asdso 2015 ne jyoung
TRANSCRIPT
Small Wonder: Big on Dam Safety
Jeremy Young, PE Dave Twing, PE Jason Arndt, PEMay 13, 2015
Presentation Outline
Evolution of Dam Safety in DE DNREC/DelDOT Partnership DelDOT Dam Prioritization DE Dam Preservation Program Data Review CFD Pilot Project Recommended Modeling Approaches
#49!
1974
First Comprehensive Statewide Inventory by DNREC and University of Delaware
1978-1981
USACE Developed Initial DE NID Dataset
Conducted Phase I Inspections
State Dam Safety Legislation Introduced Never Passed
Dam Safety in DE
In the Beginning…
1998 FEMA NDSP Participation
1999UDWRA Formed
2000DNRECDam Safety Guidance Committee Formed
2000Dam Safety Law Introduced
Dam Safety Rumblings
Law Not Passed Due to Objections from Private Owners
2003 Revised Law Introduced
2004Dam Safety Law Passed!
2006Dam Safety Regulatory Advisory Committee Formed
2009Dam Safety Regulations Adopted!
Back to the Drawing Board
2003Records Pond Upgrading Design
2006 Evaluation of Haven and Silver Lake Dams
1999 Initial Inspections
of 10 High Hazard Dams
2008Update Statewide Inventory of Dams
Let’s Get to Work!Keep up the Good Work!
2009-2012 DNREC Contracts
4 Prime Consultants
42 Dams
Dam Inspections
37 Dams
Bathymetric Surveys
42 Dams
Sunny Day DBAs
11 Dams
H&H/IFAs
Abbotts Pond Dam Griffith Lake Dam
Emergency Dam Repairs
DNREC/DelDOT Partnership
2010
DelDOT began assisting with dam inspections
2011
First MOA between DNREC and DelDOT to share resources
Updated prioritization ranking for state-owned dams
DelDOT Dam Prioritization
Deficiency Point Formula and Index Factors
Deficiency Points
Risk Index Factors (55%)• Dam Characteristics• PAR
Conditional Index Factors (30%)• Physical Condition
Functional Importance Factors (15%)• Road Type• Avg Daily Traffic • Evacuation Route
Deficiency Point Index Factors
Embankment and Spillway
Condition Ratings
Annual Inspection
Spillway Capacity
PAR
Desktop Review/Update
Data Entry/Spreadsheet
Higher Score = Higher RiskResults Ranked
DelDOT Dam Prioritization Process
Planned Upgrading Projects
Hearns Pond Dam
Overtopped 2001/2006
Est. Constr. 2015
Records Pond Dam
High PAR
Est. Constr. 2017
Gated Spillway Improvements
Griffith Lake
Portsville Mill Pond
2013-2014: Program developed through 2nd MOA between DNREC and DelDOT
2014: DelDOT awarded 5-yr contract Evaluate 39 Dams Build upon work completed under 2009 DNREC
Contracts Dam Breach Analyses Incremental Flooding Analyses Inundation Mapping
Dam Preservation Program
2009-2012 DNREC Contracts
4 Prime Consultants
42 Dams
Dam Inspections
37 Dams
Bathymetric Surveys
42 Dams
Sunny Day DBAs
11 Dams
H&H/IFAs
Compiled/ReviewedReports/Data/Models/Etc.
Established 63 Unique H&H Related Fields
Developed Spreadsheet Database
Developed Summary Sheets for Each Dam
Assess Accuracy/Completeness of
Available DataAvoid Duplication of Effort
Critical First Step!
Data Review
Sample Summary Sheet
Sample Summary Sheet
Sample Summary Sheet
Sample Summary Sheet
Sample Summary Sheet
GIS Mapping Tool
Various H&H Models Hydrology: HEC-1 vs. HEC-HMS Spillway Modeling: HEC-1 SS/ST Cards, Rating
Curves, HEC-RAS Dam Breach Modeling: HEC-1 vs. HEC-RAS Flood Routing: HEC-RAS Unsteady
Data Acceptable for FY 2015 Dams
Data Review Findings
DELMARVA Unit Hydrograph Paxson & Welle (2006) Lag Time Method
Challenges with H&H Modeling in DE
Flatland Hydrology
Challenges with H&H Modeling in DE
Weir Submergence
Challenges with H&H Modeling in DE
Spillway Configurations
Challenges with H&H Modeling in DE
Breach Submergence
H&H Analyses – Common Tools
HEC-1
HEC-HMSEmpirical Deterministi
cHEC-RAS
1-DInundation
Map
Water
Hydraulic Structures
Dam Breaks
Coastal
River Hydraulics
Computational Fluid Dynamics
3D CFD Modeling for Spillways
Graphics courtesy of Schnabel Engineering and Flow3D
2D CFD Modeling
More detailed
Consider Breach Submergence
Consider Floodplain Storage
Graphics!!
