ML15279A261
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SOCH MODEL 2.4A-1WATTS BARWBNP-1142.4A SOCH MODELNote: Appendix 2.4A contains information regarding the SOCH model that is used in Sections 2.4.4, 2.4.11, and 2.4.14.8.Runoff and Stream Course Model The runoff model used to determine Tennessee River flood hydrographs at Watts Bar Nuclear Plant is divided into 40 unit areas and includes the total watershed above Chickamauga Dam. Unit hydrographs are used to compute flows from the unit areas. The watershed unit areas are shown in Figure 2.4-9. The unit area flows are combined with appropriate time sequencing or channel routing procedures to compute inflows into the most upstream tributary reservoirs which in turn are routed through the reservoirs using standard routing techniques. Resulting outflows are combined with additional local inflows and carried downstream using appropriate time sequencing or routing procedures including unsteady flow routing. Unit hydrographs were developed for each unit area for which discharge records were available from maximum flood hydrographs either recorded at stream gaging stations or estimated from reservoir headwater elevation, inflow, and discharge data using the procedures described by Newton and Vineyard Reference 1. For non gaged unit areas synthetic unit graphs were developed from relationships of unit hydrographs from similar watersheds relating the unit hydrograph peak flow to the drainage area size, time to peak in terms of watershed slope and length, and the shape to the unit hydrograph peak discharge in cfs per square mile. Unit hydrograph plots are provided in Figure 2.4-10 (11 Sheets).
Table 2.4-13 contains essential dimension data for each unit hydrograph.
Tributary reservoir routings, except for Tellico and Melton Hill, were made using standard reservoir routing procedures and flat pool storage conditions. The main river reservoirs, Tellico, and Melton Hill routings were made using unsteady flow
techniques.Unsteady flow routings were computer solved with the Simulated Open Channel Hydraulics (SOCH) mathematical model based on the equations of unsteady flow Reference 2. The SOCH model inputs include the reservoir geometry, upstream boundary inflow hydrograph, local inflows, and the downstream boundary headwater discharge relationships based upon operating guides or rating curves when the structure geometry controls. Seasonal operating curves are provided in Figure 2.4-3 (12 Sheets).Discharge rating curves are provided in Figure 2.4A-11 (13 Sheets) for the reservoirs in the watershed at and above Chickamauga. The discharge rating curve for Chickamauga Dam is for the current lock configuration with all 18 spillway bays available. Above Watts Bar Nuclear Plant, temporary flood barriers have been installed at four reservoirs (Watts Bar, Fort Loudoun, Tellico and Cherokee Reservoirs) to increase the height of embankments and are included in the discharge rating curves for these four dams. Increasing the height of embankments at these four dams prevents embankment overflow and failure of the embankment. The vendor supplied temporary flood barriers were shown to be stable for the most severe PMF 2.4A-2SOCH MODEL WATTS BARWBNP-114headwater/tailwater conditions using vendor recommended base friction values. A single postulated Fort Loudoun Reservoir rim leak north of the Marina Saddle Dam which discharges into the Tennessee River at Tennessee River Mile (TRM) 602.3 was added as an additional discharge component to the Fort Loudoun Dam discharge rating curve. Seven Watts Bar Reservoir rim leaks were added as additional discharge components to the Watts Bar Dam discharge rating curve. Three of the rim leak locations discharge to Yellow Creek, entering the Tennessee River three miles downstream of Watts Bar Dam. The remaining four rim leak locations discharge to Watts Creek, which enters Chickamauga Reservoir just below Watts Bar Dam. The unsteady flow mathematical model configuration for the Fort Loudoun Tellico complex is shown by the schematic in Figure 2.4A-12. The Fort Loudoun Reservoir portion of the model from TRM 602.3 to TRM 652.22 is described by 29 cross sections with additional sections being interpolated between the original sections for a total of 59 cross-sections in the SOCH model, with a variable cross-section spacing of about 1 mile. The unsteady flow model was extended upstream on the French Broad and Holston Rivers to Douglas and Cherokee Dams, respectively.The French Broad River from the mouth to Douglas Dam at French Broad River mile (FBRM) 32.3 was described by 25 cross sections with additional sections being interpolated between the original sections for a total of 49 cross sections in the SOCH model, with a variable cross section spacing of about 1 mile. The Holston River from the mouth to Cherokee Dam at Holston River mile (HRM) 52.3 was described by 29 cross sections with