HomeMy WebLinkAboutFAIRMONT PARK EAST IMPACT ANALYSIS
TOC - 1
Klotz Associates Project No. 0127.012.000 City of La Porte
November 2009 Impact Analysis for Fairmont Park East
TABLE OF CONTENTS
Page
EXECUTIVE SUMMARY ........................................................................................... 1
INTRODUCTION.......................................................................................................... 2
Background.......................................................................................................... 2
Purpose and Scope............................................................................................... 2
Regulatory Policy................................................................................................. 3
DRAINAGE ANALYSIS .............................................................................................. 4
Data Collection.................................................................................................... 4
Topography.......................................................................................................... 4
Existing Conditions.............................................................................................. 4
Hydrology............................................................................................................ 5
Hydraulics............................................................................................................ 6
Inlet Capacity....................................................................................................... 7
Tailwater Conditions............................................................................................ 7
Results.................................................................................................................. 8
Proposed Conditions............................................................................................ 9
IMPACT ANALYSIS .................................................................................................... 10
Overview.............................................................................................................. 10
HEC-HMS Modeling........................................................................................... 11
Calculation of Impact on WSEL in B106-02-00................................................. 13
CONCLUSIONS ............................................................................................................ 14
TOC - 2
Klotz Associates Project No. 0127.012.000 City of La Porte
November 2009 Impact Analysis for Fairmont Park East
TABLE OF CONTENTS – continued
TABLES
1. Tc&R Calculations Using TSARP Methods
2. Tc&R Calculations With Calibration to XP-SWMM
TOC - 3
Klotz Associates Project No. 0127.012.000 City of La Porte
November 2009 Impact Analysis for Fairmont Park East
TABLE OF CONTENTS – continued
EXHIBITS
1. Project Location
2. Existing Conditions Model Drainage Areas
3. Existing Conditions Model Reality vs Model – 25-yr Event
4. Proposed Conditions Model Extents of Re-grading
5. Existing TSARP HMS Model
6. Revised Sub-TSARP HMS Model
TOC - 4
Klotz Associates Project No. 0127.012.000 City of La Porte
November 2009 Impact Analysis for Fairmont Park East
TABLE OF CONTENTS – continued
FIGURES
1. 5 Year Design Rainfall Event
2. 10 Year Design Rainfall Event
3. 25 Year Design Rainfall Event
4. 100 Year Design Rainfall Event
5. Inlet Depth Capacity Rating
6. Fleetwood Outfall Tailwater
7. Proposed Vertical Alignment of Fleetwood Drive
8. Existing Flow at Fleetwood Outfall
9. Proposed Flow at Fleetwood Outfall
10. Exiting and Proposed WSEL in Existing Fleetwood Trunk Sewer
11. Proposed WSEL in Proposed Fleetwood Relief Sewer
TOC - 5
Klotz Associates Project No. 0127.012.000 City of La Porte
November 2009 Impact Analysis for Fairmont Park East
TABLE OF CONTENTS – continued
APPENDICES
Appendix A – Photographs of typical street flooding
1
Klotz Associates Project No. 0127.012.000 City of La Porte
November 2009 Impact Analysis for Fairmont Park East
EXECUTIVE SUMMARY
Project Introduction
Klotz Associates, Inc. was authorized by the City of La Porte (City) to perform professional
engineering services for the preliminary design of drainage improvements for the Fairmont Park
East subdivision (see Exhibit 1).
The subdivision frequently experiences flooding and inconvenient street and yard ponding for
various storm events. Pior study by Klotz Associates (Fairmont Park East & Brookglen
Drainage Study, May 2009 and Fairmont Park East & Brookglen Drainage Study - Addendum,
August 2009) identified a combination of relatively low storm sewer capacity and absence of an
overland sheet flow path as being the major contributors to the specific drainage problem within
Fairmont Park East.
