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Limited Flood Study(_) Limited Flood Study FOR Creek Meadows Subdivision Section 7, Phase One & Two AND Peach Creek South -Tributary 16.4.3 R.S. 1 +51 to R.S. 9+89 March 27, 2015 Prepared For: Creek Meadow Partners, L.P. 3988 Greens Prairie Road College Station, TX 77845 Prepared By: RME Consulting Engineers Texas Firm Registration No. F-4695 P.O. Box 9253 College Station, TX 77845 RME No. 26-0551 Limited Flood Study FOR Creek Meadows Subdivision Section 7, Phase One & Two AND Peach Creek South -Tributary 16.4.3 R.S. 1 +51 to R.S. 9+89 March 27, 2015 Prepared For: Creek Meadow Partners, L.P. 3988 Greens Prairie Road College Station, TX 77845 Prepared By: RME Consulting Engineers Texas Firm Registration No. F-4695 P.O. Box 9253 College Station, TX 77845 RME No. 26-0551 Limited Flood Study Creek Meadows Subdivision Section 7, Phase One & Two Peach Creek South -Tributary 16.4.3 TABLE OF CONTENTS: PAGE 1.0 General Information .....................................................•........•....................................................................... 1 1. I Scope of Report ....................................................................................................................................... I I .2 General Location ..................................................................................................................................... I I .3 Description of Existing & Developing Conditions .................................................................................. 1 1.4 FEMA Information .................................................................................................................................. 3 2.0 Watersheds & Sub-Drainage Basins ...........................................•................................................................. 3 2.1 Peach Creek South -Tributary 16.4.3 ..................................................................................................... 3 3.0 Hydrologic Modeling ..................•.•.......•..............•...............•............................•...••....................................... 3 3.1 SCS -TR20 Formula & Methodology .................................................................................................... 3 3.2 Cumulative Precipitation "P" .................................................................................................................. 5 3.3 SCS Runoff Curve Numbers "CN" ......................................................................................................... 5 3.4 Time of Concentration & Lag .................................................................................................................. 6 4.0 HEC-HMS Computations & Results .............................................................................•...........•.................. 8 4.1 Basin Model Summary ............................................................................................................................ 8 4.2 Meteorological Model Summary ............................................................................................................. 9 4.3 Control Specification Summary .............................................................................................................. 9 4.4 Storm water Runoff Quantities ................................................................................................................. 9 5.0 Hydraulic Modeling ..................................................................................................................•.................. 10 5.1 HEC-RAS Modeling & Methodology ................................................................................................... I 0 5.2 Geometric Data ...................................................................................................................................... 10 5.3 Manning's "N" Coefficient. ................................................................................................................... 11 5.4 Flow Data .............................................................................................................................................. 12 5.5 Plan Data ............................................................................................................................................... 12 6.0 HEC-RAS Computations & Results ............................•.•..•......................................................................... 12 6.1 Existing Floodplain Model .................................................................................................................... 12 6.2 Proposed Floodplain Model. .................................................................................................................. 12 7.0 Certification ...............•.........•................................•....................................................................................... 14 260-0551 Flood Study.docx Page -i LIST OF TABLES: PAGE Section 3.0 -Hydrologic Modeling Table #1: Rainfall Depth ........................................................................................................................................ 5 Table #2: Composite Curve Number ...................................................................................................................... 6 Table #3: Tu -Overland Sheet Flow ..................................................................................................................... 7 Table #4: T 12 -Shallow and/or Concentrated Flow ................................................................................................ 7 Table #5: Tc Summary ........................................................................................................................................... 7 Table #6: SCS TL Summary ................................................................................................................................... 8 Section 4.0 -HEC-HMS Computations & Results Table #7: Routed Runoff Values .......................................................................................................................... 10 Section 6.0 -HEC-RAS Computation & Results Table #8: Existing vs. Proposed Conditions Floodplain Comparison .................................................................. 13 LIST OF FIGURES: PAGE Section 1.0 -General Information Figure 1 -Standard Unit Hydrograph ..................................................................................................................... 