one additional cross section being interpolated between each of the original sections for a total of 57 cross sections in the SOCH model, with a variable cross section spacing of about 1 mile.The Little Tennessee River was modeled from Tellico Dam, Little Tennessee River mile (LTRM) 0.3 to Chilhowee Dam at Little Tennessee River mile (LTRM) 33.6. The Little Tennessee River from Tellico Dam to Chilhowee Dam at LTRM 33.6 was described by 23 cross sections with additional sections being interpolated between the original sections for a total of 49 cross sections in the SOCH model, with a variable cross-section spacing of up to about 1.8 miles.Fort Loudoun and Tellico unsteady flow models are joined by an interconnecting canal. The canal was modeled using nine cross sections with an average cross section spacing of about 0.18 miles.The Fort Loudoun Tellico complex was verified by two different methods as follows:
Using the available data for the March 1973 flood on Fort Loudoun Reservoir and for the French Broad and Holston rivers. The verification of the 1973 flood is shown in Figure 2.4A-13 (2 Sheets). Because there were limited data to verify against on the French Broad and Holston rivers, the steady state HEC RAS model was used to replicate the Federal Emergency Management Agency (FEMA) published 100 and 500 year profiles. Tellico Dam was not closed until 1979, thus was not in place during the 1973 flood for verification.
SOCH MODEL 2.4A-3WATTS BARWBNP-114Using available data for the May 2003 flood for the Fort Loudoun Tellico complex. The verification of the May 2003 flood is shown in Figure 2.4A-14 (3 Sheets). The Tellico Reservoir steady state HEC RAS model was also used to replicate the FEMA published 100 and 500 year profiles.A schematic of the steady state SOCH model for Watts Bar Reservoir is shown in Figure 2.4A-15. The model for the 72.4 mile long Watts Bar Reservoir was described by 39 cross sections with two additional sections being added in the upper reach for a total of 41 sections in the SOCH steady state model with a variable cross section spacing of up to about 2.8 miles. The model also includes a junction with the Clinch River at Tennessee River mile (TRM) 567.7. The Clinch River arm of the model goes from Clinch River mile (CRM) 0.0 to CRM 23.1 at Melton Hill Dam with one additional section being interpolated between each of the original 13 sections and cross section spaces of up to about 1 mile. Another junction at TRM 601.1 connects the Little Tennessee River arm of the model from the mouth to Tellico Dam at LTRM 0.3 with cross section spaces of about 0.08 miles. The time step was tested between 5 and 60 seconds which produced stable and comparable results over the full range. A time step of 5 seconds was used for the analysis to allow multiple reservoirs and/or river segments to be coupled together with different cross section spacing. The verification of Watts Bar Reservoir for the March 1973 and the May 2003 floods are shown in Figure 2.4A-16 and Figure 2.4A-17, respectively. A schematic of the unsteady flow model for Chickamauga Reservoir is shown in Figure 2.4A-18. The model for the 58.9 mile long Chickamauga Reservoir was described by 29 cross sections with one additional section being interpolated between each of the original 29 sections for a total of 53 sections in the SOCH model with a variable cross section spacing of up to about 1 mile. The model also includes a junction with the Dallas Bay embayment at TRM 480.5. The Dallas Bay arm of the model goes from Dallas Bay mile (DB) 5.23 to DB 2.86, the control point for flow out of Chickamauga Reservoir. Another junction at TRM 499.4 connects the Hiwassee River arm of the model from the mouth to the Charleston gage at HRM 18.9. The time step was tested between 5 and 50 seconds producing stable and comparable results over the full range. A time step of 5 seconds was used for the analysis to allow multiple reservoirs and/or river segments to be coupled together with different cross section spacing. The verification of Chickamauga Reservoir for the March 1973 and the May 2003 floods are shown in Figure 2.4A-19 and Figure 2.4A-20, respectively.Verifying the reservoir models with actual data approaching the magnitude of the PMF is not possible, because no such events have been observed. Therefore, using flows in the magnitude of the PMF (1,200,000 - 1,300,000 cfs), steady state profiles were computed using the HEC RAS steady state model and compared to computed elevations from the SOCH model. An example of the comparison between HEC RAS and SOCH profiles is shown for Chickamauga Reservoir in Figure 2.4A-21. This approach was applied for each of the SOCH reservoir models. Similarly, the tailwater rating curve was compared at each project as shown for Watts Bar Dam in Figure 2.4A-22. In this figure, the initial tailwater curve is compared to results from the HEC RAS or SOCH models.
