Section 1 Introduction ........................................................................................... 4
1.1 Propose...................................................................................................................... 4
1.2 Project Authority....................................................................................................... 4
1.3 Project Location ........................................................................................................ 5
1.4 Hydrologic and Hydraulic Methods.......................................................................... 5
1.5 Acknowledgment ...................................................................................................... 6
1.6 Study Results ............................................................................................................ 6
Section 2 Local Government Abstract ................................................................ 10
2.1 Project Contact Information.................................................................................... 10
2.2: General Information ............................................................................................... 10
2.3: Mapping Information ............................................................................................. 10
2.3: Hydrology .............................................................................................................. 10
2.4: Hydraulics .............................................................................................................. 11
Section 3 Survey and Mapping Information ........................................................ 11
3.1 Digital Projection Information ................................................................................ 11
3.2 Mapping .................................................................................................................. 11
Section 4 Hydrology ............................................................................................ 11
4.1 Method Description ................................................................................................ 11
4.2 Parameter Estimation .............................................................................................. 12
4.2.1 Drainage Area .................................................................................................. 12
4.2.2 Watershed Work Map ...................................................................................... 12
4.2.3 Gage Data......................................................................................................... 12
4.2.4 Spatial Parameters ............................................................................................ 12
4.2.5 Precipitation ..................................................................................................... 12
4.2.6 Physical Parameters ......................................................................................... 13
4.3 Issues Encountered During the Study ..................................................................... 13
4.3.1 Special Problems and Solutions ....................................................................... 13
4.3.2 Modeling Warning and Error Messages .......................................................... 13
4.4 Calibration............................................................................................................... 13
4.5 Final Results........................................................................................................ 14
4.5.1 Hydrologic Analysis Results........................................................................ 14
4.5.2 Verification of results .................................................................................. 14
Section 5 Hydraulics ........................................................................................... 15
5.1 Method Description ................................................................................................ 15
5.2 Work Study Maps ................................................................................................... 15
5.3 Parameter Estimation .............................................................................................. 15
5.3.1 Roughness Coefficients ................................................................................... 15
5.3.2 Expansion and Contraction Coefficients ......................................................... 16
5.4 Cross-Section Description ...................................................................................... 16
5.5 Modeling Consideration.......................................................................................... 16
5.5.1 Hydraulic Jump and Drop Analysis ................................................................. 16
5.5.2. Bridges and Culverts ....................................................................................... 16
5.5.3 Levees and Dikes ............................................................................................. 16
5.5.4 Non-Levee Embankments ................................................................................ 16
5.5.5 Island and Flow Splits...................................................................................... 16
5.5.6 Ineffective Flow Areas ..................................................................................... 16
2

5.6 Floodway Modeling ................................................................................................ 17
5.7 Issues Encountered.................................................................................................. 17
5.7.1 Special Problems and Solutions ....................................................................... 17
5.7.2 Model Warnings and Errors ............................................................................. 17
5.8 Calibration............................................................................................................... 17
5.9 Final Results............................................................................................................ 17
5.9.1 Hydraulic Analysis Results .............................................................................. 17
5.9.2 Verification of Results ..................................................................................... 18
Section 6 Erosion and Sediment Transport ........................................................ 18
List of Tables
Table 0 Summary of Results ............................................................................................... 6
Table 1 Methods used for a PC-Hydro analysis ............................................................... 13
Table 2 Watershed Characteristics.................................................................................... 13
Table 3 Summary of the Hydrologic Analysis ................................................................. 14
Table 4 Comparison of a peak discharge .......................................................................... 14
List of Figures
Figure 1.1 Watershed Map.................................................................................................. 7
Figure 1.2 Study Limits ...................................................................................................... 8
Figure 1.3 Soil Classification.............................................................................................. 9
Appendix A: References
Appendix B: FEMA MT-2 Forms, General Documentation and Correspondence
Appendix C: Survey Field Notes
Appendix D: Hydrologic Analysis, Supporting Documents
Appendix E: Hydraulic Analysis, Supporting Documents
Appendix F: Erosion Analysis, Supporting Documents
Exhibit
Exhibit 1 100-yr floodplain limit for the Unnamed Wash 1
Exhibit 2 Annotated Flood Insurance Rate Map for the Unnamed Wash 1

