Section 3.0 Existing Systems Hydrology and Hydraulics

Section 3.0 Existing Systems Hydrology and Hydraulics This chapter summarizes the results and methodology of MACTEC s evaluation of the existing drainage systems and lakes for the City of Maitland, Florida. The purpose of this study was to update the City of Maitland s 1996 SLMP to include annexations incorporated to the City of Maitland and to integrate the stormwater drainage system with lake basins. This study also provides information necessary to determine if the capacity of the city s major drainage systems is adequate to convey the stormwater associated with the 10-year/24-hour, 25-year/24-hour, and 100-year/24-hour design storms. Characteristics of the basins within and draining to the City of Maitland, along with information derived from previous studies, were used to determine the hydrologic and hydraulic modeling parameters used in this report. The main lake basin parameters include drainage area, imperviousness, slope, hydraulic width, lake stage elevation, and geometry of lakes. The main pipe parameters include length, Manning s roughness coefficient, geometry, and upstream/downstream invert elevations. The U.S. Environmental Protection Agency s (EPA) Storm Water Management Model (SWMM) Version 5.0.001 software was used to model the hydrology and hydraulics of each basin within the city. 3.1 Background The EPA SWMM is a dynamic rainfall-runoff simulation model used for single event or long-term (continuous) simulation of runoff quantity and quality from primarily urban areas. SWMM has the capability of simulating both the quantity and quality of runoff generated within each subcatchment, and the flow rate, flow depth, and quality of water in each pipe and channel during a simulation period (EPA 2005). This application focused upon water quantity, i.e., the hydrologic and hydraulic response of the stormwater system to rainfall events. Water quality can be added to the model by adding pollutant loads and calibrating the resulting pollutographs to measured downstream data. SWMM can simulate simple first order treatment kinetics in any pipe or storage system. However, because of their complexity, detailed within-lake water quality processes should be evaluated separately. The runoff component of SWMM operates on a collection of subcatchment areas that receive precipitation and generate a runoff hydrograph. The routing portion of SWMM transports this runoff through a network of pipes, channels, storage/treatment devices, pumps, and regulators. SWMM models a stormwater system as a link-node network, with pipes becoming the links and manholes and inlets becoming the nodes. For each section of the catchment (pervious and impervious), the rainfall loss is the difference between the rainfall depth and the depth of runoff. This is made of various components as illustrated in Figure 3-1. 3-1 MACTEC

Figure 3-1. SWMM Hydrology EVAPORATION RAINFALL RUNOFF Source: Huber and Dickinson, 1988 INFILTRATION The reader should note that SWMM assumes an idealized rectangular catchment with a slope, s, and hydraulic width, W. Runoff is calculated based upon a two step process. First, the average height of overland flow runoff is calculated in equation (1) from Huber et al. (1988): where d t = i * + WCON d [ ] 5 / 3 d = difference in water depth from beginning to the end of a time step, mm. t = time step, seconds, or minutes, depending upon units used d = average water depth over time step, feet d p = depression storage, feet d p (1) WCON = constant defined as: A = area of unit, feet W = width of unit, feet n = Manning s n, in units of 1/ Ws WCON = An 1/ 3 tl s = subcatchment slope, m/m, or dimensionless i* = effective rainfall, or what is left after infiltration, (if pervious), in units of L/t 2 This equation can be solved iteratively using the Newton Rhapson solution method. Next, runoff, or outflow from each catchment is calculated with equation (2) from Huber and Dickinson (1988): W 3 1/ 2 Q = [ d d ] 5 / p S (2) n where: Q = flow rate, ft 3 /s 3-2 MACTEC

SWMM uses a variety of processes to calculate infiltration losses; in this case the Horton method was chosen. The Horton equation describes the process of infiltration in an exponential fashion, whereby infiltration capacity is reduced from an initial, maximum rate to a final constant rate as follows (AAS 2005a): where: f capac c K ( f f ) e o c t = f + (3) f capac = Maximum infiltration capacity of the soil f o = Initial infiltration capacity f c = Final (constant) infiltration capacity t = Elapsed time from start of rainfall K = Decay time constant Major conveyance facilities consist primarily of overland flow, gutter, and swale runoff to outfall channels and pipe networks. These systems were modeled using invert elevations for outlets obtained from survey data. In this SWMM study, conveyance systems with an equivalent 36-inch pipe or larger were incorporated into the model. This is consistent with 1996 SLMP, the approved scope of work, and the need to comply with NPDES MS4 Permit requirements which classify these pipes as major outfalls. These larger pipes also have higher flow rates and velocities and thus more potential for causing extensive flooding and erosion problems than minor or smaller systems not inventoried or studied. The previous 1996 SLMP using Advanced Interconnected Channel & Pond Routing Model (adicpr) and assumed the outlets were submerged due to the lack of a detailed survey data on invert elevations. This study did not make that assumption because some data on pipe sizes, type, length, and invert elevations from as-built drawings were provided by the City of Maitland and/or Orange County. For those piped systems not having as-built drawings, MACTEC estimated invert elevations based on one-foot topographic data from SJRWMD GIS data website and upstream/downstream control elevations. The advantage of providing more detailed pipe data is a more accurate simulation of the hydrologic/hydraulic conditions within the City of Maitland. In addition, pipe slope calculated based on invert elevation is critical to estimate the pipe flow capacity following Manning s formula. The stormwater management systems were analyzed using 10-year/24-hour, 25-year/24-hour, and 100-year/24-hour storm Florida Zone 7 rainfall data obtained from the FDOT. Another major difference between adicpr and SWMM is adicpr uses SCS-based hydrology, whereas SWMM uses a nonlinear reservoir routing algorithm stated previously. Some of the data used to create the SWMM model was imported from previous studies and not recreated. The studies referenced include lake and interconnection modeling conducted by the SJRWMD, Orange County Stormwater Management Department (OCSMD), and the 1996 SLMP. The following lists studies that were consulted in model development: SJRWMD HEC-1 hydrologic model for the Howell Creek Basin (SJRWMD 1994) 3-3 MACTEC

