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The DPM is a multi-year program of high-flow field experiments conducted within the Everglades in an area that has been isolated from flow for sixty years. The work was supported by the U.S. Army Corps of Engineers and the research undertaken by scientists from the South Florida Water Management District, U.S. Geological Survey, Florida International University, University of Hawaii, and University of California-Berkeley. The purpose of the DPM experiments were to provide scientific information to help guide the congressionally authorized Everglades restoration project known as the Comprehensive Everglades Restoration Plan (CERP). At a cost of ten billion dollars, CERP outlines an Everglades-wide restoration project that will protect internationally valued wildlife resources and the potable water supply for south Floridians while also increasing resilience to drought. The DPM project will inform one of CERP's centerpiece projects, the Decompartmentalization and Sheet Flow Enhancement Project (DECOMP). Specifically, the DPM experiment will identify factors that influence effectiveness of restoration, specifically how effective flow restoration is in protecting highly valued ecological resources.
Twenty-three specific physical and biological hypotheses are addressed by the experiment and are detailed in the DPM Science Plan (DPM Science Team, 20101). The central research questions addressed by the DPM are summarized as follows:
Sheet Flow Questions: How does sheet flow improve the long term stability of the disappearing and highly valued ridge and slough landscape? To what extent do entrainment, transport, and settling of suspended particulates differ in ridge and slough habitats under high and low flow conditions? Also, does high flow cause changes in water chemistry and consequently changes in sediment and periphyton metabolism and organic matter decomposition that influence function and stability of the ridge and slough landscape and its valued support of fish and wildlife?
Canal Backfill Questions: Will canal backfill treatments act as sediment traps, reducing overland transport of sediment? Will high flows entrain nutrient-rich canal sediments and carry them into the water column downstream? To what extent are these functions altered by the various canal backfill options, including partial and full backfills?
DPM was designed to test the benefits of sheet flow by evaluating surface water flows and interactions with vegetation and bed sediment that affect suspended particle entrainment and phosphorus transport. Measurements were made along a gradient of increased sheet flow as it varies with distance from the location of breaches in the levee. Field monitoring of hydrologic and biological parameters at DPM were conducted under low-flow (baseline) and high-flow (impact) conditions in the affected flow way and in non-impacted wetland and canal “control” sites. The operational window of the S-152 culverts was subject to certain water level and phosphorus concentration triggers limiting operation to the months of November, December and January. The first high-flow event was initiated on 11/5/2013 and the second on 11/6/2014, and the third on 11/16/2015 and 11/19/2015. The third high-flow event had two high-flow pulses. The first one was between 11/16/2015 and 11/17/2015, and the second one was between 11/19/2016 and 1/28/2016. Here we summarize objectives, methods, and data collected by the USGS National Research Program, Eastern Branch, in Reston, Virginia and by the University of California, Berkeley. Many complementary studies are being conducted by collaborators, including investigations of how levee removal and canal backfilling are affecting fish movement between previously isolated areas. In addition to serving Everglades restoration, the DPM will inform similar adaptive management programs throughout the nation’s network of federally managed river corridors, floodplains, and riparian ecosystems.
Site Locations, Time Period of Operation, and Overview of Data Collection
The DPM infrastructure included gated culverts and levee gaps that moved flow from one basin to another and that increased sheet flow through an area of the Everglades known as the “pocket”, a 2-km wide wetland that has been hydrologically isolated between levees for approximately 60 years. The ten gated culverts (S-152) conveyed flow beneath the L-67A levee (see location map) and had a combined capacity to produce sheet flows that generated water velocities approximately ten times greater than current flows. At a location 2.5 kilometers downstream, the experimental wetland was modified by removal of a 3,000 foot portion of the L-67C levee that allowed water to cross a canal into a different sub-basin. Three degrees of backfilling of the L-67C canal gap were tested in terms of how backfilling affected transport of sediment and phosphorus to downstream areas.
A hydrologic modeling network was set up at DPM to measure the movement of water, solutes, and suspended materials with sheet flow. Fourteen stations were routinely visited through the wet season during which instruments were calibrated for quality assurance and data were downloaded. The hydrologic monitoring network served as a framework for measuring other physical and ecological processes such as flow field dynamics, suspended particle sources and concentrations, physical characteristics of particles such as size and organic content, particle-phosphorus content, and the role of vegetation community type and stem density in influencing flow and particle dynamics. In addition, various environmental and introduced tracers were measured during the flow releases to capture local scale and larger scale surface water and groundwater flow patterns.
The high-flow measurement network included fourteen measurement sites. From northwest to southeast the sites were Z51, Z51_USGS, Z53NE_2014, Z53NE_2015, RS1U, RS1D, RS1SE, Z53B, RS2, S1, UB1, UB2, UB3, DB1, DB2, DB3 and MB0, MB1, MB2, MB3 along the L67C canal (see location map). There are also two control stations (C1 and C2) that were located in areas removed from the main influence of sheet flow enhancement. Three of the measurement sites (UB1, UB2, UB3) were located on the upstream side of the L-67C canal in the vicinity of where the levee had been removed, allowing flow to cross from the pocket into Water Conservation Area 3B. There were also four sites located in the L-67C canal (MB0, MB1, MB2, and MB3) and three sites located on the downstream side of the canal (DB1, DB2, DB3) (see location map).
The USGS-Reston measurements at DPM are categorized either as continuous/autonomous (i.e., self-collecting instruments emplaced for the wet season) or discrete/portable (e.g. measurements made over a period of hours to days). Data collection occurred from 2010 to 2016 between the onset of the wet season (usually August) through the onset of the dry season (usually March). The 2010-2011 wet season was brief and ended with a severe fire that burned vegetation (but not peat) throughout the experimental area. Measurements between 2010 and 2013 provided baseline low-flow data before the construction of the culverts and levee gaps that allowed high-flow to begin. The construction of culverts and the levee gap and canal backfill treatments were completed in summer of 2013 and the DPM experiment became operational in early November of 2013 with the first high-flow experiment lasting through December of that year. The following year the flow enhancement experiment began in early November and lasted through the end of January 2015. Between middle of November 2015 and end of January 2016, there were two high-flow experiments (11/16/2015 – 11/17/2015 and 11/19/2015 – 1/28/2016).
Methods
DPM Experimental Structures and Operations
-- Benchmark Elevation Surveying
-- Microtopography
-- Surface Water and Groundwater Levels
-- Surface Water Flow Velocities and Shear Stress
-- Suspended Particle Sizes and Concentrations
-- Biogeochemical Sampling
-- Vegetation Influence on Sheet Flow
-- Water Quality Monitoring
-- Groundwater- Surface Water Interactions Detected using Heat as a Tracer
Download methodology and data plots (.pdf, 34 MB)
If you cannot fully access the information in this document, please contact Heather S. Henkel at hhenkel@usgs.gov.
1 Decomp Physical Model Science Team (DPMST) (2010), The Decomp Physical Model Science Plan. 52pp.
U.S. Department of the Interior, U.S. Geological Survey
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