CFD PILOT PROJECTSilver Lake DamMilford, DE
Silver Lake Dam
Pertinent Data
Silver Lake Dam
Parameter Silver Lake DamDrainage Area 27.8 sq. mi.Top of Dam (uneven) EL 12.8 ft to 13.5 ftMaximum Dam Height 13.5 ftDam Length 550 ftNormal Pool EL 5.9 ftNormal Pool Storage 116 acre-ftNormal Pool Area 32.2 acresTop of Dam (EL 13.0) Pool Storage 474 acre-ftTop of Dam (EL 13.0) Pool Area 59 acres
Sunny Day Breach Analysis (Pool @ TOD)
Spillway Discharge Rating Curve Developed in HEC-RAS/Steady Flow Considering Tailwater Effects
Breach Outflow Hydrograph Developed in HEC-1 and Included Tailwater Rating
Incremental Flooding Assessment Performed in HEC-RAS/Un-Steady Flow
Recommended SDF = 0.2 PMF
Silver Lake Dam
Previous Analyses (2006-2009)
3D CFD Spillway Model (2014)
Silver Lake Dam
3D CFD Results
3D CFD Results
Silver Lake Dam
CFD Model Estimated Higher Spillway Capacity than 2009 HEC-RAS
Spillway Modeled as XS, Inline Structures, Bridges in HEC-RAS
Interpolations between XS in HEC-RAS
Challenges Numerically Solving HEC-RAS Model
Different Equations Simulating the Flow
And Computing Tailwater Submergence
Differences in Spillway Ratings May Be Due To…
Silver Lake Dam
Variety of Acceptable Tools for Developing Spillway Ratings
Need Good Engineering Judgement and Understanding of Spillway
3D CFD Can Confirm Previously Developed Spillway Ratings
Particularly for Spillways Subject to Tailwater and Close to Bridges
Refinement of Spillway Rating May Reduce/Eliminate Costly Rehabs
3D CFD Conclusions
Silver Lake Dam
Dam Breach Modeling
Silver Lake Dam
Scenario AnalysisStarting Pool EL
(ft)
Peak Flow(cfs)
Peak Reservoir Elevation
(ft)
Inflow Outflow
0.2 PMF – Breach2009 HEC-1 5.9 4,710 7,170 15.5
2014 HEC-RAS 5.9 4,710 4,790 13.4• 2009 Analysis is conservative • Higher peak outflow computed by HEC-1 would produce a
larger inundation area• HEC-1 (emprical methods) has been superceded by HEC-
RAS (flood routing)
Flow-3D (Shallow Water Module)
GIS Data, Surveys, Site Plans
1.2M Cells/10-ft Grid
Scenarios
0.2 PMF No Breach
0.2 PMF Breach
Sunny Day Breach
Silver Lake Dam
2D CFD Flood Routing
More Detailed Results (vs. HEC-RAS)
More Robust Analysis (vs. Interpolated HEC-RAS XS)
Computed 0 to -3-ft Difference Depth (vs. HEC-RAS)
Smaller Inundation Areas
Longer Computation Time
May Not Be Appropriate/Efficient for IFAs
Could be Used to Refine Inundation Analysis to Better Define Hazards
Silver Lake Dam
2D CFD Results
Silver Lake Dam
Moving Forward - Update Previous Analysis
Model Dam Breach in HEC-RAS
‘Calibrate’ HEC-RAS Spillway Model to 3D CFD
Update IFA in HEC-RAS/Unsteady and Recommend New SDF
Depending on Results, Run 2D CFD for New SDF
Update Maps with Either HEC-RAS or CFD Result
Consider 3D CFD to Model Spillways Subject to Tailwater and Close to Bridges
Develop Breach Outflow Hydrograph in HEC-RAS
Perform Initial IFA with HEC-RAS/Unsteady
Consider 2D CFD for IFA on Case by Case Basis
Consider 2D CFD to Refine Inundation Limits and Estimate Potential Hazards
Recommended Modeling Approaches for Future Studies in DE
Questions/Comments?