2.4A-4SOCH MODEL WATTS BARWBNP-114The reservoir operating guides applied during the SOCH model simulations mimic, to the extent possible, operating policies and are within the current reservoir operating flexibility. In addition to spillway discharge, turbine and sluice discharges were used to release water from the tributary reservoirs. Turbine discharges were also used at the main river reservoirs up to the point where the head differentials are too small and/or the powerhouse would flood. All discharge outlets (spillway gates, sluice gates, and valves) for projects in the reservoir system will remain operable without failure up to the point the operating deck is flooded for the passage of water when and as needed during the flood. A high confidence that all gates/outlets will be operable is provided by periodic inspections by TVA plant personnel, the intermediate and five-year dam safety engineering inspections consistent with Federal Guidelines for Dam Safety, and the significant capability of the emergency response teams to direct and manage resources to address issues potentially impacting gate/outlet functionality.Median initial reservoir elevations for the appropriate season were used at the start of the PMF storm sequence. Use of median elevations is consistent with statistical experience and avoids unreasonable combinations of extreme events.The flood from the antecedent storm occupies about 70% of the reserved system detention capacity above Watts Bar Dam at the beginning of the main storm (day 7 of the event). Reservoir levels are at or above guide levels at the beginning of the main storm in all but Apalachia and Fort Patrick Henry Reservoirs, which have no reserved flood detention capacity. REFERENCES (1)Newton, Donald W., and Vineyard, J. W., "Computer-Determined Unit Hydrographs From Floods," Journal of the Hydraulics Division, ASCE, Volume 93, No. HY5, September 1967.
(2)Garrison, J. M., Granju, J. P., and Price, J. T., "Unsteady Flow Simulation in Rivers and Reservoirs," Journal of the Hydraulics Division, ASCE, Volume 95, No. HY5, Proceedings Paper 6771, September 1969, pages 1559-1576."
2.4A-5HYDROLOGIC ENGINEERINGWATTS BARWBNP-114Figure 2.4A-11 Discharge Rating Curve, Chickamauga Dam (Sheet 1 of 13)
Figure 2.4-11 (Sheet 1 of 13)
WATTS BAR NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Discharge Rating Curve, Chickamauga DamFigure 2.4A-11
2.4A-6HYDROLOGIC ENGINEERINGWATTS BARWBNP-114Figure 2.4A-11 Discharge Rating Curve, Watts Bar Dam (Sheet 2 of 13)Figure 2.4A-11 2.4A-7HYDROLOGIC ENGINEERINGWATTS BARWBNP-114Figure 2.4A-11 Discharge Rating Curve, Fort Loudoun Dam (Sheet 3 of 13)Figure 2.4A-11 HYDROLOGIC ENGINEERING2.4A-8WATTS BARWBNP-114Figure 2.4A-11 Discharge Rating Curve, Tellico Dam (Sheet 4 of 13)
Figure 2.4A-11 HYDROLOGIC ENGINEERING2.4A-9WATTS BARWBNP-114Figure 2.4A-11 Discharge Rating Curve, Boone Dam (Sheet 5 of 13)
Figure 2.4-11 (Sheet 5 of 13)