3

Section 1 Introduction
1.1 Propose
This Technical Data notebook (TDN) has been prepared to study a portion of the Pegler
Wash (PGR) located in Pima County, Arizona. The objective of the TDN is provide
regulatory discharge rates and floodplain limits along the Pegler Wash using better
topographic, hydrologic, and hydraulic data.
This TDN was prepared in accordance with the “Instructions for Organizing and
Submitting Technical Documentation for Flood Studies” prepared by the Arizona
Department of Water Resources, Flood Mitigation Section (Arizona State Standard, SSA
1-97) and FEMA Guideline. FEMA LOMR forms are included in this TDN.

1.2 Project Authority
The State of Arizona has delegated the responsibility to each county flood control district
to adopt floodplain regulations designed to promote the public health, safety and general
welfare of its citizenry as provided under the Arizona Revised Statutes, Title 48, Chapter
21, Article 1, Sections 48-3601 through 3627. More specifically, A.R.S. 3609 directs
county flood control districts to adopt floodplain regulations that:
A. Regulate all development of land, construction of residential, commercial or
industrial structures or uses of any kind which may divert, retard or obstruct flood
water and threaten public health or safety or the general welfare; and
B. Establish minimum flood protection elevations and flood damage prevention
requirements for uses, structures and facilities which are vulnerable to flood
damage; and
C. Comply with state and local land use plans and ordinances, if any.
In conformance with A.R.S. 3609, this ordinance provides for protection of the
public health safety and welfare by regulation of flood and erosion hazard areas to
control flood hazards and prevent repetitive loss from flood damage.
D. The flood hazard areas of Pima County are subject to periodic inundation which
may result in loss of life and property, create health and safety hazards, disrupt
commerce and governmental services, require extraordinary public expenditures for
flood protection and relief, and impair the tax base, all of which adversely affect the
public health, safety, and general welfare.
E. These flood losses are caused by the cumulative effect of obstructions in areas of
special flood hazards which increase flood heights, flow velocities, and cause flood
and erosion damage. Uses that are inadequately flood-proofed, elevated, or
otherwise protected from flood damage, also contribute to the flood loss. (Ord. 2010
FC-5 (part), 2010).

4

Section 16 of the Pima County Ordinance describes the provisions for floodplain
regulation in Pima County.
This study has been prepared by the Pima County Regional Flood Control District
(RFCD):
Pima County Regional Flood Control District
97 East Congress, Tucson, AZ 85701
The project was prepared by:
Akitsu Kimoto, Ph.D., C.F.M., Principal Hydrologist.
Pima County Regional Flood Control District
97 East Congress, Tucson, AZ 85701

1.3 Project Location
The study reach of the Pegler Wash (PGR) is located upstream of a Federal Emergency
Management Agency (FEMA)-designated “Zone A” flood-hazard area, as depicted on
FIRM Map Panel Number 04019C1660L and 1680L (June 16, 2011). The site includes
Sections 25, 26, 34, 35, and 36 of Township 12 South, Range 13 East, Section 30 and 31
of Township 12, Range 14, and Section 03, 04, and 09 of Township 13, Range 13, Pima
County, Arizona. The objective of the TDN is provide regulatory discharge rates and
floodplain limits along the Pegler Wash using better topographic, hydrologic, and
hydraulic data.
The study reach of the Pegler Wash is located primarily east of La Cholla Bld (Fig. 1.1).
The Pegler Wash enters study limit from the east and flows west. The study limit for the
Pegler Wash is from La Cholla Bld. to Northern Ave.
LOMR Case# 08-09-1616P (Effective Date 12-19-2008) re-mapped the Pegler Wash
between La Cholla Blvd. and Orange Grove Rd. LOMR Case# 09-09-0020P (Effective
Date 11-20-2009) re-mapped the wash from the Sotomayor Ranch Subdivision (including
a levee) to Orange Grove Rd. Case# 04-09-0465X (Effective Date 04-22-2004) remapped near the downstream of the wash from the Rillito River. All three LOMRs were
incorporated into FIRM panels 04019C1660L and 1667L.

