Base Level Engineering Elizabeth Savage, RPML, H2O Partners Diane Howe, FEMA Region 6. May 4, 2017

Transcription

1 Base Level Engineering Elizabeth Savage, RPML, H2O Partners Diane Howe, FEMA Region 6 May 4, 2017

2 What is Base Level Engineering Measuring stick to allow FEMA to assess its current flood maps. Cursory engineering analysis to provide predicted areas of flood risk. Flood risk data that provides a platform for broader risk communications. Engineering modeling that may be used and leveraged by local communities to review effect of development in and around the floodplain. 1

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4 Base Level Engineering 1D Inventory Mileage Current (CNMS) 5,403 New (BLE) 2,355 Total 7,

5 Base Level Engineering 2D Three HUC8 Watersheds Low lying & complex hydraulics 2D Analysis 4 Region 6 works with State CTP partners to select modeling analysis approach

6 5 So What?

7 Region 6 CNMS Validation Status 6

8 It takes a village Internal FM&I Internal MSC SHMO Local Staff Internal Outreach USGS Internal MSC NFIP Coordinators CTPs USACE NWS Internal External Affairs Internal HMA Internal Risk Analysis Building Inspectors FMAs Local Planner 7

9 Region 6 Base Level Engineering 8

10 What is Base Level Engineering Minimum Data Purchase Hydraulic Modeling (10%, 4%, 2%, 1%, 1%+, 1%-, and 0.2%) 10%, 1% and 0.2% Floodplains 1% and 0.2% Water Surface Grids 1% and 0.2% Flood Depth Grids Hazus Level 2 9

11 Flood Inventory Maturity Flood prone, No SFHA Determined 4M miles of stream with a drainage area of 1 square mile or larger Current inventory is approximately 1.2M miles Numerous participating NFIP communities have no flood data Paper Inventory, Minimal SFHA Available 92% of population initiated Map Modernization project 62% of contiguous 48 states land mass was modernized 20% of existing inventory remains unmodernized Modernized FIRM, Miles Not Model Backed Flood prone areas with an identified SFHA, identified on modernized digital FIRM Technical data is lacking to back-up SFHA depicted on the FIRM Areas may be detailed or approximate study methods, engineering library no longer has technical data Modernized FIRM, Model Backed on LiDAR Current standard of FEMA s mapping program Tier 3 miles are identified on a modernized digital FIRM (available in database format) Analysis is supported by high quality topography and recent engineering analysis. Multiple flow frequencies and water-surface elevations are readily available for release Risk Based Analysis, Climate Informed Science Tier 4 areas represent an upgrade of information where the current flood hazard conditions have been analyzed and consideration for future conditions 10 have beendeveloped. These areas consider the consequences of the hazard to specific locations, such as structures, and the flood risk of the area can be understood.

12 Base Level Engineering is a Mindset Without data, how can communities make informed decisions? 11

13 Base Level Engineering is a Mindset Base Level Engineering results are available through the Estimated BFE Viewer. 12

14 Base Level Engineering is a Mindset Data visualization opens the conversation. 13

15 Base Level Engineering is a Mindset Detailed w/ Floodway Detailed Study Limited Detail Study Base Level Engineering Scalable models allow communities to maintain the inventory. 14

16 Base Level Engineering This approach teams: + High resolution ground elevation data + Regression equation based hydrology + Highly automated hydraulic modeling + Lessons learned in Map Modernization + Cross-section location and orientation review + Structure cross-sections included in modeling To create: + Baseline models equivalent to Zone A floodplains 15 + Scalable models that can be further refined

17 Refinement of Base Level Engineering Dams & Reservoirs (Before Overtopping) Base Level Engineering Refined Modeling Effort Water in model will stack up on the back of the dam Water will have to overtop the dam in order to have water and flow on the other side Larger floodplain upstream, smaller floodplain downstream Livestock ponds and Gravity dams (update unnecessary) 16 Water will stack up until it can flow into the outlet structure Water in model will be able to flow on the downstream side of the dam earlier Smaller floodplain upstream, LARGER floodplain downstream Rating curves, outlet as-builts and surveys assist this data entry

18 Refinement of Base Level Engineering Culverts Base Level Engineering Water in model will stack up on the back of the culvert crossing Water will have to overtop the culvert crossing in order to have flow on the other side Larger floodplain upstream, smaller floodplain downstream Small culverts (designed for 10, 25 yr event) will be significantly overtopped during 1% event 17 Refined Modeling Effort Water will stack up until it is able to enter the culvert Water in model will be able to flow on the downstream side of the structure earlier Smaller floodplain upstream, LARGER floodplain downstream Rating curves, outlet as-builts and field surveys assist the data collection and entry

19 Base Level Engineering When should we do it? BLE HERE No Additional Mapping: Local support for adoption of BLE information FIRM Map BLE Data (Zone A): FIRMs can be produced immediately following Discovery Refined Engineering & FIRM Update: Lengthens time to prelim, allows detailed studies 18

