Research Needs and Performance Measures
The White Paper offers numerous prioritized recommendations for research on the influence of flow in the Everglades, with particular focus on the ridge and slough landscape. The “higher” and “medium” priority recommendations are summarized below.
The White Paper makes the following high-priority recommendations.
Conduct a comprehensive multidisciplinary study of the paleoenvironmental history of the Everglades to determine the historical extent and the pre-and post-disturbance dynamics of the ridge and slough landscape and other landscape types.
By means of a broad and thorough geomorphic review, develop alternative conceptual models of the formation and maintenance of the ridge and slough landscape; develop lists of specific questions and hypotheses that could be used to evaluate each model; and select the most likely conceptual models and use them to inform the design of further research.
Quantify the spatial and temporal distribution of sediment transport in the ridge and slough landscape to assess its role in landscape formation and maintenance.
Conduct synoptic measurements of flow over short temporal scales and large spatial scales to quantify current flow patterns.
The White Paper makes the following medium-priority recommendations.
Develop a simple carbon balance model for the ridge and slough landscape that can provide a basis for understanding peat accumulation and decomposition in ridges and sloughs; and collect the necessary data to quantify a carbon budget for the landscape.
Continue to collect and analyze remotely sensed images of the ridge and slough landscape in order to track changes due both to degradation and restoration; and develop systems models and estimate their parameters, collecting new field data (such as surface geophysics) where necessary.
Develop a seasonal water balance for the entire Everglades; and use the water balance to estimate pre- and post-disturbance flows into the ridge and slough landscape.
In general, these research recommendations will address many of the important gaps in our understanding of the role of flow, as identified in the White Paper and elsewhere in the scientific literature. It is important that a flow research program be carefully designed and focused to provide useful information in a timeframe relevant to the restoration. Immediate attention should be given to the development of alternative conceptual models of the formation and maintenance of the ridge and slough landscape (White Paper higher priority recommendation 2). This could be achieved at least partially by convening a workshop on peat accumulation and decomposition. As recommended in the White Paper, the most compelling models should be used to develop research hypotheses and questions that can be used to guide the design of a research program. Careful attention should be paid to research on well-studied peat landscapes with similar features, such as the wetlands of the Okavango Delta in Africa (McCarthy et al, 1986, for related research see <http://www.wits.ac.za/science/geology/vango_research.htm>) and the patterned peatlands of the boreal zone (Glaser et al., 1981; Glaser, 1983; Glaser and Janssens, 1986), though these are not entirely analogous.
As is stated in the White Paper, a research program on flow in the Everglades should include a study of the paleoenvironmental history of the Everglades. It should also include the following: measurements of flow and sediment transport and accumulation, development of carbon budgets, monitoring and analysis of remotely sensed data on landscape geometry, and development of seasonal water balances for Everglades landscapes. All studies should be designed to address questions and hypotheses associated with the leading conceptual models of landscape formation and maintenance, primarily focusing on ridges, sloughs, and tree islands. Whenever possible, studies should be paired between relatively intact landscapes and degraded ones.
Regarding flow and sediment, the committee agrees with the White Paper that research should be conducted to better understand processes. It is particularly important to measure flow and sediment flux during extreme events. This will be challenging and expensive, and should be co-located with sites where other related research on the ridge and slough landscape is occurring. The White Paper’s recommendation of “synoptic measurements of flow...conducted over short time scales and large spatial scales in order to quantify ranges of flow velocity and direction and to delineate major flow pathways” may provide useful information. However, barring technological advances, such measurements will be very expensive to make and may have limited value in view of the likely importance of large events in the system.
Simple measurements of organic sediment accumulation can also provide useful information on sediment transport. For example, the hypothesis that maintenance of the ridge and slough pattern requires transport of organic sediment can be tested readily by measuring accumulations of this sediment at major barriers to flow, such as in the canals flanking Alligator Alley and the Tamiami Trail.