SJRWMD HEC-1 hydrologic model for the Little Wekiva River Basin (SJRWMD 1989). OCSMD adicpr hydrologic model for Lake Love, Lake Charity, Lake Hope, and Lake Faith (OCSMD 1993). City of Maitland adicpr hydrologic model summary (SLMP 1996). 3.2 Basin Boundaries The lakes within the City of Maitland are part of two major basins: the Howell Creek Basin and the Little Wekiva River Basin. Some basins in Maitland do not discharge to either of these systems and are thus designated as being land-locked. In previous studies (listed above), basins were modeled in their entirety, including areas outside the boundaries of this study and the City of Maitland. These previous models, particularly the model developed for the previous SLMP, were used to create the SWMM model associated with this report. This model was created using the adicpr Version 1.40 software developed by Streamline Technologies, Inc. The SWMM model developed as part of this report used inflow hydrographs from the SJRWMD HEC-1 model for the Howell Creek Basin and for major basins that flow into the city via Lake Gem, Lake Maitland, and Lake Minnehaha (see Figure 3-2). A routed HEC-1 hydrograph from Lake Killarney with diverted outflow, representing a drainage area of 3.20 square miles (2,048 acres), was used as an off-site inflow hydrograph to Lake Gem for each storm (see Figure 3-3). A routed HEC-1 hydrograph from Lake Osceola, representing a drainage area of 11.11 square miles (7,110 acres), was used as an off-site inflow hydrograph to Lake Maitland for each storm (see Figure 3-4). Lake of the Woods and its 0.87-square mile drainage area (557 acres) lying north of the city was routed to Lake Minnehaha for each storm as in the SJRWMD HEC-1 model. The drainage basin boundaries used for this model were imported unchanged from the 1996 SLMP with updates for annexed areas. This study used a combination of data including 1-ft contour maps prepared by the SJRWMD, the structure inventory prepared by the City of Maitland, and various reports and studies conducted for other projects to determine the basin boundaries (1996 SLMP). The basin and subbasin boundaries used in the SWMM model are listed in Table 3-1. The link-node architecture of the SWMM model is provided as a network diagram in Figure 3-5. As the basin boundary map shows, each lake basin was divided into subbasins. These subbasins are discrete portions of the lake basins that typically have separate outfalls to the lakes. Subbasin identification numbers ending in 0 represent the subbasin containing the lake water surface. Subbasin identification number ending in 90 through 99 represent subbasins lying outside City of Maitland boundaries. 3-4 MACTEC

Figure 3-2. SWMM Model of the Maitland Area Source: City of Maitland 2005 and MACTEC 2005. 3-5 MACTEC

Figure 3-3. Lake Killarney Hydrograph (Inflow to Area) 500 450 400 FLOW IN CFS 350 300 250 200 150 100 50 0 Source: SJRWMD, 1994. 10-YEAR 25-YEAR 100-YEAR 0:15 1:30 2:45 4:00 5:15 6:30 7:45 9:00 10:15 11:30 Figure 3-4. Lake Osceola Hydrograph (Inflow to Area) 500 450 12:45 TIME 14:00 15:15 16:30 17:45 19:00 20:15 21:30 22:45 0:00 FLOW IN CFS 400 350 300 250 200 150 100 50 0 0:15 1:30 Source: SJRWMD, 1994. 10-YEAR 25-YEAR 100-YEAR 2:45 4:00 5:15 6:30 7:45 9:00 10:15 11:30 TIME 12:45 14:00 15:15 16:30 17:45 19:00 20:15 21:30 22:45 0:00 3-6 MACTEC

Figure 3-5. SWMM Network Diagram Source: SLMP, 1996 and MACTEC, 2005. Table 3-1. Basin Designation and Drainage Area Basin Two-Letter Designation Basin Drainage Area Subbasins Major System Lake Bell BE N/A 3 Howell Creek Lake Catherine 20.94 CA Lake Catherine Basin 55.45 7 Land Locked Lake Charity 56.15 CH Lake Charity Basin 233.58 10 Land Locked Lake Destiny 21.2 DE Lake Destiny Basin 143.02 9 Little Wekiva Lake Eulalia 5.83 EU Lake Eulalia Basin 11.55 2 Land Locked Lake Faith 31.67 FA Lake Faith Basin 57.2 13 Land Locked Lake Gem 8.12 GE Lake Gem Basin 261.96 7 Howell Creek Lake Harvest 10.26 HA Lake Harvest Basin 35.35 2 Little Wekiva Lake Hope 29.66 HO Lake Hope Basin 71.34 8 Land Locked Lake Howell N/A HW Lake Howell Basin N/A 2 Howell Creek Lake Hungerford 15.28 HU Lake Hungerford Basin 86.37 6 Little Wekiva Lake Jackson 23.8 JA Lake Jackson Basin 66.67 9 Land Locked 3-7 MACTEC

Table 3-1. Basin Designation and Drainage Area Basin Two-Letter Designation Basin Drainage Area Subbasins Major System Lake Killarney 0 N/A Lake Killarney Basin 100 N/A N/A Lake Lily 5.38 LI Lake Lily Basin 31.12 7 Howell Creek Lake Love 4.08 LO Lake Love Basin 16.28 2 Land Locked Lake Lovely 31.41 LV Lake Lovely Basin 211.63 2 Little Wekiva Loch Lomond 7.85 LL Loch Lomond Basin 60.45 4 Little Wekiva Lake Lucien 52.81 LU Lake Lucien Basin 335.17 15 Little Wekiva Lake Maitland 177.66 MA Lake Maitland Basin 1143.26 27 Howell Creek Lake Minnehaha 94.62 MI Lake Minnehaha Basin 425.2 27 Howell Creek Lake Nina 10.2 NI Lake Nina Basin 79.29 7 Howell Creek Lake Osceola 0 N/A Lake Osceola Basin 1200* N/A N/A Park Lake 31.87 PA Park Lake Basin 121.06 14 Howell Creek Lake Seminary 0 SE Lake Seminary Basin 0 5 Land Locked Lake Shadow 74.14 SH Lake Shadow Basin 293.4 3 Little Wekiva Lake Sybelia 81.04 SY Lake Sybelia Basin 380.03 25 Land Locked Lake Waumpi 11.32 WA Lake Waumpi Basin 505.6 2 Howell Creek Lake of the Woods 0 WO Lake of the Woods Basin 556.8 2 Howell Creek Unnamed Lake 4.56 UN Unnamed Lake Basin 48.44 4 Little Wekiva Wetland WE 436.45 15 Howell Creek Source: MACTEC, 2005. Prepared: PZ Checked: DS *Note: Located outside research area. As seen in Figure 3-1 and Table 3-1, subbasins were created not only for the drainage area corresponding to each lake, but also for the lakes themselves (i.e. lake-only subbasins). Along with each basin, Table 3-1 lists the two-letter designation used in this report corresponding to each basin, the major basin system to which the lake discharges, and the number of subbasins corresponding to each basin. These were modeled after the subbasins created for the original report and are discrete portions of the lake basins that typically have separate outfalls to the lakes (SLMP 1996). Outfall types included storm drains, open channels or swales, and sheet flow. 3-8 MACTEC