1.4 Hydrologic and Hydraulic Methods
The 100-year return interval peak discharge rates were obtained by using HEC-1 and PCHydro, Version 5.4.2 (PC-Hydro). The HEC-1 peak discharges for the Pegler Wash were
provided by JE Fuller. The watershed was subdivided into 6 sub-basins for the HEC-1
analysis. There are four concentration points (CP 103,104,105 and 106) for the HEC-1

5

analysis (Fig. 1). CP 103 is located at La Canada Dr. and CP 105 is located at La Cholla
Bld. Vegetation cover of 20% and impervious cover of 25% were used for the analysis.
Upstream of the Pegler watershed was further subdivided for PC-Hydro analysis (CP C,
E, G, H, I and J). The parameters for PC-Hydro, such as rainfall intensity and subbasin
characteristics (e.g. soil, vegetation, slope, flow distance, roughness), were selected using
PC-Hydro User Guide (Arroyo Engineering, 2007). The proposed regulatory discharges
are flow rates that have a 1-percent chance of being equaled or exceeded each year (“100year” discharge rates). Hydraulic analysis was performed to delineate floodplain limit
along the study reach of the Pegler Wash using U.S. Army Corps of Engineers Computer
Backwater Model, HEC-RAS, Version 4.1 and FLO-2D, Version 2007.
.

1.5 Acknowledgment
This study relied on assistance of RFCD GIS staff, who were integral to the development
of the models and maps.

1.6 Study Results
The regulatory peak discharge rates were calculated at concentration points A to J (Fig.
1.3).
Table 0 Summary of Results
Concentration
Point

Location

Area (sq
mile)

CP 103
CP 104
CP 105
CP C
CP E
CP G
CP H
CP I
CP J

La Canada
Ina
La Cholla
La Cholla
Ina
Upstream of La Canada
Upstream of La Canada
Magee
Magee

1.60
2.03
2.43
0.11
0.19
0.55
0.36
0.15
0.42

Q100 HEC-1
or PC-Hydro
(cfs)
2050
2392
2615
367
817
1808
1253
673
1603

Q100
RRE (cfs)
1709
1982
2211
230
368
832
609
303
683

6

W HARDY RD

NO

RAC

LE

RD

Figure 1.1
Watershed Map
Pegler Wash

!
(

Discharge Point
Contours 10ft

Subbasins

CP J

!
(!
(CP I

A

W MAGEE RD

B
C

!
( CP H

D

CPG103
!
(
!
( CP G

W MAGEE RD

E
F
G
H

!
( CP E
W INA RD

I

Pac-12 Networks

!
( CPG104

E INA RD

J
Aerial : 2010 Pictometry

Study Limit

CPG105

N LA CANADA DR

Datum: NAVD 1988

Pima County Index Map

W ORANGE GROVE RD

N 1ST AV

!
(!
( CP C

E ORANGE GROVE RD

Index Map Scale 1:5,250,000

The information depicted on this display is the result
of digital analyses performed on a variety of databases
provided and maintained by several governmental agencies.
The accuracy of the information presented is limited to
the collective accuracy of these databases on the date
of the analysis. The Pima County Regional Flood Control
Department makes no claims regarding the accuracy of the
information depicted herein.
This product is subject to the Department of Transportation
Technical Services Division's Use Restriction Agreement.

1,000

N LA CHOLLA BL

!
( CPG106

500

0

1,000 Feet

Pima County Regional Flood Control District

07/2012
\\gislib\rfcd\projects\imd\xavi\mxd\AKITSU\Pegler\Pegler_wash_watershed_Fig1_1.mxd