The proposed drainage improvement project includes the addition of a new trunkline sewer along
Fleetwood Drive to give additional subsurface drainage capacity up to the 5-year event and a
revision of the vertical alignment of Fleetwood Drive to allow the drainage of ponded areas on
the side streets, especially on Idlewood, Dogwood and Linwood.
Analysis of the proposed and existing conditions result in a channel flow far less than is expected
by analysis derived from the effective HCFCD models, and far less than the capacity of B106-
02-00. Consequently, it is the conclusion of this report that there is no adverse impact to the
receiving stream as the stream has more than sufficient capacity to handle the changes in flow.
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Klotz Associates Project No. 0127.012.000 City of La Porte
November 2009 Impact Analysis for Fairmont Park East
INTRODUCTION
Background
Klotz Associates, Inc. was authorized by the City of La Porte (City) to perform professional
engineering services for the preliminary design of drainage improvements for the Fairmont Park
East subdivision (see Exhibit 1). The neighborhood frequently experiences flooding and
inconvenient street and yard ponding for various storm events. Recognizing citizen concerns
about these drainage problems, the City is implementing proposed drainage improvements to
raise the level of flood protection. Pior study by Klotz Associates (Fairmont Park East &
Brookglen Drainage Study, May 2009 and Fairmont Park East & Brookglen Drainage Study -
Addendum, August 2009) identified a specific drainage problem within Fairmont Park East and
proposed several alternative relief strategies. The City chose one of the recommended
alternatives to be implemented as a drainage improvement project.
The proposed drainage improvement project includes the addition of a new trunkline sewer along
Fleetwood Drive to give additional subsurface drainage capacity up to the 5-year event. A
revision of the vertical alignment of Fleetwood Drive was also proposed to allow the drainage of
ponded areas on the side streets, especially on Idlewood, Dogwood and Linwood.
In relieving the neighborhood of frequent flooding, it is recognized that there may be adverse
impacts to areas downstream which may require mitigation.
Purpose and Scope
The scope of services for this project includes an impact analysis of the proposed drainage
improvement project and the preparation of a report for submittal to the Harris County Flood
Control Department (HCFCD) for review. The purpose of this report is to demonstrate that,
although there is an increase in flow at the outfall between the existing and proposed conditions,
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Klotz Associates Project No. 0127.012.000 City of La Porte
November 2009 Impact Analysis for Fairmont Park East
the improvements have no adverse impact on the current receiving stream as it has a capacity in
excess of the 100-year flow. This excess capacity is determined from standard HCFCD
methodology which assumes full conveyance of the runoff to B106-02-00.
This is an initial conservative impact analysis report to show to HCFCD the potential changes in
flows to B106-02-00. A preliminary engineering report (PER) in being prepared that will
include more detailed modeling of the existing storm drainage system as well as the proposed
system. This additional PER will be available in a few months, however, this impact analysis
was prepared early in the design of the system to assist in the coordination with HCFCD and to
determine if any mitigation is needed.
Regulatory Policy
Harris County Criteria require that new development that is proposed to drain directly to county
facilities must be reviewed by HCFCD before issuing a permit for construction. In Section 1.3
of the Policy and Criteria, Procedures Manual for Approval and Acceptance of Infrastructure by
HCFCD, there is Policy I: “Primary Function of a HCFCD Facility 1.3.1”. This policy states,
“The primary function of a HCFCD facility is to accomplish the responsibilities established by
the State Legislature and authorized by Commissioners Court. Consequently, proposed projects
by others must be compatible with the primary function of the HCFCD facility. HCFCD
reserves the right to withhold approval of any proposed project that, in the opinion of HCFCD,
is not compatible with the primary function of the HCFCD facility.” The proposed drainage
improvements fall under the regulatory authority of this policy.
In accordance with this HCFCD policy, findings are presented here as to the potential impacts
associated with the proposed Fairmont Park East subdivision drainage improvements.