3.3 Hydrologic Parameters The SWMM model requires input hydrologic parameters in order to simulate the system. These parameters included data for the lake basins themselves as well as data for the pipe systems that connect or flow into them. The majority of input data used in this study was taken from the previous SLMP report, with updates for the newly incorporated areas. The pipe system data is new to this study, however, and was obtained, where available, from the City of Maitland, the SJRWMD, FDOT, and MACTEC field efforts. After discussions with the City, Lake Lovely was eliminated from SWMM modeling due to lack of comparable input data. 3.3.1 Lake and Basin Parameters The following are hydrologic parameters necessary for the SWMM model that pertain to the lakes and their basins within the City of Maitland: Drainage Area. The drainage areas corresponding to the basin boundaries from PBS&J s previous study were used to calculate the drainage areas used for the SWMM model. Since the basin boundaries from the previous report were used unchanged and only pipe systems were added, the drainage areas for the basins were computed by subtracting small areas from the previously computed drainage areas to be allocated as subbasins contributing to inlets and pipe systems. Next, the drainage areas for the lake-only basins were subtracted from their corresponding basins to get different drainage areas for the two basins (the lake basin and the lake-only basin). Input values for drainage areas are listed in Table 3-1. Imperviousness. The imperviousness of the land cover in each basin is a characteristic of the volume of runoff associated with the basin. As the ground becomes less pervious, the potential for absorption into the earth decreases and thus runoff increases. Imperviousness was entered into the SWMM model as a percentage and was calculated as a composite ratio of imperviousness of typical land covers (CDM 2004). A percent impervious of 100 was used for the lake itself. The imperviousness value used for each basin is listed in Table 3-2. Slope. The slope of each basin is also a characteristic of the volume of runoff associated with the basin. The steeper the basin, the faster the runoff travels downhill giving it less time to be absorbed or evaporated and thus increasing the volume of runoff. Slope was entered into the SWMM model as a percentage and was calculated using the ArcView 3.2 GIS Spatial Analyst s slope analysis tool, overlaying each drainage basin with a slope raster map created from a USGS 1-ft topographic map. A slope of 0.001% was used for the lake-only basins for modeling purposes. The slope input value for each basin is listed in Table 3-3. 3-9 MACTEC

Table 3-2. Land Cover and Imperviousness by Land Use Land Cover (Acres) Total Basin Area Impervious Ratio Basin AG COM HDR MDR IND INS LDR REC TRN WAT WET w/ Lake w/o Lake w/o lake lake itself Impervious % 5 90 82.5 35 90 90 15 5 90 100 100 Lake Catherine 3.14 3.00 0.00 0.00 0.00 0.73 48.24 0.34 0.00 20.94 0.00 76.39 55.45 19.42 100 Lake Charity 82.63 0.00 0.00 152.07 0.00 20.78 0.08 5.11 10.43 56.15 17.73 344.98 288.83 35.81 100 Lake Destiny 4.09 35.34 12.11 90.90 0.00 0.00 0.00 0.58 0.00 37.99 0.00 181.01 143.02 51.63 100 Lake Eulalia 1.61 0.00 0.00 0.00 0.00 0.00 9.94 0.00 0.00 5.83 0.00 17.38 11.55 13.61 100 Lake Faith 0.53 14.71 8.93 103.01 0.00 2.82 0.00 13.27 8.86 31.67 0.00 183.80 152.13 44.61 100 Lake Gem 0.00 112.69 41.42 69.74 0.00 17.35 0.00 23.87 15.39 8.12 0.00 288.58 280.46 67.98 100 Lake Harvest 0.00 0.00 0.00 0.98 0.00 0.00 13.63 20.27 0.00 10.26 0.47 45.61 35.35 10.95 100 Lake Hope 24.76 0.00 6.06 63.89 0.00 0.00 0.00 8.95 0.00 29.66 14.51 147.83 118.17 36.86 100 Lake Hungerford 0.00 31.47 0.00 21.03 0.00 0.00 14.01 1.69 18.17 15.28 0.00 101.65 86.37 62.78 100 Lake Jackson 0.73 1.01 0.00 68.59 0.00 0.00 0.00 22.84 7.00 23.80 0.00 123.97 100.17 32.34 100 Lake Lily 0.00 30.99 1.84 0.00 0.00 0.94 0.13 6.55 8.17 5.28 0.00 53.90 48.62 78.06 100 Lake Love 15.01 0.07 0.00 1.20 0.00 0.00 0.00 0.00 0.00 4.08 0.00 20.36 16.28 7.58 100 Lake Lucien 25.68 156.68 0.00 1.31 0.00 6.71 0.74 47.93 80.73 52.81 18.75 391.34 338.53 71.69 100 Lake Maitland 1.38 32.58 30.83 163.65 0.00 8.06 574.20 77.62 4.70 436.80 0.00 1329.82 893.02 23.92 100 Lake Minnehaha 0.00 47.60 8.40 348.90 0.00 0.00 0.00 15.23 32.33 94.62 24.91 571.99 477.37 47.48 100 Lake Nina 0.69 5.94 7.09 28.85 0.00 0.48 16.60 7.45 3.74 11.78 8.45 91.07 79.29 45.96 100 Lake Sybelia 18.81 29.16 17.83 313.01 0.00 41.69 51.51 7.68 1.85 81.04 0.00 562.58 481.54 41.27 100 Lake Lomond 3.95 52.87 2.95 0.00 0.00 0.00 0.00 0.68 0.00 7.85 0.00 68.30 60.45 83.12 100 Park Lake 2.18 4.34 46.83 30.74 0.00 3.79 13.76 19.13 0.00 31.87 0.29 152.93 121.06 49.67 100 Unnamed Lake 2.44 31.27 0.00 1.51 0.00 3.81 0.00 0.00 9.41 4.56 0.00 53.00 48.44 84.00 100 Source: MACTEC, 2005. Prepared: PZ Checked: DS Note: AG = Agricultural COM = Commercial HDR = High Density Residential IND = Industrial INS = Institutional LDR = Low Density Residential MDR = Medium Density Residential REC = Recreational TRN = Transportation WAT = Open Water WET = Wetlands 3-10 MACTEC