2 Figure 2 -Routed Unit Hydrograph w/Detention ................................................................................................... 2 260-0551 Flood Study.docx Page -ii ATTACHMENTS: Appendix A -General Information Vicinity Map DFIRMMap Appendix B -Watersheds & Sub-Drainage Basins Limited Flood Study -Hydrologic & HydrauJjc Data Appendix C -Hydrologic Modeling GLO Location "P" Parameter Map GLO Scale "a" Parameter Map GLO Shape"µ" Parameter Map Hydrologic Soil Group Data Appendix D -HEC-HMS Computations & Results 50% Simulation Run 20% Simulation Run 10% Simulation Run 4% Simulation Run 2% Simulation Run 1 % Simulation Run 0.2% Simulation Run Appendix E -Hydraulic Modeling GP-0 I: Site Grading & Drainage Plan Limited Flood Study -Hydrologic & Hydraulic Data Appendix F -HEC-RAS Computations & Results HEC-RAS Model Output Data 260-0551 Flood Study.docx Page -iii Limited Flood Study Creek Meadows Subdivision Section 7, Phase One & Two Peach Creek South -Tributary 16.4.3 1.0 GENERAL INFORMATION 1.1 Scope of Report: This drainage study' s scope includes the hydrologic and hydraulic evaluation, for LIMITED floodplain modeling, of Peach Creek South -Tributary 16.4.3 at current/existing conditions, and the proposed conditions with the channel realignment. All standard rainfall events were analyzed, however, the design and analyzed frequencies were the 4% and 1 % rainfall frequencies. This report, or proposed improvements, does not require procurement through the Federal Emergency Management Agency (FEMA) since the proposed improvement is unmapped floodplain. However, this report will be utilized as "better data" for modeling of the proposed channel realignment, to insure no-adverse impacts (zero-rise) to adjacent upstream landowners. The hydro logic and hydraulic models were analyzed in accordance with the criteria outlined in the "Unified Stormwater Design Guidelines" (USDG) manual of the City of College Station (CoCS) and acceptable FEMA standards. 1.2 General Location: The unstudied portion of Peach Creek South -Tributary 16.4.3, is located within the southern portion of Brazos County, Texas (and located within the corporate city limits of College Station). At this location the tributary generally runs north and south (north being upstream), within the project area. Ultimately the tributary discharges into the main stem of Peach Creek and thence into the Navasota River. The subject channel realignment is generally identified on the Vicinity Map, with its relationship to Bryan/College Station area, and is also approximately located at latitude 30°31'37.12"N and longitude 96°17'0. l O"W. This exhibit is contained in the "Attachment -Appendix A" section of this report. The specific portion of Peach Creek South -Tributary 16.4.3 that will be studied, in this report, is described by River Station (RS) 1 +51 (downstream limit of Creek Meadows Sudivision) to RS 9+80. At RS 1 +51 the creek has an approximate flowline of 281 .2 feet Mean Sea Level (MSL) and an upper flowline of 283.7 feet at RS 9+80. At Bridge 0.245 the flowline is approximately 181 feet. The studied length of creek is approximately 829 feet of river. 1.3 Description of Existing & Developing Conditions: EXISTING CONDITIONS: Currently, Peach Creek South -Tributary 16.4.3 has a very low to moderate developed/urbanized watershed with very little of its rivervine system experiencing 260-055 l Flood Study.docx Page - I Creek Meadows Subdivision Limited Flood Study RME Consulting Engineers March 27, 2015 channel modifications and minor disturbances due to upland urbanization. The vast majority of the tributary watershed is unimproved and rural in nature. The Brazos County soil maps, as reported on the NRCS Web Soil Survey web-based program, indicates that the watershed area is primarily comprised of Type C and D soils. These soils generally consist of clays or silty clay/sand mixtures with low absorption rates. DEVELOPING CONDITIONS: As mentioned above the Peach Creek South -Tributary 16.4.3 watershed is for all practical purposes undeveloped and primarily rural. However, some of the upstream limits of the watershed has experienced noticeable development. Therefore, as it is typical with urbanization, the low flow/high frequency rainfall events ( < 2-Yr Storm) generally flow through the detention facilities, where they exist, unimpeded and thus create greater occurrences of "bank-full" flows in the creek and therefore destabilize the creek creating scouring and erosion. Also typical with urbanization the recession limb of the hydro graph will grow in volume and length as the upstream detention facilities attenuate increased impervious runoff. This is further illustrated in Figure 1 -"Standard Unit Hydrograph" and Figure 2-"Routed Hydrograph w/Detention". WI.OW HYOflOGRAPH Time to Peak ,._ ... P ak Rec uionUmb Buetlow TI me TimeBaa• Figure I -Standard Unit Hy drograph .301--~-+--E~l~--t~~+--~+-~-t-~--t~~t-~-t-~-1 -" I 0 201----lf---o'. 260-0551 Flood Study.docx 12 13 14 15 16 TIME -HOURS Figure 2 -Routed Hydrograph w/Detention Page -2 Creek Meadows Subdivision Limited Flood Study 1.4 FEMA Information: RME Consulting Engineers March 27, 2015 Peach Creek South -Tributary 16.4.3 is currently unmapped floodplain as graphically depicted on the Federal Emergency Management Agency (FEMA)-Flood Insurance Rate Map (FIRM) Community/Panel number 480083 0325E, with an effective date of May 16, 2012. A portion of the FIRM Panel Map, with the studied limits of Thompson Creek identified, is illustrated on DFIRM Map and is located in the "Attachment-Appendix A" portion of this study. There are no known hydrologic and hydraulic studies performed on this portion of the tributary. 2.0 WATERSHEDS & DRAINAGE AREAS 2.1 Peach Creek South -Tributary 16.4.3: As previously discussed the tributary is a secondary drainage system of the Navasota River. An exhibit of this watershed is provided and is entitled Limited Flood Study -Hydrologic & Hydraulic Data. This exhibit is contained within the "Attachment-Appendix B" section of report. As shown, the studied portion of the tributary is located within the upper reach of the Peach Creek main stem. Details of this secondary drainage basin is as follows: • Peach Creek South -Tributary 16.4.3 runs generally from south to north and encompasses an area of approximately 0.512 square-miles of drainage area; • The watershed of Peach Creek South -Tributary 16.4.3 has a approximate elevation range of 281' to 358' (MSL); 3.0 HYDROLOGIC MODELING 3.1 SCS -TR 20 Formula and Methodology: The Natural Resources Conservation Service (NRCS), formerly the Soil Conservation Service, developed the runoff curve number method as a means of estimating the amount of rainfall appearing as runoff. The SCS-TR 20 formula calculates the peak discharge and volumes in a reliable fashion for moderate sized (50 to 400 acres) watersheds. The SCS unit hydrograph procedure (also known as the TR-20 runoff method) generates a runoff hydrograph by the following basic steps. (For brevity, this is a simplified description.) The SCS-TR20 methodology was employed for hydrologic computations of the Thompson Creek watershed. 