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Klotz Associates Project No. 0127.012.000 City of La Porte
November 2009 Impact Analysis for Fairmont Park East
DRAINAGE ANALYSIS
Data Collection
The City provided some as-built drawings for storm sewer improvements, water lines, sanitary
lines, and subdivision plats for the Fairmont Park East subdivision. A variety of other data
sources were used, including earlier studies and reports from the City and HCFCD; hydraulic
and hydrologic models from the Federal Emergency Management Administration (FEMA)
obtained by HCFCD; plans and profiles of existing storm drainage systems; 2008 aerials from
the Houston-Galveston Area Council (HGAC); field reconnaissance; and information provided
by residents and City Staff.
Topography
LiDAR elevation grids developed from data collected in 2008 comes from HCFCD. The
horizontal datum is the North American Datum of 1983 (NAD83) and the vertical datum is the
North American Vertical Datum of 1988 (NAVD88), 2001 Adjustment.
Existing Conditions
Due to the nature of the drainage problem and of the proposed solution it was decided that it was
important to model both the subsurface drainage and the associated overland flow and storage.
The Stormwater and Wastewater Management Model (SWMM) engine is commonly used to
handle the modeling of one-dimensional (1D) dendritic pipe networks. XP Software has an
implementation of the SWMM engine (XP-SWMM) that also incorporates a two-dimensional
(2D) overland flow modeling component. This 2D component uses a surface grid and overland
roughness data to determine how water that cannot enter the subsurface 1D system would be
stored and perhaps flow on the surface. The following text describes the determination of the
physical parameters used in the development of the existing conditions XP-SWMM model.
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Klotz Associates Project No. 0127.012.000 City of La Porte
November 2009 Impact Analysis for Fairmont Park East
Hydrology
XP-SWMM has separate calculation modes that can be run concurrently. The runoff mode
determines the hydrologic behavior of the network and develops flows for use in the hydraulic
mode.
The first step in developing the runoff model is to develop sub-catchments that define the
drainage area to a particular collection point (usually an inlet for storm sewer modeling). The
existing storm sewer network was available in GIS format, so the inlet locations were used to
develop drainage areas (see Exhibit 2).
The drainage area parameters required to be developed for the XP-SWMM runoff mode are:
area, percent imperviousness, width, and the representative drainage area slope.
The area in acres was calculated in GIS. The drainage areas are all generally the same width as
they are delineated from one ridgeline along the center of the road and another at the rear
property line. Consequently the widths were set at the average width of 135 feet. The slope of
each drainage area was developed by generating a best-fit trend plane through the LiDAR data
within the extent of each drainage area. The imperviousness was generated from the USGS
Impervious Cover Dataset from 2001. A GIS process called Zonal Statistics was used to develop
an area weighted average imperviousness for each drainage area. The average percent
imperviousness for the Fairmont Park East watershed is 64.5% with a minimum value of 38%
and a maximum of 78%.
The next step was to develop a design rainfall event. The aim of the project was to design a
subsurface system with a 5-year capacity; therefore a 5-year rainfall event must be developed for
sewer design. On the other hand, the impact analysis uses a 100-year event; therefore rainfall for
the 100-year event also needs to be developed. In order to see the benefits at intermediate
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Klotz Associates Project No. 0127.012.000 City of La Porte
November 2009 Impact Analysis for Fairmont Park East
events, rainfall for the 10-year and 25-year events were also developed. The average intensity
and total rainfall depth for each return period was developed using the
intensity/duration/frequency curves from the City of La Porte Storm Sewer Design Criteria
Manual.
Frequency e, b, d Values
Average
Intensity (i)
Total Rainfall
Depth
5 0.7881, 84.14, 17.8 0.2702 6.48
10 0.7742, 93.53, 18.9 0.3322 7.97
25 0.7808, 115.9, 21.2 0.3918 9.40
100 0.7500, 125.4, 21.8 0.5304 12.73
The resulting hyetographs were developed using the balanced storm method as outlined in the
TxDOT Hydraulic Design Manual (see Figures 1- 4).
