Greater Everglades Ecosystem Restoration Conference

Flow Workshop Summary Concurrent Session III Hydrology and Hydrologic Modeling - December 13, 2000

Flow Workshop Agenda

FLOW WORKSHOP: How important is the flow for Everglades Restoration?
Session Moderator:	Nicholas G. Aumen, National Park Service
8:00am - 8:15am	Opening Remarks - Session Overview
8:15am - 9:15am	Brief overview by Workshop Panelist Christopher McVoy, Tom MacVicar, Randy VanZee, Steve Davis, Dan Childers, and Peter Stone
WORKSHOP QUESTIONS: What were the historic patterns of flow in the greater Everglades both temporally and spatially? What is the linkage between flow and landscape patterns? How important is flow for restoration of the remnant greater Everglades and coastal ecosystems?
9:15am - 10:15am	Discussion and Interactions between Panel Members
10:15am - 10:30am	Refreshment Break Orchid Atrium & Solarium South (Level One) (Poster Session I displays MUST be removed by this time)
10:30am - 11:00am	Audience and Panel Discussion
11:00am - 11:30am	Closing remarks

Introduction

This report presents a summary of the panel and audience discussions that took place during the Flow workshop held at the Greater Everglades Ecosystem Restoration (GEER) Conference on Wednesday, December 13, 2000. The discussions generally followed the format shown in the agenda, and this was the only session that followed this format. One change from the published format was that two panel members, Randy Van Zee and Christopher McVoy, presented background information to frame the discussion, followed by open discussion between the panel members.

The panel members included the following:

• Randy Van Zee: A South Florida Water Management District employee with responsibility for developing the Water Management Model (SFWMM), the Natural Systems Model (NSM) and "next generation" hydrologic models.
• Christopher McVoy: An employee of the South Florida Water Management District working on historical reconstruction of the hydrologic systems in the Everglades.
• Peter Stone: An employee of South Carolina Health and Environment whose areas of study included wetlands, paleoecological studies and tree islands. Also, Peter was a former employee of the South Florida Water Management District.
• Steve Davis: An employee of the South Florida Water Management District with responsibilities including developing conceptual models and uncertainty models for Everglades Restoration.
• Dan Childers, Professor of Biology, Florida International University.

Presentation by Randy Van Zee - Natural Systems Model

The current version of the Natural Systems Model (V4.5) is linked to the SFWMM with data adjusted to represent pre-drainage conditions. The model was calibrated using water elevations rather than flows due to the difficulty in measuring the very small surface flow velocities. Regional flow patterns are very sensitive to ground surface gradients – the model is topography-driven. A cautionary note was included that the NSM should not be used as the ultimate authority on patterns of flow in the Everglades, but as a tool to give some insight into what these patterns might be.

Model output could be used to address two of the three questions posed for the panel discussion. Information derived from the model to address the question, "What were the historic patterns of flow in the Greater Everglades both temporally and spatially?" were as follows:

• Pre-drainage flow in the Everglades was expansive, slow moving, affected by dense vegetation and was predominantly low gradient sheet flow with a general absence of rivers or streams.
• The topography was a "sawgrass plain" south of Lake Okeechobee in the now Everglades Agricultural Area (EAA) and a "ridge and slough" pattern south of this area.
• Flow vectors from the model were uniform, indicating uniform flow conditions.
• Flow originated from Lake Okeechobee overflow, inflow from peripheral areas such as the western basins and from direct rainfall.
• Annual flows between 25,000 and 100,000 acre ft/yr per 2x2 mile grid cell characterized Everglades wetlands.
• Within the Everglades, water ponded over most of the year, indicating potential for flow.
• Modeled surface water flow velocities over most of the Everglades fell between 1000 and 2500 ft/d. The maximum flow velocity across the Tamiami Trail calculated by the model was 3190 ft/d.
• Soil loss calculated as elevation differences between the SFWMM and the NSM 3.4 to 4.5 feet in the Everglades, 2.5 to 10 feet in the EAA, and 0.5 to 2.5 feet in the Water Conservation Areas.