1. A rainfall distribution is selected which indicates how the storm depth will be distributed over time. This is usually a standardized distribution, such as the SCS ~ III storm, and often a standardized duration of 24 hours is selected; 2. The design storm depth is determined from rainfall maps, based on the return period being modeled. Combined with the rainfall distribution, this specifies the cumulative rainfall depth at all times during the storm; 260-0551 Flood Study.docx Page -3 Creek Meadows Subdivision Limited Flood Study RME Consulting Engineers March 27, 2015 3. Based on the Time-of-Concentration (Tc), the storm is divided into "bursts" of equal duration. For each burst, the SCS runoff equation and the average Curve Number (CN) are used to determine the portion of that burst that will appear as runoff; The SCS runoff equation determines the precipitation excess runoff that results from a given cumulative precipitation: (P-fa)2 Q= ------------(Q=O if P<la) (P-Ia)+S 1000 S= ----------10 CN with Ia= 0.2 s (P-.2S)2 Q= ------------ (P+. 8S) where, Q =Precipitation excess runoff (inches); P =Cumulative precipitation (inches)-Table C-6 of the USDG-further discussion in the next sub-section; Ia= Initial abstraction (inches); S =Potential maximum retention (inches); CN =Curve Number -The Antecendent Mositure Condition (AMC) 1 and 3 are implemented by adjusting the Curve Numbers. The AMC specifies the moisture level in the ground immediately prior to the storm. Four conditions are defined: 1 - I Dry 2 -II Normal 3 -III Wet 4 -Frozen or Saturated It is common policy to use AMC 2 for most design work. Other values should be used only under special circumstances. AMC 3 is sometimes used to study wet conditions, such as a spring rainfall event. AMC 3 usually causes a dramatic increase in runoff, and is not normally used for design purposes. Unless otherwise specified AMC 3 will be utilized for all hydrologic computations that employ the SCS-TR 20 method since it will yield the most conservative flood conditions. 4. A Unit Hydrograph, in conjunction with the Tc, is used to determine how the runoff from a single burst is distributed over time. The result is a complete runoff hydrograph for a single burst; 5. Individual hydrographs are added together for all bursts in the storm, yielding the complete runoff hydro graph for the storm. 260-0551 Flood Study.docx Page -4 Creek Meadows Subdivision Limited Flood Study 3.2 Cumulative Precipitation "P": RME Consulting Engineers March 27, 2015 As sited earlier the NRCS SCS-TR20 methodology utilizes rainfall depth "P" at various storm durations for the various storm frequencies that will be analyzed. The information reported in the SCS TP40 is provided in Table C-6 of the USDG, for Brazos County, TX, and is summarized as follows in Table #1 -"Rainfall Depth". However, these distribution maps do not include the 500-year rainfall frequency which is also required to be studied and modeled by FEMA. Therefore, in order to determine the rainfall depth "P" for this recurrence interval the Generalized Logistic Distribution equation, found in the USGS Water Resources Investigations Report 98-4044, will be utilized and is as follows. GLO, Xd(t) = p +(a/µ.)* {1 -((1-F) I F]ll} where, Xct(f) =Precipitation Depth for a give Rainfall Frequency (inches); ~' a, µ=Location, Scale, and Shape Parameters for the GLO Distribution. The appropriate maps are attached in the "Attachment -Appendix C" section of report; F = Annual non-exceedance probability; TABLE #1 Rainfall Depth Storm Duration 2-YR 5-YR 10-YR 25-YR 50-YR 100-YR 500-YR 24-hr 4.50 6.20 7.40 8.40 9.80 11.00 16.17 Where, ~ = 3 .50 a = 0.85 µ = -0.25 F = 0.998 3.3 SCS Runoff Curve Numbers "CN": The Soils Conservation Service (SCS) runoff Curve Number, for each sub-drainage basin, was determined by composite method of percentage of land cover to the total sub-drainage basin. These CNs were estimated from the NRCS, Urban Hydrology for Small Watersheds, TR 55 (June 1986) by comparison of runoff surface types. Runoff surface types where determined by field reconnaissance, aerial maps, and utilizing the NRCS Web Soil Survey web-based program. The associated sectional maps and Hydrologic Soil Group Data figures and tables which substantiate the selection of these CNs are contained in the "Attachment -Appendix C" section of the Drainage Study. Calculations for the composite runoff CNs are illustrated below in Table #2-"Composite Curve Number" and the resulting Composite CN of 82 will be utilized. 260-0551 Flood Study.docx Page -5 Creek Meadows Subdivision Limited Flood Study Drainage Area l.D. Peach Creek S. 16.4.3 TABLE#2 Composite Curve Number (CNwtd) TypeC TypeD Open Space Pasture Fair Fair Woods Good Rural Condition Condition Condition Residential CN=77 CN=84 CN=77 CN=80 4.5% 2.0% 20.4% 53 .7% 3.4 Time of Concentration & Lag: RME Consulting Engineers March 27, 2015 High Density w/Detention Composite CN=85 CNwtd 19.4% 82 The Time-of-Concentration (Tc), for each watershed, is used to determine the intensity of the rainfall event for the corresponding drainage basin. Time-of-Concentration is defined as the time required for the surface runoff to flow from the most hydraulically remote point in a watershed to the point of analysis. The Tc is the summation of the flow time for overland sheet flow plus shallow overland flow and/or concentrated flow to the lower reach of the watershed. Overland sheet flow is a method developed by Overton and Meadows and is typically used for flow distances of 300 feet or less. Concentrated flows are estimated by velocities determined by use of the Manning's Equation. These two types of flow time calculations are further explained as follows. Overland Sheet Flow, Tt = {0.0197 (n L)0·8} I {Pi112 s0·4} where, Tt = travel time (hours); n =Manning's roughness