Songo Beach, Sebago Lake State Park -- 1962. This natural beach
has now been largely destroyed by erosion from lake regulation in the 1980s
and 1990s.
11. Analysis of history of lake-level management at Sebago
Lake.
Statements in FERC (1997), State of Maine DEP reports and the 1990 EBASCO
report imply that shoreline erosion at Sebago Lake is an "ongoing natural
process" and "has been a problem for a long time on Sebago Lake."
These statements fail to accurately characterize the erosion and recession
history of Sebago Lake. A review of the historical evidence is important
because the EBASCO Report is one basis of FERC's prior decisions.
FERC (1997) has mentioned that older shore protection exists which indicates
that erosion is not a recent problem on Sebago Lake. FERC (1997) does not
mention that records show that in 1917 the lake was allowed to rise one
foot over the Eel Weir dam. At this height and with strong wave action Sebago
Lake is flooded and water level is against the banks or are above them.
Immediately after 1917, Herbert and Edna Moody of Long Point constructed
shore protection. Levels above full pond 266.65 msl have occurred at least
18 times since 1917. Even S.D. Warren was aware of the potential for damage.
They paid for and constructed shore protection along thousands of feet of
Standish shoreline. This was a massive construction project. It is peculiar
that S.D. Warren now claims it has no records of this project especially
since it involved their legal difficulty with not owning flowage rights
to 267.15 msl as they have on most other properties around the lake.
It is inaccurate for FERC or S.D. Warren to state that S.D.Warren owns flowage
rights to 267.15 on all lake shore property. FOSL believes that S.D. Warren's
work protected the embankment that was present in 1878. During the 1920s,
when the annual mean was significantly above the average, bluffs exposed
to long fetches were destabilized by erosion. Southwest Fryes Island, Long
Point, and Rt. 35 bluffs suffered recession. It is interesting that significant
erosion did not occur on Sebago Lake bluffs and beaches until 40 to 50 years
after the new Basin Dam was constructed raising the spillway height to 266.65
msl.
Most erosion occurs around a lake soon after the water height is raised
and then tapers off as the shorelines reach equilibrium. This would indicate
that the average annual water level was not significantly increased in the
30 to 40 years after the raising of the Basin dam height in 1878. Bluff
areas which eroded in the 1920s restabilized naturally with tree growth.
Trees grew on these embankments for 60 years until the late 1980s and 1990s.
The water level management upon which the pre-1987 Eel Weir license is predicated
was not perfect. Uniform outflow produced higher above average lake levels
when precipitation was high. However, this was balanced by accretion and
restabilization during years when precipitation was lower.
The licensee and others assert that the Eel Weir dam raised Sebago Lake
significantly above its natural range. At present we do not know the exact
levels of the lake before the first dams were built. We do know that beaches
protecting lacustrine wetlands were well developed prior to 1987. Lake levels
need to fluctuate significantly for large beaches to develop (Parkin and
Lortie 1989). Nine Sebago Lake beaches were rated as the only outstanding
natural beaches in organized townships in a Maine by consultants hired by
the Maine State Planning Office (Parkin and Lortie 1989). If erosion was
an ongoing problem these beaches would not exist. These beaches developed
under natural lake levels and were not significantly compromised after the
completion of the the present dam in 1878. Because of the presence of very
large and old trees on the berms of these beaches it is probable that the
post-1878 water levels management of uniform outflow (a more natural hydrograph)
caused little harm to these beaches.
Records show that lake levels between 266 and 267 msl did occur prior to
1878. In Wells (1867), the manager of Cumberland Mills describes the height
of water on the dam. This gives an insight to the heights of the lake reached
before 1878. Hammond describes a four foot head on the old Basin Dam dam
for 30 days continuous with all gates open, and still, the water rose 6
inches more. This means the lake was at least above 266 msl. In 1872 a Cumberland
Mills water chart shows the height of the dam at 266 msl.
In the early 1900s the Basin Dam was rebuilt with larger gate capacity.
Before this construction, S.D. Warren (Presumpscot Water and Power Company)
had difficulty keeping the lake from rising. The events of 1998 gives us
an insight for even higher Sebago Lake levels controlled by the old pre-1878
Basin Dam than the documented 266 msl levels. In June of 1998 the lake height
was 9 inches above the height at the dam because White's Bridge acts as
a hydraulic control for the lake when outflows at the dam are high. Certainly
levels could have reached 9 inches higher on Sebago Lake than was recorded
at the pre-1878 dam. Before dams were built on Sebago Lake it is a guess
that lake levels still ranged widely. How much they ranged would depend
upon the configuration of the outlet. A huge boulder pile exists on the
lake side at White's Bridge. This boulder pile originates from the channel
where the boulders were removed to provide more clearance for navigation.
It is quite possible that the White's Bridge area was very shallow and caused
a significant natural hydraulic control for the lake. The natural lake hydrograph
would have shown a high period in the spring with a rather steep decline
into the late spring and summer. A field study of core samples of sediment
would yield clues as to prior lake levels.
A historical study of review of the Sebago Lake levels would greatly add
to the knowledge that is needed to predict future rates of erosion of Sebago
Lake shorelines. The decisions of FERC in this relicensing will greatly
affect this important natural resource. This is a much too important relicensing
for decisions based on non-scientific information and unsubstantiated historical
information. FOSL requests that FERC include an historical analysis in an
EIS for the Eel Weir Dam. FOSL requests that the licensee allow FERC to
review all historical information about Sebago Lake water levels. This would
include all Basin Dam dam records of Cumberland Mills, all legal and historical
records pertaining to the building of the 1878 Basin dam, the Eel Weir dam
in 1903 and the flowage right records of Sebago Lake properties.
NEXT
BACK TO SHORE
BACK TO SCOPING COMMENTS TABLE OF CONTENTS