Presentation by Christopher McVoy – Historical Landscape Ecology

The historical landscape ecology approach differs from the NSM in that it uses pre-drainage conditions, post-drainage changes, and causal mechanisms, while the NSM is based on an objective observation, scenario testing, and capture of a quantitative picture. Main features of this presentation were:

• In the Everglades, this research cannot provide absolute surface water velocities and volumes; rather spatial patterns and changes can be studied.
• There is considerable uncertainty with respect to pre-drainage topography and this topography cannot be precisely determined.
• Historic landscape patterns can be studied in three scales: 1) Everglades basin scale; 2) landscape scale (2 or 3 landscapes can be differentiated); and 3) fine scale within each landscape.
• Everglades National Park (ENP) is different from the rest of the basin.
• The Everglades Basin is essentially a V-shaped basin with expansion and contraction at the edges of the basin.
• The Transverse Glades were formed due to periodic overflow from the Everglades basin, and this origin gives some idea of the water levels which must have occurred in the Everglades basin in order to spill over into the Transverse Glades.
• The pre-drainage land surface in the Everglades ranged from 21 feet (above NGVD) to sea level. The water surface was smooth and parallel to the land surface as opposed to the ponding that occurs today due to man-made flow obstructions.
• The pre-drainage Everglades was characterized by "wall-to-wall" sawgrass, flat topography, with slow, sheetflow water movement.
• The system was broken up into a "ridge and slough" pattern, as shown in 1940 aerial photographs. The same pattern exists today as can be shown by a recent (1995) photograph. This pattern is not captured in the NSM, but the topography is represented as a uniform system.
• The drainage pattern follows the ridge and slough pattern as shown in an early pre-drainage map by Parker and confirmed by recent systematic mapping of flow patterns. The drainage pattern is mainly uniform with some exceptions (North New River Ares, and northeast of ENP close to Dade/Broward line) where flow diverges with some flow going eastward.
• Because the area is developed, the flow to the east cannot be restored to pre-drainage conditions.
• Hypothesis: ridge and slough pattern formed not through oxidative decomposition, but most likely through a flow-related mechanism such as floc transport.
• Conclusions:
  1. Substantial landscape information, as well as documentary information, is available from which to estimate pre-drainage Everglades conditions.
  2. Both information types indicate a large Ridge and Slough landscape with highly directional microtopography and vegetation patterns.
  3. Ridge and slough pattern, water flow, and topography all seem to have shared the same directionality.
  4. Directionality, historical observations, and river capacity indicate two parallel basins, discharging eastward and southwestward.
  5. At present, more than half the remaining Ridge and Slough landscape shows signs of deteriorating pattern.
  6. The mechanism maintaining the pre-drainage Ridge and Slough pattern is not known. The shape of the patterns and evaluation of alternate mechanisms suggests water flow.
• If water flow and floc transport were responsible for the pre-drainage pattern, then restoration of original flow directions and complete removal of obstructions will be required to preserve the Ridge and Slough landscape.

