Canal key to flood control
By MARCIA FORD
Temple Terrace, at the downstream
edd of a levee that can be used to
hold back headwaters by tempo-
BROOKSVILLE To the South-
west Florida Water Management
District, "red alert" means wide-
It also invokes a very specific
game plan for dealing with a dis-
tressed public and local govern-
ments counting on help.
High on the priority list is keep-
up water control equipment
Siic pl damage can block water
'where it should be escaping or free
water where it should be held back.
The staff's game plan, called the
Flood Emergency Plan, shows vari-
ous phases of alertness, labeled
green, amber, orange and finally
They are triggered by certain
water elevations or severe weather
predictions. Early phases call for
stepped-up efforts to keep track of
conditions and daily reports so they
can be published.
The red phase calls for key staff
to be on duty around the clock,
ti rice-daily reports and emergency
radio system readiness in case tele-
phone lines go out.
Recent 10-year floods on the
Peace and Myakka Rivers carried
the district into an orange alert
situation stepping up monitoring
S iedules, contacts with other agen-
es and general public information
One important function of the
public information office is to be
ready to explain to people what the
district doesn't do, according to
Jimmy Brooks, supervisor of struc-
There are more places where
the district has no water controls
than where it does, he said. "There's
a ioi of places where we just can't do
anything." he said.
The district doesn't try to predict
the weather, added public informa-
tion specialist Donna Parkin-Welz.
"we leave that up to the National
Weather Service in Ruskin," she
THE TAMPA TIMES, Friday, July 2, 1982
The district's technical informa-
'oneon however. can draw
upon itstatistical records to anc
pate where flooding may occur. It
maintains extensive flood plain map-
ping. But Ruskin does actual river
Even where the district main-
tains water controls, many are fixed
structures. They don't open or close
or'raise or lower, but merely let
water flow over when it reaches a
certain depth. This, for example, is
the case with the four most seaward
dams on Channel G, which is the
south part of northwest Hillsbor-
ough's Sweetwater Creek, channe-
lized in a previous U.S. Soil Conser-
vation Service program.
The district, encompassing. 13
counties and parts of three others
stretching north and south of
Tampa, takes care of water control
devices at 81 locations.
Some are used to keep lakes at
"desired" levels officially adopted
by the district governing board.
These levels vary with the sea-
son, drawn down in early summer to
provide stormwater storage capacity
during the rainy season and allowed
to rise in the fall to help the lakes'
natural shoreline plant system and
get a good head start for the dry sea-
The district inherited many of its
water controls from other agencies
such as the U.S. Army Corps of Engi-
neers, the U.S. Soil Conservation Ser-
vice, county governments and local
Some other agencies still control
their own dams within the district,
like the Winter Haven Canal Com-
mission, which oversees that city's
chain of lakes.
According to Jimmy Brooks, su-
pervisor of structure operations for
the water district, its biggest control
project is the Tampa Bypass Canal.
It is designed to lessen the im-
pacts of a flooded Hillsborough
River on downtown Tampa.
The canal originates north of
Key to the canal operation, it
also intercepts the Hillsborough
River at another point farther down-
This is via the connecting Har-
ney Canal, at the southeast corner of
The dam between the river and
Harney Canal lies at the upstream
end of t t clLty uf Tampa's drinking
water reservoir, which on a map
looks like a wide portion of the wind-
Thus through the Harney Canal,
Brooks said, the district can lower
the reservoir without allowing any
more water to rush out into the river
downstream, where severe storms
also could mean high tides.
The lower end of the reservoir is
at a dam just south of Busch Gar-
dens, he said. Downstream from
there, the river runs through down-
Between the upper reach of the'
reservoir and the upstream levee,
flood relief through the Harney
Canal can help drain Temple Ter-
race and the University of South
Florida area, Brooks said.
Because of the intensity of devel-
opment there, this area creates a sig-
nificant amount of stormwater run-
off, he said.
There are four major water con-
trol points on the Tampa Bypass
At the north, upstream end, a
dam crosses the river at the levee
and can be used to back up the river
into the park. Nearby is another
dafn on Cowhouse Creek, whose
basic function is to maintain flow in
that creek, Brooks said.
Below the levee is the main
water level control in the bypass
canal, Brooks said. The potential
drop in elevation here is so great
that the U.S. Army Corps of Engi-
neers, in designing the system,
placed two smaller dams immedi-
ately downstream to lessen the se-
verity of the drop, he said.
Harney Canal is a structure basi-
cally to hold the water high enough
to maintain water in the Harney
Flats, a natural flood plain, Brooks
The final dam is where the canal
dumps water into the Palm River to
discharge it into McKay Bay.
The district has yet to make use
of the bypass canal north of the Har-
ney Caaal, Brooks said. Construction
on the northern portion was com-
pleted only last year, and in fact
final inspection of the group of three
major water level control dams has-
n't been done, he said.
But the Harney Canal is proving
to be more versatile than anticipat-
ed, he said.
For example, he said, it can be
used to help Tampa avoid concen-
trations of tannic acid, which causes
a brownish discoloration, in its
reservoir during certain upstream
flow conditions. Tannic acid re-
moval is an expensive part of the
water treatment process, he said.
The Corps is writing the final
guidelines for flood control use of
the bypass canal and its system of
dams, Brooks said. The water dis-
trict cooperated in developing the
plan, but the Corps is responsible for
publishing it, he said.
Another useful tool in making
decisions about dam manipulations,
Brooks said, is the Tampa Bay Re-
gional Planning Council's "slosh
Developed with the planning
council's hurricane preparedness
plan, the "slosh model" is a com-
puter program used to predict storm
tides and flooding potential, taking
into account various potentials for
windspeed and direction, Brooks
In case of an approaching hurri-
cane, the water district staff would
be put on round-the-clock duty 24
hoprs before the storm.
Bypass Canal Dam
Bypass Canal Dam