Martin Rule Curve Study Ashley McVicar, APC Maurice James, Water Resources Consulting LLC

Martin Rule Curve Study  Purpose Preliminary modeling study to determine the feasibility of a higher winter pool at Martin in accordance with MIG 3 Project Operations Study Plan. Preliminary modeling study to determine the feasibility of a higher winter pool at Martin in accordance with MIG 3 Project Operations Study Plan.

Martin Rule Curve Study  Design Flood Study Approach Determine historical flood event to model for the 100 year design flood Determine historical flood event to model for the 100 year design flood Replicate operations for the actual flood event in an operation spreadsheet Replicate operations for the actual flood event in an operation spreadsheet Evaluate a higher winter pool vs. baseline of elevation 480’ Evaluate a higher winter pool vs. baseline of elevation 480’ Compare Results Compare Results

“100 Year Flood”  Has a specific definition US Dept of Interior Bulletin 17B US Dept of Interior Bulletin 17B  Applied by Regulating Agencies (FEMA, COE, FERC, the States, etc.)  Frequency Analysis of Maximum Annual Flood Events.  1% chance of occurrence in each year.  Generally concerned with peak flow  For Reservoirs – volume also critical

How is this Analysis Done?  Select Maximum Flood Event for each year. Prefer 30+ year record. Prefer 30+ year record.  Apply a specific frequency analysis to data. COE Frequency Analysis program COE Frequency Analysis program Project to 1% probability of exceedence. Project to 1% probability of exceedence.

Monthly Analysis  Not an established procedure.  Referred to as a “Partial Duration” Only considering part of the record. Only considering part of the record.  Maximum event in month for the period of record.  Annual peak procedures may not apply.  Will still have a probability of exceedence but not necessarily 1%.

What does all this say?  There is a chance that the 100 year flood could occur in any month of the year.  The greatest chance would be during the months of Dec. through April.  Not necessary for the record to have an event near or greater than the 1% event.

Martin Rule Curve Study  APC Flood Frequency Analysis Model developed by COE – Hydrologic Engineering Center in Davis, CA Model developed by COE – Hydrologic Engineering Center in Davis, CA Utilizes the COE unimpaired flow database created as part of the ACT Comprehensive Study Utilizes the COE unimpaired flow database created as part of the ACT Comprehensive Study Submitted to the COE by APC in November 2005 Submitted to the COE by APC in November 2005

Martin Rule Curve Study  Martin flow 100 yr flow unregulated = 130,000 cfs-days 100 yr flow unregulated = 130,000 cfs-days March 1990 flow unregulated = 125,019 cfs- days (96% of 100 year flood) March 1990 flow unregulated = 125,019 cfs- days (96% of 100 year flood) March 1990 inflow regulated used in Martin Rule Curve evaluation (with Harris and Martin in place) = 92,307 cfs-days (71% of 100 year unregulated flood) March 1990 inflow regulated used in Martin Rule Curve evaluation (with Harris and Martin in place) = 92,307 cfs-days (71% of 100 year unregulated flood)

Basin Wide Rainfall

Current Martin Flood Control Guidelines Pre-Turbine Upgrades

Martin Rule Curve Study Post Turbine Upgrades  General Assumptions Martin Turbine Capacity = (based on upgrades completed in 2004) Martin Turbine Capacity = (based on upgrades completed in 2004) Yates Turbine Capacity = Yates Turbine Capacity = Thurlow Turbine Capacity = Thurlow Turbine Capacity = spillway gates 20 spillway gates Ability to open 2 spillway gates an hour Ability to open 2 spillway gates an hour

Martin Rule Curve Study  Design Flood Evaluation Operational criteria set forth in model accurately replicated historical conditions Operational criteria set forth in model accurately replicated historical conditions

Martin Rule Curve Study  Evaluation of Winter Pool of 480’ vs. 483’ Used current operational criteria set forth by March 1990 flood historical operations and began pool at both 480’ and 483’ Used current operational criteria set forth by March 1990 flood historical operations and began pool at both 480’ and 483’

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

Martin Rule Curve Study  Elevation 480’ vs 483’ Results Martin pool kept below top of easement elevation 490 for both Martin pool kept below top of easement elevation 490 for both Beginning winter pool elevation of 483’ results in earlier releases as well as approximately 25-30k higher discharge during the peak Beginning winter pool elevation of 483’ results in earlier releases as well as approximately 25-30k higher discharge during the peak  Resulting outflows passed downstream with HEC-RAS model

Martin Rule Curve Study  Results Elevations downstream result in a 1’ – 3’ higher elevation downstream to Alabama River. Elevations downstream result in a 1’ – 3’ higher elevation downstream to Alabama River. COE uses FEMA’s requirement of “no increase of peak elevation downstream” COE uses FEMA’s requirement of “no increase of peak elevation downstream” FERC defers to the COE for flood analysis FERC defers to the COE for flood analysis FERC would require a full analysis of flood, environmental and recreational impacts of proposed vs. current operation FERC would require a full analysis of flood, environmental and recreational impacts of proposed vs. current operation

Martin Rule Curve Study  Further Study during Relicensing Required MIG 3 proposals evaluated MIG 3 proposals evaluated Look at different winter pool elevation and/or shape of Rule Curve Look at different winter pool elevation and/or shape of Rule Curve Look at different operational plans Look at different operational plans Further evaluate downstream flood & environmental impacts and present these effects and associated mitigation measures to FERC Further evaluate downstream flood & environmental impacts and present these effects and associated mitigation measures to FERC FERC will then evaluate and balance all interests FERC will then evaluate and balance all interests