XP-SWMM_Modeling_Summary.pdf

Metropolitan St. Louis

Sewer District

Harlem-Baden Relief Phase IV (Hebert) Model Setup and Calibration

October 2010

Prepared by

Parsons Water & Infrastructure Inc.

M3 Engineering Group, PC

Harlem-Baden Relief Phase IV (Hebert) Model Setup and Calibration

Prepared For

Date:_________________

Edward M. Sweet, Jr. P.E.

Parsons Water & Infrastructure, Inc.

Civil Engineer

License #E-17987

Date:_________________

Todd D. Williams. P.E.

M3 Engineering Group, PC

Civil Engineer

License #2000150085

Parsons Water & Infrastructure Inc.

400 Woods Mill Road South, Suite 330 Chesterfield, Missouri 63017

Phone: 314-819-5058 Certificate No. 2003025986

TABLE OF CONTENTS

Page

XP-SWMM Modeling Summary ii Rev. 0

SECTION 1 Introduction ......................................................................................... 1-1

SECTION 2 Input Parameters ................................................................................. 2-1

2.1 Hydraulics Module Inputs ............................................................................... 2-1

2.1.1 Collection System Element Data ................................................................ 2-2

2.1.2 Boundary Conditions .................................................................................. 2-4

2.1.3 Base (Dry Weather) Flows ......................................................................... 2-5

2.2 Runoff Module Inputs ..................................................................................... 2-9

2.2.1 Catchment Delineation ............................................................................... 2-9

2.2.2 Impervious Area ......................................................................................... 2-9

2.2.3 Ground Surface Area ............................................................................... 2-10

2.2.4 Ground Slope ........................................................................................... 2-11

2.2.5 Percent Impervious Area .......................................................................... 2-11

2.2.6 Characteristic Width ................................................................................. 2-12

2.2.7 Ground Infiltration Losses ......................................................................... 2-12

2.2.8 Evaporation .............................................................................................. 2-12

2.2.9 Ground Cover Roughness ........................................................................ 2-13

2.2.10 Depression Storage .............................................................................. 2-13

2.2.11 Precipitation .......................................................................................... 2-13

SECTION 3 Model Calibration and Verification ....................................................... 3-1

3.1 Conclusions ................................................................................................... 3-3

TABLE OF CONTENTS

Page

XP-SWMM Modeling Summary iii Rev. 0

List of Tables

Table 2-1: Manning's Roughness coefficients .............................................................. 2-4

Table 2-2: Typical Inlet Capacities ............................................................................... 2-4

Table 2-3: Average values and typical ranges of infiltration parameters .................... 2-12

Table 2-4: Precipitation Data ...................................................................................... 2-14

Table 3-1: Calibration Comparison ............................................................................... 3-2

List of Figures

Figure 1-1: Example model display .............................................................................. 1-1

Figure 2-1: Model Output - Link L159 (FM3040) .......................................................... 2-1

Figure 2-2: Dry Season Flow Comparison ................................................................... 2-6

Figure 2-3: Ponding Area in Barrett Brothers Park. ..................................................... 2-8

Figure 2-4: Railroad ditch ............................................................................................ 2-8

Figure 2-5: Example input hyetograph and output hydrograph in Runoff module ...... 2-10

Figure 3-1: Volume Calibration Plot ............................................................................. 3-2

Figure 3-2: Peak flow and hydrograph shape calibration plot ....................................... 3-3

XP-SWMM Modeling Summary 1-1 Rev. 0

SECTION 1

INTRODUCTION

XP-SWMM, by XP Software Inc., is a link-node model used by the Metropolitan St.

Louis Sewer District (MSD) to model its combined sewer systems. This document presents the XP-SWMM model setup and calibration for the existing and future condition models, for the Harlem-Baden Relief Phase IV (Hebert) project, (HB Hebert).

XP-SWMM is used to simulate the full hydrologic cycle from generating stormwater and sanitary design flows to routing resultant flows through the collection system. Two modules are used in developing a combined sewer system model. The “Runoff” module develops hydrographs for input to the hydraulic components of the model, based on user-defined rainfall hyetographs, antecedent conditions, land use and topography. The

“Hydraulics” module reads the Runoff hydrographs and dynamically routes the storm and sanitary flows through the collection system.

