This is a report on a walkaroundthedam, on the Big Sable
River in
the
Ludington
State
Park, on
Thursday,
January
10,
2013.
As you
can see
by the
pictures,
there
had not
been
much
precipitation
in the
preceding
weeks .


All six of the gates were open.
The four
north
spillways
had
their
weirs
all the
way down
and had
14
inches
of water
going
over
them.
The two
south
spillways
had
their
sluice
gates
open,
but
there
was
no water
flowing
thru
them as
their
lip was
six
inches
above
the
water.


This
diagram
shows
the
conditions
of the
four
north
spillways
at this
time.
The
water
going
over the
lip of
the dam
was
measured
as 14
inches
deep.
The Lake
level
gage
indicated
5.3
feet.
By
difference
the lip
of the
dam
would be
at 4.1
feet on
the Lake
Level
Gage. 

The
Francis
Formula
was used
to
calculate
the flow
of water
over a
weir.
The
formula
accounts
for the
resistance
caused
by the
sides,
and the
increase
in flow
with
depth.
The weir
coefficient
was
selected
from
literature
based on
the
shape of
the dam.
In this
case
only
four
spillways
operating. 
Width of the weir, w 
11.0 
feet 
Depth of water going over the weir, h 
14.4 
inches 

1.20 
feet 
Effective width of weir, w0.2h 
10.8 
feet 
Weir Coefficient, c 
3.25 
sqrt(ft) per second 
Francis Formula 
q = c*(w0.2h)*h^1.5 
Flow over one weir, q 
46.0 
cubic feet per second 
Number of weirs 
4 
each 
Flow over the Hamlin Dam 
184 
cubic feet per second 

82,500 
gallons per minute 

119 
million gallons per day 

This
picture
shows
one of
the two
south
spillways
with the
fixed
panel
preventing
water
from
flowing.
The
affixed
panel is
20
inches
tall
with 14
inches
of water
against
it on
the
upstream
side.
The
sluice
gate is
above
the
fixed
panel
and one
of the
two
rods
that
lift it
are
visible.
The
space
between
the
affixed
panel
and the
sluice
gate is
open so
you can
see the
trees
beyond
the dam. 

This
diagram
shows
the
conditions
of the
two
south
spillways
at this
time.
Water is
prevented
from
going
over the
lip of
the dam
by the
fixed
panel.
Water
only
overflows
into
these
spillways
when the
lake
level is
above
5.8
feet.
the
level in
Hamlin
Lake is
higher
in the
Winter
because
of these
two
fixed
panel. 

In order
to
calculate
what the
level of
Hamlin
Lake
would be
with six
identical spillways
operating,
we
assumed
that the
amount
of water
going
over the
dam (119
MGD)
would be
the same
with
either 4
or 6
spillways
operating.
With six
identical spillways,
with
weirs,
operating,
the
calculations
show
that
only 11
inches
of water
would be
going
over the
dam so
Hamlin
Lake
would be
3 to 4
inches
lower
than
at present. 
Width of the weir, w 
11.0 
feet 
Depth of water going over the weir, h 
11.0 
inches 

0.91 
feet 
Effective width of weir, w0.2h 
10.8 
feet 
Weir Coefficient, c 
3.25 
sqrt(ft) per second 
Francis Formula 
q = c*(w0.2h)*h^1.5 
Flow over one weir, q 
30.7 
cubic feet per second 
Number of weirs 
6 
each 
Flow over the Hamlin Dam 
184 
cubic feet per second 

82,600 
gallons per minute 

119 
million gallons per day 

It
appears
that the
existing
sluice
gates
have two
bad
features:
1. They
increase
the lake
level in
the
winter
which
results
in the
possibility
of
creating
more
shore
damage.
2. They
reduce
the
capacity
of the
dam to
pass
water
during a
highwater
event.
Before
we can
draw any
conclusions
or make
any
recommendations,
we need
to know
what
reasons
supported
the
installation
of these
sluice
gates.
Lacking
any
compelling
reason
not to,
the full
capacity
of the
dam
should
be
returned
to its
previous
flow.
Jim
Clark 


