Lake Panasoffkee SWIM Plan - Southwest Florida Water ...

Proiect Title: Bathymetric Mapping
Summary:
To make accurate estimates of the amount of material to be removed, an updated
bathymetric map (i.e., contour map of the lake bottom) of the lake is needed. Estimates of
sediment volumes used to compute dredging and other costs presented in the Lake
Panasornee Restoration Council Reporf, November 25, 1998 were based on a bathymetric
map prepared by Greiner (1978). Their map was developed using data collected in 1955 and
spot checked with soundings made in 1973. The lake’s bottom contours have changed due
to the accumulation of sediment that has occurred during the nearly twenty-five years that
have elapsed since the bathymetric map was made. Although sediments accumulate at a
relatively low rate in Lake Panasoffkee, neither the map prepared by Greiner (1978) nor the
sediment thickness map prepared by Belanger et al. (1993) were constructed with sediment
dredging in mind. Although sufficient for estimation purposes, bidding and budgeting of
projects requiring sediment removal will require more accurate estimates of the volumes of
sediment involved. It will also be necessary to know the depth of sediment overlying hard
bottom. While this type of information was gathered by Belanger et al. (1993), coverage is
not as detailed as needed, particularly for work proposed in Step Two.
Agency or Local Government Partnerina:
See Step 2 under priority projects. This project will be rolled into the work performed for the
design of the Step 2 project.
Project Title: Vegetative Mapping
Summary:
Lake Panasoffkee is a lake dominated by aquatic vegetation with the dominant submersed
plants a mix of eelgrass, coontail and pondweed. Submersed plants cover 70-80 percent of
the lake and extend upward in the water column ofien to the surface. While dense submersed
plant populations can pose a navigation problem, particularly under low water level conditions,
these plant beds maintain the generally good water clarity and quality characteristic of Lake
Panasoffkee. It was recognized by the agencies represented on the Council’s Advisory Group
and acknowledged by the Council that maintenance of desirable submersed vegetation is
important for sustaining the ecological health and character of Lake Panasoffkee, and that
dredging and other restoration techniques that might be employed should not cause
submersed plant coverage to go below 60 percent. To insure that adequate submersed plant
19