The XP-SWMM model is capable of:

Generating baseline sanitary and infiltration flows, and estimating storm flows given user-defined rainfall hyetographs;

Estimating hydraulic grade lines, volumes and flow rates of water in the modeled collection system;

Estimating flow capacity of gravity sewers;

Estimating peak system flows during dry and wet weather periods;

Simulating system performance using either discrete events or continuous data;

and, Displaying model using graphical user interface, as shown in Figure 1-1.

Figure 1-1: Example model display

XP-SWMM Modeling Summary 2-1 Rev. 0

SECTION 2

INPUT PARAMETERS

The combined sewer system model uses the Runoff and Hydraulics modules. This section describes the development of the inputs for the model.

2.1 HYDRAULICS MODULE INPUTS

The Hydraulics module simulates the hydraulic flow routing of the combined sewer system. The model is a node-link description of the combined sewer system whereby a series of node elements (e.g., manholes, outfalls, storage areas, etc.) are connected by link elements (e.g., sewers, overland flowpaths, etc.). The node elements receive hydrograph input from the Runoff module or by direct user input (e.g., sanitary flow).

The model then dynamically routes the received flows through the combined sewer system to receiving waters. An example results file is provided in Figure 2-1.

Figure 2-1: Model Output - Link L159 (FM3040)

The Dynamic Wave hydrograph method is utilized to perform the hydraulic routing. In this method, the model is based on the gradually-varied, one-dimensional, unsteady flow (St. Venant) equations for open channels. When the flow in a conduit becomes

XP-SWMM Modeling Summary 2-2 Rev. 0 pressurized, the free surface condition is maintained by using the Preissman slot to account for compressibility effects during surcharging.

The following are input to the Hydraulics module:

Collection System Physical Data;

Flow Diversion Elements;

Base (Dry Weather) Flows; and, Boundary Conditions.

2.1.1 Collection System Element Data

Collection system element data include the following:

Sewer and manhole names;

Sewer size;

Sewer shape;

Sewer length;

Manhole and sewer upstream and downstream invert elevations; and Manhole surface (rim) elevations.

These hydraulic parameters were developed using detailed survey data and CCTV inspections, which provided sewer locations and configurations, including diversion structure locations and flow configurations, structure top elevations, and pipe invert elevations. Additional sources, such as historical surveys, record drawings or studies were utilized to supplement field inspection data. In some cases, sufficient data was not available. In such instances, pipe invert elevations were interpolated. All major junctions and diversions incorporated in the model were field-verified (e.g., surveys, CCTV, as-built drawings).

2.1.1.1 Collection System Extents

The hydraulic model incorporates all public sewers within the project area. All MSD structures and node points (including manholes and junctions) are included within the model extents, regardless of distance between modeled nodes. In this manner, searches for specific structures or conduits are expedited, and the model represents the connectivity of the system.

XP-SWMM Modeling Summary 2-3 Rev. 0

2.1.1.2 Labeling nomenclature

MSD’s labeling standard has been modified for all collection system elements. When

Inlet Capacities Routines are used, node names are restricted to eight characters and links are restricted to ten characters by XP-SWMM. Consequently, MSD’s standard node name could not be used. The project area falls within basemap areas, 16G and

16H. Standard MSD structure names, 16G1-001C, exceed the eight character limit when inlet capacities routines are utilized. In order to use the inlet capacity routines, the node names have been shortened by removing the “16” and the “-“ from the structure name. MSD’s pipe naming convention, which consists of a colon between the upstream and downstream structure numbers, cannot be used. Therefore, links were named using the XP-SWMM default value.

Node numbers for unmapped structures will be established by MSD. Map corrections will be submitted to MSD’s mapping department, and a new structure number will be issued by MSD based on the map corrections. Once the new structures have been named, the model will be updated using the new numbers. At this time, they are named based on the CCTV temporary naming conventions.

2.1.1.3 Sewer shapes

A spreadsheet (HBPIV Horseshoe Sewers.xlsx) containing MSD’s standard sizes and shapes of horseshoe configurations has been created. A tab has been added within the template to include each size of sewer identified during the field investigation. The input data was imported into the XP-SWMM model using the XPX import commands.

2.1.1.4 Pipe Roughness

The Manning’s roughness coefficient for each sewer is based on the surface material of the sewer’s wetted perimeter. Table 2-1 below presents the roughness coefficient values used in the model. Where pipe material information is unavailable, a conservative value of 0.015 is used due to the age of the combined sewer system.