Discharge Rating Curve, Boone Dam WATTS BAR NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORTFigure 2.4A-11 HYDROLOGIC ENGINEERING2.4A-10WATTS BARWBNP-114Figure 2.4A-11 Discharge Rating Curve, Cherokee Dam (Sheet 6 of 13)Figure 2.4A-11 Figure 2.4-11 (Sheet 6 of 13)
Discharge Rating Curve, Cherokee Dam WATTS BAR NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORTFigure 2.4A-11 2.4A-11HYDROLOGIC ENGINEERINGWATTS BARWBNP-114Figure 2.4A-11 Discharge Rating Curve, Douglas Dam (Sheet 7 of 13)
Figure 2.4-11 (Sheet 7 of 13)
Discharge Rating Curve, Douglas Dam WATTS BAR NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORTFigure 2.4A-11 HYDROLOGIC ENGINEERING2.4A-12WATTS BARWBNP-114Figure 2.4A-11 Discharge Rating Curve, Fontana Dam (Sheet 8 of 13)
Figure 2.4-11 (Sheet 8 of 13)
Discharge Rating Curve, Fontana Dam WATTS BAR NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORTFigure 2.4A-11 2.4A-13HYDROLOGIC ENGINEERINGWATTS BARWBNP-114Figure 2.4A-11 Discharge Rating Curve, Fort Patrick Henry Dam (Sheet 9 of 13)
Figure 2.4-11 (Sheet 9 of 13)
Discharge Rating Curve, WATTS BAR NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Fort Patrick Henry DamFigure 2.4A-11 HYDROLOGIC ENGINEERING2.4A-14WATTS BARWBNP-114Figure 2.4A-11 Discharge Rating Curve, Melton Hill Dam (Sheet 10 of 13)
Figure 2.4-11 (Sheet 10 of 13)
Discharge Rating Curve, Melton Hill Dam WATTS BAR NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Figure 2.4A-11 2.4A-15HYDROLOGIC ENGINEERINGWATTS BARWBNP-114Figure 2.4A-11 Discharge Rating Curve, Norris Dam (Sheet 11 of 13)
Figure 2.4-11 (Sheet 11 of 13)
Discharge Rating Curve, Norris Dam WATTS BAR NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORTFigure 2.4A-11 HYDROLOGIC ENGINEERING2.4A-16WATTS BARWBNP-114Figure 2.4A-11 Discharge Rating Curve, South Holston Dam (Sheet 12 of 13)
Figure 2.4-11 (Sheet 12 of 13)
Discharge Rating Curve, WATTS BAR NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT South Holston Dam Figure 2.4A-11 2.4A-17HYDROLOGIC ENGINEERINGWATTS BARWBNP-114Figure 2.4A-11 Discharge Rating Curve, Watauga Dam (Sheet 13 of 13)
Figure 2.4-11 (Sheet 13 of 13)
Discharge Rating Curve, Watauga Dam WATTS BAR NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORTFigure 2.4A-11 HYDROLOGIC ENGINEERING2.4A-18WATTS BARWBNP-114Figure 2.4A-12 Fort Loudoun - Tellico SOCH Unsteady Flow Model Schematic Figure 2.4-12 WATTS BAR NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Fort Loudoun - Tellico SOCH Unsteady Flow Model Schematic Figure 2.4A-12 2.4A-19HYDROLOGIC ENGINEERINGWATTS BARWBNP-114Figure 2.4A-13 Unsteady Flow Model Fort Loudoun Reservoir March 1973 Flood (Sheet 1 of 2)
Figure 2.4-13 (Sheet 1 of 2)
Unsteady Flow Model Fort Loudoun WATTS BAR NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Reservoir March 1973 FloodFigure 2.4A-13 HYDROLOGIC ENGINEERING2.4A-20WATTS BARWBNP-114Figure 2.4A-13 Unsteady Flow Model Fort Loudoun Reservoir March 1973 Flood (Sheet 2 of 2)
Figure 2.4-13 (Sheet 2 of 2)
Unsteady Flow Model Fort Loudoun WATTS BAR NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Reservoir March 1973 FloodFigure 2.4A-13 2.4A-21HYDROLOGIC ENGINEERINGWATTS BARWBNP-114Figure 2.4A-14 Unsteady Flow Model Fort Loudoun - Tellico Reservoir May 2003 Flood (Sheet 1 of 3)
