Sediment Transport Through Lake Clarke and Lake Aldred

Topics • Introduction and Background • Study Goals • Model Development • Model Calibration

Introduction and Background • Recent Interest in the Lower Susquehanna River Reservoirs ü Dynamic

Introduction and Background • Safe Harbor Dam ü Constructed 1931 ü 75 feet tall,

Study Goals • Develop unsteady, 1 D sediment transport model ü Marietta, PA to

Study Goals – Model Improvements • Improve upon past studies using U. S. Army

Model Boundary Conditions and Setup • Geometric Data • Flow & Temperature Data •

Model Calibration and Verification • Hydraulic Calibration at Marietta, PA • Sediment Volume Change

Model Calibration and Verification (2) • Sediment Transport Calibration ü January 2008 – August

Summary of Results and Limitations • Additional Runs ü Historical flow events applied to

Summary of Results and Limitations (2) • Model Limitations ü One-dimensional model cannot replicate

Summary of Results and Limitations (3) • Rating Curve Limitations ü Hysteresis and variance

Conclusion • 1 D HEC-RAS 5. 0 sediment transport model as part of multi-model

Questions? Holtwood Dam, September 10, 2011 (The. Gates 1210 on You. Tube) 13

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Sediment Transport Through Lake Clarke and Lake Aldred Jon Viducich, EI Martin J. Teal, PE, PH, D. WRE April 5, 2017 Preliminary Data – Subject to Revision

Topics • Introduction and Background • Study Goals • Model Development • Model Calibration and Verification • Summary of Results and Limitations • Conclusion 1 Preliminary Data – Subject to revision

Introduction and Background • Recent Interest in the Lower Susquehanna River Reservoirs ü Dynamic equilibrium ü Potential impacts on Chesapeake Bay water quality ü Past studies Lake Clarke Lake Aldred Conowingo Reservoir Figure 1 -2 from Lower Susquehanna River Watershed Assessment (2015) 2 Preliminary Data – Subject to revision

Introduction and Background • Safe Harbor Dam ü Constructed 1931 ü 75 feet tall, impounds Lake Clarke (7, 360 acres) • Holtwood Dam ü Constructed 1910 ü 55 feet tall, impounds Lake Aldred (2, 400 acres) Safe Harbor Dam, October 24, 2010 (U. S. C. G. Aux 5 DNR on Flickr) 3 Preliminary Data – Subject to revision Holtwood Dam, December 2015 (http: //suereno. blogspot. com)

Study Goals • Develop unsteady, 1 D sediment transport model ü Marietta, PA to Holtwood Dam (20. 4 miles) • Aid in parameterization of Chesapeake Bay Watershed Model • Input for HDR model of Conowingo Pond 4 Preliminary Data – Subject to revision

Study Goals – Model Improvements • Improve upon past studies using U. S. Army Corps of Engineers HEC-RAS 5. 0 Model (unsteady) ü Solves the unsteady flow equation, routing flow and explicitly accounting for storage and travel time ü Conserves volume, important in reservoir systems ü Cohesive and non-cohesive sediments Figure 17 -1 HEC-RAS Version 5. 0 User’s Manual (2016) 5 Preliminary Data – Subject to revision

Model Boundary Conditions and Setup • Geometric Data • Flow & Temperature Data • Sediment Data Safe Harbor Dam ü Bed sediment (12 size classes) ü Inflow loads • Transport Function • Sediment Parameters • Dam Operations ü Rating curves 6 Preliminary Data – Subject to revision Holtwood Dam

Model Calibration and Verification • Hydraulic Calibration at Marietta, PA • Sediment Volume Change ü 2008 -2013 (calibration) ü 2013 -2015 (verification) 7 Preliminary Data – Subject to revision

Model Calibration and Verification (2) • Sediment Transport Calibration ü January 2008 – August 2013 ü Several large events, including Tropical Storm Lee • Sediment Transport Verification ü August 2013 October 2015 ü Unusually low flows 8 Preliminary Data – Subject to revision Observed vs. Modeled Cumulative Volume Change: Lake Clarke Sub-Areas 1 -5, January 2008 – October 2015 Observed vs. Modeled Cumulative Volume Change: Lake Aldred Sub-Areas 3 -6, January 2008 – October 2015

Summary of Results and Limitations • Additional Runs ü Historical flow events applied to end of simulation • Results Increased transport on rising limb Decreased transport on falling limb 9 Preliminary Data – Subject to revision

Summary of Results and Limitations (2) • Model Limitations ü One-dimensional model cannot replicate two-dimensional processes ü Uncertainties in input data (geometry, flow, sediment) and calibration data (measurements) ü Lack of actual dam operation data ü Lack of extreme (>700, 000 cfs) events during simulation/measurement periods Sediment Loading (tons/d) Marietta, PA Sediment Loading 10, 000 1, 000 100, 000 10, 000 Obs Data 1, 000 HEC-RAS Initial Values 100 10 1, 000 100, 000 Discharge (cfs) 10 Preliminary Data – Subject to revision

Summary of Results and Limitations (3) • Rating Curve Limitations ü Hysteresis and variance at large discharges limits rating curves’ usefulness during extreme events ü Mass balance suggests better representation for Lake Clarke than Lake Aldred 11 Preliminary Data – Subject to revision

Conclusion • 1 D HEC-RAS 5. 0 sediment transport model as part of multi-model study • Applied inputs to model sediment change 2008 -2015 • Calibrated model successfully simulated bed changes • Results used to develop sediment rating curves for other researchers 12 Preliminary Data – Subject to revision

Questions? Holtwood Dam, September 10, 2011 (The. Gates 1210 on You. Tube) 13