XP-SWMM Modeling Summary 2-4 Rev. 0

Table 2-1: Manning's Roughness coefficients

Sewer Material Coefficient Sewer Material Coefficient

Cured-in-Place

(CIPP)

0.012 Clay (VCP) 0.013

Ductile Iron (DIP) 0.012 Concrete

(RCP)

0.013

Plastic (PVC) 0.012 Brick 0.015

Cast Iron (CIP) 0.013 All Others 0.015

2.1.2 Boundary Conditions

The HB Hebert project model has been incorporated into the Black & Veatch watershed model. No changes to the Black & Veatch boundary conditions model were made.

2.1.3 Inlet Restrictions

Many of the inlets within the project area have restricted openings due to street debris, pavement re-surfacing, and collapsed or otherwise impaired structures among other reasons. Inlet capacity was restricted using XP-SWMM’s inlet restriction capabilities based on field investigations and photos of each inlet. When flow exceeded the inlet capacity, a mechanism for storing or conveying excess flows was provided. This topic is discussed in Section 2.1.4.2 below.

Table 2-2: Typical Inlet Capacities

Inlet Type

Maximum

Capacity

(cfs)

Typical

Model

Capacity

(cfs)*

Efficiency

Reduction for

Trash/Debris*

Efficiency

Reduction for

Full of Silt*

Standard Curb Inlet 4 2 0.5 0.1

Double Curb Inlet 6 3 0.5 0.1

Standard Grate Inlet 4 2 0.5 0.1

Multiple Grate Inlet Varies 4 0.5 0.1

Individual inlet capacities and efficiencies in the model were set based on photographs of each inlet, and descriptions from the field survey.

XP-SWMM Modeling Summary 2-5 Rev. 0

2.1.4 Base (Dry Weather) Flows

Average base (dry weather) flows that include infiltration were estimated using flow meter information. Diurnal patterns and average daily flow rates were identified using

MSD’s Dry-Season Flow Data Spreadsheet Tool (Harlem Baden IV Dry Weather.xlsm).

Base flows were derived from data sets of 5 or more continuous days of dry weather.

Comparison of average daily flow rates from the flow meter data set provided starting and ending points for the dry weather periods.

Dry weather flows were applied using the Dry Flow dry weather flow generation method in XP-SWMM. The developed diurnal pattern (temporal variation) and average daily flow rate are direct inputs. The balance of flow from un-metered branches of the collection system was re-distributed to the appropriate sub-catchments based on their characteristics, primarily area or land use. Residential flow rates were based on the parcel mapping using standard MSD contributions. Commercial/Industrial contributions are based on 100 Gal/acre per day. Adjustments were made for large commercial properties with large storage areas, such as the Junk Yard. See Appendix “A” for the

“Sanitary Sewer Shed Maps” detailing the sewershed delineation for the model.

2.1.4.1 Dry Weather Infiltration

Once the pattern of dry weather flow is calibrated, the presence or absence of dry weather infiltration becomes apparent when meter and model output are compared.

The dry weather flows for FM3040 for 2005 based on the population and commercial contribution estimates provided a good match to peak, volume, and pattern, with no dry weather infiltration; however, FM3040-3041 for 2006 has significantly more dry weather infiltration. As a result, constant inflow (0.6 cfs) was added to the system to account for the dry weather infiltration. Figure 2-2 shows the results of the dry weather calibration.

XP-SWMM Modeling Summary 2-6 Rev. 0

Figure 2-2: Dry Season Flow Comparison

2.1.4.2 Surface Storage and Overland Flow Routing

Surface flooding volumes are essential to the HB Hebert Project, in order to design the proposed regional detention basin. Flooding analysis requires an accurate representation of existing drainage patterns to properly understand the collection system’s response to wet weather events. For this reason, surface storage and overland flow routing were discussed with the MSD project manager and it was agreed that restricting inlet capacities, determining overland flowpaths, and defining ponding areas are essential to understanding the existing system.