Hydraulics
The development of the existing hydraulic model was done in two main phases. First, the 1D
dendritic network was developed from the best available data; and, second, the 2D surface was
developed from 2008 LiDAR.
The basic network topology was already defined in a GIS dataset. The sewer and manhole
inverts, sizes, and rim elevations were extracted from as-built plans from the City. The plans
were on an unknown vertical datum and therefore could be adjusted only approximately. The
manhole rim elevations from the plans were compared to the elevations from LiDAR. The
average difference of 1.19 ft was subtracted from the as-built plan values to give approximate
NAVD88 2001 adjustment elevations. The GIS network was then imported into XP-SWMM
using the GIS import tool.
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Klotz Associates Project No. 0127.012.000 City of La Porte
November 2009 Impact Analysis for Fairmont Park East
Inlet Capacity
The capacity of a storm sewer network can be as much about the capacity of the inlets as it is
about the capacity of the storm sewers themselves. It is important to estimate the effectiveness
of the inlets to the system and to model them correctly. All but one of the inlets are Type “BB”,
with the other being a double grated inlet due to its proximity to a driveway.
A rating curve was developed for the inlets using the method outlined in Section 5 of TxDOT
Hydraulic Design Manual – Curb Inlets in Sag Configuration. This method calculates the
capacity of the inlet as a weir until the flow depth is equal to the opening height, then has a
transition phase until the flow depth is 1.4 times the opening height, and finally uses the orifice
equation thereafter (see Figure 5).
Tailwater Conditions
Two boundary conditions need to be set for the 1D and 2D models. A tailwater condition is
required at the 1D network outfall, while a flow or head boundary is required for the 2D
network. In order to make the model run more efficiently it was determined that a 2D head
boundary should be created near the 1D network outfall and that both should be set to the same
value. The system outfall discharges to HCFCD Unit No. B106-02-00, which is an unmodeled
tributary to the modeled HCFCD Unit No. B106-00-00.
In order to determine the water surface at the Fleetwood Drive outfall an approximate HEC-RAS
model was built of the B106-02-00 reach. This was done using the HEC-GeoRAS modeling
tools to develop planimetric data and to extract elevation data from the 2008 HCFCD LiDAR.
Planimetric data for the 2 culverts was estimated from aerial photographs, while the approximate
geometry of the culverts was estimated from oblique birds-eye views.
On this basis the tailwater elevation was developed for the 5-, 10-, 25- and 100-year events:
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Klotz Associates Project No. 0127.012.000 City of La Porte
November 2009 Impact Analysis for Fairmont Park East
Frequency Flow WSEL at Outfall
5 268.8 14.78
10 332.6 15.17
25 399.5 15.54
100 509.7 16.08
These values were entered into both the 2D head boundary element and into the outfall elements
static tailwater value.
Results
In order to determine if the existing model accurately represents reality, a comparison of
structure locations suffering repetitive losses was made with those predicted by the model (see
Exhibit 3). The model predicts that 41 structures are likely to flood during the 100-year storm,
21 at the 25-year event, 9 at the 10-year event, and 6 at the 5-year event. As can be seen, the
location of predicted residence flooding compares favorably with the locations of known
repetitive flood losses. The model predicts more flooded homes than has been reported
especially in the vicinity of North and South Spruce Drive. This could be for three main reasons.
First, it is unknown what storm event caused the flooding in the reported incidents, so they may
have occurred at storm events other than those modeled. Second, at the time of this impact
analysis, there was no information about the finished floor elevation; therefore it was assumed
that the finished floor was at grade. This assumption more than likely causes an over-prediction
of flooding as many of the homes are likely to be constructed on a raised slab foundation. Third,
the exact dimensions of the inlets are unknown and therefore the rating curves used are generic
in nature and identical for all inlets. With more detailed inlet information, inlet rating curves
could be established for each individual inlet, and therefore result in a slightly different flooding
pattern. Overall the strong correlation between predicted and realized flood loss patterns
confirms the validity of the model.