20 Does BLE replace our current FIRMs? Base Level Engineering (BLE) information does not replace your current Flood Insurance Rate Map (FIRM) This information can be adopted by locals without any FIRM The BLE results may be used in areas where no flood hazard information is shown on your FIRM Where BLE is similar OR more conservative it may be used to provide Estimated Base Flood Elevations to residents Where BLE is smaller than current FIRM, BLE should NOT be used to provide Estimated Base Flood Elevations Data may be used for local planning 19 purposes

21 Base Level Engineering Creates Scalable Flood Hazard Modeling 60.3a 60.3b 60.3c 60.3c & 60.3d No FIRM Large Scale Automated Engineering Non-Regulatory Base Level Engineering Regulatory Zone A (no structures) Limited Detail (Limited structure info) Detailed & with Floodway (Detailed Structure Information) Highly automated modeling, no cross-section review. Used for CNMS Review ONLY 20 Difference between BLE & Zone A is minimal Community test-drive Top of Road and stream invert based on LiDAR, Culvert size, type grouping based on visual inspection Detailed structure input based on asbuilt drawings or field survey. Floodways can be added to assist development regulation

22 Base Level Engineering Release Strategy Base Level Engineering Reviewed by Community Community adoption and use of Base Level Engineering for planning and floodplain management purposes Discovery meeting held to identify projects moving forward Select Zone A mileage moves unmapped/unmodernized 21 Counties/parishes to digital FIRMs Goal: Provide a flood hazard maps to support local floodplain management in an efficient manner Create Digital FIRMs for: - Current CNMS Inventory - Significant areas of change - Current/Future Development Areas - Other areas selected with input from community Paper Inventory Reduction Projects

23 Why? Zone A Maps First? Community Based Maps 22 County/Parishwide Maps

24 Base Level Engineering Release Strategy Modernized FIRM with stream coverage identified by FEMA and community input (Zone A model backed) & Base Level Engineering data Structure or other model refinement to raise above Zone A on FIRM Model refined to include development activity 23 Goal: Ownership at local level for FIRM maintenance & coordination for update LOMRs used to: - Include development changes within community - Raise level of detail above Zone A Physical Map Revisions are also possible in the Risk MAP process to provide additional detail

25 Where Modernized Countywide Maps Exist Stream not included in current FIRM Zone X Stream included in current FIRM Zone A Stream included in current FIRM Zone AE Stream included in current FIRM Zone AE w/ Floodway BLE Information: - May be refined (structures added) and submitted via LOMR to update FIRMs and include Zone AE (limited detail) for stream in question. - Local adoption is advantageous for floodplain mapping purposes, use data for hazard mitigation planning and other local planning purposes. BLE Information: - May be refined (structures added) and submitted via LOMR to update FIRMs and elevate existing Zone A to Zone AE (limited detail) on current FIRM. - May only be used locally if BLE floodplains are MORE conservative than the current FIRM panel. - May be used for BFE estimation if similar to effective FIRM BLE Information: - Should be reviewed in detail by community prior to use, review flow information, add structures to BLE modeling, review resultant floodplains against current FIRM. - Communities should use caution when reviewing BLE information in detailed study areas, use BLE models as a building block and add detail to review current flood risk BLE Information: - Must be elevated to a study level that includes floodway analysis, can be submitted through LOMR process to update FIRMs 24 - Communities should use caution when reviewing BLE information in detailed study areas, use BLE models as a building block and add detail to review current flood risk

26 PRELIMINARY ISSUANCE EFFECTIVE ISSUANCE EFFECTIVE ISSUANCE Future Study Timelines Enhanced LOCAL LOMR SUBMITTAL TO UPDATE FIRM BLE info available LOCAL MODEL REFINEMENT LOMR REVIEW PRELIM TIME (months) DISCOVERY RISK IDENTIFICATION PRELIM POST PRELIMINARY LFD FEMA INITIATES FLOOD RISK PROJECT TO UPDATE FIRM CCO MEETING APPEAL & COMMENT 25

27 Watershed Hydrology Assessments Trinity River Basin 26

28 Base Level Engineering Unlocking the Power of the BLE Datasets We wont get anywhere if we approach things like this We need more of this 27

29 Our Vision for Communities 28

30 Base Level Engineering Unlocking the Power of the BLE Datasets Public outreach and communication Updating local mitigation plans Taking mitigation action Community planning Response and recovery The REAL power comes from combining with local data parcels, buildings, and critical facilities! 29

31 Base Level Engineering Unlocking the Power of the BLE Datasets 30

32 Base Level Engineering Unlocking the Power of the BLE Datasets 31

33 Base Level Engineering Unlocking the Power of the BLE Datasets Higher Standards Possibilities Freeboard Grids 32

34 Base Level Engineering Unlocking the Power of the BLE Datasets Higher Standards Possibilities Freeboard Grids 33

35 Practical Uses for Flood Risk Products 34

36 What comes next? 35 Slide credit: David Key, ESP Associates

37 Questions? 36