Surface storage areas were identified using MSD’s LIDAR data and GIS tools to determine large ponding areas. The GIS tools determine the extent of ponding, and provide a stage-area relationship to determine the volume. For smaller areas identified during field visits, storage was accomplished by using the “ponding” option within the

Hydraulics node dialog box. Figure 2-3 provides a picture of a ponding area in Barrett

Brothers Park. In this photo, remnants of previous ponding are evident.

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F lo w (c fs

Hour

Dry Season Flow Comparison - FM0340-0341- HB Herbert

Modeled Flow (2005) Metered Flow (2005)

Metered Flow (2006) Model (2006 Infiltration)

XP-SWMM Modeling Summary 2-7 Rev. 0

Overland flow routing was incorporated to accurately model the existing system. For example, if an inlet is clogged on a paved surface with a constant slope, the flooded flows were redirected through a surface conveyance system to the next downstream inlet. Alternatively, some overland flow paths do not follow the typical street drainage pattern. In these cases, MSD topographic data was utilized to determine the direction and slopes of the overland flow path. In one extreme case, the system is surcharging adjacent to the railroad corridor. In this case, the surface water flows overland to the ditch in the railroad corridor. Some of the water continues down the ditch and some enters the telecommunications conduits. The water that enters the telecommunications conduit is lost out of the system. Figure 2-4 provides a picture of the railroad ditch.

See Appendix “A” for the “Overland Flow Path Maps” detailing the large ponding areas and overland flow paths that were identified during the GIS analysis and modeling.

XP-SWMM Modeling Summary 2-8 Rev. 0

Figure 2-3: Ponding Area in Barrett Brothers Park.

Figure 2-4: Railroad ditch

XP-SWMM Modeling Summary 2-9 Rev. 0

2.2 RUNOFF MODULE INPUTS

The Runoff module simulates the hydrology of the combined sewer system and generates the stormwater runoff quantities for input to the Hydraulics module. The model simulates runoff conditions by distributing a user-defined rainfall hyetograph over the modeled sub-catchment area. Based on the characteristics of the sub-catchment area, the program estimates overland flow quantities, surface detention, infiltration losses, and evaporation losses over a user-defined time period. The output from the

Runoff module is a hydrograph, as shown in Figure 2-5, for input to the Hydraulics module.

The SWMM Runoff Non-Linear Reservoir Method was utilized to perform the hydrograph generation. In this method, overland flow hydrographs for each sub-catchment area are generated by nonlinear reservoir routing using Manning’s equation and lumping the continuity equation with depression storage and impervious area parameters.

2.2.1 Catchment Delineation

A total of 262 catchments were defined for the entire area, adding up to 362 acres. The individual areas ranged from a minimum of 0.01 acres to a maximum of 43 acres, with a median area of 1.29 acres. The catchment boundaries were delineated digitally in GIS for each in the project area. See Appendix “A” for the “Drainage Area Maps” detailing the Catchment Delineation.

2.2.2 Impervious Area

Impervious areas were determined in GIS using layer data provided my MSD. The layer data includes numerous distinct feature classes that supported the development of a detailed representation of impervious versus pervious area, rather than a simple impervious fraction. Each catchment was divided into two subcatchments with following characteristics: 1) All the catchment area except directly connected roof drains., and 2)

Directly connected roof drainage. This approach will allow the model to be readily modified to simulate different inflow reductions options, for example separation of streets and/or disconnections of roof drains.

XP-SWMM Modeling Summary 2-10 Rev. 0

Figure 2-5: Example input hyetograph and output hydrograph in Runoff module

The following parameters with their typical units in parentheses are input to the Runoff module:

Ground Surface Area (acre);

Ground Slope (foot/feet);

Percent Impervious Area (percentage);

Characteristic Width (feet);

Evaporation (inch/day);

Ground Cover Roughness;

Depression Storage (inches); and, Precipitation (inch).

2.2.3 Ground Surface Area

For purposes of analyses, the project area is divided into sub-catchment areas. Sub-catchments were defined for each inlet within the existing system. Estimated ground surface areas for each sub-catchment are calculated by delineating MSD’s facility maps

(infrastructure maps) and digitizing the boundary using GIS software to create a polygon feature class. One of the inherent characteristics of a polygon feature class is calculation of the shape’s area for each polygon. The individual sub-catchments were field verified and adjusted as necessary.

XP-SWMM Modeling Summary 2-11 Rev. 0

Sewershed areas differ somewhat from watershed areas. Therefore, a separate sewershed map was developed for the dry weather flows and roof drainage connections.

