SUMMARY OF PAPERS DESCRIBING RESTORATION OF 

 FRESHWATER INFLOW TO AN ESTUARY IN 

 CONJUNCTION WITH URBAN DEVELOPMENT 



The Marco Island development 

 proceeded concurrently with changing 

 wetland regulations. Permits to con- 

 struct sold lands were denied. The 

 developer has proposed a substitute 

 plan calling for development of 1,500 

 acres of uplands and 2,500 acres of 

 wetlands located near the estuary. 

 13,000 acres of wetlands would be 

 placed in "preservation" status. A 

 key feature of the new plan is the 

 proposed restoration of freshwater 

 inflow to fringing estuary wetlands 

 impacted by prior construction of 

 roads and drainage works. 



Vegetation in the general area 

 now proposed for development grades 

 from farmlands and uplands in the 

 north to tidal mangroves in the 

 south. Portions of the proposed de- 

 velopment tract consist of a perched 

 mangrove forest which lies within an 

 artificial impoundment created by 

 construction of a golf course, air- 

 port, and access road. The fill uti- 

 lized in this construction came from 

 a man-made lake. This man-made lake 

 is approximately 30 feet deep and has 

 become strongly stratified with 

 approximately eight feet of fresh 

 water floating above denser naturally 

 occurring hypersaline ground water. 

 The fresh surface layer has high 

 dissolved oxygen and low nutrient 

 concentrations. The chemocline is 

 stable and observations indicate that 

 neither wind nor temperature could 

 cause an overturn. The saline lower 

 layer has no dissolved oxygen and 

 higher nutrient concentrations than 

 the surface layer. The developer's 

 additional proposed man-made lakes 

 will have essentially the same 

 characteristics as the existing 

 man-made lake. 



Ground water inputs to the pro- 

 posed development area are calculated 

 from observed groundwater contours 

 and literature transmissivity values. 

 Ground water in the shallow aquifer 

 moves toward the coast with average 

 flows of 208,000 gallons per 

 day per linear mile of aquifer width. 

 A freshwater lens replenished by 

 rainfall and excess applied irriga- 

 tion water exists in the filled land 

 comprising the previously mentioned 

 golf course. This freshwater lens 

 may act as a piezometric barrier to 

 groundwater flow to the south. 



Measurement of present surface 

 water runoff from the area has been 

 facilitated because man-made altera- 

 tions have diverted all runoff to- 

 ward a set of three culverts. By 

 continuously measuring the head dif- 

 ference across these culverts an ac- 

 curate evaluation of runoff is ob- 

 tained. Comparison with rainfall 

 data yields a runoff coefficient of 

 53 percent (on a yearly basis). The 

 above described golf course piezo- 

 metric barrier may indicate that 

 groundwater flows derived from 

 areas north of the proposed develop- 

 ment site become a component of the 

 measured surface runoff. All sur- 

 face runoff is presently channelized 

 by roadside ditches directly to ti- 

 dal waters changing timing, quanti- 

 ty, and location of pre-construction 

 sheet flow discharge. 



Water quality in man-made lakes 

 in proposed developments is influ- 

 enced by inflows from rainfall, sur- 

 face runoff, interflow and ground 

 water; and by outflows via surface 

 runoff, ground water and evaporation. 

 All flows are pathways for water 



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