surface elevations are reached. Potential temporal change or reduction in the number of days of
direct connection between the channel/floodplain at the floodplain/vegetation cross-sections on
the Alafia, Myakka and Peace rivers was estimated through the alteration of the historic flow
record and the HEC-RAS models. Target elevations corresponding to features of interest, such
as the median elevation of cypress swamps or the top of the river banks, were identified during
the vegetative surveys. The HEC-RAS model was then used to determine the flow necessary at
the downstream gage to inundate the features with flow from the river. The HEC-RAS model
thus allows the elevations, identified at different transects, to be compared as the flow required at
the gage site, to reach the corresponding elevation at the upstream cross-section where the
elevation was identified. The daily historic record from the gage site was then examined. All
days during the flow period of interest were checked to determine if the flow of interest was
exceeded. The total number of days during each year of the historic record that the flow of
interest was reached or exceeded were then tallied. Because the HEC-RAS model estimates the
water surface elevation at cross sections, based on flows at the down stream gage, the reduction
in the total number of days a flow is exceeded is equivalent to the reduction in total number of
days that the corresponding water surface elevation is exceeded, at any cross section. The flow
record was then reduced incrementally, until the percent flow reduction required to reduce the
number of days a flow was reached or exceeded was reduced by 15 percent.
A measure of spatial loss of habitat at each cross-section was also estimated using the
HEC-RAS model output and historic flow records. For each flow profie calculated in the
model, the top width (linear distance in a cross section of water's edge to water's edge) at each
cross section is derived. The sum of top widths at all cross sections in the model is computed for
each flow profie. This provides an estimate of the area inundated. Once top width was