point, possibly because it "looks better" or "seems more natural" or "is less work."

I looked at a few rivers along the south coast to see how they had been tagged and it seems most have the coastline up to the tidal limit. However the coastline around the mouth of the Dart has recently been modified to cut across the mouth, and Salcombe Harbour is also mapped this way.

Is there a consensus for a particular definition of "coastline" in tidal estuaries? Should we try to keep a consistent paradigm, or doesn't it matter?


 

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Re: Coastline and tidal rivers

Colin Smale

On 2018-08-28 16:43, David Groom wrote:

whilst in theory I'd say yes, in practice I'd say consensus is hard to achieve.
 
OK, I might as well give up now then. If everybody started thinking "I don't know why I bother," like I am now, where would we be?
 

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Re: Coastline and tidal rivers

Mike Evans
In reply to this post by David Groom
On Tue, 28 Aug 2018 11:09:47 +0000
"David Groom" <[hidden email]> wrote:

> There is no consensus.
>
> Personally I'm not in favour of the view that any body of water which is
> tidal should be bounded by a way tagged as coastline.
>
> Reasons for this
>
> 1) Ask any one who lives in say central London "do you live on the
> coast" or do you live beside a river", most would I'm sure say beside a
> river, so surely our data should reflect that.  I think this probably is
> what you mean by "seems more natural"
Well if they're in Central London then it is an estuary at that point so they'd be incorrect. Hence the expression "estuary English", and not "river English".
To quote Wikpedia "The district of Teddington a few miles south-west of London's centre marks the boundary between the tidal and non-tidal parts of the Thames".

Perhaps "A History of the Foreshore and the Law Relating Thereto",  published 1888 would be a useful reference.
https://archive.org/details/ahistoryforesho00hallgoog


>
> 2)  In part because the converse is not true, we bound large non tidal
> water areas as coastline
Examples?

>
> 3) If knowledge that a body of water is tidal is important it can be
> tagged "tidal = yes"
But then the decision has to made as to where to draw the line and tag one side as "tidal = yes" and the other side not tagged but assumed to, in fact, be tidal. This just introduces an extra arbitrary boundary the inner end of which again becomes non-tidal.

The American Submerged Lands Act of 1953 does appear to define the line at which the coastline extends into estuaries etc., but this does not apply to the UK.  That act seems to been precipitated as a result of disputes over oil drilling rights.

Mike


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Re: Coastline and tidal rivers

David Groom


------ Original Message ------
From: "Mike Evans" <[hidden email]>
Cc: "David Groom" <[hidden email]>
Sent: 28/08/2018 19:22:16
Subject: Re: [Talk-GB] Coastline and tidal rivers

On Tue, 28 Aug 2018 11:09:47 +0000
"David Groom" <[hidden email]> wrote:
 
There is no consensus.
 
Personally I'm not in favour of the view that any body of water which is
tidal should be bounded by a way tagged as coastline.
 
Reasons for this
 
1) Ask any one who lives in say central London "do you live on the
coast" or do you live beside a river", most would I'm sure say beside a
river, so surely our data should reflect that. I think this probably is
what you mean by "seems more natural"
Well if they're in Central London then it is an estuary at that point so they'd be incorrect. Hence the expression "estuary English", and not "river English".
Both the Oxford and Cambridge Dictionaries define as estuary as part of a river.


To quote Wikpedia "The district of Teddington a few miles south-west of London's centre marks the boundary between the tidal and non-tidal parts of the Thames".
The Wikipedia quote to which you refer suggests to  me that this should be tagged as a river, since the Thames is a river, parts of which are tidal and parts of which are not.  But it's still a river. 


 
Perhaps "A History of the Foreshore and the Law Relating Thereto", published 1888 would be a useful reference.
 
 
 
2) In part because the converse is not true, we bound large non tidal
water areas as coastline
Examples?
 
