SMART Planning Utilizing Risk Assessment Methodologies for Public Safety and Flood Risk Management

Transcription

1 SMART Planning Utilizing Risk Assessment Methodologies for Public Safety and Flood Risk Management Brian Harper USACE, Institute for Water Resources Jason Needham Risk Management Center US Army Corps of Engineers

2 Today s Agenda Risk Assessment concepts Public Safety and Planning What Metrics Should be Used? How are the metrics generated? Examples More info in Dam Safety Reg ER ions/er_ pdf (Ch 2&5 for concepts, Ch 3 for risk assessments, Ch 9 for modification studies) 3 3

3 What is a Risk Assessment? An approach to quantifying and describing the nature, likelihood, and magnitude of risk HAZARD (What can cause harm?) PERFORMANCE (How will the system react?) EXPOSURE (Who and What can be harmed?) VULNERABILITY (How susceptible to harm?) CONSEQUENCE (How much harm?) INUNDATION RISK (Likelihood and severity of adverse consequences) 4 4

4 Risk Analysis 3 Integral Parts RISK ASSESSMENT Technical Analysis RISK MANAGEMENT Decision Making and Societal Values RISK COMMUNICATION 5

5 Risk Assessment 4 Questions What can go wrong? How can it happen? What is the likelihood? What are the consequences? Helps to answer the risk management question: What are the best options for reducing the risk? 6 6

6 Risk Assessments in the Safety Programs The Dam and Levee Safety Programs use scalable risk assessments Typically three levels of rigor Screening level assessment (equiv to Recon) Issue evaluation (equiv to Recon, early feas) Modification Study (equiv to feasibility level) 7 7

7 Planning and the Safety Programs From February webinar 11 dam safety modification studies (DSMS) in progress 53 in Issue Evaluation Many of these 53 will lead to modification studies (DSMS) Similar needs in levee portfolio (2700 segments of concern) 2,500 M 2,000 M 1,500 M 1,000 M 500 M $2B projects in USACE Dam Safety Portfolio - 11 Dam Safety Modification Studies (DSMS) currently underway - 53 Projects currently in the Issue Evaluation Study phase, many of which will move on to DSMS phase 0 M FY13FY18FY23FY28FY33FY38FY43FY48FY53FY58 8 8

8 Risk Metrics and Public Safety Good Expected annual life loss Expected annual damages Individual risk Not So Good Life loss (single event) Damage (single event) Performance or condition Population at risk Evacuation routes Average depth Etc 9 9

9 A Note About Population at Risk Commonly discussed in FRM reports Population of the area is often used as metric Not very helpful in evaluation and comparison between plans or between with- and without The procedures and tools of the safety programs help to define the factors that put the population at risk 10 10

10 Life Loss vs. PAR 11 11

11 For formulation Why is that important? What factors drive safety risk for the population? Failure modes probability, location, time to progress Population - location, density, demographics Warning times, response, and evacuation capacity For comparison, selection & justification What is the difference in effectiveness between plans? What are the incremental costs and benefits? 12 12

12 How do we Compute Life Risk (and use that information to make decisions)? Screening Levee Screening Tool Decision - Initial Risk Characterization (LSAC) Issue evaluations and Mod studies Potential Failure Modes Analysis Brainstorming with the right people in the room Event-based risk engines Event-tree risk assessments or HEC-WAT/FRA Decision - Tolerable risk framework 13 13

13 Screening 1.E+00 1.E-01 Likelihood of Breach 1.E-02 1.E-03 1.E-04 1.E-05 1.E-06 1.E Average Life Loss 14 14

14 Life Safety Risk Nonstructural Contributors 100% 90% 19% 6% 16% 80% 35% 70% 60% 37% 46% Unacceptable Minimally Acceptable Acceptable 50% 40% 30% 20% 44% 59% 38% 10% 0% Evacuation Planning Community Awareness Flood Warning Effectiveness 15

15 Event-Tree Risk Assessments 16

16 HEC-WAT/FRA (Watershed Analysis Tool) A planning tool for reconnaissance and feasibility studies; incorporates social and environmental consequences. Integrates existing event-based models (hydrologic, hydraulic, consequence, etc) FRA compute option applies the Monte Carlo simulation & allows for a life-cycle type computation of consequences (economic and lossof-life) and associated performance indices. 17

17 USACE Life Loss Estimation Methods Decision Driven Screening - Minimal resource requirement Dams - Modified USBR Method Screening - Simplified Jonkman s Method HEC-FIA Screening validation, CIPR, issue evaluation and periodic assessments - Moderate resource requirement LifeSim Same as HEC-FIA, evac. modeling - Larger resource requirement Scalable methods effort from one applicable to more rigorous method 18

18 Life Loss Estimation Essential Elements Initial distribution of people Redistribution of people Warning Evacuation Effectiveness Response Evacuation potential Flood characteristics Arrival time, depth, velocity Shelter provided by final location Fatality rates 19

19 Flow into leveed area Breach prior to OT (50-75% load) Full Breach Collapse of Embankment Failure mode initiates Intervention Attempted Voluntary Warning Issuance Mandatory Warning Issuance Muddy flow observed 0-4 hrs 0-2 hrs 1% - 25% 20 evac Best = 5% Time 60-80% >=95% evac PLANNING evac SMART Best <5% = knuckleheads 70%

20 Tolerability of Risk (TRG) f, Probability of Failure 1.E-01 1.E-02 1.E-03 1.E-04 1.E-05 1.E-06 1.E-07 1.E-08 Dallas Floodway - West Levee PFM 2 West - Overtopping PFM 8 West - Heave PFM 7 West - Internal Erosion PFM 13b - Progressive Instability Societal Tolerable Risk Limit Risks are tolerable only if they satisfy ALARP requirements ,000 10,000 N, Number of Fatalities Risks are unacceptable, except in exceptional circumstances Risks may be unacceptable or tolerable, but will be examined thoroughly and must at a minimum satisfy ALARP requirements Risks that are Commensurate with Benefits Risks that Society does not believe are negligible Risks that owners keep under review Risks that are reduced further if warranted (ALARP) 21

21 Questions? Type questions in the chat box. We will answer as many as time allows. POC s for Risk Assessments: Jason Needham, RMC jason.t.needham@usace.army.mil Tim Smith, LRH and MMC timothy.l.smith@usace.army.mil POC s for Planning: Brian Harper brian.k.harper@usace.army.mil Maria Wegner-Johnson maria.m.wegner-johnson@usace.army.mil US Army Corps of Engineers