coefficient -This represents the flow-ability of runoff across a particular surface type and is a dimensionless coefficient. These coefficients are obtained from Table C-5 of the USDG; Pi = ith-year recurrence interval for the 24-hour rainfall depth (inches) -Rainfall depths are obtained from Table C-6 of the USDG; S =land slope (feet/foot) Shallow Concentrated Flow, Tt = D/(60V) where, Tt =Travel time (minutes); D =Flow distance (feet); V = Average velocity of runoff (ft/sec) -These values are determined from interpolation velocities recorded in Table C-4 of the USDG; Table #3 -"Tu-Overland Sheet Flow" and Table #4 -"Tt2-Shallow Concentrated Flow" illustrates the flow travel times for each segment of the sub-drainage basin in respect to the condition of the flow. The Tc's for each sub-drainage basin where then computed and are summarized below in Table #5 -"Tc Summary" which also includes the Basin Lag Time (TL). Basin lag is the time from the center of mass of rainfall excess to the hydro graph peak. Steep slopes, compact shape, and an efficient drainage network tend to make lag time short and peaks high. Flat slopes, elongated shape, and an inefficient drainage network tend to make lag time long and peaks low. The TL can be calculated using the Tc of the sub-drainage basin with the following equation. 260-0551 Flood Study.docx Page -6 Creek Meadows Subdivision Limited Flood Study RME Consulting Engineers March 27, 2015 Basin Lag Time, TL= (0.60) Tc where, Tc = Time of Concentration (minutes); TABLE#3 Ttl -Overland Sheet Flow Overland Average Flow Land Travel Drainage Area Manning's Distance Pi Slope Time I.D. "n" (L) (100-vear) (S) (Tc) PC 0.03 150 11.0 0.0075 0.050 TABLE#4 Tt2 -Shallow and/or Concentrated Flow Shallow Creek Flow (1) Flow Average Flow Average Drainage Area Distance Velocity Distance Velocity I.D. (DI) (VI) (D2) (V2) PC 730 2.2 760 4.1 TABLE#4 Tt2 -Shallow and/or Concentrated Flow Branch Flow (1) Branch Flow (2) Flow Average Flow Average Drainage Area Distance Velocity Distance Velocity I.D. (D2) (V2) (D2) (V2) PC 4126 3.8 5190 3.4 1) Shallow Flow average velocities were estimated using the following equation V = 16.13 5 *S05 where, V =fj:>s S = average slope Assumptions -Manning's N = 0.05 & Hydraulic radius = 0.4 ft Time (Tc) 8.62 Time (Tc) 43 .54 2) Channel Flow average velocities were estimated using the following equation V = 20.328*S05 where, V = fj:>s S = average slope Assumptions -Manning's N = 0.025 & Hydraulic radius = 0.2 ft 3) Creek Flow average velocities were approximated from estimated 25- year flows inputted into the HEC-RAS model; TABLE#5 Tc SUMMARY Combined Drainage LagTime Drainage Area Overland Concentrated Basin "Tc" (0.6*Tc) I.D. Flow Time Flow Time (min) (min) PC 0.050 52.16 55.2 33 .1 An alternative method of determining the Basin Lag Time (TL) is by the SCS Lag Time Equation which is as follows. Using this equation the TL'S for each sub-drainage basin were then computed and are summarized below in Table #6-"SCS TL Summary". 260-0551 Flood Study.docx Page -7 Creek Meadows Subdivision Limited Flood Study RME Consulting Engineers March 27, 2015 SCS Lag Time, TL= Lo.s [(S+t)0•7 I1900*Yo5] TL= basin lag time (hours); L =hydraulic length of the watershed (feet); Y =watershed slope(%); where, S =maximum retention in the watershed (in); where, S = (1000/CN)-10 CN = SCS composite curve number for the sub-drainage basin; TABLE#6 SCS TL -Summary Basin scs Hydraulic Watershed Curve Basin Lag Drainage Length Slope Number Retention Time Area l.D. (L) (Y) (CN) (S) (min) Thompson Creek 8,565 0.80 82 2.20 111.5 Note: The hydraulic length for each drainage basin was reduced by 15% to illustrate a "valley" length in lieu of the actual creek flow line length; As illustrated the SCS equation TL'S yielded flow times that were near the magnitude of two-times greater than those calculated by segment analysis. Therefore, since the Basin Lag Times, generated by the segment analysis equations, would generate more conservative hydrologic output/runoff the TL = 33.1 minutes will be utilized. 4.0 HEC-HMS COMPUTATIONS & RESULTS All runoff calculations for this Drainage Study will utilize the Hydrologic Modeling System (HEC-HMS) program. This program is a product of the US Army Corps of Engineers' (USACE) research and development program, and is produced by the Hydrologic Engineering Center (HEC). The program simulates precipitation-runoff and routing processes, both natural and controlled. The program is the successor to and replacement for the Flood Hydrograph Package HEC-1 DOS based program. 4.1 Basin Model Summary: The first step in the hydrologic program process of the HEC-HMS program was to create a "skeleton" or schematic layout of the Peach Creek South-Tributary 16.4.3 watershed with its sub-drainage basins as described in Section 2.1. The schematic layout will generally consist of three (3) basic components (Sub-basins, Reaches, and Junctions). The modeling of the Thompson Creek watershed, for the purposes of this report, is a simplified approach therefore there will only be "Sub-Basin" component of the HEC- HMS model. The assumptions for this is identified and summarized as follows. 260-0551 Flood Study.docx Page -8 Creek Meadows Subdivision Limited Flood Study SUB-BASINS: RME Consulting Engineers March 27, 2015 The Thompson Creek watershed is outlined in Section 2.3 of this report. Losses utilized for the drainage area is computed and reported in Section 3 .3 and the transform component of Time Lag (TL) is illustrated and explained in Section 3.4. Other basic modeling methods and assumptions are as follows: • Loss Method: SCS Curve Number; • Transform Method: SCS Unit Hydrograph; • Initial Abstraction = 0 • Impervious = 0% • Transform Graphing Type: Standard; REACHES: There are no reaches for this HEC-HMS model. JUNCTIONS: There are no junctions for this HEC-HMS model. 