Table 3-3. Basin Slope Zone Standard Overall Area with Area w/o Basin Code Count Max Mean Deviation Slope water (acres) water (acres) Final Slope Lake Bell* 8 809 4.07 1.08 1.07 0.33 Lake Catherine 10 345 16.73 5.15 4.63 1.57 76.39 55.45 2.16 Lake Charity 23 1572 17.55 4.38 3.72 1.34 344.98 288.83 1.60 Lake Destiny 27 738 9.70 2.25 2.03 0.69 181.01 143.02 0.87 Lake Eulalia 9 79 18.48 9.12 5.41 2.78 17.38 11.55 4.18 Lake Faith 21 873 15.81 3.13 3.22 0.95 183.80 152.13 1.15 Lake Gem 6 1365 14.20 2.07 1.81 0.63 288.58 280.46 0.65 Lake Howell* 18 3699 12.76 2.00 1.74 0.61 Lake Harvest 14 207 4.38 1.32 0.97 0.40 45.61 35.35 0.52 Lake Hope 22 634 20.08 4.83 4.03 1.47 147.83 118.17 1.84 Lake Hungerford 13 455 18.54 2.53 5.58 0.77 101.65 86.37 0.91 Lake Jackson 12 564 13.83 1.69 1.50 0.52 123.97 100.17 0.64 Lake Lily 5 235 13.58 3.81 3.63 1.16 53.90 48.62 1.29 Loch Lomond 25 306 6.46 1.56 1.34 0.48 68.30 60.45 0.54 Lake Love 19 2491 16.74 2.35 2.32 0.72 556.80 530.99 0.75 Lake Lucien 16 1752 18.54 1.26 1.53 0.38 391.34 338.53 0.44 Lake Maitland 3 6058 18.58 2.20 2.65 0.67 1329.82 893.02 1.00 Lake Minnehaha 17 2699 14.98 2.91 2.79 0.89 571.99 477.37 1.07 Lake Nina 4 412 11.66 3.40 2.75 1.04 91.07 79.29 1.19 Park Lake 7 695 15.90 3.45 3.06 1.05 152.93 121.06 1.33 Lake Seminary 20 1312 11.40 2.20 2.42 0.67 282.58 228.05 0.83 Lake Shadow 15 1512 8.48 1.81 2.08 0.55 315.91 241.76 0.72 Lake Sybelia 11 2373 29.18 3.02 4.08 0.92 562.58 481.54 1.07 Unnamed Lake 24 275 7.57 3.08 1.84 0.94 53.00 48.44 1.03 Lake Waumpi 1 3439 15.19 2.14 2.34 0.65 505.60 455.00 0.72 Wetland 2 2174 16.56 3.33 3.36 1.02 476.20 476.20 1.02 Lake Wood 26 370 14.10 3.26 3.17 0.99 81.10 77.40 1.04 Source: MACTEC, 2005. Prepared: PZ Checked: DS *Note: Located outside research area Hydraulic Width. The hydraulic width of each basin was required input for the SWMM model. Theoretically, it should be calculated by dividing basin area by its hydrologic length, which is obtained by identifying the hydrologically farthest point from the basin boundary point. In this model, it was first approximated by taking the square root of the basin area and then adjusting the value so that the 25-year peak stage corresponded to the output from the original model to within 20%, thus calibrating the SWMM model with the adicpr model. The width used for each basin is listed in Table 3-4. Lake Control Elevation. Lake control elevations were entered for each of the three outfalls and for each storage basin (lake). The three outfalls (Howell, Spring, and Shadow) and the storage basins can be seen with their corresponding invert elevations in Appendix A. Geometry. The geometry of each lake, which functioned as a storage unit, was defined by a maximum depth, initial depth, and stage-storage table. The maximum depth limits the height of the water in the lake, the initial depth lets the model know the original depth of water before an event, 3-11 MACTEC

and the stage-storage table gives the volume of water that the lake can hold. Geometric parameters for the lakes can be seen in Appendix A. These hydrologic parameters are summarized in Table 3-4. The actual input tables used for the SWMM model can be seen in Appendix A. Table 3-4. Hydrologic Lake Parameter Totals Basin Percent Impervious Percent Slope Width Lake Bell* N/A N/A N/A Lake Catherine 100 0.001 955 Lake Catherine Basin 19.42 2.16 1554 Lake Charity 100 0.001 1564 Lake Charity Basin 35.81 1.6 3189 Lake Destiny 100 0.001 1200 Lake Destiny Basin 51.63 0.87 2496 Lake Eulalia 100 0.001 504 Lake Eulalia Basin 13.61 4.18 709 Lake Faith 100 0.001 1173 Lake Faith Basin 44.61 1.15 1578 Lake Gem 100 0.001 594 Lake Gem Basin 67.98 0.65 10000 Lake Harvest 100 0.001 400 Lake Harvest Basin 10.95 0.52 500 Lake Hope 100 0.001 1137 Lake Hope Basin 36.86 1.84 1763 Lake Howell* N/A N/A N/A Lake Howell Basin* N/A N/A N/A Lake Hungerford 100 0.001 816 Lake Hungerford Basin 62.78 0.91 1940 Lake Jackson 32.34 0.001 1018 Lake Jackson Basin 100 0.64 1704 Lake Killarney* N/A N/A N/A Lake Killarney Basin* 25 0.5 5000 Lake Lily 100 0.001 484 Lake Lily Basin 78.06 1.29 1164 Lake Love 100 0.001 422 Lake Love Basin 7.58 2 842 Lake Lucien 100 0.001 500 Lake Lucien Basin 71.69 0.44 600 Lake Maitland 100 0.001 10000 Lake Maitland Basin 23.92 1 30000 Lake Minnehaha 100 0.001 5000 Lake Minnehaha Basin 47.48 1.07 20000 Lake Nina 100 0.001 667 Lake Nina Basin 45.96 1.19 5000 Lake Osceola* N/A N/A N/A Lake Osceola Basin* 50 1 30000 Lake Seminary* N/A N/A N/A 3-12 MACTEC

Table 3-4. Hydrologic Lake Parameter Totals Basin Percent Impervious Percent Slope Width Lake Seminary Basin* N/A N/A N/A Lake Shadow 100 0.001 1797 Lake Shadow Basin 70 0.72 3677 Lake Sybelia 100 0.001 10000 Lake Sybelia Basin 41.27 1.07 15000 Lake Waumpi Lake Waumpi Basin 25 0.72 4693 Lake of the Woods* N/A N/A N/A Lake of the Woods Basin 25 0.75 4925 Loch Lomond 100 0.001 585 Loch Lomond Basin 83.12 0.54 1634 Park Lake 100 0.001 2000 Park Lake Basin 49.67 1.33 6000 Unnamed Lake 100 0.001 446 Unnamed Lake Basin 84 1.03 1453 Wetland 60 1.02 4360 BMP Pond 100 0.001 448 Source: MACTEC, 2005. Prepared: PZ Checked: DS *Note: Located outside research area. 3.3.2 Conveyance Systems Parameters The following are hydrologic parameters necessary for the SWMM model that pertain to the pipe systems joining the lakes within the City of Maitland: Length. The lengths of the conduits in Maitland were entered into the model and are listed in Table 3-5. Manning s roughness coefficient. Manning s n is a factor that accounts for channel roughness. Typical Manning s n values for concrete channels range from 0.012 to 0.018 and the value for a smooth concrete channel is typically 0.011 (Aldridge 87). The Manning s n values used for this study are listed in Table 3-5. Geometry. The cross-sectional shape and size were entered for every pipe modeled. The shapes included circular, closed-rectangular, trapezoidal, and open-rectangular. Pipe sizes ranged from 1.5 to 12 feet tall and varied greatly in width. A maximum depth value was entered for each of the pipe junctions in Maitland s system, which is the distance from invert elevation to surface elevation. The geometry of each pipe modeled in this study is listed in Table 3-5. Invert Elevations. Each pipe junction was assigned an invert elevation that was obtained from survey data as well as as-built drawings. The input list of invert elevations use for this study can be seen in Table 3-5. 3-13 MACTEC