Roof areas were represented in a sub-catchment separate from other directly connected impervious areas (e.g., street inlets) to facilitate modeling of anticipated scenarios (particularly roof drain disconnects). This was accomplished using different sub-catchments in the same Runoff node. The ground surface area was not a calibration parameter.

See Appendix “A” for the Sewer Shed map for the HB Hebert watershed. In addition, the directly connected roof drains are identified.

2.2.4 Ground Slope

Ground slopes were calculated using MSD’s LIDAR Data. Using GIS spatial analyst, the average slope of the sub-catchment was calculated, and not adjusted during calibration.

2.2.5 Percent Impervious Area

MSD maintains an impervious area database and a paved area database in polygon feature class format. Impervious percentages were calculated by intersecting the impervious area and paved area databases with the sub-catchment polygon feature class.

The impervious area database is based on accurate mapping of sidewalks, driveways, parking lots and structures (roofs). The paved area database is similarly based on accurate mapping of roads and highways. Both databases are complete within the combined sewer system and, due to their detail, are thought to be at a relatively high degree of accuracy. Therefore, percent impervious area was not used as a calibration parameter.

XP-SWMM Modeling Summary 2-12 Rev. 0

2.2.6 Characteristic Width

The characteristic width is defined as the distance over which surface flow exits the sub-catchment and enters the modeled trunk sewer. The XP-SWMM User Manual recommends that the width be initially entered as the quotient of the sub-catchment area divided by the average path length of overland flow, with the knowledge that this hypothetical parameter is a key calibration parameter. This parameter was estimated using GIS tools and adjusted as necessary to meet calibration requirements.

2.2.7 Ground Infiltration Losses

Ground infiltration losses are estimated on the basis of the Green-Ampt equation for continuous simulation purposes. St. Louis soils tend to be characterized as clays and consequently have low infiltration values. Since soil conditions are not expected to be uniform across a watershed, the ground infiltration parameters were adjusted during calibration. Calibrated values and typical ranges for the input parameters are presented in Table 2-3 below.

Table 2-3: Average values and typical ranges of infiltration parameters

Infiltration Parameter Calibrated

Value

Typical

Range

Average Capillary Suction (inches) 10 3 - 10

Initial Moisture Deficit 0.21 0.16 - 0.25

Saturated Hydraulic Conductivity

(in/hr)

0.25 0.01 - 0.5

2.2.8 Evaporation

The model simulates the portion of precipitation that falls on the sub-catchment and evaporates prior to running off into the combined sewer system. Evaporation was also used to renew surface depression storage, which is discussed in Section 2.2.10.

Evaporation was not expected to be a significant calibration parameter; consequently, the XP-SWMM default value of 0.1 inch/day was utilized.

XP-SWMM Modeling Summary 2-13 Rev. 0

2.2.9 Ground Cover Roughness

The model uses Manning’s roughness coefficients for pervious and impervious ground cover areas. Values of Manning’s roughness coefficient are not as well known for overland flow compared to channel flow. The ground cover roughness values used in other MSD models are 0.3 and 0.013 for pervious and impervious areas, respectively.

These values generally correspond to turf for pervious surfaces and asphalt or concrete paving for impervious surfaces, according to the XP-SWMM User Manual. This description is consistent with the urban watersheds associated with MSD’s combined sewer service area. Therefore, ground cover roughness coefficients were set to the values above and not adjusted during calibration.

2.2.10 Depression Storage

Depression storage is the volume that must be filled prior to the occurrence of runoff.

This value represents the loss caused by phenomena such as surface ponding and allows for evaporation. During calibration, depression storage was set to 0.1-inches for both pervious and impervious areas.

2.2.11 Precipitation

Precipitation (Radar Rainfall and Synthetic Design Storms) data was provided by MSD and entered through the Rainfall global database. Radar Rainfall was provided for the project area for the 2005 and 2006 flow monitoring periods.

MSD provided design storms for analysis. MSD utilizes two types of events: cloudburst and synoptic. Cloudburst events are characterized by short durations (typically 1 to 3 hours), high central core rainfall intensities, and significantly lower rainfall intensities away from the central core of the storm. Synoptic events are characterized by longer durations, lower rainfall intensities, and more uniform rainfall amounts. For analysis of the existing conditions combined sewer system, the cloudburst storms were used.