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Klotz Associates Project No. 0127.012.000 City of La Porte
November 2009 Impact Analysis for Fairmont Park East
Proposed Conditions
The proposed conditions model was developed using the existing conditions model as the base.
There are three main differences between the existing and proposed conditions. First, there is an
additional parallel trunkline sewer added under Fleetwood Drive. Second, Fleetwood Drive and
each of the side streets have been re-graded. Finally a swale has been added at the south end of
Fleetwood Drive to allow overland flow to be safely conveyed to B106-02-00. The extent of the
re-grading can be seen in Exhibit 4 and the approximate vertical alignment is given in Figure 7.
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Klotz Associates Project No. 0127.012.000 City of La Porte
November 2009 Impact Analysis for Fairmont Park East
IMPACT ANALYSIS
Overview
The drainage analysis and system modeling in XP-SWMM described up to this point has been
for the purpose of system design. The existing model was built in order to verify that the 1D and
2D system reflect the reality experienced by the residents of Fairmont Park East. It was then
used as a base to test the proposed design. This ensures that the design solves the right problem
and in an efficient manner.
The flow magnitudes predicted at the Fleetwood Drive outfall using the XP-SWMM existing and
proposed models are considerably lower than would be expected to be generated using the
existing (effective) HEC-HMS models. This is due to the fact that the HMS models use a
modified Clark’s Unit Hydrograph Tc&R method as described in Hydrology for Harris County
(HCFCD, March 3, 1988). This method uses average sub-basin parameters to describe the
runoff characteristics in terms of a time of concentration (Tc) and a retention time (R).
The Tropical Storm Allison Recovery Project (TSARP) completed by HCFCD in 2004 resulted
in hydrologic models that cover the entire county and hydraulic models covering the major
watercourses. The Fairmont Park East subdivision lies within the B106C sub-basin of the
Armand Bayou Watershed (see Exhibit 5). The parameters for calculation of Tc&R for sub-
basin B106C are:
Watershed Length (mi.) (L) 1.988
Length to Centroid (mi.) (Lca) 0.581
Channel Slope (ft./mi) (S) 5.8
Overland Slope (ft./mi.) (So) 8.8
Percent Urban Development (DLU) 83.5
Percent Channel Improvement (DCI) 100
Percent Channel Conveyance (DCC) 100
Percent Ponding (DPP) 0
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Klotz Associates Project No. 0127.012.000 City of La Porte
November 2009 Impact Analysis for Fairmont Park East
HEC-HMS Modeling
In order to determine the impact of the increased runoff to the receiving stream it was decided to
breakdown sub-basin B106C and construct a more detailed HEC-HMS hydrologic model of the
areas upstream of the Fleetwood outfall that contribute to B106-02-00 (see Exhibit 6).
The composition of the Fairmont Park East and surrounding subdivisions is representative of the
entire B106C sub-basin. Consequently, the DLU, DCI, DCC and DPP were kept the same for
the smaller sub-basins. The physical parameters L, Lca, S and So, however, are dependent on the
size and shape of the new areas and were therefore recalculated. The parameters were entered
into the Tc&R calculation and can be seen in Table 1. These Tc&R values were then entered
into the new HEC-HMS model which can be termed the “Expected Conditions” model. This
Expected Conditions model represents findings based on typical analyses normally performed
for HCFCD acceptance criteria.
