http://maps.google.co.uk/maps?hl=en&...03433&t=h&z=19

Salmons Brook and Pymmes Brook both have dividing walls in their centre. The
walls end where the two brooks meet and then a new dividing wall starts
after the junction. Why is this?

If you track the combined brook southwards, it nearly meet the Lea at
Stonebridge Locks, but has its own channel alongside it to just past
Tottenham Locks. Why is the brook deliberately kept apart from the Lea
Navigation?

"Basil Jet" wrote in message
news

http://maps.google.co.uk/maps?hl=en&...03433&t=h&z=19

Salmons Brook and Pymmes Brook both have dividing walls in their centre.
The walls end where the two brooks meet and then a new dividing wall
starts after the junction. Why is this?

Maybe the walls were built to provide support for a cover that was either
never built, or subsequently removed?

If you track the combined brook southwards, it nearly meet the Lea at
Stonebridge Locks, but has its own channel alongside it to just past
Tottenham Locks. Why is the brook deliberately kept apart from the Lea
Navigation?


The plumbing in this area is very complicated; you can get an idea from the
diagram on this page:

http://en.wikipedia.org/wiki/River_Lee_Navigation

Presumably there isn't any need for water from the brook to feed the Lea
Navigation between Stonebridge and Tottenham Locks. If the brook is ever at
a lower level than the Navigation then that's your answer. Failing that, it
could be something to do with the Lea and New River being major sources of
fresh water for London.

D A Stocks

On 10 Aug, 02:25, "Basil Jet"
wrote:
http://maps.google.co.uk/maps?hl=en&...8,-0.044458&sp...

Salmons Brook and Pymmes Brook both have dividing walls in their centre. The
walls end where the two brooks meet and then a new dividing wall starts
after the junction. Why is this?

If you track the combined brook southwards, it nearly meet the Lea at
Stonebridge Locks, but has its own channel alongside it to just past
Tottenham Locks. Why is the brook deliberately kept apart from the Lea
Navigation?

On the last bit I'd guess it's at a different level, so has to join on
the south side of the lock or else be a waterfall?

On the first, I wonder if it's a way of blocking one side at a time to
clear it out or control the flow? I can't remember seeing that
elsewhere except when there's a structure on top of the river (or one
side of it), but going into the canal maybe means it has to be
controlled.

"Basil Jet" wrote

[snip]

Salmons Brook and Pymmes Brook both have dividing walls in their
centre. The walls end where the two brooks meet and then a new
dividing wall starts after the junction. Why is this?

Interesting question. I haven't the slightest idea of the correct
answer, but I'm prepared to guess.

The gap where brooks meet might be to keep the volume or level equal
on each side of the wall

Salmons Brook and Pymmes Brook have a fairly tarmac'd over watershed,
and so are probably subject to flash flooding whenever there's heavy
rain. Perhaps two small flows would do less damage than one big one.
Perhaps the wall creates some fundamental change in the flow, laminar
flow as compared to turbulent, for example.

It seems the tradition among water engineers that rather than slow
the water flow down in wet weather, as would have occurred naturally
in prehistoric times, when the watershed was all trees, instead they
encourage the water to whoosh down as quickly as possible so that it
leaves their patch, and becomes somebody else's problem. Admittedly
that seems rather illogical if the Environmental Agency controls
everything, but still ...

If you track the combined brook southwards, it nearly meet the Lea
at Stonebridge Locks, but has its own channel alongside it to just
past Tottenham Locks. Why is the brook deliberately kept apart from
the Lea Navigation?

If the water comes down like a flushing toilet when it rains, that
might be a reason.

Stream routes in the flatter parts of Britain are not very natural.
There were already about 6000 water mills at the time of the domesday
book, needing channels to and from the mill. With eating fish
compulsory on Fridays, fish farming in stream fed ponds was
widespread, as were ponds with decoy ducks for duck hunting. I'm not
sure when irrigated water meadows came in, but that caused more
stream diversions.. There were other events, too, as when the Saxons
diverted the River Lea, to leave a Viking fleet, moored there, high
and dry, and attackable. The Lea navigation added bits of canal.
Things got moved for the reservoirs, and an extra River Lea was built
as a sort of storm drain

Doing strange things to rivers was an issue in Magna Carta

Jeremy Parker

On 10 Aug, 15:09, MIG wrote:
On 10 Aug, 02:25, "Basil Jet"
wrote:

http://maps.google.co.uk/maps?hl=en&...8,-0.044458&sp...