During the design process, the synoptic storms will also be evaluated.

Depth area reduction factors (DARFs) were not used for this project. The 2005 and

2006 Precipitation data is summarized in Table 2-4 below.

XP-SWMM Modeling Summary 2-14 Rev. 0

Table 2-4: Precipitation Data

Date Rain (in) Duration

(hr)

Return

Interval Date Rain (in)

Duration

(hr)

Return

Interval

4/7/2005 0.01 0.25 < 2‐Month 3/22/06 0.59 4.25 < 2‐Month

4/11/2005 0.25 3.75 < 2‐Month 3/24/06 0.04 0.25 < 2‐Month

4/12/2005 0.35 1.50 < 2‐Month 3/27/06 0.3 3.25 < 2‐Month

4/13/2005 0.06 0.75 < 2‐Month 3/30/06 0.05 0.5 < 2‐Month

4/20/2005 0.3 1.75 < 2‐Month 3/31/06 0.07 0.25 < 2‐Month

4/21/2005 0.63 2.25 < 2‐Month 4/2/06 0.33 3 < 2‐Month

4/22/2005 0.3 2.25 < 2‐Month 4/5/06 0.22 0.5 < 2‐Month

4/23/2005 0.1 2.25 < 2‐Month 4/6/06 0.37 2.25 < 2‐Month

4/25/2005 0.16 4.00 < 2‐Month 4/15/06 0.02 0.5 < 2‐Month

4/26/2005 0.12 2.75 < 2‐Month 4/18/06 0.22 0.5 < 2‐Month

4/28/2005 0.21 4.50 < 2‐Month 4/23/06 0.03 0.75 < 2‐Month

4/29/2005 0.2 4.25 < 2‐Month 4/29/06 0.5 8.5 < 2‐Month

5/8/2005 0.03 0.50 < 2‐Month 4/30/06 0.23 2.25 < 2‐Month

5/9/2005 0.03 0.50 < 2‐Month 5/1/06 0.84 1.75 ~ 2‐Month

5/14/2005 0.27 3.00 < 2‐Month 5/3/06 0.2 2 < 2‐Month

5/19/2005 0.47 1.00 < 2‐Month 5/9/06 0.18 2.25 < 2‐Month

5/20/2005 0.01 0.25 < 2‐Month 5/10/06 0.68 9 < 2‐Month

5/22/2005 0.07 1.25 < 2‐Month 5/11/06 0.12 0.75 < 2‐Month

5/27/2005 0.06 1.25 < 2‐Month 5/12/06 0.05 0.25 < 2‐Month

6/6/2005 0.44 0.50 < 2‐Month 5/14/06 0.06 1.5 < 2‐Month

6/8/2005 0.48 2.75 < 2‐Month 5/15/06 0.05 1.25 < 2‐Month

6/9/2005 0.7 1.50 ~ 2‐Month 5/16/06 0.25 2.25 < 2‐Month

6/11/2005 0.46 1.00 < 2‐Month 5/31/06 0.58 1.75 < 2‐Month

6/13/2005 0.17 2.00 < 2‐Month 6/1/06 1.96 3 ~ 2‐Year

7/4/2005 0.16 1.50 < 2‐Month 6/10/06 1 4.75 ~ 2‐Month

7/11/2005 1.03 9.50 < 2‐Month 6/11/06 0.31 4 < 2 ‐ Month

7/12/2005 0.47 7.00 < 2‐Month 6/17/06 0.06 1 < 2‐Month

7/14/2005 0.03 0.50 < 2‐Month 6/22/06 0.15 1.75 < 2‐Month

7/15/2005 0.15 1.00 < 2‐Month 6/23/06 0.01 0.25 < 2‐Month

7/18/2005 0.17 1.00 < 2‐Month 6/27/06 0.23 0.5 < 2 ‐ Month

7/26/2005 0.18 2.00 < 2‐Month 6/29/06 0.14 0.75 < 2‐Month

7/27/2005 0.06 1.50 < 2‐Month 7/3/06 0.04 0.5 < 2‐Month

8/4/2005 0.02 0.25 < 2‐Month 7/11/06 0.2 1.25 < 2‐Month

8/5/2005 0.01 0.25 < 2‐Month 7/12/06 0.01 0.25 < 2‐Month

8/11/2005 0.19 0.75 < 2‐Month 7/13/06 0.02 0.5 < 2‐Month

8/12/2005 0.01 0.25 < 2‐Month 7/14/06 0.04 0.5 < 2‐Month

8/13/2005 0.93 3.25 ~ 2‐Month 7/19/06 0.15 1 < 2‐Month

8/14/2005 0.27 2.25 < 2‐Month 7/21/06 0.55 1.25 < 2‐Month

Used for Calibration/Verification

2005 2006

XP-SWMM Modeling Summary 3-1 Rev. 0

SECTION 3 0

MODEL CALIBRATION AND VERIFICATION

Adjustment of the model’s hydrologic and hydraulic parameters is necessary to better reflect field-measured results. The term “better reflect” could suggest an infinite process of adjusting the parameters. Therefore, calibration procedures and goals were established to identify the boundaries of the adjustment process. The model is calibrated using flow and rainfall monitoring results. The model was calibrated to a variety of storms to establish confidence in the results for the range of expected conditions. The model was calibrated to the parameters and tolerances provided below.