All three models were then run and the resulting peak flows for the Fairmont Park East
subdivision are tabulated below:
Model Type
100-year Peak Flow
from Subdivision
(cfs)
TSARP B106C1 HEC-HMS 243.5
Expected Conditions HEC-HMS 173.5
Existing Conditions XP-SWMM 113.4
Proposed Conditions XP-SWMM 173.4
1 Pro-Rated by area
The peak flow generated for the Fleetwood sub-basin in the expected conditions model (173.5
cfs) was compared to that generated in existing conditions (113.4 cfs). The difference can be
accounted for by the amount of significant overland flow and storage that is anticipated in the
existing conditions model but not the expected conditions.
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Klotz Associates Project No. 0127.012.000 City of La Porte
November 2009 Impact Analysis for Fairmont Park East
The flow difference is significant however; the TSARP analysis was developed at a much larger
scale than the Fairmont Park East analysis. The large sub-drainage areas such as B106C and
their associated parameters are developed based on large conveyance systems such as B106-02-
00. The DCC, DCI, and DPP parameters start to break down when considering smaller drainage
areas with sub-surface drainage systems. As such the hydrologic model needs to be “calibrated”
to give peak runoff values in line with XP-SWMM.
Normally, DCC and DCI are the main parameters used in calibration along with other physically
based elements such as infiltration loss rates. Testing of the model showed that the peak flow
was relatively insensitive to changes in DCC and DCI. Adjusting these values was also
eliminated based on the fact that the areas did not have channels that could be assessed for
conveyance or improvement. Adjusting DPP for calibration purposes is normally not a good
idea as any adjustment has different effects for different return periods. In this case however, it
was decided to use DPP to attempt to account for the large amount of storage in the streets of
Fairmont Park East (See Appendix A). This was determined to be appropriate for two reasons;
firstly, DPP is a parameter that is used to reduce flows due to storage and secondly, as this
impact analysis is only based on the 100-year event, there is no need for consistency across
multiple return periods.
To estimate the magnitude of the require DPP adjustment, the Tc&R values for the Fairmont
Park East sub-basin were adjusted until the peak flows matched (113.4 cfs). The DPP value that
gives rise to these Tc&R values was then calculated to be 30.5 %. It was then assumed that, as
all of the sub-basins are similar in nature, they too would have similar DPP values. The final
Tc&R values can be seen in Table 2.
The expected conditions model was saved as two separate versions representing the XP-SWMM
existing and proposed conditions. The Fleetwood basin was removed from each and replaced by
an inflow hydrograph element. In the existing conditions HEC-HMS model, the output
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Klotz Associates Project No. 0127.012.000 City of La Porte
November 2009 Impact Analysis for Fairmont Park East
hydrograph from the existing conditions XP-SWMM model was entered. In the proposed
conditions HEC-HMS model, the output hydrograph from the proposed conditions XP-SWMM
model was entered. In the other sub-basins the Tc&R values were updated to account for the
revised DPP values.
These revised existing and proposed conditions models were then run and the resulting peak
flows in B106-02-00 at the outfall location were compared.
Model Type
100-year Peak Flow
in B106-02-00
(cfs)
100-year WSEL in
B106-02-00
(ft)
Expected Conditions HEC-HMS 509.7 16.08
Existing Conditions HEC-HMS 341.4 15.23
Proposed Conditions HEC-HMS 402.0 15.56
Calculation of Impact on WSEL in B106-02-00
In order to determine the impact of the proposed drainage improvements in terms of a water
surface elevation the B106-02-00 HEC-RAS model was used.
The existing flow of 341.4 cfs produced a WSEL of 15.23 ft, while the proposed flow of 402.0
cfs resulted in a WSEL of 15.56 ft. This means that the impact on B106-02-00 in terms of
change in WSEL is 0.33 ft. However, the expected flow of 509.7 cfs results in a WSEL of 16.08
ft. This means that although the proposed condition when compared “apples to apples” with the
existing condition shows an impact of 0.33ft, it is considerably less (0.52 ft) than the WSEL that
would be expected using typical HCFCD acceptance criteria.