4.2 Meteorological Model Summary: The Meteorological Model portion of the HEC-HMS program is the component that "controls" the rainfall aspect of the watershed simulation. With the SCS Storm method the rainfall depth data reported in Table #1 will be utilized. Other standard assumptions for meteorological conditions are as summarized below. • Precipitation: SCS Storm; • Duration: 24 hours; • Storm Type: Type III; 4.3 Control Specification Summary: The Control Specification aspect of the HEC-HMS program is simply the input data for the length that the program will simulate the rainfall event. Therefore the "start time" to "end time" will be the equivalent of the storm duration reported in Section 4.2. As reported in the Technical Reference Manual for the HEC-HMS program the computational interval, Lit, must be less than 29% of TL so that adequate definition of the ordinates on the rising limb of the SCS Unit Hydrograph can be generated (see Figure 1). Therefore, in this case a 6 minute time interval was selected. Lit= 29%TL = 0.29 * 33.1 min = 9.6 minutes where, TL is from Table #5 4.4 Stormwater Runoff Quantities: Stormwater runoff quantities were calculated, using the SCS-TC 20 formula with the assistance of the Hydrologic stormwater modeling program HEC-HMS. Runoff values for the analyzed studied points (Junctions) are summarized below in Table #9 -"Routed Runoff Quantities". 2-YR, 5-YR, 10-YR, 25-YR, 50-YR, 100-YR & 500-YR Simulation Runs and their supporting data/hydrographs are contained "Attachment -Appendix D" section of the report. 260-0551 Flood Study.docx Page -9 Creek Meadows Subdivision Limited Flood Study TABLE#7 ROUTED RUNOFF QUANTITIES Study Pomt of Rainfall Peach Creek South Event Trib 16.4.3 50% 422 20% 666 10% 840 4% 985 2% 1, 188 1% 1,362 0.20% 2,104 RME Consulting Engineers March 27, 2015 CONSIDERATION & CALIBRATION: The studied portion of Peach Creek South - Tributary 16.4.3 has not been "officially" studied in the past and therefore there is no comparable data for hydrologic output information. Also this creek has no historical measured data (rainfall and/or timing information) therefore very little, in the means of program calibration, can be accomplished. However, the above reported runoff rates do seem reasonable for this watershed and will be utilized for this Limited Flood Study. 5.0 HYDRAULIC MODELING 5.1 HEC-RAS Modeling & Methodology The computation of water surface elevations along a stream/creek is called the hydraulic analysis. These water surface elevations are computed using an iterative application of the Manning's Equation called the standard step. The accepted and well-used computer program, for this type of computation, is the HEC-2 and more recently its modem version, HEC-RAS. HEC-RAS uses the same theoretical computational methods as HEC-2, but this program is a Windows based software, therefore providing a more user-friendly approach. Since the HEC-RAS program is a more flexible tool, offers more powerful modeling options, and no precedence has been established for this section of Thompson Creek, HEC-RAS will be utilized. The hydraulic analysis is divided into the four (4) following master components (Geometric Data, Manning's "N", Flow Data, and Plan Data) which are detailed below. 5.2 Geometric Data The geometry data, for HEC-RAS, contains all of the geometric data for the river system being analyzed. The geometric data consist of: cross section information; hydraulic structures data (e.g., bridges and culverts); roughness coefficients; and modeling approach information. There will be two (2) geometric model contained within this hydraulic study. They are labeled as stated and described for the following purposes. 260-0551 Flood Study.docx Page -10 Creek Meadows Subdivision Limited Flood Study RME Consulting Engineers March 27, 2015 Existing Conditions -This model contains geometric data for Peach Creek South - Tributary 16.4.3 at existing/current conditions. Data used to develop this geometrical layout and cross-sections was a combination of the following information. This geometrical data is further illustrated on the GP-01: Site Grading & Drainage Plan which is contained "Attachment-Appendix E" section of the report. (1) Within the creek banks(+/-200' either side of the bank) an on-the-ground survey data was performed by Vannoy Surveying at the proposed channel realignment location. This on-the-ground survey utilized CoCS Monuments (NA VD 29) for both horizontal and vertical control; (2) Cross-sectional data for overland areas utilized the CoCS topographical maps. This data was considered accurate since very little development has occurred within the overland flow areas of Peach Creek South-Tributary 16.4.3; Proposed Conditions -This model contains geometric data for Peach Creek South - Tributary 16.4.3 at existing/current conditions and integrates the proposed channel realignment information. Data used to develop this geometrical layout and cross-sections will be compared to the existing conditions Water Surface Elevations (WSE) to measure impacts of the proposed improvements. This geometrical data is further illustrated on the GP-01: Site & Grading & Drainage Plan which is contained "Attachment -Appendix E" section of the report. 5.3 Manning's "N" Coefficient Roughness coefficients are one of the main variables used in calibrating a hydraulic model. Generally, for a free flowing stream, creek or river, roughness decreases with increased stage and flow. However, if the banks of a river are rougher than the channel bottom, due to trees and brush, then the composite ''N" value will increase with increased stage. Sediment and debris can also play an important role in changing the roughness. More sediment and debris in a river will require the modeler to use higher ''N" values in order to match observed water surfaces. Manning's ''N"s for the described geometrical scenarios in Section 5.2 was made from field reconnaissance along the studied portion of Peach Creek South -Tributary 16.4.3 . Roughness coefficients were determined by comparison with accepted standards and the current FIS. Typical values for stream over-bank, along natural channels, range from 0.07 to 0.09 (0.060-0.090 FIS), and typical values for natural stream channels range from 0.03 to 0.06 (0.014 -0.065 FIS). The U.S. Geological Survey has published a book, dated 1987, and entitled "Roughness Characteristics of Natural Channels". Field reconnaissance was made during the spring of 2015 (high growth season). Vegetation was at medium to high levels, therefore, the ''N"s utilized are considered to be conservative for flow resistance levels. These roughness coefficients should yield conservative Water Surface Profiles (WSP). 260-0551 Flood Study.docx Page-11 Creek Meadows Subdivision Limited Flood Study 5.4 Flow Data RME Consulting Engineers March 27, 2015 Flow data for the HEC-RAS modeling will utilize the hydrologic runoff values reported in Section 4.4 (Table #7) and the upstream boundary cross-section stated in that table. Flow data was entered into the HEC-RAS model as a "steady state" flow condition. Also in the "Flow Data" component of HEC-RAS is the inputting of the starting Water Surface Elevation (WSE). This starting WSE can be defined by several different methods. When the hydraulic model is not starting at a previously studied location and the starting WSE is unknown, then the most common method of establishing a starting WSE is by the Normal Depth method and equation. Otherwise it is best utilize a starting WSE. Since the FIS has calculated WSE for Peach Creek South -Tributary 16.4.3, immediately downstream, this information will be utilized. 