APPENDIX H LAKE OKEECHOBEE FLOOD ROUTINES

Transcription

1 1 2 3 APPENDIX H LAKE OKEECHOBEE FLOOD ROUTINES

2 LAKE OKEECHOBEE FLOOD ROUTINGS TO DETERMINE THE STAGE-FREQUENCY RELATIONSHIP INTRODUCTION This report presents the flood routings performed to determine the stage-frequency relationship for Lake Okeechobee. The 100-year and Standard Project Flood (SPF) routings, performed in 1959 to design the levee system around Lake Okeechobee, were provided in Central and Southern Florida (C&SF) Project, Part IV, Supplement 2, Section 7. The stage-frequency relationship for Lake Okeechobee presented in this report considers the stage duration data obtained from Run 25, the rainfall data available for the period , and modified project conditions for the Kissimmee River. DRAINAGE BASIN INFORMATION Figure 1 shows the drainage area for Lake Okeechobee, St. Lucie canal, and Caloosahatchee River. A total drainage area of about 5,540 square miles contribute discharges to Lake Okeechobee. The areas for sub-basins are listed in Table 1. INFLOWS A HEC-1 model was used to generate hydrographs for each sub-basin. Inflows to Lake Okeechobee were restricted by the SPF design capacities of the inlet structures. Discharges from pumped areas were limited to the pump station capacities. Daily rainfall values over Lake Okeechobee were converted to daily discharges after subtracting the evapotranspiration losses. The inflow hydrographs are listed in Table 5. Figures 4 and 5 show that the discharges estimated by the current study compare well with the 1959 study. ROUTINGS A computer program, listed in Table 9, was used for Lake Okeechobee flood routings. Current regulation schedules for Lake Okeechobee, shown in Figure 6, and stage-storage data were included in the program. Losses due to S-308 and stage-discharge data for St. Lucie Canal were used in the routings. A stage-duration curve computed from Run 25 stages for the winter season, shown in Figure 7, was used as initial condition for routings. The stage duration curve was considered as a step function with six elevations to simplify the analysis. Routings were performed on a daily basis. Discharges through St. Lucie Canal and Caloosahatchee River were decreased to accommodate local discharges if the combined discharges exceeded the capabilities of S-80 and S-79, respectively. RAINFALL Lake Okeechobee Vol 3 Appendix H-1 December 2005

3 Figure 1 shows seven rain gages used in the analysis for the period Rainfall data recorded at Kissimmee and Kissimmee 2 gages were combined to obtain a continuous period of data. Theissen weights were computed for each gage as listed in Table 2. Basin average rainfall values were computed using recorded rainfall at all the seven gages and the corresponding Theissen weights. Annual maximum basin average rainfall series were computed for durations ranging from one day through 364 days. Log-Pearson Type III method, as incorporated in the HEC Flood Frequency Analysis computer program, was used to analyze the annual maximum rainfall series. The results of the Log-Pearson Type III analysis listing mean, standard deviation, skew, outlier, and estimated rainfall for frequencies ranging from 50 percent to one percent chance storm events. Computed rainfall listed in Table 2 were graphically smoothed to obtain the basin average rainfall for various durations and frequencies as shown in Table 3. SPF rainfall values for all durations were taken as 125 percent of the one percent storm for the corresponding duration. Balanced storms were used to distribute the computed rainfall for a year with the highest rainfall in September. TOTAL LOSSES The relationships between monthly rainfall and monthly losses presented in C&SF Project, Part VI, Section 8 were adopted for the analysis of two percent, one percent, and SPF events. A runoff curve number of 56 was estimated from the monthly rainfall and runoff for such rare events with wet moisture conditions. A runoff curve number of 36 was estimated for other more frequent flood events assuming average moisture conditions. Daily total losses were obtained by uniformly distributing monthly losses for all months except September. An evapotranspiration value of 3.8 inches, taken from the 1985 report of the Kissimmee River, was uniformly distributed in September. The difference between the total losses and evapotranspiration losses for September was distributed daily proportional to the rainfall excess over the evapotranspiration. Table 4 lists monthly values of the rainfall, total loss, and rainfall excess. Figures 2 and 3 show the rainfall and the rainfall excess over a period of one year for 1 percent chance event and the Standard Project Storm events, respectively. UNIT HYDROGRAPHS The discharge hydrograph obtained from the Kissimmee River 1135 project for the one percent chance flood event was optimized by HEC-1 to determine a unit hydrograph at S- 65D for a drainage area of 2,300 square miles. A unit hydrograph at the same location was also optimized from the SPF for comparison. The unit hydrograph was extrapolated to the mouth for a drainage area of 2,456 square miles. The unit hydrographs for Lake Istokpoga area, Fisheating Creek, and Taylor Creek area were estimated from the design reports. Instantaneous unit hydrographs were used for the lake and other areas serviced by pump stations. Figure 8 shows the stage hydrographs for the one percent chance flood for six initial lake levels. Figure 9 provides similar information for the SPF. Figure 10 shows the stage hydrographs for frequencies ranging from 50% to SPF for an initial lake Lake Okeechobee Vol 3 Appendix H-2 December 2005