W HARDY RD

NO

RAC

LE

RD

Figure 1.2
Study Limit
Pegler Wash

I
J
H

!
(!
(

F

!
(

CP H

Subbasins

G

Existing FEMA Floodplain
ZONE A

CPG103 CP G

W MAGEE RD

Discharge Points
River

CP J CP I
W MAGEE RD

!
(

!
(
!
(

ZONE AE

E

ZONE X - SHADED

D

!
(

W INA RD

!
(

Aerial : 2010 Pictometry

CP E

CPG104
E INA RD

C
Study Limit

CPG105 CP C

N LA CANADA DR

B
Pima County Index Map

W ORANGE GROVE RD

A

E ORANGE GROVE RD

Index Map Scale 1:5,250,000

The information depicted on this display is the result
of digital analyses performed on a variety of databases
provided and maintained by several governmental agencies.
The accuracy of the information presented is limited to
the collective accuracy of these databases on the date
of the analysis. The Pima County Regional Flood Control
Department makes no claims regarding the accuracy of the
information depicted herein.
This product is subject to the Department of Transportation
Technical Services Division's Use Restriction Agreement.

CPG106
N LA CHOLLA BL

!
(

N 1ST AV

!
(!
(

Pima County Regional Flood Control District

1,000

500

0

07/2012
\\gislib\rfcd\projects\imd\xavi\mxd\AKITSU\Pegler\Pegler_wash_Watershed_Fig1_2.mxd

1,000 Feet

W HARDY RD

NO

RAC

LE

RD

Figure 1.3
Soil Classification
Pegler Wash

I
J

Subbasins

Soil Classification

H
W MAGEE RD

F

Soil Group: A (100%)

G

Soil Group: B (100%)
Soil Group: B (50%) C (50%)
Soil Group: C (100%)

W MAGEE RD

Soil Group: C (53%) D (47%)

E

Soil Group: D (100%)

D

Aerial : 2010 Pictometry

E INA RD

W INA RD

Study Limit

W ORANGE GROVE RD

A

Pima County Index Map

N 1ST AV

C

N LA CANADA DR

B

E ORANGE GROVE RD

Index Map Scale 1:5,250,000

The information depicted on this display is the result
of digital analyses performed on a variety of databases
provided and maintained by several governmental agencies.
The accuracy of the information presented is limited to
the collective accuracy of these databases on the date
of the analysis. The Pima County Regional Flood Control
Department makes no claims regarding the accuracy of the
information depicted herein.

N LA CHOLLA BL

This product is subject to the Department of Transportation
Technical Services Division's Use Restriction Agreement.
Pima County Regional Flood Control District

1,000

500

0

07/2012
\\gislib\rfcd\projects\imd\xavi\mxd\AKITSU\Pegler\Pegler_wash_Watershed_Fig1_3.mxd

1,000 Feet

Section 2 Local Government Abstract
2.1 Project Contact Information
Contact Information:
Akitsu Kimoto
Pima County Regional Flood Control District
97E Congress, Tucson, AZ 85705
Akitsu.Kimoto@pima.gov
Local Technical Reviewer:
Terry Hendricks
Pima County Regional Flood Control District
97E Congress, Tucson, AZ 85705
Terry.Hendricks@pima.gov
Date Study Submitted: _________________________
Date Study Approved: __________________________

2.2: General Information
Community: Pima County Regional Flood Control
County: Pima County
River or Stream Name: Pegler Wash
Reach Description: Wash in Catalina Foothills
Study Type: Hydrology and Hydraulics study of a Riverene System
Purpose of the Study: Estimate regulatory discharge and map a floodplain boundary

2.3: Mapping Information
Digital Projection Information: PAG 2011 orthophoto
USGS Quad Sheets if available:
Mapping for Hydrologic Study: LiDAR based on 2008 flight used to derive 2’ contour
interval maps using ARC-GIS 10.0
Mapping for Hydraulic Study: LiDAR based on 2008 flight used to derive a DEM (5-ft
cell size) for use with HEC-GeoRAS

2.3: Hydrology
Model or Method Used: PC-Hydro, version 5.4.2, HEC-1
Storm Duration:
Hydrograph Type:
Frequencies Determined: 100 yr

10

List of Gages used in Frequency Analysis or Calibration: None
Rainfall Amounts and Reference: NOAA 14 Upper 90% Confidence Interval
Unique Conditions and Problems: None
Coordination of Q’s: Comparison with a USGS Regression Equation

2.4: Hydraulics
Model or Method Used: HEC-RAS 4.1, HEC-GeoRAS, FLO-2D
Regime: Modeled as subcritical
Frequencies for which Profiles were computed: 100 yr
Method of Floodway Calculation: No Floodway
Unique Conditions and Problems: Boundary set at normal depth.