Table 3-5. Hydrologic Conveyance System Parameters Pipe Size Pipe ID Pipe Type (ft) Pipe Length (ft) Inlet Node Inlet Elev.(ft) Outlet Node Outlet Elev. (ft) Slope Manning Coeff, N Geom1 Geom2 Geom3 Geom4 B3.3-B3.1 Circular 7.0 206.5 B3.3 89.90 B3.1 89.50 0.002 0.011 7.0 0 0 0 8.66 38.48 1.64 333.18 BMPPOND1-SHADOW Trapezoidal 6*60*Slope2 156.0 BMPPOND1 81.8 SHADOW 81.50 0.002 0.03 6 60 2 2 6.35 432.00 10.80 2742.08 C9.2-C9.1 Circular 4.0 162.8 C9.2 75.0 C9.1 73.00 0.012 0.011 4 0 0 0 15.01 12.57 0.50 188.66 E12.2-E12.1 Circular 3.0 122.1 E12.2 69.2 E12.1 68.00 0.010 0.011 3 0 0 0 11.08 7.07 0.25 78.35 E4.15-E4.6 Circular 3.0 379.9 E4.15 76.3 E4.6 72.50 0.010 0.011 3 0 0 0 11.18 7.07 3.02 79.05 E4.17-E4.15 Circular 3.0 253.2 E4.17 78.8 E4.15 76.30 0.010 0.011 3 0 0 0 11.11 7.07 2.50 78.54 E4.2-E4.1 Circular 4.5 13.9 E4.2 69.0 E4.1 68.00 0.072 0.011 4.5 0 0 0 39.34 15.90 15.30 625.71 E4.4-E4.2 Circular 4.5 205.4 E4.4 71.0 E4.2 69.00 0.010 0.011 4.5 0 0 0 14.46 15.90 15.00 229.95 E4.5-E4.4 Circular 4.5 97.8 E4.5 72.0 E4.4 71.00 0.010 0.011 4.5 0 0 0 14.82 15.90 14.80 235.64 E4.6-E4.5 Circular 4.5 48.3 E4.6 72.5 E4.5 72.00 0.010 0.011 4.5 0 0 0 14.91 15.90 14.50 237.09 EU-CA Rect Closed 12*12 50.0 EULALIA 65.1 CATHERIN 65.00 0.002 0.011 12 12 0 0 12.60 144.00 4.16 1814.48 F2.21-F2.2 Circular 3.5 27.8 F2.21 74.5 F2.2 74.20 0.011 0.011 3.5 0 0 0 12.87 9.62 7.29 123.85 F2.23-F2.21 Circular 3.5 217.0 F2.23 76.5 F2.21 74.50 0.009 0.011 3.5 0 0 0 11.90 9.62 7.06 114.46 F2.27-F2.23 Circular 3.0 291.3 F2.27 79.4 F2.23 76.50 0.010 0.011 3 0 0 0 11.16 7.07 6.05 78.86 F2.29-F2.27 Circular 3.0 321.8 F2.29 82.5 F2.27 79.40 0.010 0.011 3 0 0 0 10.97 7.07 5.53 77.57 F2.2-F2.1 Circular 4.5 24.6 F2.2 74.2 F2.1 74.00 0.008 0.011 4.5 0 0 0 13.22 15.90 21.00 210.29 F2.31-F2.29 Circular 3.0 323.9 F2.31 85.5 F2.29 82.50 0.009 0.011 3 0 0 0 10.76 7.07 5.01 76.07 F2.3-F2.2 Circular 3.5 17.6 F2.3 74.4 F2.2 74.20 0.011 0.011 3.5 0 0 0 13.21 9.62 13.40 127.09 F2.4-F2.3 Circular 3.5 138.5 F2.4 75.5 F2.3 74.40 0.008 0.011 3.5 0 0 0 11.05 9.62 13.20 106.27 F2.5-F2.4 Circular 3.0 245.1 F2.5 78.0 F2.4 75.50 0.010 0.011 3 0 0 0 11.29 7.07 12.80 79.83 G8.21-G8.6 Circular 3.0 131.6 G8.21 79.3 G8.6 78.00 0.010 0.010 3 0 0 0 12.22 7.07 18.80 86.40 G8.2-G8.1 Circular 3.5 115.3 G8.2 69.2 G8.1 68.00 0.010 0.011 3.5 0 0 0 12.64 9.62 20.10 121.61 G8.3-G8.2 Circular 3.5 38.0 G8.3 69.5 G8.2 69.20 0.008 0.011 3.5 0 0 0 11.01 9.62 19.80 105.92 G8.4-G8.3 Circular 3.0 52.9 G8.4 70.0 G8.3 69.50 0.009 0.011 3 0 0 0 10.87 7.07 0.25 76.85 G8.5-G8.3 Circular 3.0 252.8 G8.5 77.0 G8.3 69.50 0.030 0.011 3 0 0 0 19.26 7.07 19.30 136.14 G8.6-G8.5 Circular 3.0 33.5 G8.6 78.0 G8.5 77.00 0.030 0.011 3 0 0 0 19.33 7.07 19.00 136.66 G8.7-G8.21 Circular 3.0 75.4 G8.7 80.0 G8.21 79.30 0.009 0.011 3 0 0 0 10.77 7.07 12.80 76.15 G8.8-G8.7 Circular 3.0 150.4 G8.8 81.5 G8.7 80.00 0.010 0.011 3 0 0 0 11.17 7.07 12.50 78.94 H18.3-H18.2 Circular 4.0 153.6 H18.3 70.0 H18.2 67.00 0.020 0.011 4 0 0 0 18.93 12.57 4.01 237.89 H24.2-H24.1 Circular 5.0 219.0 H24.2 68.0 H24.1 66.50 0.007 0.011 5 0 0 0 13.01 19.63 0.50 255.42 J3.2-J3.1 Circular 3.0 63.4 J3.2 69.5 J3.1 68.50 0.016 0.011 3 0 0 0 14.04 7.07 7.76 99.26 J3.3-J3.2 Circular 3.0 39.4 J3.3 70.0 J3.2 69.50 0.013 0.011 3 0 0 0 12.60 7.07 7.50 89.04 K8.2-K8.1 Circular 8.0 219.0 K8.2 76.0 K8.1 72.00 0.018 0.011 8 0 0 0 29.06 50.27 9.01 1460.69 LI-MA Circular 1.5 770.0 LILY 68.3 MI-NI-MA 66.30 0.003 0.013 1.5 0 0 0 3.04 1.77 5.63 5.37 LO-CH Circular 1.5 220.0 LOVE 66.7 CHARITY 66.00 0.003 0.024 1.5 0 0 0 1.77 1.77 0.41 3.12 M15.10-M15.47 Circular 3.0 32.6 M15.10 85.0 M15.47 84.50 0.015 0.011 3 0 0 0 13.85 7.07 4.50 97.88 M15.26-M15.3 Circular 5.0 280.8 M15.26 78.0 M15.3 75.40 0.009 0.011 5 0 0 0 15.12 19.63 17.30 296.97 M15.2-M15.1 Circular 5.0 15.7 M15.2 75.2 M15.1 75.00 0.013 0.011 5 0 0 0 17.74 19.63 17.80 348.33 M15.3-M15.2 Circular 5.0 16.7 M15.3 75.4 M15.2 75.20 0.012 0.011 5 0 0 0 17.20 19.63 17.60 337.74 M15.47-M15.9 Circular 3.0 16.6 M15.47 84.5 M15.9 84.00 0.030 0.011 3 0 0 0 19.41 7.07 5.27 137.17 M15.6-M15.26 Circular 3.0 37.6 M15.6 78.4 M15.26 78.00 0.011 0.011 3 0 0 0 11.53 7.07 6.31 81.48 M15.7-M15.6 Circular 3.0 304.7 M15.7 81.4 M15.6 78.40 0.010 0.011 3 0 0 0 11.09 7.07 6.04 78.43 M15.8-M15.7 Circular 3.0 13.4 M15.8 81.5 M15.7 81.40 0.007 0.011 3 0 0 0 9.65 7.07 5.76 68.20 M15.9-M15.8 Circular 3.0 289.0 M15.9 84.0 M15.8 81.50 0.009 0.011 3 0 0 0 10.40 7.07 5.51 73.51 M16.15-M16.38 Circular 5.0 173.8 M16.15 88.0 M16.38 86.50 0.009 0.011 5 0 0 0 14.60 19.63 13.10 286.76 M16.18-M16.40 Circular 5.0 359.3 M16.18 91.2 M16.40 89.20 0.006 0.011 5 0 0 0 11.73 19.63 8.31 230.25 M16.19-M16.18 Circular 3.0 393.0 M16.19 93.2 M16.18 91.20 0.005 0.011 3 0 0 0 7.98 7.07 7.02 56.38 M16.34-M16.36 Circular 5.0 155.9 M16.34 81.5 M16.36 80.30 0.008 0.011 5 0 0 0 13.79 19.63 15.80 270.77 M16.36-M16.7 Circular 5.0 256.0 M16.36 80.3 M16.7 79.10 0.005 0.011 5 0 0 0 10.76 19.63 16.10 211.30 M16.37-M16.8 Circular 5.0 157.4 M16.37 85.5 M16.8 84.00 0.010 0.011 5 0 0 0 15.35 19.63 14.60 301.33 M16.38-M16.37 Circular 5.0 80.3 M16.38 86.5 M16.37 85.50 0.012 0.011 5 0 0 0 17.54 19.63 14.30 344.41 M16.40-M16.15 Circular 5.0 203.0 M16.40 89.2 M16.15 88.00 0.006 0.011 5 0 0 0 12.09 19.63 12.30 237.30 M16.8-M16.34 Circular 5.0 292.6 M16.8 84.0 M16.34 81.50 0.009 0.011 5 0 0 0 14.53 19.63 15.30 285.27 Velocity (ft/sec) Area (sq ft) Pipe Peak Flow (cfs)* Pipe Flow Capacity (cfs) 3-14 MACTEC