Panel Discussion

• Geologic evidence does not appear to support the flow hypothesis. No sign that export of detrital floc is related to the creation or maintenance of the topographic lows (Stone).
• Nutrient spiraling may be a mechanism involved in sough creation/maintenance south of Tamiami Trail. Does observe floc transport as well as the collection of floc in bed traps (Childers).
• Nutrient-enriched zone found at the interface between fresh and saline ground water may be related to the movement of floc. Obstructions to flow could result in reduction of the productivity of this zone.
• CERP includes projects which would implement McVoy hypothesis (L-28 and L-29 modifications). Removing other obstructions such as L-67 would result in hydrologic impacts (drain the system) (Davis).
• Critical questions to resolve flow issue are: 1) What are the information needs? 2) How do we maintain the ridge and slough system? 3) What will be the impact of sea level rise? and 4) What are the ecological components sensitive to flow (Aumen).
• Not much information available on direct measurements of historical flow magnitudes. Few formal observations from the 1800s appear unreasonably high relative to modeled flow magnitudes.
• Importance of scale should not be overlooked. We should also be careful to base restoration on plausible possibilities. The floc layer may only be important at the origin of the flow and where it is deposited.
• Historic water level data can be deduced from vegetative reconstruction of the peat material. Studies of cores showed clear vegetative shifts with depth (time) – sloughs to sawgrass plain to terrestrial (Willard).
• Need to understand natural variability which is climatically driven (Cronin).
• Could pattern be "braided", caused by extreme catastrophic events (such as 1928 hurricane (Wanless)?
• Seiche action causes movement of floc in Lake Okeechobee and could be a similar mechanism in the Everglades (Zebuth).
• Concern about CERP design of Tamiami Trail reconstruction, which is based on flow-through volume rather than how the system works biologically (Zebuth).
• Will the current 4-bridge design be adequate (Chrisman)?
• Models do not adequately show effects of roads such as I-75 and other linear obstructions. Ocalacoochee slough, Taylor slough, Shark Slough, and East Slough are all blocked. For large-scale restoration, these obstructions need to be removed. Also need high accuracy topographic data and good soils data due to very low topographic gradient (Partridge).
• Is there enough water to meet all water supply needs as modeled by NSM (Rutchey)?
• Available water will need to be redistributed (Todd).
• Need improved flow measurements to quantify velocities (Swain) and sediment transport (Mitchell).
• How would water quality changes caused by diverting water with higher nutrient content from the EAA into the pristine Everglades affect the ridge and slough system? There is ample evidence that adding phosphorus to the sloughs would result in cattail invasion (Mitchell).
• Use flow data from NSM to calculate how processes operate. May be combination of processes (floc transport, extreme events, or biological processes). Need to understand the flow regime to determine how different parts of the system may be responding (Anderson).
• Direct (eyewitness) evidence that coastal creeks and tidal channels have filled in over the past 40 years. These may need to be mechanically opened (Browder).
• Control of salinity is important; need to pay attention to timing of flows. When do the animals that use the estuary as a nursery need lower salinity (Browder)?
• Need flow rather than having the water impounded (cf. coastal marshes in Louisiana) Dosing studies by FIU show that closed systems react to phosphorus addition differently from open systems (Browder).
• Can the 245,000 acre-feet of additional water which the ENP wants be delivered without affecting areas north of the Park (Duncan)?
• Additional water from urban areas may be available for backpumping if the water quality concerns can be taken care of. Adverse impacts to the WCAs would not be tolerated as a tradeoff for additional water to ENP (Davis). This will be further studied in CERP, including effects on stages and other factors affecting vegetation and wildlife (Punnett).
• Need to factor in ground water/surface water interactions, including recharge of contaminants to the shallow aquifer and re-emergence of the contaminants to surface water and the role of the shallow aquifer in supporting ecosystem processes (providing moisture, controlling the biogeochemistry) (Harvey).
• Need knowledge of vegetation versus hydrologic processes rather than elaborate hydrologic and landscape models. For example one of the best areas of sawgrass does not receive flow. Studies show that adding nutrients to sawgrass does not result in cattail invasion but adding flow does (Curtis Richardson).

Panel Recommendations for Future Research

• Relative importance of storms, uplands runoff, and wind-driven changes in hydroperiod in moving nutrients in sloughs.
• Export to estuaries.
• Peatland processes – are some of these suggested processes (such as role of flow processes in slough maintenance) critically important?
• Slough processes including rate of filling in, rate of material removal, and material transport processes.
• Estuarine productivity peak at the fresh water/salt water interface.
• Sea level rise impacts.
• Causal factors – water quality, water depth, and hydroperiod necessary to preserve the ridge and slough system.
• Develop model of hydrology near flow obstructions such as Alligator Alley.
• Study floc transport – where the material is coming from, where it is going, and what is its fate as it spirals down the system.