Section 3 Survey and Mapping Information
3.1 Digital Projection Information
Projection: State Plane, Arizona central Zone
Horizontal Datum: NAD83-92 (HARN)
Vertical Datum: NAVD88
Units: International Feet

3.2 Mapping
The topographic data was obtained using ArcGIS. Digital Elevation Model (DEM)
derived from 2008 Light Detection and Ranging (LiDAR) data was used to create 2-foot
interval contour map.
The following data was used in this TDN;
The aerial photo: 2008 PAG aerial photo
Projection: UTM, Zone 12
Units: International feet
The contour interval of the topographic map is 2 feet.

Section 4 Hydrology
4.1 Method Description
The 100-year peak discharges for the Pegler Wash were estimated using HEC-1 for
downstream CPs and PC-Hydro for upstream subbasins. HEC-1 peak discharges were
obtained by JE Fuller. The PC-Hydro uses a semi-empirical method, which is similar to
11

the Rational Formula. The method is unique to Pima County. Pima County has been
using the Pima County Hydrology Procedures (PC-Hydro method) for over 30 years for a
floodplain management. The method has been deemed as a FEMA-accepted hydrologic
method for prediction of 100-yr peak discharge in Pima County. The method was used
for the Friendly Village LOMR (case# 08-09-0473P) and it was approved by FEMA. The
PC-Hydro method generally produces higher discharge values compared to HEC-1 or
HEC-HMS or USGS Regression equations. Peak discharge values produced by the PCHydro would be conservative, compared to using HEC-HMS or USGS Regression
equations. The PC-Hydro model requires the parameters regarding rainfall, topography,
soil, and vegetation to determine peak discharge. Those parameters were determined
following the PC-Hydro User Guide (Arroyo Engineering, 2007). The PC-Hydro model
is included in Appendix D. Data for HEC-1 provided by JE Fuller is also included in
Appendix D.

4.2 Parameter Estimation
4.2.1 Drainage Area
Subbasin boundaries were delineated using the hydrology function of ArcGIS with 2008
LiDAR Data. A 2-ft contour map was used to make sure if the subbasin delineation was
reasonable.

4.2.2 Watershed Work Map
A watershed work map is included in Exhibit 1.

4.2.3 Gage Data
No gage data were used in this TDN.

4.2.4 Spatial Parameters
No spatial parameters were used in this TDN.

4.2.5 Precipitation
One-hour rainfall was used to estimate 100-year peak discharge for the upstream PCHydro subbasins (CPs C, E, G, H, I and J). No area reduction factor was applied.
Summary of the HEC-1 analysis is included in Appendix D.

12

4.2.6 Physical Parameters
Methods are summarized in Table 1. The PC-Hydro model calculates runoff coefficients
using adjusted Curve Number (CN), which has been developed based on the results of the
USDA-ARS research. This procedure assumes that high intensity, short duration storms
result in raindrop impacts causing the surface of soils to seal up, resulting in reducing
infiltration (Caliche Effect). The CN in the PC-Hydro model increases with increasing
rainfall depth and intensity. The detail of the method was described in PC-Hydro User
Guide (Arroyo Engineering, 2007).
Table 1 Methods used for a PC-Hydro analysis

Rainfall Depth
Rainfall Distribution
Rainfall Loss
Time of Concentration
Transform
Routing

Selected Method
NOAA 14, upper 90% Confidence Interval
3-hr SCS Type II Storm
SCS Curve number
SCS Segmental Method
SCS Unit Hydrograph
Modified-Puls
Table 2 Watershed Characteristics

SubBasin

PGR C
PGR E
PGR G
PGR H
PGR I
PGR J

Area
(sq
mile)
0.11
0.19
0.55
0.36
0.15
0.42

Impervious Area

Vegetation Cover

(%)
20.0
20.0
20.0
20.0
20.0
20.0

(%)
20.0
20.0
20.0
20.0
20.0
20.0

4.3 Issues Encountered During the Study
4.3.1 Special Problems and Solutions
None

4.3.2 Modeling Warning and Error Messages
None

4.4 Calibration
No calibration was conducted in this study.

13

4.5 Final Results
4.5.1 Hydrologic Analysis Results
The 100-year peak discharges at CPs were determined using HEC-1 (provided by JEFuller) and PC-Hydro. The results are summarized Tables 3.
Table 3 Summary of the Hydrologic Analysis
Concentration
Point