In addition to collecting remotely-sensed images of the ridge and slough landscape, water and soil surface elevations should be monitored on selected portions of the landscape. Topographic mapping at a spatial resolution of 1-3 m and vertical accuracy of 0.1-0.25 m would allow analysis of scale-dependent landscape pattern, microtopography and geomorphic processes. Airborne LIDAR (Light Detection and Ranging) offers a good option for such monitoring, although there are technical challenges to operational monitoring using this technology (Ritchie, 1996; Marks and Bates, 2000; Mertes, 2002; Schmugge et al., 2002). Such data could be tied to the sparser grid of high-precision elevation control points
being collected by the U.S. Geological Survey (for more information on the measuring and mapping the topography of the Florida Everglades for ecosystem restoration, see <http://erg.usgs.gov/isb/pubs/factsheets/fs02103.html>). LIDAR output could be applied to characterizing ridge and slough topography and flowpaths, and used to drive more detailed hydrological models of selected areas to explore the relationship between water levels and flow regime. Multi-temporal imaging could be used to evaluate impacts of large storms and changes in water management over the ridge and slough landscape, as demonstrated in the Dade County East-West Transect study (<http://www.ihc.fiu.edu/ihc/lcrweb/e-w_fiu.htm>).
Topographic data also would provide information on whether all sloughs in relatively intact areas are unrestricted flow paths. Aerial photographs of such areas show sloughs that appear to dead end. Under a natural flow regime, the flow rate required to create flow connectivity of the sloughs might be a critical threshold.
Finally, if major linear structures are blocking the transport of organic sediment, it should be possible to document its resulting accumulation at or near these structures.
One major purpose of performance measures is to show how well restoration efforts are working. They form the basis of the Restoration Plan’s monitoring program, recently evaluated in NRC (2003). The Restoration Plan’s Monitoring and Assessment Plan (MAP) describes performance measures as quantitative measures of conditions in the natural and human systems that have been selected as targets for restoration. They are environmental response variables or system attributes that are expected to change as a consequence of alterations in water depth, hydroperiod, and/or water quality and are ecosystem characteristics that could be monitored to determine progress towards restoration goals and objectives (e.g., number of nesting wading birds). Some of the performance measures (e.g., extent of plant cover) have characteristics of broad ecological indicators such as measures of ecological condition, ecosystem functioning, or ecological capital, as described by the NRC (2000). Others are more site-specific (e.g., phosphorus concentration).
For monitoring and assessment of the Everglades restoration, the White Paper recommends consideration of new performance measures that quantify temporal variations in the geometry of ridges, sloughs, and tree islands. The recommended measures, all of which can be obtained from remotely sensed data, are areal extent and spatial orientation of the three landform types and average length-to-width ratios of ridges and sloughs. These are potentially good measures that fit the definition of ecological indicators as described by the NRC (2000). They are particularly attractive because they are low cost in comparison to many of the performance measures, yet they provide integrated information about the condition of the ecosystem.
Work is currently under way to define the spatial characteristics of the ridge and slough, and tree island patterns thought to represent well-preserved to highly degraded patterns with respect to historical landscape patterns (Nungesser et al., 2003; Wu et al., 2003). Such characteristics include number of ridges and tree islands, area of ridge/tree islands in the landscape, length-to-width ratio of ridges/tree islands, perimeter-to-area ratios of these features, orientation of ridges and tree islands in the landscape, and average length and width of uninterrupted slough along north-to-south and west-to-east transects, respectively.
These indicators, while useful, are insufficient for determining how the landscape is responding to water level, hydroperiod, and flow, because major changes in elevation may occur before degradation is reflected in such indicators. For example, a region in western Water Conservation Area 3 (Figure 2-1)– previously classified as “pristine” based on length- to-width ratio and perimeter-area relationships–has now been recognized as being “degraded” because the elevation difference between the ridges and sloughs is now about 20 cm, whereas historically the difference was between 30 and 90 cm (Sklar et al., 2003). To monitor the response of the ridge and slough system, it will be necessary to consider the topographic relationship between ridges and sloughs, as well as area, directionality, and connectivity of the landscape patterns.
Regardless of the mechanism(s) responsible for creation and maintenance of the ridge and slough and tree island patterns, performance measures must be developed so that these patterns can be monitored. Once there is sufficient scientific evidence to establish the role of flow and the flow rates required to maintain these landscape patterns, flow-related performance measures should be developed and added to the MAP. How these new performance measures are incorporated into the Restoration Plan will be a test of the plan’s ability to incorporate new information in a framework of adaptive management.