Participants' Recommendations for Future Research

Two-year priority

• Velocity required to mobilize slough sediments? To retain sediments in the water column? Use field and flume studies.
• Why does "H" patterns of flow associated with culverts under a road (e.g., Tamiami Trail) seemingly not work unobtrusively on flow?
• Recommendation of Mod Waters Tamiami Trail preferred alternative.
• Re coastal interface: change in vegetation patterns in relation to change in flow, then subsequent change in flow potential in relation to change in vegetation.
• Evaluate whether natural systems can handle increased flow from re-establishment of flow paths.
• What are the relative rates of flow through different community types (e.g., sawgrass, sloughs, willow heads, etc.)?
• Improve ecological and hydrological simulation models at landscape scale.
• Obtain detailed soil and topographic survey data to verify and adjust NSM assumptions. Include samples for historic plant community.
• More detailed study of water and materials budget in sloughs, sawgrass plains, near obstructions to flow, etc., under different hydrological conditions. Include surface/ground water interactions.
• Establish restoration target. Natural system underwent change, so how do you pick a target and allow it to evolve, once it is restored?
• Obtain high-accuracy elevation data.
• Use Mod Waters implementation as an adaptive management experiment to evaluate the manifold effects of flow restoration to a previously non-flowing area (e.g., WCA-3B).
• Obtain baseline data on threatened and endangered species.
• Define what is meant by flow – typical velocities, extreme values, occurrence of laminar flow.
• Determine why ridge/slough reformed to match the high flows, velocities, and sediments coming through culverts, S-12s, etc.?
• Initiate a modern soil survey mapping of WCAs, ENP, and BCNP, and include detailed laboratory analysis of each identified soil type or series. Needed for models.
• Determine hydrologic effects of removing causeways and replacing with bridges.
• Investigate the potential effects of a sea level rise of 1 ft during CERP implementation, and 2 ft over the life-span of CERP projects.
• Determine biological impact of resistance to flow, particularly for US 41 and I-75 (how much do we need to raise roads with bridges to restore biological connections?).
• Define the role and impacts of man-made obstacles in flow patterns, and in the establishment and maintenance of ridge/slough systems.
• Constrain estimates of groundwater discharge to estuaries.
• Determine water stage that would have been required to over-flow the peat and marl transverse glades.
• Determine size of flocs and their settling velocity.
• Evaluate and model flow through causeway culverts.
• Investigate maintenance of ridge/slough environment, especially the biological components of that maintenance.
• Investigate effect of extensive road network in ENP on flow and floc movement.
• Investigate role of extreme events (e.g., 140+ mph wind) in ridge/slough maintenance and particulate transport.
• Determine rate of ecosystem recovery at sites adjacent to bridge construction.
• How do hydrology and fire interact to sustain ridge/slough and tree island habitat?
• Obtain supporting data from peat cores to verify ridge/slough hypotheses.
• Determine fate (immobilization, recharge rates, etc.) of surface water contaminants recharged to shallow ground water.
• Establish accurate elevations throughout landscape.
• High-resolution hydrologic modeling.
• Determine minimum flow for sustainability of diverse habitats in Everglades.
• Determine relationship between flow into estuaries and ecosystem structure and function.
• Determine size and effect of pond apple forest (south of Lake Okeechobee) on nutrient uptake, hydropattern, and habitat.
• Conduct additional research of effectiveness of agricultural BMPs to minimize downstream impacts.
• Additional determination of flow direction, stage, volume, and rates for water entering ENP, to better design Tamiami Trail modifications.
• Gain better understanding of production, fate, transport, and characteristics of organic floc, and relating its transport to the estuarine ecotone and to oligohaline productivity.

