Integrated Approach to Quantifying the Effects of Climate Change on Water Resources and Coastal Infrastructure in Urban Miami-Dade County Eric D. Swain, Ph.D. US Geological Survey Virginia Walsh, Ph.D., P.G. Miami-Dade Water and Sewer Department & Wellfields Northwest Wellfield Miami Springs Wellfields West Wellfield & Wellfield South West Wellfield Snapper Creek Wellfield & Wellfield & Wellfield & Wellfield & Wellfield Wellfields & Wellfield Miami-Dade Water and Sewer Department Water & Wastewater Treatment Facilities Miami-Dade County in Cooperation with the US Geological Survey has one of the most technically advanced monitoring network for Salt Water Intrusion in the World Climate change and SLR assessment is now a critical component of Water and Sewer Department (WASD) planning CDWWTP Storm Tide Analysis CDWWTP is in Flood Zone AE (10) Effective Water Treatment Plant operations require proper control of flooding from both stormwater and tidal sources 1) background information on the site stormwater and tidal conditions 2) projections of potential increases in sea levels 3) potential ranges of effects on the WTP stormwater management system, and site grading considerations and access for proper operations. S-21 salinity control structure SLR based on USACE guidance document 50 year: 0.57, 1.05, 2.55 ft Results: Designed at 9 ft NAVD • Well above peak stage of C-1 Canal for a 100-year rainfall event at existing tide levels and the high projections of SLR http://pubs.er.usgs.gov/publication/sir20145162 http://pubs.usgs.gov/tm/6a50/ Average water-table drawdown and interface position Increased sea level Scenario 2 & Wellfields Northwest Wellfield Miami Springs Wellfields West Wellfield & Wellfield South West Wellfield Snapper Creek Wellfield & Wellfield & Wellfield & Wellfield & Wellfield Wellfields & Wellfield Miami-Dade Water and Sewer Department Water & Wastewater Treatment Facilities Extensive instrumentation in wellfield: Groundwater levels at all depths Pressure in production wells Temperature and flow data in wells and canal Evapotranspiration, precipitation and atmospheric gas data Summary of Wellfield Optimization, Drainage, and Storm Surge Components of Integrated Proposal Optimize wellfield operations based on environmental and operational criteria, including potential future scenarios Delineate drainage structure characteristics that affect rainfall-runoff process Determine potential effects of storm events and storm surge on coastal canals and county facilities SLOSH D ra in ag e S tru c tu re /A re a H y d ro lo g y D ata B IS E C T S L R an d S to rm M o d el M u ltiv aria te A n a ly s is S M H S m a ll-S ca le M o d el D e lin e a te R u n o ff/D ra in a g e W e llfield O p tim iz a tio n U n d er C lim a te Va riab ility D e te rm in e E ffec t o f S L R a n d S to rm S u rg e R e p re se n t P o te n tia l S M H W e llfie ld E ffe c ts Numerical Tools • UMD model with SWR package canal and control structure operations and groundwater • BISECT model with SWIFT2D hydrodynamic coastal flow and groundwater • South Miami Heights smaller-scale model with URO surface-drainage and wellfield effects • SLOSH models of storm surge dynamics but no groundwater • GWM Groundwater Management Process solves several types of groundwater management formulations to optimize stresses such as wells. Task 1: Data Collection • Suite of measurements to define hydrology of South Miami Heights area (see main description) • Drainage data collected including depths in drainage structures, isotope and VOC data, rainfall, and flows in canals • Provides necessary information for small-scale model develpement With the study of hydrology for the planned South Miami Heights Wellfield, investigating the runoff and stormwater drainage process involves much of the same field data and computer modeling The drainage system predominantly involves on-site drainage with some connectivity to the canal system Synoptic measurement of water levels in catch basins will be made periodically, after storm events and subsequent periods. Water samples will also be collected for isotope, VOC, and pesticide analysis. Resources are conserved by combining the drainage information with the monitoring of canal flows and groundwater levels to support the numerical model of the drainage and groundwater flow evapotranspiration rainfall surface water control structure direct runoff retention pond control structure Impervious Area seepage to canals culvert infiltration The numerical model will utilize the MODFLOW groundwater code and the Urban RunOff (URO) package to represent the system. It serves the purpose of representing the system for both the potential for wellfield withdrawals and delineating the rainfall-runoff-drainage process. 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Products: Drainage Study Monitoring results and information that can be used to evaluate the current drainage scheme in the study area and develop drainage criteria. • A small-scale numerical model to represent drainage in the study area and test proposed modifications to the system • A statistically-derived rainfall-runoff formulation that can be applied to different drainage basins to make stand-alone computation or utilized in a larger-scale hydrologic model • Better-informed rainfall-runoff representations in hydrologic models of South Florida areas and higher confidence in simulations of storm effects. • USGS Scientific-Investigations Report documenting the integration of the field data, statistical analyses, and numerical modeling along with a complete description of the developed rainfall-runoff formulation. • Task 2: Local-scale model of drainage/recharge in South Miami Heights area • MODFLOW-based groundwater model with Urban RunOff (URO) module to represent drainage • Integrates drainage data and other hydrology • Simulating the localized effects of storm events • Tool to represent operations of future wellfield and effects Task 3: County-scale well field optimization using existing integrated County model • Use of operating rules for canal-control structures • Utilizing GWM to optimize wet-season ground-water withdrawals for ASR under varied climatic conditions • Representation of storm impact effects during optimization Task 4: Development of storm surge model using BISECT and SLOSH • Current hydrodynamic representations of storm surge in BISECT can use SLOSHgenerated surge-wave momentum • BISECT simulation determines long-term impact on surface-water and groundwater salinity • Combination of SWR for the canal effects and SWIFT2D for the overland hydrodynamics of the storm surge • Windfield, storm surge, and rain from day of Great Miami Hurricane applied to September 18, 1996 • Comparison of hydrologic effects made to Hindcast simulated Great Miami Hurricane • 1926 simulation with Great Miami Hurricane repeated with 1996 sea levels S a lin ity in P S U G re a t M ia m i H u rrica n e in 1 9 2 6 G re a t M ia m i H u rrica n e in 1 9 9 6 G re a t M ia m i H u rrica n e in 1 9 2 6 w ith M o d e rn S L Salinity and inundations before and after hurricane Inundation increase for storm in 1926 is 24,374 acres Inundation increase for storm in 1996 is 20,609 acres However, the 1996 simulation started with 4522 acres more inundated than the 1926 simulation and ended with 757 more acres inundation UTM Easting, in meters 480000 500000 520000 540000 560000 580000 2860000 30 2840000 25 20 15 10 2820000 5 0 2800000 2780000 1926 1996 Difference in salinity induced by hurricane The recent storm with higher sea level brought more salinity on the eastern side Change in salinity, PSU UTM Northing, in meters 35