State Road 29 and U.S.-41 were constructed in Collier County in 1926 and 1928 respectively, by excavating a canal and using the excavated material to build a road above the surrounding water level. This process was repeated during ensuing years to produce a haphazard series of canals for logging trams. This “ditch and drain” method picked up speed with ditches dug to drain land for agriculture and drain wetlands for mosquito control. By the early 1960’s residential projects had been built by excavating canals to lower the water table and raise the ground elevation of houses.
Early Urban Drainage
The planned drainage of lands in Collier County was initially designed on a relatively small scale and served to more rapidly convey storm run-off away from some of the low-lying developed sites. However, as the use of manmade drainage controls increased, the effects of urbanization began to be observed. The increase in impervious surfaces produced more and faster moving stormwater runoff while decreasing percolation to the groundwater system. As a result, the capacities of the natural and previously constructed drainage facilities were frequently inadequate and stormwater flooding increased, thus increasing the demand for further drainage improvements.
Water Quality Problems Develop
In addition to creating new flooding problems, the drainage plans for stormwater had a detrimental effect on stormwater quality. Soil eroding from development sites and materials such as fertilizer, pesticides, oil and grease from urban land uses are washed by run-off into the stormwater drainage systems and result in an increased pollutant loading to the receiving waters.
One very important effect of the construction of an extensive system of drainage facilities was the lowering of the water table. The canals excavated to convey stormwater in the wet season served to over-drain land in the dry season. This resulted in large tracts of wetland drying out to become more susceptible to destruction by fire, estuarine degradation, loss of wildlife habitat, and contamination of the freshwater drinking supply by saltwater intrusion into the groundwater system.
Correcting the Problems
Original drainage patterns have been greatly altered by the addition of roadside canals and canals built to drain land for human habitation. To keep from over-draining the land, helping to raise groundwater levels and to preserve wetlands, some canals have been fitted with water level control structures.
A greater understanding of the importance of surface water for a healthy environment has helped focus attention on the need to develop a total stormwater management design instead of solely a drainage design. Current Basin Planning, Stormwater Capital Improvement and Land Development Permitting programs reflect this philosophy.
A Primary and a Secondary canal system form a major surface water / stormwater control network in the County. Together, their function is for flood prevention and stormwater quality treatment, wetlands preservation, and surface recharge of the groundwater aquifers.
The Secondary system consists of a network of ditches, canals, weirs and pump stations that collect stormwater run-off from neighborhoods and public roadside drainage systems. It is linked to, and operates in close cooperation with, the Primary system.
The Primary system consists of canals and water level control structures that store stormwater run-off from the Secondary system, roadways and neighborhoods.
Private stormwater management systems also exist in Community Development Districts (CDDs) and some Planned Unit Developments (PUDs) and are regulated under terms and conditions set forth in their individual Stormwater Management System permits authorized by the South Florida Water Management District.