Five-year priority

• Map velocity distributions under variety of flow conditions, projected to 1-in-20 and 1-in-50 flow events.
• What does maintain sloughs? Alternatively, what maintains the strands that define the sloughs?
• Recommend restoration from a proportional aspect. Restore the smaller present surface area proportional to historical proportions of sawgrass/ridge and slough.
• Salinity patterns in relation to flow – volume, timing, and rate of change.
• Improve water quality protection and clean-up in upper watersheds where hydrologic restoration occurs (e.g., to deal with low-level pesticides).
• Evaluate the effect that peat loss (subsidence) has on the direction of flow in areas where hydropatterns are restored.
• How does each vegetative community and its elevation influence total volumes of flow?
• Obtain detailed topographic data at coarse (0.25-mile) scale over entire region, and fine (10-50 m) scale in selected ridge/slough areas, and all of mangrove transition zone.
• Include water quality and ground water interaction into the 2X2 model, or a more detailed version of the conceptual models.
• Study what natural succession an unimpacted Everglades would have exhibited. Does this succession path meet our expectations?
• Obtain small-scale soil data with permeability.
• Evaluate effects of flow on the ecosystem from major changes already made, with emphasis on indicator species.
• Measure the biological attributes influenced by flow conditions.
• Concurrently, conduct forensic study of soil profiles to determine historic soil and plant conditions.
• Investigate surface water and ground water interactions.
• Measure flow velocities in the field at tree islands and sloughs.
• Determine physical transport mechanism for detritus, and its importance to the Everglades and estuaries.
• Understand groundwater and surface water interactions at all scales across all landscape types.
• Obtained detailed topographic data, and improve historic topographical information.
• Improve performance measures.
• Assure that climate variability change (historical/paleo) is an integral part of flow evaluation.
• Conduct research and modeling to obtain accurate flows and velocities and to determine sediment transport capabilities.
• What geomorphological alterations are necessary to restore storm/overbank flow throughout ENP? Determine role of increased flow in removal of sediments.
• Determine how estuarine productivity will change in response to flow restoration and sea level rise.
• Conduct research to investigate the possibility of creating an enriched habitat in restored Everglades because of historical evidence of such a zone.
• Determine role of narrow freshwater lens on top of surficial aquifer in maintenance of ecosystem processes.
• Incorporate nutrient supply (loads and concentration) into flow issues and hydrologic restoration.
• High-resolution elevation maps.
• Utilize isotopic signatures to examine the relationships between food web processes and changes in flow and habitat.
• Determine how changes in estuary physical structure due to sea level rise will affect the relationship between flow and ecosystem structure and function.
• Determine if there is enough flow to fill a replacement slough between the Lake and the Everglades.
• Obtain better soil profile data throughout Everglades to better identify sediment transport trends and historic flow patterns.
• Determine historical patterns of flows in the eastern and western flow paths in the Everglades.
• Obtain historical information on soil development and past vegetative cover (paleo-soil work).

Workshop Critiques

Irv Kantrowitz:

Summary: I believe all three questions were answered to varying degrees. Historic patterns of flow seem to be simulated quite well by the NSM. This is verified by McVoy's work with the possible exception that McVoy indicates that flow across the coastal ridge to the Atlantic coast. One note: temporal patterns of flow were largely unaddressed.

McVoy made an excellent case for the linkage between flow and landscape patterns, particularly in the ridge and slough area. Presumably, the featureless sawgrass plain is a function of uniform sheet flow and therefore also related to flow.

McVoy and the comments of several others have shown that flow is critical for restoration of the Everglades (for maintaining sloughs and tree islands and coastal ecosystems, and for maintaining proper salinity gradients in estuaries and transporting nutrients and organic material).

Critique: There was some very good exchange between participants (panelists and audience) but some questions from planners and advocates, although interesting, were irrelevant to the topic. Perhaps a workshop interfacing potential users with the modelers would be useful.

Research Needs: Long Term: Expanded study of the origin and maintenance of sloughs. Short term: Effect of ignoring the concentration of flow in the sloughs in the NSM. How does our land surface datum used in the NSM compare to the bottom of the sloughs or the altitude of the ridge, and how does this affect calculations of dry periods and how does it affect the cross-sectional area of flow and therefore the flow velocities? What would be the effects of stage and volume of water delivered to the ENP if more water in the NSM were routed to the east coast? In other words, if the southern Everglades historically received less water, how would that affect their need for future water?

Bill Cogger:

The flow workshop was essentially a free-flowing dialogue that aired out a series of technical viewpoints and convictions. No one seemed to doubt that flow is the predominant impact mechanism at every level of interest. At the same time, other mechanisms, essentially, the dynamics of ecological interactions, were viewed collectively as no less important, if either a direct or indirect product of water movement. Attempts to blend the obviously overriding importance of quantity, timing, and location with the major concerns of the numerous competing interests understandably revealed some furrowed brows. Some "givens" were suggested away, such as the need to remove phosphorus regardless of form, and the potential effects of freshwater outflows on Biscayne and Florida Bays.