Table 3-5. Hydrologic Conveyance System Parameters Pipe Size Pipe ID Pipe Type (ft) Pipe Length (ft) Inlet Node Inlet Elev.(ft) Outlet Node Outlet Elev. (ft) Slope Manning Coeff, N Geom1 Geom2 Geom3 Geom4 M6.25-M5 Circular 4.0 31.4 M6.25 75.7 M6.5 75.40 0.010 0.011 4 0 0 0 13.24 12.57 6.83 166.38 M6.5-M6.4 Circular 4.0 57.5 M6.5 75.4 M6.4 74.90 0.009 0.011 4 0 0 0 12.63 12.57 7.08 158.73 M6.6-M6.25 Circular 4.0 314.8 M6.6 78.0 M6.25 75.70 0.007 0.011 4 0 0 0 11.58 12.57 6.55 145.51 M6.7-M6.6 Circular 4.0 168.1 M6.7 79.5 M6.6 78.00 0.009 0.011 4 0 0 0 12.80 12.57 6.28 160.79 M6.8-M6.7 Circular 3.0 70.3 M6.8 80.0 M6.7 79.50 0.007 0.010 3 0 0 0 10.37 7.07 4.27 73.32 M6.9-M6.8 Circular 3.0 314.4 M6.9 82.5 M6.8 80.00 0.008 0.011 3 0 0 0 9.97 7.07 4.01 70.48 n0.10-n0.9 Circular 3.0 73.2 n0.10 74.4 n0.9 74.40 0.001 0.011 3 0 0 0 2.61 7.07 11.10 18.48 n0.11-n0.10 Circular 3.0 119.5 n0.11 76.2 n0.10 74.44 0.015 0.011 3 0 0 0 13.50 7.07 10.80 95.39 n0.1-howell Trapezoidal 8*60*Slope2 400.0 n0.1 66.8 HOWELL 53.60 0.033 0.03 8 60 2 2 30.93 608.00 14.30 18807.03 n0.2-n0.1 Circular 4.5 122.3 n0.2 67.3 n0.1 66.80 0.004 0.011 4.5 0 0 0 9.37 15.90 14.40 148.97 n0.3-n0.2 Circular 4.5 71.5 n0.3 67.6 n0.2 67.30 0.004 0.011 4.5 0 0 0 9.49 15.90 14.10 150.96 n0.4-n0.3 Circular 4.0 191.5 n0.4 68.4 n0.3 67.60 0.004 0.011 4 0 0 0 8.76 12.57 13.90 110.03 n0.5-n0.4 Circular 4.0 211.1 n0.5 69.3 n0.4 68.40 0.004 0.011 4 0 0 0 8.84 12.57 13.60 111.14 n0.6-n0.5 Circular 4.0 80.8 n0.6 69.5 n0.5 69.30 0.002 0.011 4 0 0 0 6.74 12.57 13.30 84.69 n0.7-n0.6 Circular 4.0 93.1 n0.7 70.3 n0.6 69.50 0.009 0.011 4 0 0 0 12.63 12.57 12.80 158.74 n0.8-n0.7 Circular 3.0 294.3 n0.8 70.8 n0.7 70.31 0.002 0.011 3 0 0 0 4.65 7.07 11.60 32.90 n0.9-n0.8 Circular 3.0 323.1 n0.9 74.4 n0.8 70.82 0.011 0.011 3 0 0 0 11.77 7.07 11.40 83.20 n1.1-n0.11 Circular 3.0 49.7 N1.1 76.4 n0.11 76.18 0.004 0.011 3 0 0 0 7.44 7.07 10.50 52.59 N1.2-N1.1 Circular 3.0 211.5 N1.2 77.0 N1.1 76.40 0.003 0.011 3 0 0 0 5.96 7.07 10.30 42.09 N1.3-N1.2 Circular 3.0 136.4 N1.3 77.5 N1.2 77.00 0.004 0.011 3 0 0 0 6.77 7.07 10.00 47.85 OCB3.1-LUC-HAR Trapezoidal 4*20*Slope2 182.0 B3.1 89.6 LUC-HAR 89.50 0.001 0.05 4 20 2 2 1.44 112.00 1.63 161.14 OCC9.1-CHA Trapezoidal 4*30*Slope2 288.0 C9.1 73.0 CHARITY 67.50 0.019 0.03 4 30 2 2 14.82 152.00 0.75 2253.21 OCE12.1-FAITH Trapezoidal 4*20*Slope2 50.0 E12.1 68.0 FAITH 67.50 0.010 0.05 4 20 2 2 6.14 112.00 0.50 687.45 OCE4.1-FAITH Trapezoidal 4*30*Slope2 151.0 E4.1 68.0 FAITH 67.50 0.003 0.03 4 30 2 2 6.17 152.00 15.60 938.24 OCF2.1-MINIMA Trapezoidal 8*50*Slope2 1990.0 F2.1 74.0 MI-NI-MA 66.30 0.004 0.04 8 50 2 2 7.78 528.00 21.10 4109.17 OCG8.1-WETLAND Trapezoidal 6*80*Slope2 1000.0 G8.1 68.0 WETLAND 60.50 0.008 0.04 6 80 2 2 9.64 552.00 19.90 5322.13 OCH18.2-MINIMA Trapezoidal 6*30*Slope2 500.0 H18.2 67.0 MI-NI-MA 66.30 0.001 0.03 6 30 2 2 5.02 252.00 3.99 1263.95 OCH24.1-MINIMA Trapezoidal 6*50*Slope2 10.0 H24.1 66.5 MI-NI-MA 66.30 0.020 0.03 6 50 2 2 20.10 372.00 0.51 7478.03 OCJ3.1-LILY Trapezoidal 6*60*Slope2 20.0 J3.1 68.5 LILY 68.30 0.010 0.03 6 60 2 2 14.47 432.00 7.76 6252.91 OCK8.1-GEMPARK Trapezoidal 6*60*Slope2 96.0 K8.1 72.0 GEM-PARK 69.40 0.027 0.04 6 60 2 2 17.87 432.00 9.29 7717.81 OCM15.1-SYBELLA Trapezoidal 8*60*Slope2 230.0 M15.1 75.0 SYBELLIA 72.90 0.009 0.011 8 60 2 2 44.37 608.00 17.90 26979.73 OCM16.7-JACKSON Trapezoidal 6*60*Slope2 100.0 M16.7 79.1 JACKSON 78.40 0.007 0.03 6 60 2 2 12.11 432.00 16.80 5231.56 OCM6.4-SYBELIA Trapezoidal 8*60*Slope2 449.0 M6.4 74.9 SYBELIA 72.90 0.004 0.03 8 60 2 2 11.36 608.00 7.25 6909.63 OCP1.2-SHADOW Trapezoidal 6*60*Slope2 330.0 P1.2 82.0 SHADOW 81.50 0.002 0.03 6 60 2 2 5.63 432.00 2.74 2433.94 P1.5-P1.2 Circular 3.5 98.30 P1.5 83.0 P1.2 82.00 0.010 0.011 3.5 0 0 0 12.50 9.62 2.50 120.25 P1.8-P1.5 Circular 3.0 138.7 P1.8 84.0 P1.5 83.00 0.007 0.011 3 0 0 0 9.49 7.07 1.00 67.11 t1.1bmppond1 Rect Open 7*40 20.0 t1.1 81.9 BMPPOND1 81.80 0.005 0.011 7 40 0 0 28.69 280.00 2.78 8034.26 t1.2-t1.1 Circular 3.5 100.9 t1.2 82.3 t1.1 81.90 0.004 0.011 3.5 0 0 0 7.80 9.62 2.78 75.08 t1.3-t1.2 Circular 3.5 108.7 t1.3 82.6 t1.2 82.30 0.003 0.011 3.5 0 0 0 6.72 9.62 2.77 64.69 t1.4-t1.3 Circular 3.5 229.1 t1.4 83.2 t1.3 82.62 0.003 0.011 3.5 0 0 0 6.29 9.62 2.51 60.51 t1.5-t1.4 Circular 3.5 58.3 t1.5 86.1 t1.4 83.21 0.050 0.011 3.5 0 0 0 27.60 9.62 2.50 265.51 t2.1bmppond1 Rect Open 7*40 20.0 t2.1 82.0 BMPPOND1 81.80 0.010 0.011 7 40 0 0 40.58 280.00 5.57 11362.17 t2.2-t2.1 Circular 3.5 113.7 t2.2 82.5 t2.1 82.00 0.004 0.011 3.5 0 0 0 8.14 9.62 5.56 78.28 t2.2-t2.3 Circular 3.0 80.5 t2.3 83.0 t2.2 82.49 0.006 0.011 3 0 0 0 8.90 7.07 5.56 62.90 t2.4-t2.3 Circular 3.0 62.9 t2.4 83.0 t2.3 83.00 0.001 0.011 3 0 0 0 2.82 7.07 5.30 19.94 t2.5-t2.4 Circular 3.0 148.9 t2.5 83.1 t2.4 83.04 0.000 0.011 3 0 0 0 2.24 7.07 5.02 15.87 t2.6-t2.5 Circular 3.0 400.5 t2.6 83.6 t2.5 83.10 0.001 0.011 3 0 0 0 3.95 7.07 4.78 27.93 t2.7-t2.6 Circular 3.0 158.2 t2.7 83.8 t2.6 83.60 0.001 0.011 3 0 0 0 3.67 7.07 4.76 25.91 t2.8-t2.7 Circular 3.0 50.0 t2.8 85.8 t2.7 83.77 0.041 0.011 3 0 0 0 22.53 7.07 2.25 159.27 Source: MACTEC, 2005. Prepared: PZ Checked: DS *Note: The peak flow is calculated by SWMM using a 25-year/24-hour duration storm for Florida Zone 7. The total rainfall is 8.4 inches. Velocity (ft/sec) Area (sq ft) Pipe Peak Flow (cfs)* Pipe Flow Capacity (cfs) 3-15 MACTEC