5.5 Plan Data A "Plan" in HEC-RAS is the combination of the various Geometric Data and Flow Data to develop the desired WSPs. For this hydraulic analysis, there were two (2) Plans created for computation, review, and comparison. These Plans are as identified below. EX-FP -Floodplain model with existing geometrical data and flow schemes generated with the methods described in Section 4.0 ofthis report for all analyzed rainfall events; PR-FP -Floodplain model with proposed geometrical data and flow schemes generated with the methods described in Section 4.0 ofthis report for all analyzed rainfall events. This floodplain model will include the proposed channel realignment; 6.0 HEC-RAS COMPUTATIONS & RESULTS 6.1 Existing Floodplain Model This section will contain the hydraulic modeling results for the first "Plan" that was listed under Section 5.5 of this report. This Plan is reiterated and more fully described below. EX-FP -This hydraulic floodplain model utilized the "original" existing geometrical data and flow schemes generated with the methods described in Section 4.0 of this report for all analyzed rainfall events. The hydraulic model consisted of "original" existing geometric conditions as described in Section 5.2, flow data as summarized in Section 5.4, and special considerations needed for the generation of the hydraulic models. 6.2 Proposed Floodplain Model This section will contain the hydraulic modeling results for the second "Plan" that was listed under Section 5.5 of this report. This Plan is reiterated and more fully described below. 260-0551 Flood Study.docx Page -12 Creek Meadows Subdivision Limited Flood Study RME Consulting Engineers March 27, 2015 PR-FP -This hydraulic floodplain model utilized the "original" existing geometrical data, where applicable, and flow schemes generated with the methods described in Section 4.0 of this report for all analyzed rainfall events. Also the proposed channel realignment is modeled in the geometric data. This channel cross-section is further described below and is also illustrated on GP-01: Site & Grading & Drainage Plan which is contained "Attachment-Appendix F" section of the report. The hydraulic model consisted of"proposed" geometric conditions as described in Section 5.2, flow data as summarized in Section 5.4, and special considerations needed for the generation of the hydraulic models. These special considerations are briefly summarized as follows. SPECIAL CONSIDERATIONS: 1. At RS 3+86 & RS 5+24 the proposed channel realignment cross-section and Manning's "N" will be integrated into the creek data; 2. At RS 3+86 & RS 5+24 proposed fill will be placed to elevate the proposed lots above the 100-year floodplain elevation; 3. RS 3+86 & RS 5+24, the flow conveyed by the tributary will experience a noticeable change in flow regime due to the proposed fill. Therefore the contraction and expansion coefficients were changed from typical values of 0.1 and 0.3 to 0.3 and 0.5, respectively; Based on the above mentioned geometric, flow data, and special considerations, the following results are reported for the "Existing Conditions" and "Proposed Conditions" floodplain hydraulic model. This data is summarized in Table #8 -"Existing vs. Proposed Conditions Floodplain Comparison". Output data for additional analyzed rainfall events are contained in Existing & Proposed Conditions HEC-RAS Model Output Data which is in the "Attachment -Appendix F" section of the report. TABLE#8 EXISTING vs. PROPOSED CONDITIONS FLOODPLAIN Existing Proposed River Station 1% Freq. 1% Freq. Di ff. (RS) (ft) (ft) (ft) 151 288.18 288.18 0.00 386 288.75 288.69 -0.06 524 288.65 288.17 -0.48 755 290.45 290.25 -0.20 989 290.94 290.82 -0.12 As illustrated in Table #8 the Vehicular Bridge No. 1 improvements have an impact on the floodplain elevations by less than two-inches. Therefore this will be considered a negligible influence. 260-0551 Flood Study.docx Page -13 Creek Meadows Subdivision Limited Flood Study 7.0 CERTIFICATION 260-0551 Flood Study.docx Rabon Metcalf, P .E. State of Texas P.E. No. 88583 RME Consulting Engineers March 27, 2015 Page -14 Appendix A GENERAL INFORMATION CREEK MEADOWS: SECTION 7, PH. 1 VICINITY MAP NOT TO SCALE N NOTTO SCALE Appendix B WATERSHEDS & SUB-DRAINAGE BASINS Appendix C HYDROLOGIC MODELING GLO Location "13" Parameter Map U> ~ co~ ~ § (.) 0 I-(.) GLO Scale "a" Parameter Map GLO Shape "µ" Parameter Map »' 32'46"N »' 31'21"N 759200 :;;:: &l ~ N A Hydrologic Soil Group-Brazos County, Texas (Peach Creek South Trib 16.4.3) 759500 7fi0400 Map Scale: 1:12,700 if prinlEd on A portrait (8.5" x 11") sheet ------<=====-------------===========Meiers 0 150 300 600 900 -------======-------------============f€ft 0 500 1000 2000 3000 Map projection: Web Mertator Comerandin<tes: WGS84 Edge tics: UTM Zone 14N WGS84 USDA Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 760700 761000 3/3/2015 Page 1 of4 »' 32'46"N Hydrologic Soil Group-Brazos County, Texas (Peach Creek South Trib 16.4.3) MAP LEGEND MAP INFORMATION Area of Interest (AOI) D Area of Interest (AOI) Soils Soll Rating Polygons D A D AID DB D B/D D c D C/D D D D Not rated or not available Soll Rating Lines A AID ,_,. B ,_,. B/D c CID D -; Not rated or not available Soll Rating Points A AID • B • B/D Natural Resources Conservation Service c CID D C Not rated or not available Water Features Streams and Canals Transportation H-t Rails """"' Interstate Highways f/lllWllJ US Routes Major Roads Local Roads Background • Aerial Photography Web Soil Survey National Cooperative Soil Survey The soil surveys that comprise your AOI were mapped at 1 :20,000. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: http://websoilsurvey.nrcs.usda.gov Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Survey Area Data: Brazos County, Texas Version 12, Sep 29, 2014 Soil map units are labeled (as space allows) for map scales 1 :50,000 or larger. Date(s) aerial images were photographed: Jan 27, 2011-May 16,2011 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. 