Alafia River Minimum Flows and Levels - Southwest Florida Water ...

experts for initial evaluation. The proposed suitability curves were based on flow
criteria for redbreast sunfish (Aho and Terrell 1986) modified according to
published literature on the biology of spotted sunfish. Respondents were given
approximately 30 days to review the proposed habitat suitability criteria and to
suggest modifications. Six of the fourteen experts provided comments. In
accordance with Delphi techniques, the suggested modifications were
incorporated into the proposed curves. Suggested modifications that fell outside
of the median and 25% interquartile range of responses were not considered
unless suitable justification could be provided.
Modified Type II habitat suitability criteria for the largemouth bass (Micropterus
salmoides) and bluegill Lepomis macrochirus, two other common species in the
Alafia River, were established using USFWS/USGS “blue book” criteria (Stuber
et al. 1982). Curves for these species have been widely used in PHABSIM
applications.
Type III habitat suitability criteria for macroinvertebrate community diversity were
established based on suitability curves published by Gore et al. (2001). Modified
substrate and cover codes used for criteria development were established
through consultation with SWFWMD and Florida Fish and Wildlife Conservation
Commission personnel. For this effort, emphasis was placed on invertebrate
preference for macrophytes, inundated woody debris and root wad habitats.
4.3.3 Recent and Long-term Positional Hydrographs
Recent and Long-term Positional Hydrograph (RALPH) analyses are used to
illustrate the number of days during a defined period of record that a specific flow
or level (elevation) was equaled or exceeded at individual river cross-sections,
including streamflow gaging sites (Figure 4-8). The plots are developed using
measured elevations for habitats or other features and HEC-RAS model output.
RALPH plots also allow examination of how future changes in flow could affect
the number of days of inundation during a particular span of time (Figure 4-9).
For the purpose of developing minimum flows and levels, percent-of-flow
reductions that result in greater than a 15% reduction in habitat from historic
conditions are characterized as limiting factors.
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