Location

Area
(sq
mile)

CP 103
CP 104
CP 105
CP 106
CP C
CP E
CP G
CP H
CP I
CP J

La Canada
Ina
La Cholla
Shannon
La Cholla
Ina
Upstream of La Canada
Upstream of La Canada
Magee
Magee

1.60
2.03
2.43
2.78
0.11
0.19
0.55
0.36
0.15
0.42

Rainfall
Depth
at Tc
(in)
6.99
8.22
6.84
7.09
8.14
7.75

Q100
(cfs)

Time of
Concentration
(min)

2050
2392
2615
2770
367
817
1808
1253
673
1603

13.1
14.5
20.4
19.2
15.4
16.6

4.5.2 Verification of results
The estimated peak discharge at CP A was also compared with the peak discharge
obtained from USGS Regression Equation 13 (Thomas et al., 1997) (Table 4). The
comparison showed that the PC-Hydro-derived peak discharge is 12.5% higher than the
one derived from the Regression Equation.
Table 4 Comparison of a peak discharge
Concentration
Point

Location

Area
(sq
mile)

CP 103
CP 104
CP 105
CP C
CP E
CP G
CP H
CP I
CP J

La Canada
Ina
La Cholla
La Cholla
Ina
Upstream of La Canada
Upstream of La Canada
Magee
Magee

1.60
2.03
2.43
0.11
0.19
0.55
0.36
0.15
0.42

Rainfall
Depth
at Tc
(in)
6.99
8.22
6.84
7.09
8.14
7.75

Q100
(cfs)

Time of
Concentration
(min)

2050
2392
2615
367
817
1808
1253
673
1603

13.1
14.5
20.4
19.2
15.4
16.6

RRE: USGS Regression Equation 13

14

Section 5 Hydraulics
5.1 Method Description
The hydraulic modeling for the Pegler Wash was performed using HEC-RAS, Version
4.1 (HEC-RAS), HEC-GeoRAS, Version 10 (HEC-GeoRAS), ArcGIS, Version 10, and
FLO-2D (Version 2007-6).
Steady flow analysis was performed to determine 100-year water surface elevations for
downstream of La Cholla by using HEC-RAS. The model name is PGR, and the plan
name is Plan 01. The locations of the stream centerline, cross-sections, and bank of the
Campbell Wash were determined using the 2-ft contour map and 2008 PAG aerial
photos. The geometric data, including stream centerline, flow paths and cross-sections,
were digitized in HEC-GeoRAS. The digitized data was exported to create geospatially
referenced geometric data (cross section, reach profile) in HEC-RAS. Other parameters
for the steady-state analysis in HEC-RAS, such as Manning’s n-values, expansion and
contraction coefficients, boundary condition, and ineffective flow areas were manually
input into HEC-RAS. The hydraulic data obtained from HEC-RAS were imported into
HEC-GeoRAS to delineate a floodplain boundary for the Pegler Wash. Normal depth was
assumed for a downstream boundary condition. The hydraulic data obtained from HECRAS were imported into HEC-GeoRAS to delineate a floodplain boundary of the Pegler
Wash for downstream of La Cholla Bld.
FLO-2D was used for upstream of La Cholla Bld. Geometric data for the FLO-2D model
were derived from the 2008 LiDAR data. Grid cell size of 20 feet was used to map a
floodplain in the downstream area. The time interval used for the computation was 1
minutes. Hydrographs at CPs G, H, I and J, obtained by using PC-Hydro, were used as
inflow.

5.2 Work Study Maps
The work study map for the Pegler Wash is included in Exhibit 2.

5.3 Parameter Estimation
5.3.1 Roughness Coefficients
Manning’s n values were determined by a combination of a site visit and 2008 PAG
aerial photo.