3/3/2015 Page 2 of 4 Hydrologic Soil Group-Brazos County, Texas Hydrologic Soil Group Hydrologic Soll Group-Summary by Map Unit-Brazos County, Texas (TX041) Map unit symbol Map unit name Rating BwC Burlewash fine sandy D loam, 1 to 5 percent slopes ChC Chazos loamy fine sand, c 1 to 5 percent slopes GrC Gredge fine sandy loam, D 1 to 5 percent slopes KrD Koether-Rock outcrop D complex, 3 to 12 percent slopes MaA Mabank loam, 0 to 1 D percent slopes SkB Shiro loamy fine sand, 1 D to 3 percent slopes SnB Singleton fine sandy D loam, 1 to 3 percent slopes TaA Tabor fine sandy loam, 0 D to 2 percent slopes Totals for Area of Interest USDA Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey Acres inAOI 10.8 13.7 31 .3 2.9 13.8 3.1 210.9 21 .0 307.4 Peach Creek South Trib 16.4.3 Percent of AOI 3.5% 4.5% 10.2% 0.9% 4.5% 1.0% 68.6% 6.8% 100.0% 3/3/2015 Page 3 of 4 Hydrologic Soil Group-Brazos County, Texas Peach Creek South Trib 16.4.3 Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (ND, B/D, and CID). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (ND, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. Rating Options Aggregation Method: Dominant Condition Component Percent Cutoff: None Specified Tie-break Rule: Higher USDA Natural Resources aiii Conservation Service Web Soil Survey National Cooperative Soil Survey 3/3/2015 Page 4 of 4 Appendix D HEC-HMS COMPUTATIONS & RESULTS Project: 0551 HEC-HMS-R1 Simulation Run: 2YR Start of Run: 01Jan2015, 12:00 Basin Model: Peach Creek S End of Run: 02Jan2015, 12:06 Meteorologic Model: 2-YR Compute Time:03Mar2015, 21 :54:15 Control Specifications:Peach Creek Hydrologic Drainage Area Peak Dischar~ eTime of Peak Volume Element (Ml2) (CFS) (IN) PC 0.512 422.5 02Jan2015, 00:36 2.61 Subbasin "PC" Results for Run "2YR" 0.00 ,-----:-----:---111111!111--- a 0.20 --1 ~ 0.30 0.40---~~---~~~~~~~~~~~~~~~~~~~~ 400 -1 -E-: 300 ......... JQ 200 + + -(.) "-" ~ 100 0 L-----1---LL 0 --r--f 12:00 15:00 18:00 01Jan2015 21:00 00:00 I 03:00 06:00 09:00 12:00 02Jan2015 Run :2YR Element:PC Result:Precipitation Run:2YR Element:PC Result:Precipitation Loss --Run:2YR Element:PC Result:Outflow Run:2YR Element:PC Result:Baseflow Project: 0551 HEC-HMS-R1 Simulation Run: 5 YR Start of Run : 01Jan2015, 12:00 Basin Model: Peach Creek S End of Run: 02Jan2015, 12:06 Meteorologic Model: 5-YR Compute Time:03Mar2015, 21 :54:33 Control Specifications:Peach Creek Hydrologic Drainage Area Peak Discharg eTime of Peak Volume Element (Ml2) (CFS) (IN) PC 0.512 666.1 02Jan2015, 00:36 4.14 Subbasin "PC" Results for Run "5 YR" 0.0 I ......... -+. c -0.2 ..c -a. 0.4 Q) 0 600 --i---t---+---- ~ 400 --F-r ~ 200 -I I ~- ~ o.l--_JL-_ _j. ____ ~::::::::==-l--_JL-=:=:::::!:::::====~=====;1 12:00 15:00 18:00 21 :00 00:00 03:00 06:00 01Jan2015 I --Run:5 YR Element:PC Result:Precipitation --Run:5 YR Element:PC Result:Precipitation Loss Run :5 YR Element:PC Result:Outflow Run :5 YR Element:PC Result:Baseflow 09:00 12:00 02Jan2015 Project: 0551HEC-HMS-R1 Simulation Run: 10 YR Start of Run: 01Jan2015, 12:00 Basin Model: Peach Creek S End of Run : 02Jan2015, 12:06 Meteorologic Model: 10-YR Compute Time:03Mar2015, 21:49:50 Control Specifications:Peach Creek Hydrologic Drainage Area Peak Dischar~ eTime of Peak Volume Element (Ml2) (CFS) (IN) PC 0.512 840.1 02Jan2015, 00:36 5.25 Subbasin "PC" Results for Run "10 YR" 0.0.------.----:---,.....- ~ - 0. 0.4 -------------------------.----......---, ID _,__ -+---~~----+ 0 0.6- -(/) 800 600 't5 400 -~ 200 0 LL 0 - - -----< I --,____ - -1 I I A ; I\ J I \ ~ _ _: l k_ ~ -,__. I I I I I I I I 12:00 15:00 18:00 21 :00 00:00 03:00 06:00 09:00 12:00 01Jan2015 I 02Jan2015 Run: 10 YR Element: PC Result: Precipitation Run:10 YR Element:PC Result:Precipitation Loss Run:10 YR Element:PC Result:Outflow Run:10 YR Element:PC Result:Baseflow Project: 0551 HEC-HMS-R1 Simulation Run: 25 YR Start of Run: 01Jan2015, 12:00 Basin Model: Peach Creek S End of Run: 02Jan2015, 12:06 Meteorologic Model: 25-YR Compute Time:03Mar2015, 21 :54:30 Control Specifications:Peach Creek Hydro logic Drainage Area Peak Dischar~ eTime of Peak Volume Element (Ml2) (CFS) (IN) PC 0.512 985.4 02Jan2015, 00:36 6.20 0.0 ......... c: 0.2 -£ 0.4 a. Q) 0 0.6 :§' (.) - 0.8 1,000 800 600 400 200 -0 ------- --- -- - Subbasin "PC" Results for Run "25 YR" . I I I --1 I -----t---r--- -=----1 f-I I I I Pr-I I -+----\ ~ -·~ -I --+-~ "'---- I I I I I I 12:00 15:00 18:00 21 :00 00:00 03:00 06:00 09:00 12:00 01Jan2015 I 02Jan2015 --Run:25 YR Element:PC Result:Precipitation --Run:25 YR Element:PC Result:Precipitation Loss --Run:25 YR Element:PC Result:Outflow Run:25 YR Element:PC Result:Baseflow Project: 0551 HEC-HMS-R1 Simulation Run: 50 YR Start of Run : 01Jan2015, 12:00 Basin Model: Peach Creek S End of Run: 02Jan2015, 12:06 Meteorologic Model: 50-YR Compute Time:03Mar2015, 21:54:37 Control Specifications:Peach Creek Hydrologic Drainage Area Peak Dischar~ ~Time of Peak Volume Element (Ml2) (CFS) (IN) PC 0.512 1188.4 02Jan2015, 00:36 7.53 -c: ..._.. .I::. -Q. <l> 0 0.0 0.2 0.4 0.6 0.8 1,200 800 400 0 - - -- Subbasin "PC" Results for Run "50 YR" ----- I --~~\] ---------.... -~ -t---- I I I I I I I 12:00 15:00 18:00 21 :00 00:00 03:00 06:00 09 :00 12:00 01Jan2015 I 02Jan2015 --Run:50 YR Element:PC Result:Precipitation Run:50 YR Element:PC Result:Precipitation Loss Run :50 YR Element:PC Result:Outflow Run :50 YR Element:PC Result:Baseflow Project: 0551 HEC-HMS-R1 Simulation Run: 100 YR Start of Run: 01Jan2015, 12:00 End of Run: 02Jan2015, 12:06 Compute Time:03Mar2015, 21 :56:12 Basin Model: Peach Creek S Meteorologic Model: 100-YR Control Specifications:Peach Creek Hydrologic Drainage Area Peak Discharg eTime of Peak Volume Element (Ml2) (CFS) (IN) PC 0.512 1362.0 02Jan2015, 00:36 8.68 -c -..c. ... 0. Q) 0 Subbasin "PC" Results for Run "100 YR" 0.0 - 0.3 I I - 0.6 --- 0.9 1,200 _, __________ ,__ __ 800 400~---+---+---l--- o ,____ --. I I ! - + - "" 12:00 15:00 18:00 21 :00 00:00 03:00 06:00 09:00 12:00 01Jan2015 I 02Jan2015 --Run:100 YR Element:PC Result:Precipitation --Run:100 YR Element:PC Result:Precipitation Loss --Run:100 YR Element:PC Result:Outflow Run: 100 YR Element: PC Result: Baseflow Project: 0551HEC-HMS-R1 Simulation Run: 500 YR Start of Run : 01Jan2015, 12:00 End of Run: 02Jan2015, 12:06 Compute Time:03Mar2015, 21 :54:41 Basin Model: Peach Creek S Meteorologic Model: 500-YR Control Specifications:Peach Creek Hydro logic Drainage Area Peak Dischar~ 1emme of Peak Volume Element (Ml2) (CFS) (IN) PC 0.512 2103.6 02Jan2015, 00:36 13.71 Subbasin "PC" Results for Run "500 YR" 0.0 -c 0.4 -..c. ...... 