The parameters are listed in order of importance:

Volume (+/- 20%) Peak flow (+/- 10%) Hydrograph shape

A volume calibration plot is provided in Figure 3-1; an example of an acceptable peak flow/hydrograph shape calibration plot is provided in Figure 3-2. Final calibration plots were exported to a spreadsheet software program for detailed analysis and comparison.

The detailed graphical data are included on the Model CD in the Wet Season

Calibration Folder. Table 3-1 provides the calibration comparison for the selected storms.

XP-SWMM Modeling Summary 3-2 Rev. 0

Figure 3-1: Volume Calibration Plot

Table 3-1: Calibration Comparison

0 50 100 150 200 250 300 350

M o d e l P e ak F lo w (c fs

Meter Peak Flow (cfs)

Harlem Baden Relief Phase IV (Hebert) Peak Flow Comparison

Meter 3040‐3041

Peak Flow Comparison

+10%

‐10%

Linear (+10%)

Linear (‐10%)

Meter Basin Year Meter Model

Differen ce Meter Model

Differen ce Comment 0340-0341HBPIV 2006 904010 925110 2% 291.2 288.2 -1% ~ 2-year event.

0340-0341HBPIV 2006 406397 470071 16% 125.1 129.7 4% ~ 2-month event.

0340-0341HBPIV 2006 489251 497631 2% 51.1 37.9 -26%

~ 2-month event. Radar Rainfall pattern may be in error.

0340 HBPIV 2005 80447 229841 186% 44.3 50.4 14%

~ 2-month event. 2005 Baseflow is significantly lower than 2006 (~0.6 cfs) resulting in higher than expected peak and volume differences

0340 HBPIV 2005 552684 737772 33% 62.0 62.0 0% ~ 2-month event.

3040 HBPIV 2005 184127 229841 25% 44.9 50.4 12%

Rerun of the June 6-7, 2005 event with the baseflow set to the 2005 levels.

2536469 2860424 13% 556.7 556.5 0%Totals

Table 3-1 HBPIV - Wet Season Calibration Results Volume (cu.ft.) Peak Flow (cfs)

June 1-2 May 1-2

Storm Date

June 6-7

June 10-11

June 6-7

August 13-14

XP-SWMM Modeling Summary 3-3 Rev. 0

Figure 3-2: Peak flow and hydrograph shape calibration plot

3.1 CONCLUSIONS

The flow metering periods (2005 and 2006) were extremely dry years for wet weather calibration. For the meter period, the June 1, 2006 event was the largest storm event with estimated return interval of 2-years. All remaining storms, with usable flow meter data were estimated to be a 2-month event or less. With the limited availability of larger storms within the metering period, the June 1, 2006 event became the main focus of calibration. This is the only storm during the meter period that caused surcharging in the system. The calibrated model for this event provides excellent prediction of the system response for both peak and volume, as summarized above. In addition, the calibrated model provides good prediction that is within the target ranges for the smaller

2-month events.

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R ai n fa ll (I n ch e s)

Fl o w (c fs

Time (Hours)

Metered vs. Modeled Flow Meter 0340‐0341 ‐ June 1‐2, 2006

Rainfall Data

Meter Data

Model Data