3.4 Model Calibration Originally, the SWMM model was created by inputting data obtained from the 1996 SLMP. The model was then calibrated to match the 1996 output for the 25-year peak stage to within 20%. Calibration was achieved by varying the width of the basins. Once our SWMM model output aligned with the 1996 adicpr output, it was updated with information to include annexations incorporated into the City of Maitland and improvements made to the stormwater drainage system since preparation of the last SLMP in 1996. 3.5 Model Results Using the physical characteristics of the basin and the hydrological parameters discussed above, the SWMM model computes time-dependent runoff rates, peak discharges from each subbasin, lake elevations, and the water surface elevation of the major conveyance systems between lakes. The following methods are used: The SWMM model develops a runoff hydrograph of each subbasin within the model. A runoff hydrograph is a relationship between time and discharge from a subbasin. From the hydrologic parameters developed for a subbasin, the model computed the discharge rate and volume of runoff for each time interval specified. For this study, a time interval of fifteen (15) minutes was used, which means that for the 24-hour duration storms, the discharges and volumes were computed every 15 minutes. The peak discharge of each runoff hydrograph is recorded. The model routes and combines runoff hydrographs from each subbasin into a composite hydrograph to each lake. Because a subbasin hydrograph is time dependent, adding them together will produce an accurate composite hydrograph of flow into the lake. The routed off-site hydrographs from the SJRWMD HEC-1 model are also assigned to the appropriate lakes (i.e. Lakes Gem and Maitland). Using the stage-storage-discharge relationship of a lake, the inflow hydrographs are hydraulically routed through the lakes. Lake stage (i.e. elevation), storage volume and the amount of discharge (if the lake has a discharge) into and from each lake is computed for each time interval. For this study, a time interval of 15 minutes was used, which means that for the 24-hour duration storms, the lake stages, volumes, and discharges were computed every 15 minutes. The peak stage, volume, and discharge for each lake is recorded. The stage-storage-discharge relationship expresses the storage volume available in the lake and the discharge capacity of the lake s outfall structure at stages above the control elevation. Stage-storagedischarge data for approximately half of the lakes in this study was obtained from the SJRWMD HEC-1 models for the Howell Creek (SJRWMD 1994) and Little Wekiva River studies (SJRWMD 1989) and the Orange County lake study (OCSMD 1993). Where previous modeling data was not available, storage was computed for a lake internally by SWMM for stages above control elevation using the lake s area; discharge was also computed internally by SWMM for outfall structures (e.g. pipes, weirs, etc.) obtained form best available information. If the lake discharges or has an outfall, a discharge hydrograph is computed and, using the geometry of the channel or pipe connecting lakes, this discharge hydrograph is routed to the next lake, where it becomes an inflow component to that lake. 3-16 MACTEC