4 level of 17.0 ft. NGVD. Table 6 provides the results of daily routings for the one percent event with an initial water level of 17.0 ft. NGVD. Table 7 lists similar information for the SPF event. STAGE-FREQUENCY Peak stage-frequency data were plotted for all six initial lake levels. Table 8 shows the durations for six initial lake levels, stage-frequency data for all initial conditions, and computed combined frequencies. Figure 11 shows the stage frequency data obtained from flood routings and plotting positions of observed stages since The adopted stage frequency curve for Lake Okeechobee is also shown in Figure Lake Okeechobee Vol 3 Appendix H-3 December 2005

5 FIGURES

6 1 FIGURE 1 LAKE OKEECHOBEE DRAINAGE BASIN 2 Lake Okeechobee Vol. Figure-1 December 2005

7 1 FIGURE 2 BASIN AVERAGE 1% RAINFALL Lake Okeechobee Vol. Figure-2 December 2005

8 1 FIGURE 3 BASIN AVERAGE SPF RAINFALL Lake Okeechobee Vol. Figure-3 December 2005

9 1 2 FIGURE 4 LAKE OKEECHOBEE 1% FLOOD INFLOW 3 Lake Okeechobee Vol. Figure-4 December 2005

10 1 FIGURE 5 LAKE OKEECHOBEE SPF INFLOW 2 Lake Okeechobee Vol. Figure-5 December 2005

11 1 2 FIGURE 6 LAKE OKEECHOBEE INTERIM REGULATION SCHEDULE 1994 RUN 25 3 Lake Okeechobee Vol. Figure-6 December 2005

12 1 FIGURE 7 LAKE OKEECHOBEE STAGE DURATION Lake Okeechobee Vol. Figure-7 December 2005

13 1 FIGURE 8 LAKE OKEECHOBEE 1% FLOOD HYDROGRAPH 2 Lake Okeechobee Vol. Figure-8 December 2005

14 1 FIGURE 9 LAKE OKEECHOBEE SPF HYDROGRAPH 2 Lake Okeechobee Vol. Figure-9 December 2005

15 1 2 FIGURE 10 LAKE OKEECHOBEE FLOOD HYDROGRAPHS (INITIAL LEVEL 17 FT) 3 Lake Okeechobee Vol. Figure-10 December 2005

