HEC Software and FEMA Submittals

Transcription

1 HEC Software and FEMA Submittals EWRI Workshop HEC Users Conference Larry Voice Risk Analysis FEMA Region VI April 12, 2010

2 Overview Flood Hazard Analysis Overview of Map Changes Accepted Model List Guidance Common submittal challenges Technical Issues With Models Submittal Completeness Map Modernization to 2

3 Flood Hazard Analysis Revisions Failing to keep pace with the changing and dynamic nature of watersheds ultimately leads to unwise decisions that place homeowners and communities at increased risk of flooding. 3

4 Flood Hazard Analysis Revisions If your community s FIRM panels require update: Letters of Map Change Letters of Map Amendment (LOMA) Letters of Map Revision (LOMR) Physical Map Revision Appeals/Protests Restudy Revisions to the FIRM panels require technical supporting data Hydrologic Modeling Hydraulic Modeling 4

5 Consequences of Incomplete/Incorrect Submittals Incomplete/Incorrect Submittals Increase chances submittal will be rejected Increase time to receive change For CLOMR and LOMR FEMA will notify requester and community within 60 days if more data required FEMA provides a LOMR or CLOMR or other written determination within 90 days from the last piece of information received May lead to additional fees 5

6 Accepted Model List : Hydrology Single Event HEC-1 (Versions and up) HEC-HMS (Versions 1.1 and up) Continuous Event HEC-HMS (Versions 3.0 and up) 6

7 Accepted Model List : Statistical For Gage Analysis HEC FFA (Version 3.1) Flood Frequency Analysis Bulletin 17B analysis prevent/fhm/en_stat.shtm 7

8 Accepted Model List : Hydraulics One-Dimensional Steady Flow HEC-2 (Version 4.6.2) HEC-RAS (Versions and up) One Dimensional Unsteady Flow HEC-RAS (Versions and up) UNET (Version 4.0) Two-Dimensional Steady/Unsteady Flow Models TABS-RMA2 (Version 4.3) TABS-RMA4 (Version 4.5) 8

9 Accepted Models 9

10 Common Submittal Challenges Common Technical Issues With Models Ineffective Flows Split Flows X-Sections Model Calibration Tie-Ins Floodways Other Common Submittal Issues All Necessary Models Not Included Topographic Data Notices to Affected Landowners 10

11 Common Technical Issues Ineffective Flow Not Considered at Upstream and Downstream Faces of Bridges and Culverts Split Flows Incorrectly Modeled Separate x-sections needed for each channel Discharges should be adjusted through iterative process X-Sections Too Far Apart Frequently See X-Section 2000 or 4000 feet apart For some applications this is fine, but not for FEMA flood insurance studies X-Sections Do Not Contain Flow X-Sections Not Surveyed 11

12 Common Technical Issues Model Calibration Model are should be calibrated if practical Hydrology is usually calibrated. Hydraulics are rarely calibrated. Don t adjust parameters to values outside of normal range Need to investigate why model is giving poor results 12

13 Common Technical Issues Tie-Ins Models must tie into the effective BFE within 0.50 Match within 0.10 preferred. Must tie in visibly, using available topography as a guide. A 90 bend at the property line is not acceptable Model far enough to achieve both tie ins, regardless of how long the model must be. Duplicate effective, corrected effective, existing, and proposed conditions model should agree at a common crosssection near the limits of your models. Otherwise - probably have not a satisfactory tie in. 13

14 Tie-Ins 645 TIE-IN POINT REVISED AREA 640 EFFECTIVE 100-YEAR PROFILE 635 AS-BUILT 100-YEAR PROFILE 630 TIE-IN POINT 625 M STREAM DISTANCE IN FEET ABOVE CONFLUENCE WITH CREEK 14

15 Floodways Observe equal conveyance reduction criteria (Method 4) Rerun floodway with final limits set using Method 1 to ensure a hydraulically smooth floodway boundary Use correct maximum floodway surcharges Floodway must be contained within SFHA Floodway can not be within the channel banks or inside levees Retain existing floodway where possible 15

16 Incorrect Hydraulic Model Submittal If the effective model will be changed via the LOMR process a number of models are required to be submitted. Effective Model Duplicate Effective Recreation of the Effective Model Corrected Effective Corrections to Effective Model Existing Conditions Additional XS, updated flow, structures not previously included Proposed or As-Built Hydraulics. 16

17 Common Issues With Topographic Workmaps No contours provided Too few cross sections used or shown on map Physical features shown but not modeled (or vice versa) Floodplain or Floodway Incorrectly Drawn 1% annual chance floodplain is delineated inside floodway Floodplain boundaries not consistent BFE Floodplain delineation inconsistent with topography Floodway width not consistent with information shown in model or Floodway Data Table 17

18 Notifications Community acknowledgement for ALL affected communities A letter stating all communities affected by floodway changes will adopt and enforce the new floodway Evidence of property owner notification for any increase in WSEL, SFHA or any change in the floodway delineation 18

19 Additional Guidance And Tools Guidelines and specifications for Flood Hazard Mapping Partners Volume 2: Map Revisions and Amendments Appendix C: Riverine Analysis and Mapping Procedure Memorandums Check-2 and Check-RAS What s New In Flood Hazard Mapping 19

20 Final Thought Ongoing MT-2 Applications In Region 6: Arkansas 10 Louisiana 3 New Mexico 10 Oklahoma 22 Texas

21 Map Modernization to Map Modernization used increasinglyavailable technology to increase the quality, reliability, and availability of flood hazard maps and data It focused on digitizing maps to provide timely, accurate information to community planners further enhances the maps, involves communities during the assessment and planning stages, and guides and encourages them to communicate risk to their constituents 21

22 Risk Mapping, Assessment, & Planning Through collaboration with State, Local, and Tribal entities, will deliver quality data that increases public awareness and leads to action that reduces risk to life and property. 22

23 : Project Planning Quality Data Topographic information is needed to produce studies in Awareness and Understanding of Local and State needs CNMS Review of National HAZUS Level 1 Run Forecasted for April 2010 Review of current Mitigation Plans for potential projects, review grant opportunities 23

24 : Project Planning Focus Areas 2010 Coastal, Levee and Other Engineering Funding will be based on Trifecta Risk + Need + Elevation Data Focus Areas 2011 Funding will be based on Superfecta Risk + Need + Elevation Data AND Partner Contribution 24

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