15

5.3.2 Expansion and Contraction Coefficients
The channel of the Pegler is assumed to have generally gradual transitions with minimum
curvature. The expansion coefficient of 0.30 and contraction coefficient of 0.10 were
used for the study reach except for immediately upstream and downstream of a culvert
(expansion 0.5, contraction 0.3).

5.4 Cross-Section Description
A 2-foot interval contour map was used to select the location of cross sections. Crosssection locations were determined primarily based on the channel topography. The crosssection lines were drawn to be perpendicular to flow paths in HEC-GeoRAS.

5.5 Modeling Consideration
5.5.1 Hydraulic Jump and Drop Analysis
No hydraulic, drop analyses or adjustment of the floodplain was conducted in this study.

5.5.2. Bridges and Culverts
There are culverts at La Cholla Bld., Ina Rd. and La Canada Dr.

5.5.3 Levees and Dikes
There are no levees or dikes located within the study limit.

5.5.4 Non-Levee Embankments
None

5.5.5 Island and Flow Splits
There were no islands or flow splits modeled.

5.5.6 Ineffective Flow Areas
Ineffective flow option was modeled in the situation that overbank areas are disconnected
and would not convey flow to the next downstream cross-section.
16

5.6 Floodway Modeling
No floodway modeling was performed in this study.

5.7 Issues Encountered
5.7.1 Special Problems and Solutions
The upstream area of the Pegler Wash is a distributary-flow area with flat topography.
Therefore, FLO-2D was applied to delineate a 100-yr floodplain for the upstream area of
the Pegler Wash. There is a recent road improvement at La Canada Dr. LiDAR 2008 used
in this study does not reflect the changes along the road. Therefore, a floodplain was not
mapped around La Canada Dr. A floodplain around La Canada Dr. will be added when a
new topography is obtained.

5.7.2 Model Warnings and Errors
No errors occurred. The following warning messages occurred:
Divided flow
Energy loss greater than 1.0
Energy equation could not be balanced and defaulted to critical.
Cross-section extended vertically.
Multiple critical depths calculated.
Conveyance ratio is less than 0.7 or greater than 1.4.
Inspection indicated that the modeling is accurate given the steep channel conditions.
Most of these errors force a critical solution which is reasonable for these steep
watercourses.

5.8 Calibration
The model was not calibrated in this study.

5.9 Final Results
5.9.1 Hydraulic Analysis Results

17

The HEC-RAS model and FLO-2D model are included in Appendix E.

5.9.2 Verification of Results
NA

Section 6 Erosion and Sediment Transport
No erosion or sediment transport analysis was conducted in this study.

18

A.1 Data Collection Summary
Aldridge, B. and J. Garrett. 1973. Roughness Coefficients for Stream Channels in
Arizona. US Department of the Interior Geological Survey. Tucson, AZ.
Arizona Department of Water Resources, Flood Mitigation Section
“Instruction for Organization and Submitting Technical Document for Flood Studies”
SSA1-97, November 1997
Arizona Department of Water Resources, Flood Mitigation Section
“Requirements for Flood Study Technical Documentation” SS1-97, November 1997
Arroyo Engineering. 2007. PC-Hydro User Guide. Pima County Regional Flood Control
District
City of Tucson (COT), Department of Transportation, 1989. Standards Manual for
Drainage Design and Floodplain Management in Tucson, Arizona. Revised in 1998.
National Weather Service. 1984. Depth-Area Ratios in the Semi-Arid Southwest
United States, NOAA Technical Memorandum NWS Hydro-40
Phillips, J., and S. Tadayon. 2006. Selection of Manning’s roughness coefficient for
natural and constructed vegetated and non-vegetated channels, and vegetation
maintenance plan guidelines for vegetated channels in central Arizona: U.S. Geological
Survey Scientific Investigations Report 2006–5108, 41 p.
Phillips, J., and T. Ingersoll. 1998. Verification of Roughness Coefficients for Selected
Natural and Constructed Stream Channels in Arizona. U.S. Geological Survey
Professional Paper 1584.
Pima County Regional Flood Control District
“Pima County Mapguide Map”, 2008
U.S. Army Corps of Engineers (COE). 1998. HEC-1 Flood Hydrograph Package, Users
Manual, CPD-1A, Hydraulic Engineering Center, Davis, CA.
U.S. Army Corps of Engineers (COE). 2001. HEC-RAS, River Analysis System,
Hydraulic
Reference Manual, CPD-69, Hydraulic Engineering Center, Davis, CA.
U.S. Army Corps of Engineers (COE). 2003. Geospatial Hydrologic Modeling Extension
HEC-GeoHMS, (v 1.1) CPD-77, Hydraulic Engineering Center, Davis, CA.
U.S. Army Corps of Engineers (COE). 2006. HEC-HMS, Hydrologic Modeling System
User’s Manual, (v. 3.1.0) CPD-74A, Hydraulic Engineering Center, Davis, CA.