0.8 c.. Q) 0 1.2 2,000 1,500 ~ u 1,000 - ~ -------- -··-r-- 500-1----t---+--- o -!---~~--..-:;====:::::::=----T--~--!.-===~::::::==;:::=====;! 12:00 15:00 01Jan2015 18:00 21 :00 00:00 03:00 06:00 09:00 12 :00 I 02Jan2015 Run:500 YR Element:PC Result:Precipitation Run:500 YR Element:PC Result:Precipitation Loss Run:500 YR Element:PC Result:Outflow - - -Run:500 YR Element: PC Result:Baseflow Appendix E HYDRAULIC MODELING Appendix F HEC-RAS COMPUTATIONS & RESULTS HEC-RAS Plan: EX-FP1 River: Peach Creek Reach: PC Reach River Sta Profile a Total Min Ch El W.S. Elev CritW.S. E.G. Elev E.G. Slope Vet Chnl Flow Area Top Width Froude# Chi (cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft) PC 151 50% 422.00 281 .20 286.29 285.33 286.47 0.003001 4.06 140.31 86.88 0.36 PC 151 20% 666.00 281 .20 286.95 285.92 287.16 0.003003 4.49 206.36 112.10 0.37 PC 151 10% 840.00 281 .20 287.32 286.20 287.54 0.003003 4.73 250.84 126.29 0.37 PC 151 4% 985.00 281 .20 287.60 286.43 287.83 0.003001 4.90 287.53 155.71 0.37 PC 151 2% 1188.00 281 .20 287.92 286.69 288.15 0.003000 5.09 349.51 231 .84 0.38 PC 151 1% 1362.00 281 .20 288.18 286.87 288.41 0.003001 5.25 420.13 314.79 0.38 PC 151 0.2% 2104.00 281.20 288.97 287.73 289.18 0.003003 5.71 818.08 689.37 0.39 PC 386 50% 422.00 281 .90 286.85 286.89 0.001174 2.27 336.30 232.64 0.23 PC 386 20% 666.00 281 .90 287.51 287.56 0.001025 2.42 496.52 254.04 0.22 PC 386 10% 840.00 281.90 287.89 287.94 0.000999 2.55 595.29 266.37 0.22 PC 386 4% 985.00 281 .90 288.17 288.22 0.001002 2.66 672.85 295.13 0.22 PC 386 2% 1188.00 281 .90 288.49 288.56 0.001045 2.86 777.03 343.72 0.23 PC 386 1% 1362.00 281 .90 288.75 288.82 0.001078 3.00 869.75 381.80 0.24 PC 386 0.2% 2104.00 281.90 289.54 289.64 0.001323 3.67 1216.55 499.12 0.27 PC 524 50% 422.00 282.30 286.87 287.33 0.005918 5.51 130.83 97.46 0.53 PC 524 20% 666.00 282.30 287.25 286.63 288.13 0.010012 7.70 173.35 130.43 0.70 PC 524 10% 840.00 282.30 287.38 287.26 288.66 0.013969 9.30 191 .20 143.72 0.83 PC 524 4% 985.00 282.30 287.88 287.88 289.06 0.011539 9.16 276.63 195.15 0.77 PC 524 2% 1188.00 282.30 288.35 288.35 289.49 0.010423 9.31 377.50 236.53 0.74 PC 524 1% 1362.00 282.30 288.65 288.65 289.79 0.010152 9.56 452.06 261 .82 0.74 PC 524 0.2% 2104.00 282.30 289.63 289.63 290.80 0.009702 10.49 755.02 366.83 0.75 PC 755 50% 422.00 283.00 287.85 288.00 0.001608 3.17 191.19 101.61 0.29 PC 755 20% 666.00 283.00 288.79 289.01 0.001778 3.87 320.60 180.07 0.31 PC 755 10% 840.00 283.00 289.40 289.63 0.001709 4.11 445.54 235.40 0.31 PC 755 4% 985.00 283.00 289.75 290.00 0.001764 4.35 533.38 267.54 0.32 PC 755 2% 1188.00 283.00 290.14 290.42 0.001866 4.68 647.54 305.05 0.33 PC 755 1% 1362.00 283.00 290.45 290.75 0.001940 4.93 744.07 334.48 0.34 PC 755 0.2% 2104.00 283.00 291.44 291 .78 0.002068 5.61 1117.70 391.83 0.36 PC 989 50% 422.00 283.70 288.31 288.66 0.004624 4.76 119.26 86.46 0.47 PC 989 20% 666.00 283.70 289.26 289.69 0.004313 5.46 239.02 165.04 0.47 PC 989 10% 840.00 283.70 289.83 290.27 0.003912 5.66 347.10 212.30 0.46 PC 989 4% 985.00 283.70 290.19 290.64 0.003844 5.89 429.12 246.38 0.46 PC 989 2% 1188.00 283.70 290.62 291 .08 0.003802 6.18 542.94 291 .07 0.46 PC 989 1% 1362.00 283.70 290.94 291.41 0.003744 6.36 642.02 325.00 0.46 HEC-RAS Plan: EX-FP1 River: Peach Creek Reach: PC (Continued) Reach River Sta Profile Q Total Min Ch El W.S. Elev CritW.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude #Chi (cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft) PC 989 0.2% 2104.00 283.70 291.98 292.43 0.003438 6.80 1001 .97 364.22 0.46 HEC-RAS River: Peach Creek Reach: PC Reach River Sta Profile Pian QTotal Min Ch El W.S. Elev CritW.S. E.G. Elev E.G. Slope Vel Chnl Flow Area Top Width Froude#Chl (cfs) (ft) (ft) (ft) (ft) (ft/ft) (ft/s) (sq ft) (ft) PC 151 50% PRFP 422.00 281 .20 286.29 285.33 286.47 0.003003 4.06 140.26 86.85 0.36 PC 151 20% PRFP 666.00 281 .20 286.95 285.92 287.16 0.003003 4.49 206.35 112.10 0.37 PC 151 10% PRFP 840.00 281 .20 287.32 286.20 287.54 0.003002 4.73 250.88 126.30 0.37 PC 151 4% PRFP 985.00 281 .20 287.59 286.43 287.83 0.003005 4.90 287.38 155.49 0.37 PC 151 2% PRFP 1188.00 281 .20 287.91 286.69 288.15 0.003004 5.09 349.26 231.58 0.38 PC 151 1% PRFP 1362.00 281 .20 288.18 286.87 288.41 0.003000 5.24 420.22 314.90 0.38 PC 151 0.2% PRFP 2104.00 281 .20 288.97 287.73 289.18 0.003003 5.71 792.17 583.09 0.39 PC 386 50% PRFP 422.00 281 .90 286.76 286.82 0.000865 2.57 320.83 209.55 0.23 PC 386 20% PRFP 666.00 281 .90 287.44 287.50 0.000832 2.82 466.41 218.86 0.24 PC 386 10% PRFP 840.00 281 .90 287.82 287.90 0.000841 3.00 552.20 224.17 0.24 PC 386 4% PRFP 985.00 281 .90 288.10 288.19 0.000861 3.15 616.11 228.98 0.25 PC 386 2% PRFP 1188.00 281 .90 288.43 288.52 0.000919 3.39 692.32 236.42 0.26 PC 386 1% PRFP 1362.00 281 .90 288.69 288.79 0.000962 3.58 753.80 242.25 0.27 PC 386 0.2% PRFP 2104.00 281 .90 289.47 289.61 0.001239 4.43 949.72 259.96 0.31 PC 524 50% PRFP 422.00 282.30 286.76 287.10 0.003378 4.67 107.62 52.23 0.45 PC 524 20% PRFP 666.00 282.30 287.28 287.88 0.005081 6.31 139.25 77.71 0.57 PC 524 10% PRFP 840.00 282.30 287.53 286.61 288.35 0.006354 7.37 161 .75 97.02 0.64 PC 524 4% PRFP 985.00 282.30 287.70 286.96 288.71 0.007458 8.21 179.45 109.86 0.70 PC 524 2% PRFP 1188.00 282.30 287.84 287.65 289.17 0.009614 9.51 194.55 119.73 0.80 PC 524 1% PRFP 1362.00 282.30 288.17 288.17 289.55 0.009262 9.81 239.04 141.69 0.80 PC 524 0.2% PRFP 2104.00 282.30 289.50 289.50 290.75 0.007048 10.10 536.53 352.03 0.72 PC 755 50% PRFP 422.00 283.00 287.55 287.73 0.002173 3.48 161.79 90.43 0.33 PC 755 20% PRFP 666.00 283.00 288.43 288.70 0.002430 4.28 260.80 146.36 0.36 PC 755 10% PRFP 840.00 283.00 288.96 289.27 0.002470 4.66 350.78 194.88 0.37 PC 755 4% PRFP 985.00 283.00 289.36 289.68 0.002429 4.87 436.25 231 .74 0.37 PC 755 2% PRFP 1188.00 283.00 289.89 287.49 290.22 0.002282 5.03 573.06 280.85 0.37 PC 755 1% PRFP 1362.00 283.00 290.25 287.82 290.59 0.002266 5.22 679.20 315.01 0.37 PC 755 0.2% PRFP 2104.00 283.00 291.33 291 .70 0.002273 5.82 1073.02 390.98 0.38 PC 989 50% PRFP 422.00 283.70 288.17 288.55 0.005399 5.00 107.78 74.71 0.50 PC 989 20% PRFP 666.00 283.70 289.07 289.57 0.005218 5.83 209.20 149.39 0.51 PC 989 10% PRFP 840.00 283.70 289.60 290.12 0.004924 6.14 299.04 192.72 0.51 PC 989 4% PRFP 985.00 283.70 289.98 290.51 0.004669 6.31 379.39 224.49 0.50 PC 989 2% PRFP 1188.00 283.70 290.47 291.00 0.004336 6.48 501.87 275.78 0.49 PC 989 1% PRFP 1362.00 283.70 290.82 291 .34 0.004147 6.61 605.55 312.94 0.49 PC 989 0.2% PRFP 2104.00 283.70 291.92 292.39 0.003613 6.93 980.52 362.24 0.47