16 FIGURE 11 STAGE FREQUENCY FOR LAKE OKEECHOBEE Lake Okeechobee Vol. Figure-11 December 2005

17 TABLES Lake Okeechobee Vol. Figure-12 December 2005

18 TABLE 1 LAKE OKEECHOBEE DRAINAGE AREAS Lake Okeechobee Vol. 3 T-1 December 2005

19 TABLE 2 LAKE OKEECHOBEE BASIN AVERAGE RAINFALL Lake Okeechobee Vol. 3 T-2 December 2005

20 TABLE 3 LAKE OKEECHOBEE BASIN AVERAGE RAINFALL IN INCHES Lake Okeechobee Vol. 3 T-3 December 2005

21 TABLE 4 LAKE OKEECHOBEE RAINFALL, TOTAL LOSS, AND RAINFALL EXCESS Lake Okeechobee Vol. 3 T-4 December 2005

22 TABLE 5 LAKE OKEECHOBEE 50% FLOOD EVENT Lake Okeechobee Vol. 3 T-5 December 2005

23 TABLE 5 LAKE OKEECHOBEE 50% FLOOD EVENT (CONTINUED) Lake Okeechobee Vol. 3 T-6 December 2005

24 TABLE 5 LAKE OKEECHOBEE 20% FLOOD EVENT Lake Okeechobee Vol. 3 T-7 December 2005

25 TABLE 5 LAKE OKEECHOBEE 20% FLOOD EVENT (CONTINUED) Lake Okeechobee Vol. 3 T-8 December 2005

26 TABLE 5 LAKE OKEECHOBEE 10% FLOOD EVENT Lake Okeechobee Vol. 3 T-9 December 2005

27 TABLE 5 LAKE OKEECHOBEE 10% FLOOD EVENT (CONTINUED) Lake Okeechobee Vol. 3 T-10 December 2005

28 TABLE 5 LAKE OKEECHOBEE 5% FLOOD EVENT Lake Okeechobee Vol. 3 T-11 December 2005

29 TABLE 5 LAKE OKEECHOBEE 5% FLOOD EVENT (CONTINUED) Lake Okeechobee Vol. 3 T-12 December 2005

30 TABLE 5 LAKE OKEECHOBEE 2% FLOOD EVENT Lake Okeechobee Vol. 3 T-13 December 2005

31 TABLE 5 LAKE OKEECHOBEE 2% FLOOD EVENT (CONTINUED) Lake Okeechobee Vol. 3 T-14 December 2005

32 TABLE 5 LAKE OKEECHOBEE 1% FLOOD EVENT Lake Okeechobee Vol. 3 T-15 December 2005

33 TABLE 5 LAKE OKEECHOBEE 1% FLOOD EVENT (CONTINUED) Lake Okeechobee Vol. 3 T-16 December 2005

34 TABLE 5 LAKE OKEECHOBEE INFLOWS SPF EVENT Lake Okeechobee Vol. 3 T-17 December 2005

35 TABLE 5 LAKE OKEECHOBEE INFLOWS SPF EVENT (CONTINUED) Lake Okeechobee Vol. 3 T-18 December 2005

36 TABLE 6 LAKE OKEECHOBEE ROUTINGS 1% FLOOD EVENT Lake Okeechobee Vol. 3 T-19 December 2005

37 TABLE 6 LAKE OKEECHOBEE ROUTINGS 1% FLOOD EVENT (CONTINUED) Lake Okeechobee Vol. 3 T-20 December 2005

38 TABLE 6 LAKE OKEECHOBEE ROUTINGS 1% FLOOD EVENT (CONTINUED) Lake Okeechobee Vol. 3 T-21 December 2005

39 TABLE 6 LAKE OKEECHOBEE ROUTINGS 1% FLOOD EVENT (CONTINUED) Lake Okeechobee Vol. 3 T-22 December 2005

40 TABLE 6 LAKE OKEECHOBEE ROUTINGS 1% FLOOD EVENT (CONTINUED) Lake Okeechobee Vol. 3 T-23 December 2005

41 TABLE 6 LAKE OKEECHOBEE ROUTINGS 1% FLOOD EVENT (CONTINUED) Lake Okeechobee Vol. 3 T-24 December 2005

42 TABLE 6 LAKE OKEECHOBEE ROUTINGS 1% FLOOD EVENT (CONTINUED) Lake Okeechobee Vol. 3 T-25 December 2005

43 TABLE 6 LAKE OKEECHOBEE ROUTINGS 1% FLOOD EVENT (CONTINUED) Lake Okeechobee Vol. 3 T-26 December 2005

44 TABLE 7 LAKE OKEECHOBEE ROUTINGS SPF EVENT INITIAL LAKE LEVEL 17 FT. Lake Okeechobee Vol. 3 T-27 December 2005

45 TABLE 7 LAKE OKEECHOBEE ROUTINGS SPF EVENT INITIAL LAKE LEVEL 17 FT. (CONTINUED) Lake Okeechobee Vol. 3 T-28 December 2005

46 TABLE 7 LAKE OKEECHOBEE ROUTINGS SPF EVENT INITIAL LAKE LEVEL 17 FT. (CONTINUED) Lake Okeechobee Vol. 3 T-29 December 2005

47 TABLE 7 LAKE OKEECHOBEE ROUTINGS SPF EVENT INITIAL LAKE LEVEL 17 FT. (CONTINUED) Lake Okeechobee Vol. 3 T-30 December 2005

48 TABLE 7 LAKE OKEECHOBEE ROUTINGS SPF EVENT INITIAL LAKE LEVEL 17 FT. (CONTINUED) Lake Okeechobee Vol. 3 T-31 December 2005

49 TABLE 7 LAKE OKEECHOBEE ROUTINGS SPF EVENT INITIAL LAKE LEVEL 17 FT. (CONTINUED) Lake Okeechobee Vol. 3 T-32 December 2005

50 TABLE 7 LAKE OKEECHOBEE ROUTINGS SPF EVENT INITIAL LAKE LEVEL 17 FT. (CONTINUED) Lake Okeechobee Vol. 3 T-33 December 2005

51 TABLE 7 LAKE OKEECHOBEE ROUTINGS SPF EVENT INITIAL LAKE LEVEL 17 FT. (CONTINUED) Lake Okeechobee Vol. 3 T-34 December 2005

52 TABLE 8 STAGE-FREQUENCY FOR LAKE OKEECHOBEE Lake Okeechobee Vol. 3 T-35 December 2005

53 TABLE 9 LAKE OKEECHOBEE MAXIMUM 30-DAY AVERAGE STAGES Lake Okeechobee Vol. 3 T-36 December 2005