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Klotz Associates Project No. 0127.012.000 City of La Porte
November 2009 Impact Analysis for Fairmont Park East
CONCLUSIONS
The proposed improvements for the Fairmont Park East subdivision change the manner in which
the overland flow is handled. Improving the capacity of the subsurface system as well as
changing the vertical alignment of the road results in less water being stored in the streets, yards,
and houses of the neighborhood. Consequently, the rate of flow that will outfall to B106-02-00
will increase.
Harris County recognizes storage within the right-of-way of streets as being a necessary part of
any drainage system; the intent is not to impact adjacent property. Current HCFCD models do
not account for this storage in the normal Tc&R calculations and as such the flow expected in
B106-02-00 is in excess of that which will actually be realized.
In comparing the proposed condition to the existing condition, it is clear that more flow will get
to B106-02-00; however, both conditions result in a channel flow far less than is expected by
analysis derived from the effective HCFCD models, and far less than the capacity of B106-02-
00. Consequently, it is the conclusion of this report that there is no adverse impact to the
receiving stream as the stream has more than sufficient capacity to handle the changes in flow.
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City of La Porte Impact Analysis for Fairmont Park East
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City of La Porte Impact Analysis for Fairmont Park East
La
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13
4
201 225
Fairmont
Main
Spencer
Center
13th
R e d B luff
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Big Island SloughBig Island Slough
AArrmmaanndd BBaayyoouu
LLiittttllee CC eeddaarr BBaayyoouu EXHIBIT 1CITY OF LA PORTE FAIRMONT PARK EASTPROJECT LOCATION KLOTZ PROJ. NO.: 0127.012.000 SCALE: 1" = 4000 'DATE: OCT 2009³
FILE PATH: J:\0127.012.000\07.00 CADD\MXDs\ExhibitsForIA\Exhibit1_Location.mxd
04,000 Feet PRELIMINARY DRAINAGE DESIGN
Ho
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!!
!!
!!
!!
!!!!
!!
!!
!!
!!
!
!
!!!!!!!!!!!!
!!
!!
!!
!!
!!
!!
!
!!!
!!!
!!!
!!!
!!
!
!!
!
!!
!!!
!!!!!!!!!!
!B106-02-00
Birch
Fleetwood
Dogwood
Mesquite
Spruce
Mulberry
Idlewood
Collingswood
Linwood
Sycamore
EXHIBIT
2
CITY OF LA PORTE
FAIRMONT PARK EAST
EXISTING CONDITIONS MODEL
DRAINAGE AREAS
KLOTZ PROJ. NO.: 0127.012.000
SCALE: 1" = 300 '
DATE: OCT 2009
³FILE PATH: J:\0127.012.000\07.00 CADD\MXDs\ExhibitsForIA\Exhibit2_DrainageAreas.mxd 0300Feet
PRELIMINARY DRAINAGE DESIGN
Legend
!Nodes
Links
Drainage Area
Drainage Area to Node
!!
!!
!!
!!
!!!!
!!
!!
!!
!!
!!
!!!!!!!!!!!!
!!
!!
!!
!!
!!
!!
!
!!!
!!!
!!!
!!!
!!
!
!!
!
!!
!!
!
!!!!!!!!!!
!B106-02-00
Birch
Fleetwood
Dogwood
Mesquite
Spruce
Mulberry
Idlewood
Collingswood
Linwood
Sycamore
EXHIBIT
3
CITY OF LA PORTE
FAIRMONT PARK EAST
EXISTING CONDITIONS MODEL
REALITY vs MODEL
KLOTZ PROJ. NO.: 0127.012.000
SCALE: 1" = 300 '
DATE: OCT 2009
³FILE PATH: J:\0127.012.000\07.00 CADD\MXDs\ExhibitsForIA\Exhibit2_DrainageAreas.mxd 0300Feet
PRELIMINARY DRAINAGE DESIGN
Legend
!(Reported Flood Losses
Predicted Flooding at:
5-yr and over
10-yr and over
25-yr and over
100-yr and over
!!