Figure 2.4-14 (Sheet 1 of 3)
Unsteady Flow Model Fort Loudoun - Tellico WATTS BAR NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Reservoir May 2003 FloodFigure 2.4A-14 HYDROLOGIC ENGINEERING2.4A-22WATTS BARWBNP-114Figure 2.4A-14 Unsteady Flow Model Fort Loudoun - Tellico Reservoir May 2003 Flood (Sheet 2 of 3)
Figure 2.4-14 (Sheet 2 of 3)
Unsteady Flow Model Fort Loudoun - Tellico WATTS BAR NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Reservoir May 2003 FloodFigure 2.4A-14 2.4A-23HYDROLOGIC ENGINEERINGWATTS BARWBNP-114Figure 2.4A-14 Unsteady Flow Model Fort Loudoun - Tellico Reservoir May 2003 Flood (Sheet 3 of 3)
Figure 2.4-14 (Sheet 3 of 3)
Unsteady Flow Model Fort Loudoun - Tellico WATTS BAR NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Reservoir May 2003 FloodFigure 2.4A-14 HYDROLOGIC ENGINEERING2.4A-24WATTS BARWBNP-114Figure 2.4A-15 Watts Bar SOCH Unsteady Flow Model Schematic Figure 2.4-15 WATTS BAR NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Watts Bar SOCH Unsteady Flow Model SchematicFigure 2.4A-15 2.4A-25HYDROLOGIC ENGINEERINGWATTS BARWBNP-114Figure 2.4A-16 Unsteady Flow Model Watts Bar Reservoir March 1973 Flood Figure 2.4-16 WATTS BAR NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Unsteady Flow Model Watts Bar Reservoir March 1973 FloodFigure 2.4A-16 HYDROLOGIC ENGINEERING2.4A-26WATTS BARWBNP-114Figure 2.4A-17 Unsteady Flow Model Watts Bar Reservoir May 2003 Flood Figure 2.4-17 WATTS BAR NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Unsteady Flow Model Watts Bar Reservoir May 2003 FloodFigure 2.4A-17 2.4A-27HYDROLOGIC ENGINEERINGWATTS BARWBNP-114Figure 2.4A-18 Chickamauga SOCH Unsteady Flow Model Schematic Figure 2.4-18 WATTS BAR NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Chickamauga SOCH Unsteady Flow Model SchematicFigure 2.4A-18 HYDROLOGIC ENGINEERING2.4A-28WATTS BARWBNP-114Figure 2.4A-19 Unsteady Flow Model Chickamauga Reservoir March 1973 Flood Figure 2.4-19 WATTS BAR NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Unsteady Flow Model Chickamauga Reservoir March 1973 FloodFigure 2.4A-19 2.4A-29HYDROLOGIC ENGINEERINGWATTS BARWBNP-114Figure 2.4A-20 Unsteady Flow Model Chickamauga Reservoir May 2003 Flood Figure 2.4-20 WATTS BAR NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Unsteady Flow Model Chickamauga Reservoir May 2003 FloodFigure 2.4A-20 HYDROLOGIC ENGINEERING2.4A-30WATTS BARWBNP-114Figure 2.4A-21 Chickamauga Steady State Profile Comparisons Figure 2.4-21 Chickamauga Steady State WATTS BAR NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Profile ComparisonsFigure 2.4A-21SOC H MODEL 2.4A-31HYDROLOGIC ENGINEERINGWATTS BARWBNP-114Figure 2.4A-22 Tailwater Rating Curve, Watts Bar Dam Figure 2.4-22 WATTS BAR NUCLEAR PLANT FINAL SAFETY ANALYSIS REPORT Tailwater Rating Curve, Watts Bar DamFigure 2.4A-22SOC H MODEL 2.4A-32HYDROLOGIC ENGINEERINGWATTS BARWBNP-114THIS PAGE INTENTIONALLY BLANK