Baltic , Caspian & Black Seas


 
3) If knowledge that a body of water is tidal is important it can be
tagged "tidal = yes"
But then the decision has to made as to where to draw the line and tag one side as "tidal = yes" and the other side not tagged but assumed to, in fact, be tidal. This just introduces an extra arbitrary boundary the inner end of which again becomes non-tidal.
 
The American Submerged Lands Act of 1953 does appear to define the line at which the coastline extends into estuaries etc., but this does not apply to the UK. That act seems to been precipitated as a result of disputes over oil drilling rights.
 
Mike
 

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Re: Coastline and tidal rivers

Mike Evans
Hi David

On Wed, 29 Aug 2018 09:09:58 +0000
"David Groom" <[hidden email]> wrote:

 

> >>There is no consensus.
> >>
> >>Personally I'm not in favour of the view that any body of water which
> >>is
> >>tidal should be bounded by a way tagged as coastline.
> >>
> >>Reasons for this
> >>
> >>1) Ask any one who lives in say central London "do you live on the
> >>coast" or do you live beside a river", most would I'm sure say beside
> >>a
> >>river, so surely our data should reflect that. I think this probably
> >>is
> >>what you mean by "seems more natural"  
> >Well if they're in Central London then it is an estuary at that point
> >so they'd be incorrect. Hence the expression "estuary English", and not
> >"river English".  
> Both the Oxford and Cambridge Dictionaries define as estuary as part of
> a river.

Dictionaries are written for writers and are not necessarily useful as a mapping resource.
There's more here: https://en.wikipedia.org/wiki/Thames_Estuary


> >
> >Perhaps "A History of the Foreshore and the Law Relating Thereto",
> >published 1888 would be a useful reference.
> >https://archive.org/details/ahistoryforesho00hallgoog
> >
> >  
> >>
> >>2) In part because the converse is not true, we bound large non tidal
> >>water areas as coastline  
> >Examples?
> >  
> Baltic , Caspian & Black Seas
>
All are tidal to small extent, see:
https://www.frontiersin.org/articles/10.3389/fmars.2016.00046/full

But none of this helps us draw an arbitrary line across a river/estuary/tidal/non-tidal water body.

Regards Mike

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Re: Coastline and tidal rivers

Warin
In reply to this post by Colin Smale
On 29/08/18 01:46, Colin Smale wrote:

On 2018-08-28 16:43, David Groom wrote:

whilst in theory I'd say yes, in practice I'd say consensus is hard to achieve.
 
OK, I might as well give up now then. If everybody started thinking "I don't know why I bother," like I am now, where would we be?

To Colin I say in a loud voice ... "Up the Rebels" :)

On the Australian talk list this came up for an import or maritime boundaries -note the last bits

Geoscience Australia definitions:

  • "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."

Probably this same distinction exists in the UK - that difference of internal waters for international law. This may help achieve a 'consensus'?



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Re: Coastline and tidal rivers

Colin Smale

On 2018-09-02 10:50, Warin wrote:

On 29/08/18 01:46, Colin Smale wrote:

On 2018-08-28 16:43, David Groom wrote:

whilst in theory I'd say yes, in practice I'd say consensus is hard to achieve.
OK, I might as well give up now then. If everybody started thinking "I don't know why I bother," like I am now, where would we be?

To Colin I say in a loud voice ... "Up the Rebels" :)

Thanks for the support...

On the Australian talk list this came up for an import or maritime boundaries -note the last bits

Geoscience Australia definitions:


  • "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."

Probably this same distinction exists in the UK - that difference of internal waters for international law. This may help achieve a 'consensus'?

The baseline is not the same as the coastline.

The Coastline is:

  • A geographic concept delimiting the dry bit from the damp and wet bits
  • Based on high water mark

The Baseline is:

  • A legal concept, used as the basis for jurisdiction over territorial waters etc
  • Based on low water mark, with international rules for handling bays, coastal islands, inlets etc

What you are referencing in Australia is the Baseline and it certainly exists in the UK, but AFAIK it is not represented directly in OSM. The 12nm territorial waters limit which should be derived from the baseline is however present in OSM.


 

 

 

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