G111 Control Structure Reservoir Report

Last Updated: December 5, 2025

The G111 Control Structure, also known as the Lake Jackson Structure, is a state-owned flood control system located in Osceola, Florida.


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Summary

Managed by the South Florida Water Management District (SFWMD) and the Florida Department of Environmental Protection, this structure plays a crucial role in reducing flood risks in the area. Completed in 1994, the G111 Control Structure is an earth dam with a height of 14 feet and a hydraulic height of 12 feet, offering flood protection for the surrounding communities.

With a maximum storage capacity of 11,000 acre-feet and a normal storage capacity of 7,500 acre-feet, the G111 Control Structure covers a surface area of 830 acres and serves a drainage area of 21 square miles. Equipped with a controlled spillway and other controlled outlet gates, this structure can handle a maximum discharge of 300 cubic feet per second. Despite its low hazard potential, the G111 Control Structure is deemed to be at a very high risk, indicating the importance of ongoing risk management and monitoring efforts to ensure its effectiveness in mitigating flood risks and protecting the local environment.

As an essential component of the water resource management infrastructure in Florida, the G111 Control Structure stands as a testament to the state's commitment to flood risk reduction and environmental protection. With its strategic location along the Jackson Canal and its vital role in regulating water levels in Lake Jackson, this structure exemplifies the collaborative efforts of state agencies and stakeholders in safeguarding communities against the impacts of extreme weather events and climate change.

Year Completed

1994

Dam Length

220

Dam Height

14

River Or Stream

JACKSON CANAL

Primary Dam Type

Earth

Surface Area

830

Hydraulic Height

12

Drainage Area

21

Nid Storage

11000

Structural Height

22

Outlet Gates

Other Controlled

Hazard Potential

Low

Foundations

Soil

Nid Height

22
       
Seasonal Comparison

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Dam Data Reference

Condition Assessment

Satisfactory
No existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading conditions (static, hydrologic, seismic) in accordance with the minimum applicable state or federal regulatory criteria or tolerable risk guidelines.
Fair
No existing dam safety deficiencies are recognized for normal operating conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action. Note: Rare or extreme event is defined by the regulatory agency based on their minimum
Poor A dam safety deficiency is recognized for normal operating conditions which may realistically occur. Remedial action is necessary. POOR may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency. Investigations and studies are necessary.
Unsatisfactory
A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.
Not Rated
The dam has not been inspected, is not under state or federal jurisdiction, or has been inspected but, for whatever reason, has not been rated.
Not Available
Dams for which the condition assessment is restricted to approved government users.

Hazard Potential Classification

High
Dams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life.
Significant
Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environment damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.
Low
Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner's property.
Undetermined
Dams for which a downstream hazard potential has not been designated or is not provided.
Not Available
Dams for which the downstream hazard potential is restricted to approved government users.