!!
!!
!!
!!!!
!!
!!
!!
!!
!
!
!!!!!!!!!!!!
!!
!!
!!
!!
!!
!!
!
!!!
!!!
!!!
!!!
!!
!
!!
!
!!
!!!
!!!!!!!!!!
!
!!!
!
!
!
!
!
!
!
!
!
!
!!
!!
!!
!!
!!!!
!!
!!
!!
!!
!
!
!!!!!!!!!!!!
!!
!!
!!
!!
!!
!!
!
!!!
!!!
!!!
!!!
!!
!
!!
!
!!
!!!
!!!!!!!!!!
!B106-02-00
Birch
Fleetwood
Dogwood
Mesquite
Spruce
Mulberry
Idlewood
Collingswood
Linwood
Sycamore
EXHIBIT
4
CITY OF LA PORTE
FAIRMONT PARK EAST
PROPOSED CONDITIONS MODEL
EXTENTS OF RE-GRADING
KLOTZ PROJ. NO.: 0127.012.000
SCALE: 1" = 300 '
DATE: OCT 2009
³FILE PATH: J:\0127.012.000\07.00 CADD\MXDs\ExhibitsForIA\Exhibit2_DrainageAreas.mxd 0300Feet
PRELIMINARY DRAINAGE DESIGN
Legend
!Existing Nodes
Existing Links
!Proposed Nodes
Proposed Links
Extent of Re-Grading
B106D
A10413A
B109A
A10407A
B106C
F216AB106BB106AB11202A
B106E
A10404AB100E
F216B
A104B
ARMAND BAYOU
CLEAR CREEK
SAN JACINTO & GALVESTON BAY
EXHIBIT
5
CITY OF LA PORTE
FAIRMONT PARK EAST
EXISTING TSARP
HMS MODEL
KLOTZ PROJ. NO.: 0127.012.000
SCALE: 1" = 2000 '
DATE: OCT 2009
³FILE PATH: J:\0127.012.000\07.00 CADD\MXDs\ExhibitsForIA\Exhibit5_HMSModel.mxd 02,000Feet
PRELIMINARY DRAINAGE DESIGN
Legend
Fairmont Park East
TSARP Drainage Lines
TSARP Watersheds
TSARP Sub-Basins
Fleetwood
DA = 110.4 ac
L = 0.63
Lca = 0.33
S = 2.20
So = 2.20
F
DA = 91.8 ac
L = 0.69
Lca = 0.32
S = 4.40
So = 4.40
E
DA = 26 ac
L = 0.38
Lca = 0.17
S = 8.80
So = 8.80
C
DA = 19.1 ac
L = 0.27
Lca = 0.08
S = 13.2
So = 13.20
D
DA = 17.7 ac
L = 0.21
Lca = 0.09
S = 10.60
So = 10.60
EXHIBIT
6
CITY OF LA PORTE
FAIRMONT PARK EAST
REVISED SUB-TSARP
HMS MODEL
KLOTZ PROJ. NO.: 0127.012.000
SCALE: 1" = 500 '
DATE: OCT 2009
³FILE PATH: J:\0127.012.000\07.00 CADD\MXDs\ExhibitsForIA\Exhibit6_PropHMSModel.mxd 0500Feet
PRELIMINARY DRAINAGE DESIGNLegend
Impact Analysis Drainage Areas
Fi
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St
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Elevation
Existing Road CL Exiting Flowline Existing Soffit Proposed Road CL Proposed Flowline Proposed Soffit
N. SYCAMORE
S. SYCAMORE
N. SPRUCE
S. SPRUCE
LINWOOD
DOGWOOD
IDLEWOOD
MULBERRY
COLLINGSWOOD
BIRCH
MESQUITE
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10
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(
m
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Flow (cfs)
Fi
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Ti
m
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(
m
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n
)
Flow (cfs)
APPENDIX A