In this way, the SWMM model accounts for the stormwater runoff over the entire basin being studied by hydrologically computing runoff in fifteen-minute increments and by hydraulically routing this runoff through the lake systems in fifteen-minute increments. Lakes with the same control elevation and a large, open water connection between them were combined into one lake node for modeling purposes. The following is a description of those lake systems for flood routing purposes: Lake Gem and Park Lake were combined to form node GEM-PARK. Lake Minnehaha, Lake Nina, and Lake Maitland were combined to form node MI-NI-MA. Lake Lucien and Lake Harvest were combined to form node LUC-HAR. A summary of Water Surface Elevations (WSEs) in 10, 25, and 100-year events for each lake is presented in Table 3-6. The SWMM model predicts lake levels during design storm conditions. Conveyance systems that have an equivalent 36-inch pipe or larger were also modeled simultaneously in SWMM in order to more accurately describe the stormwater routing relationship between storm pipe and lake system as well as to determine if there were any design deficiencies in the major drainage system within the City of Maitland. The results of the modeling did not identify any significant flooding problems as a result of the major conveyance systems, so there appear to not be any design deficiencies. The storm pipe capacity analysis based on Manning s formula justified that these systems could adequately handle the runoff from a 25-year storm 24-hour duration event. It should be noted that storm sewer pipes smaller than 36 inches were not modeled, and in some cases, a more detailed hydraulic analysis should be performed with survey data. There may be some areas of the City of Maitland that experience minor flooding problems due to inadequate inlet capacity or inadequate capacity of the minor drainage systems. Evaluation of these systems is beyond the scope of this study. Appendix B contains the SWMM model output. Table 3-6. Lake Stage Data Lake Attribute Lake Name 10-Year Storm 25-Year Storm 100-Year Storm Peak Stage Maximum Peak Stage Maximum (feet) Depth (feet) (feet) Depth (feet) Maximum Depth (feet) Peak Stage (feet) Outfall Howell 0.00 53.60 0.00 53.60 0.00 53.60 Outfall Spring 0.00 64.30 0.00 64.30 0.00 64.30 Outfall Shadow 0.00 81.50 0.00 81.50 0.00 81.50 Storage Destiny 1.42 87.62 1.65 87.85 2.19 88.39 Storage L_lomond 2.53 90.83 2.59 90.89 2.75 91.05 Storage Unnamed 6.03 91.33 6.85 92.15 7.57 92.87 Storage Luc-har* 2.17 91.67 2.50 92.00 3.32 92.82 Storage Hungerfo 1.35 95.35 1.35 95.35 1.35 95.35 Storage Jackson 1.77 80.17 1.89 80.29 2.05 80.45 Storage Sybelia 2.13 75.03 2.51 75.41 3.53 76.43 Storage Eulalia 0.32 70.32 0.37 70.37 0.49 70.49 Storage Catherin 1.05 71.05 1.25 71.25 1.79 71.79 Storage Love 0.82 68.32 0.98 68.48 1.34 68.84 Storage Faith 1.55 69.05 1.77 69.27 2.32 69.82 Storage Hope 0.62 68.12 0.68 68.18 0.82 68.32 Storage Charity 1.77 69.27 2.10 69.60 3.00 70.50 3-17 MACTEC

Table 3-6. Lake Stage Data Lake Attribute Lake Name 10-Year Storm 25-Year Storm 100-Year Storm Peak Stage Maximum Peak Stage Maximum (feet) Depth (feet) (feet) Depth (feet) Maximum Depth (feet) Peak Stage (feet) Storage Lily 3.47 71.77 4.08 72.38 5.50 73.80 Storage Gem-park * 3.23 72.63 3.66 73.06 4.72 74.12 Storage Woods 0.83 76.63 1.01 76.81 1.54 77.34 Storage Mi-ni-ma * 2.27 68.57 2.59 68.89 3.41 69.71 Storage Wetland 4.44 64.94 4.86 65.36 6.05 66.55 Storage Waumpi 3.70 63.90 4.08 64.28 5.02 65.22 Storage BMP Pond 0.19 82.09 0.21 82.11 0.24 82.14 Source: MACTEC, 2005. Prepared: PZ Checked: DS *Note: LUC-HAR represents Lake Lucient and Lake Harvest GEM-PARK represents Lake Gem and Lake Park MI-NI-MA represents Lake Minnehaha, Lake Nina, and Lake Maitland These lakes have the same start stage and peak stage elevation. 3-18 MACTEC