U.S. Department of Agriculture Natural Resources Conservation Service (NRCS), 1986.
Urban Hydrology for Small Watersheds, Technical Release 55. Washington, DC.

A 2. Referenced Documents
Arroyo Engineering. 2007. PC-Hydro User Guide. Pima County Regional Flood Control
District
Eychaner, J.H., 1984. Estimation of magnitude and frequency of floods in Pima County,
Arizona, with comparisons of alternative methods: U.S. Geological Survey WaterResources Investigations Report 84-4142, 69 p.
Haan, C.T., Barfield, B.J., Hayes, J.C. 1994. Design Hydrology and Sedimentology for
Small Catchments, Academic Press.
Thomas, B.E., H.W. Hjalmarson, and S.D. Waltemeyer. 1997. Methods for Estimating
Magnitude and Frequency of Floods in the Southwestern United States. USGS Water
Supply Paper 2433. 195 p.
U.S. Department of Agriculture Natural Resources Conservation Service (NRCS), 1986.
Urban Hydrology for Small Watersheds, Technical Release 55. Washington, DC.

Appendix B FEMA MT-2 Form, General Documentation
and Correspondence

Appendix C: Survey Field Notes

Page 1 of 1

Terry Hendricks

From: Curtis, Edward [mailto:Edward.Curtis@dhs.gov]
Sent: Tuesday, November 10, 2009 2:44 PM
To: Manny M. Rosas
Cc: Terry Hendricks; Lucero, Andrew; Caldwell, Jason; Akl, Pascal
Subject: RE: PAG 2008 Orthos/Lidar
Mr. Rosas –
I apologize for the delay in responding to you regarding the Sanborn LiDAR report. Pascal Akl of Michael Baker,
Jr. reviewed the updated July 2009 report on behalf of FEMA and advised me that all of the concerns raised in his
May 18, 2009 memorandum titled “Pima County, CA [sic] Sanborn LiDAR Report Items” were addressed in the
updated report except the comment that the original report lacked a sufficient number of checkpoints in urban
areas and dense vegetation areas. No additional checkpoints were surveyed in such arease to permit analysis of
data accuracy in these land cover categories. However, in the data voids analysis section of the updated report
(p. 16), Sanborn states the following: "Specific areas, dense vegetation or undergrowth near small streams, for
example, prevents the LiDAR pulses to fully penetrate to the true ground surface. Thus, for mapping products
such as floodplain or contour mapping, LiDAR data must often be manually supplemented with breaklines and
mass-points to accurately model the terrain surface." As long as the data is used with caution and supplemented
with additional ground survey data where necessary in accordance with this statement, I am satisfied that the
terrain data meets FEMA standards for use in detailed flood studies.
Please contact me if you have any questions regarding our review and comments.
Ed Curtis, P.E., CFM
Risk Analysis Branch
FEMA Region IX
(510) 627-7207 - office
(510) 295-5249 - mobile

2/25/2010

Appendix D: Hydrologic Analysis Supporting
Documentation
(models, spreadsheets and supporting information is provided digitally in the TDN disk)

Appendix E: Hydraulic Analysis and As-Built Drawings
for Hydraulic Structures
(models, spreadsheets and supporting information is provided digitally in the TDN disk)

Appendix F: Erosion and Sediment Transport Analysis
Supporting Documentation
None