Salmons Brook and Pymmes Brook both have dividing walls in their centre.. The
walls end where the two brooks meet and then a new dividing wall starts
after the junction. Why is this?

If you track the combined brook southwards, it nearly meet the Lea at
Stonebridge Locks, but has its own channel alongside it to just past
Tottenham Locks. Why is the brook deliberately kept apart from the Lea
Navigation?

On the last bit I'd guess it's at a different level, so has to join on
the south side of the lock or else be a waterfall?

On the first, I wonder if it's a way of blocking one side at a time to
clear it out or control the flow? *I can't remember seeing that
elsewhere except when there's a structure on top of the river (or one
side of it), but going into the canal maybe means it has to be
controlled.

I mean navigation, not canal, but same issue maybe.

David A Stocks wrote:
"Basil Jet" wrote in message
news

http://maps.google.co.uk/maps?hl=en&...03433&t=h&z=19

If you track the combined brook southwards, it nearly meet the Lea at
Stonebridge Locks, but has its own channel alongside it to just past
Tottenham Locks. Why is the brook deliberately kept apart from the
Lea Navigation?

The plumbing in this area is very complicated; you can get an idea
from the diagram on this page:

http://en.wikipedia.org/wiki/River_Lee_Navigation

Presumably there isn't any need for water from the brook to feed the
Lea Navigation between Stonebridge and Tottenham Locks. If the brook
is ever at a lower level than the Navigation then that's your answer.

Oh, I hadn't considered levels. Now, the obvious answer is that the banks of
the combined brook are lower than the water level in the Navigation until
you get below Tottenham Locks. I had no idea that the Lea Navigation was so
high (two locks worth) above the surrounding ground above Stonebridge Locks.
It suggests that the Lea Navigation was not so much dug as erected.... or
maybe a bit of both, i.e. it was deliberately built at a level such that the
earth removed from the shallow trench would exactly match the earth required
to build the low banks.

Incidentally, I just found a picture of the River Tyburn flowing through the
basement of Gray's Antiques :
http://upload.wikimedia.org/wikipedi...ivertyburn.JPG

In message , Basil Jet
writes

Incidentally, I just found a picture of the River Tyburn flowing through the
basement of Gray's Antiques :
http://upload.wikimedia.org/wikipedi...ivertyburn.JPG

Although it's widely described as the Tyburn, this is actually a little
tributary stream that rises from a nearby spring (hence its cleanliness)
and is the brook that gave its name to Brook Street. It must join the
actual course of the Tyburn close by, but the latter is really a sewer
that wouldn't support goldfish and that you wouldn't running through
your basement:

http://farm1.static.flickr.com/133/3...8e6d8c14_o.jpg

Incidentally, just the other side of Oxford Street (beneath Stratford
Place) lies London's oldest reservoir - a stone water store, built in
1216, from which the waters of the Tyburn supplied the Great Conduit
which ran through to Cheapside, to supply fresh water to the city. Like
the Roman Bath in North Audley Street (also fed by the Tyburn), it is
part of London that has disappeared into the foundations and sewers of
the modern city.

--
Paul Terry

"Basil Jet" wrote in message
...

Incidentally, I just found a picture of the River Tyburn flowing through
the basement of Gray's Antiques :
http://upload.wikimedia.org/wikipedi...ivertyburn.JPG


The Tyburn flows in a huge pipe over the platforms at Sloane Square
underground station. OMG, we're on-topic!

--
DAS

"David A Stocks" wrote in message
...
"Basil Jet" wrote in message
...

Incidentally, I just found a picture of the River Tyburn flowing through
the basement of Gray's Antiques :
http://upload.wikimedia.org/wikipedi...ivertyburn.JPG


The Tyburn flows in a huge pipe over the platforms at Sloane Square
underground station. OMG, we're on-topic!

--
DAS

Correction, the river at Sloane Sq is actually the Westbourne, related to
the Tyburn brook, which is *not* related to the River Tyburn!

--
DAS