HISTORY | of Bear Mead River scale |
In Aug 2003 it was decided to attempt to measure and record
the height of the Dorset Stour daily
at Bear Mead.
- A place was chosen, accessible from the bank but
deep enough to have river water in a severe drought, just downstream of
a large goatwillow bush which should prevent clogging of the scale by
floating vegetation [see 2701].
A 6-foot length of scaffolding was obtained
and hammered deep into the gravel bed with a post-rammer,
forming a strong anchor
for the proposed round white plastic pipe with centimeter scale
in acrylic paint. The scale could be read with fieldglasses from the bank.
A level range of
3 meters was expected, and an arbitrary zero-point scale chosen
from 100 cms to 400 cms [see 3133].
After many false starts, a pipe with
ID of 51 mms (2 inches) was chosen which just fitted round the scaffolding.
Occasional clearing of surrounding reeds was necessary;
this could be done from the bank [see 3241].
Similar pipescales were placed in 5 other parts of Bear Mead.
- This worked well for 9 years until a series of lengthy floods (reaching
390 cms in 2012) eventually snapped the pipe
where it cleared the
scaffolding [see 3361]. More internal strength
was needed to reduce bending like 2.5 metre metal pipe.
- A thicker form of pipe was located on Ebay (ID=51mm, OD=60mm)
and bought.
This was ordered in two lengths (90cms and 200 cms) to enable
the author to erect the piping while standing knee-deep in mud that overlies
the gravel on the river bed at this point.
A scale was drawn that could be read even if the pipe
rotated in strong river flow [see other styles].
An external post to prevent such rotation
could not be used as vegetation collected around it, blocking a view of
the scale [see 3429].
- A redesign was made, incorporating the 2.5 metre metal pipe for strength,
inside a 3 metre 40mm plastic pipe, inside the outer 2 inch plastic pipe.
It is hoped this will be strong enough to resist breaking even in
long floods [see 3430]. A 50mm short pipe kept the
two 60mm sections co-axial.
- To round off the new pipe-scale, a 6-inch spherical toilet float was
painted with two faces, connected to 20cms of 43mm piping, and lowered
into the top of the white pipe-scale from the bank with a 2 metre wooden
rod and hook. Later, a 7-inch threaded rod served as ears to allow turning.
See a sketch of the whole assembly in image [01].
- Maintenance. The pipe needs to be removed,
cleared of crud and repainted 4 times per year, say April, June, Aug and
November, when the river height is less then about 160. A standby set of
pipescales and head needs to be ready to replace the old. Reeds need to be
occasionally cleared from round the pipe with deck shoes and garden shears.
Damp crud removed with bucket, warm water, soft brush and washing-up liquid.
Maintenance on 19apr2014, 13jun2014.
- Strength. The new design of pipe-scale withstood
3 months of almost continuous flood, high and fast river during
15dec2013 - 06mar2014
with no apparent mechanical failure.
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3449 27may2013
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