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Performance measure development

Causes of change
Evidence of change
Formation & Maintenance
Ecological impacts
Performance measure
A centerpiece of the overall south Florida restoration effort is CERP. As a restoration priority, CERP includes re-establishment of pre-drainage hydrological parameters shown by a natural systems model. Science is to serve as the foundation of CERP, and CERP managers have chosen to use adaptive assessment as the underlying principle during the three-plus decades of the restoration implementation. Adaptive assessment provides the scientific feedback loop to restoration managers to change direction if desired outcomes are not being realized. A Monitoring and Assessment Plan is under development to provide this feedback during the restoration program, and includes conceptual ecosystem models (including a ridge and slough conceptual model) and performance measures as indicators of restoration success.

During the development of CERP, restoration of water levels, rather than water flows, dominated the consideration of performance measures. Water levels, their distribution, and their timing are vital to the Everglades. Water flow played a lesser role during the Restudy planning process because accurate modeling of water flows is much more difficult than that of water levels, and the consensus view regarding the role of flow presented in this paper was not available to the Restudy planning teams. Understanding of the relationship between water flow and water level is complicated by the presence of flow barriers in the Everglades, which have made interpretations of empirical observations difficult in a compartmentalized system. Because the consensus view presented in this paper now is available and should result in new flow-related research, flow performance measures should be developed accordingly.

Future improvements in performance measures related to flow will depend on additional research as suggested above to expand our knowledge of the role of flow. Several possible performance measures have been explored, but their interpretation is limited by the availability of field-verified quantitative measures. Additional research will allow resource managers to make better decisions when trade-offs between flow and hydroperiod (and any other hydrological parameters) may have to be considered.

Remote sensing provides one of the best tools from which to continually assess trends in ridge and slough landscape characteristics. Possible performance measure metrics to be used from image analysis include: aerial extent and temporal trends of tree island, sawgrass ridge, and slough polygons; edge-to-area ratios for landscape types; average length-to-width ratio and temporal trends of sawgrass ridges or sloughs for a defined area; and spatial orientation of the three landscape types as compared to the historic spatial orientation. Surface geophysics at set transects over time will demonstrate movement of surficial sediments, and enhance performance assessment as restoration measures are implemented.

Refinement of hydrologic models to provide velocity vectors (both magnitude and direction) and water depths would help predict where erosive and sedimentary velocities might occur, where flow directions differ from the natural direction, and where depths might be expected to alter landscape features. Spatial assessments can involve calculating suitability indices to indicate areas with: unnaturally high or slow velocities; unnaturally broad or narrow annual ranges in water depth; unnaturally high peak water levels (or low minimum water levels); and unnatural deviation in flow direction.

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U.S. Department of the Interior, U.S. Geological Survey
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Last updated: 04 September, 2013 @ 02:04 PM(TJE)