I took away a few lasting impressions of sticking points from the briefing by the panel members and the ensuing discussion:

• Many entities, such as the NPS, FWS, etc., want more flow at select times but not at the expense of flooding, which is and through time has been a limiting element to the stasis of the Everglades.
• Transport from the Lake carries vital micronutrients. For example, silicon must now be added to sugar cane fertilizers, and silicon can limit periphyton production, too.
• Loss of tree islands is inevitable with increased flow but it remains to be seen, "How much is too much?" (30% to 40% was casually offered as a starting point for analysis. A question I was unable to ask is, "Isn't ATLSS well placed to examine this issue?"
• Aquifer Storage and Recovery, impoundments, and pumpbacks all seemed problematic despite the urge to proceed with engineering solutions.
• Baseline data are needed in many areas, e.g., to support flow management after burns, etc.

Some "goodies" I took away from the forum were:

• Frog giggers (Indians included?) used their airboats to keep channels open.
• Satellite photos show the effect of interrupted surface water flow across I-75, even along the Big Cypress Swamp.
• Seepage out of the Everglades is roughly matched by east to west drainage (Did I hear right?).
• 60% to 70% of the water used by municipalities is traceable to the Everglades.
• Adaptive management begs the question of "Doing it right the first time."
• Cattails tend to flourish after long hydroperiods and drought, yet decline after freezes.
• Exotic fish species and some microbial processes (alkaline phosphatase activity) can be used as red flags within the ENP.

John Arthur Marshall:

Workshop summary on flow function submitted; peer review appreciated.

Fundamental questions going in (Conference Schedule):

• What were the historic patterns of flow in the greater Everglades, both temporally and spatially?
• What is the linkage between flow and landscape patterns?
• How important is flow [FUNCTION] for restoration of the remnant greater Everglades and coastal ecosystems?

Key Conclusions:

• Flow is the necessary function to maintain the ridge & slough system of the historic everglades (McVoy, et al.).
• It is intuitive that this is so, though we lack hard physical evidence as to why this is so (Steve Davis, et al.) [The Art Marshall approach].

Key Observations (hypotheses?):

• Floc plays a role.
• Flow is directional.
• Flow has a cause and effect relationship to biological – ecological factors.
• Flow processes caused uplifting of water table; unclear as to long-term effects.
• Flow and fill processes unclear over long period of time.

Scientists View of Nature:

• Flow Function hard to model; hard to predict, difficult to measure because it is slow.
• Observation: Hypotheses are developed based on man's view of nature, not necessarily nature itself; is this a case where nature needs to be appreciated and employed when it can't be understood? Scientists have a hard time reaching a conclusion that flow restoration is needed, and that therefore action should be taken to restore it. The debate subsumes the action required. The burden of proof should not be left to the details but to the obvious. Demonstration is the Kissimmee: when nature is given back its functions, it works. Need to focus on the self-evident.

McVoy:

• NSM: A remarkable tool for determining flow, relative to historical indications.
• My work: Historical landscape ecology; historical patterns of flow.
• Flow was on a slanted flat plane; flow is now in steps.
• This is altering ridge and sloughs patterns... turning them to mush.

Discussion:

• Debate moved back and forth from macro picture to micro picture.
• Discussion of macro picture was the most productive; there are lots of differences down in the detail; the detail remains a source of confusion; this is reflected in the information requests.
• There was no disagreement that flow was needed to maintain system, especially ridge and slough patterns; the disagreement was in the reasons for it.

Top 10 Information Needs Request Categories Distribution:

(Rough - All Categories): (From turn-in survey, number of hits +/- one, as per Nick Aumen report)
1. Flow modeling physics: magnitude, velocity & direction	13
2. Flow – ecology linkages - interdependencies; cause & effect	11
3. Peat soil studies/survey	7
4. Causeway concerns (also related to 1.)	7
5. Accurate topographic data	5
6. Floc/detritus transport	5
7. Water quality – groundwater – surface water concerns	4
8. Fire patterns	3
9. Climate change effects [trees mitigate favorably]	3
10. Coastal interface - salinity	3

NOT talked about much: