Section 1 Introduction ........................................................................................ 4
1.1 Propose...................................................................................................................... 4
1.2 Project Authority....................................................................................................... 4
1.3 Project Location ........................................................................................................ 5
1.3 Hydrologic and Hydraulic Methods.......................................................................... 5
1.4 Acknowledgment ...................................................................................................... 6
1.5 Study Results ............................................................................................................ 6
Section 2 FEMA Forms ..................................................................................... 10
2.1 Study Documentation Abstract for FEMA submittals ............................................ 11
2.1.1 Date Study Accepted........................................................................................ 11
2.1.2 Study Contractor .............................................................................................. 11
2.1.3 Local Technical Reviewer ............................................................................... 11
2.1.4 Reach Description ............................................................................................ 11
2.1.5 USGS Quad Sheets .......................................................................................... 11
2.1.6 Unique Conditions and Problems .................................................................... 11
2.1.7 Coordination of Peak Discharges..................................................................... 12
2.2 FEMA Forms .......................................................................................................... 12
Section 3 Survey and Mapping Information ................................................... 12
3.1 Field Survey Information ........................................................................................ 12
3.2 Mapping .................................................................................................................. 12
Section 4 Hydrology ......................................................................................... 12
4.1 Method Description ................................................................................................ 12
4.2 Parameter Estimation .............................................................................................. 15
4.2.1 Drainage Area .................................................................................................. 15
4.2.2 Watershed Work Map ...................................................................................... 15
4.2.3 Gage Data......................................................................................................... 15
4.2.4 Spatial Parameters ............................................................................................ 15
4.2.5 Precipitation ..................................................................................................... 15
4.2.6 Physical Parameters ......................................................................................... 15
4.3 Problems Encountered During the Study................................................................ 16
4.3.1 Special Problems and Solutions ....................................................................... 16
4.3.2 Modeling Warning and Error Messages .......................................................... 16
4.4 Calibration............................................................................................................... 16
4.5 Final Results........................................................................................................ 16
4.5.1 Hydrologic Analysis Results........................................................................ 16
4.5.2 Verification of results .................................................................................. 17
Section 5 Hydraulics......................................................................................... 17
5.1 Method Description ................................................................................................ 17
5.2 Work Study Maps ................................................................................................... 18
5.3 Parameter Estimation .............................................................................................. 18
5.3.1 Roughness Coefficients ................................................................................... 18
5.3.2 Expansion and Contraction Coefficients ......................................................... 18
5.4 Cross-Section Description ...................................................................................... 18
5.5 Modeling Consideration.......................................................................................... 18
5.5.1 Hydraulic Jump and Drop Analysis ................................................................. 18
5.5.2. Bridges and Culverts ....................................................................................... 18
2

5.5.3 Levees and Dikes ............................................................................................. 19
5.5.4 Island and Flow Splits...................................................................................... 19
5.5.5 Ineffective Flow Areas ..................................................................................... 19
5.6 Floodway Modeling ................................................................................................ 19
5.7 Problems Encountered ............................................................................................ 19
5.7.1 Special Problems and Solutions ....................................................................... 19
5.7.2 Model Warnings and Errors ............................................................................. 19
5.8 Calibration............................................................................................................... 20
5.9 Final Results............................................................................................................ 20
5.9.1 Hydraulic Analysis Results .............................................................................. 20
5.9.2 Verification of Results ..................................................................................... 20
Section 6 Erosion and Sediment Transport ................................................... 20
Section 7 Draft FIS Report Data ....................................................................... 20
7.1 Summary of Discharges .......................................................................................... 20
7.2 Floodway Data ........................................................................................................ 20
7.3 Annotated Flood Insurance Rate Map .................................................................... 20
7.4 Flood Profiles .......................................................................................................... 20
List of Tables
Table 1 Methods used for a PC-Hydro analysis ............................................................... 16
Table 2 Watershed Characteristics.................................................................................... 16
Table 3 Summary of the Hydrologic Analysis ..................Error! Bookmark not defined.
Table 4 Comparison of a peak discharge .......................................................................... 17
List of Figures
Figure 1.1 Watershed Map.................................................................................................. 7
Figure 1.2 Study Limits ...................................................................................................... 8
Figure 1.3 Soil Classification.............................................................................................. 9
Figure 4.1 Flow Chart of Mapping Process ...................................................................... 14
Appendix A: References
Appendix B: 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 Via Entrada Wash

3

Section 1 Introduction
1.1 Propose
This Technical Data notebook (TDN) has been prepared for a Letter of Map Revision
(LOMR) application for a portion of the Via Entrada Wash (VE) located in Pima County,
Arizona. The objective of the TDN and LOMR submission is provide regulatory
discharge rates and floodplain limits along the Via Entrada 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. 2005
FC-2 § 2 (part), 2005).
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:
Evan Jensen, BS, Interning Hydrologist
Akitsu Kimoto, Principal Hydrologist.
Pima County Regional Flood Control District
97 East Congress, Tucson, AZ 85701

1.3 Project Location
The study reach of the Via Entrada Wash (VE1) is located within a Federal Emergency
Management Agency (FEMA)-designated “Zone X” flood-hazard area, as depicted on
FIRM Map Panel Number 04019C1630K, 1635K, and 1637K (February 8, 1999). No
documented hydraulic analyses were found to determine the “Zone X”, and the existing
“Zone X” depiction is not consistent with current topography. The objective of the TDN
and LOMR submission is provide regulatory discharge rates and floodplain limits along
the Via Entrada Wash using better topographic, hydrologic, and hydraulic data.
The study was performed to provide drainage information for the Via Entrada Wash. The
site includes Section 05, 07, 08, 17, 18, 19 of Township 13 South, Range 14 East,
Sections 4, 5, 7, 8, 17, 18 and 19 of Township 13 South, Range 14 East; Pima County,
Arizona. Watershed is part of in Flood Insurance Rate Map (FIRM) number
04019C1630K, 1635K, and 1637K.
The watershed is 1.69 square miles. The study watershed was divided into seven subbasins (Fig.1.1). The study limits for the Via Entrada Wash extends from North of
Campbell and Skyline to the intersection of River Rd and Via Entrada (Fig.1.2).

1.3 Hydrologic and Hydraulic Methods
Hydrologic analysis was preformed to estimate regulatory discharge rate at River Rd
using PC-Hydro Version 5.4.2 (PC-Hydro). 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

5

equaled or exceeded each year (“100-year” discharge rates). Hydraulic analysis was
performed to delineate floodplain limit along the study reach of the Via Entrada Wash
using U.S. Army Corps of Engineers Computer Backwater Model, HEC-RAS.
.

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

1.5 Study Results
The regulatory peak discharge rate was calculated at CPs. The estimated discharges are
summarized in Table 3.

6

Figure 1.1
Watershed Map
Via Entrada Wash

0

Legend
(
!

Concentration Point
River

1

(
!

6

Subbasins

Name
0
1
2

3

(
!

2

3
4
5
6

4

4

3

2

(
!

20ft Contours
Aerial : 2008 Pima Association of Governments

(
!

5
6
5

(
!

Pima County Index Map

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.
Pi ma C ou nty Re gio nal F lo od Co ntrol D istrict

1
(0
(!
!

30
15
030 Feet

1/2011
\\gislib\rfcd\projects\imd\xavi\mxd\A KITSU\Via_Entrada\Via_Entrada_wash_Fig1_3.mxd

Figure 1.2
Study Limit Map
Via Entrada Wash

Study Limit

(
!

0
(
!

Concentration Point
100 yr Floodplain
Subbasins

1
(
!

3

2
(
!

Aerial : 2008 Pima Association of Governments

(
!
Pima County Index Map

Index Map Scale 1:5,250,000

6
(
!

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.
Pima County Regional Flood Control District

910

455

0

5
(4
(!
!
1/2011
\\gislib\rfcd\projects\imd\xavi\mxd\AKITSU\Via_Entrada\Via_Entrada_wash_Fig1_3.mxd

910 Feet

Figure 1.3
Soil Classification
Via Entrada Wash

0

River

subbasins
Soil Types
Soil Group: A (100%)

1
Soil Group: B (100%)

Soil Group: B (100%)

Soil Group: B (82%) C (18%)

2

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

Soil Group: C (50%), D (50%)

Soil Group: D (100%)

3

4

Soil Group: D (100%)

Aerial : 2008 Pima Association of Governments

Pima County Index Map

6

5
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.
Pima County Regional Flood Control District

1,200

600

0

1/2011
\\gislib\rfcd\projects\imd\xavi\mxd\AKITSU\Via_Entrada\Via_Entrada_wash_Fig1_3.mxd

1,200 Feet

Section 2.0 Summary of Key Facts

Section 2.1: General Information
2.1.1 Community: Pima County Regional Flood Control
2.1.2 Community Number: NFIP Community Number 04019C
2.1.3 County: Pima
2.1.4 State: Arizona
2.1.5 Date Study Accepted: Not Accepted –
2.1.6 Study Contractor: Pima County Regional Flood Control District – Evan Jensen
2.1.7 State Technical Reviewer: Not Applicable
2.1.8 Local Technical Reviewer: Suzanne Shields
2.1.9 River or Stream Name: Via Entrada
2.1.10 Reach Description: Via Entrada
2.1.11 Study Type: Hydrology and Hydraulics study of a Riverene System

Section 2.2: Mapping Information
2.2.1 FIRM Panels: 04019C1630K, 1635K, and 1637K
2.2.2 Mapping for Hydrologic Study: Lidar based on 2008 flight used to derive 2’
contour interval maps using ARC-GIS 9.3.1
2.2.3 Mapping for Hydraulic Study: Lidar based on 2008 flight used to derive a DEM
(5-ft cell size) for use with GeoRAS

Section 2.3: Hydrology
2.3.1 Model or Method Used: PC-Hydro, version 5.4.2
2.3.2 Storm Duration: NA
2.3.3 Hydrograph Type: NA
2.3.4 Frequencies Determined: 100 yr
2.3.5 List of Gages used in Frequency Analysis or Calibration: None
2.3.6 Rainfall Amounts and Reference: NOAA 14 Upper 90% Confidence Interval
2.3.7 Unique Conditions and Problems: None
2.3.8 Coordination of Q’s: Comparison with previous studies on file with RFCD and
discharge estimates

Section 2.4: Hydraulics
2.4.1 Model or Method Used: HEC-RAS 4.0, GeoRAS to parameterize
2.4.2 Regime: Modeled as subcritical
2.4.3 Frequencies for which Profiles were Computed: 100 yr
2.4.4 Method of Floodway Calculation: No Floodway
2.4.5 Unique Conditions and Problems: Boundary set at normal depth.

Section 2.5: Additional Study Information:
None

10

FOR FEMA Section 2 FEMA Forms
2.1 Study Documentation Abstract for FEMA submittals
2.1.1 Date Study Accepted: ___________________
2.1.2 Study Contractor:
Planning and Development Division,
Pima County Regional Flood Control District
97 East Congress, Tucson, AZ 85701
(520) 243-1800
Prepared by Evan Jensen, BS, Interning Hydrologist

2.1.3 Local Technical Reviewer:
Bill Zimmerman, Division Manager and Terry Hendricks, C.F.M, Chief Hydrologist
Planning and Development Division,
Pima County Regional Flood Control District
97 East Congress, Tucson, AZ 85701
(520) 243-1800

2.1.4 Reach Description
The study reach of the Via Entrada Wash is located within a Federal Emergency
Management Agency (FEMA)-designated “Zone X”, as depicted on FIRM Map Panel
Number 04019C-1635 K and FIRM number 04019-1637 K. (February 8, 1999). The
study reach of the Via Entrada Wash is located primarily north of River Rd., Pima
County, Arizona (Fig. 1.1). The study reach of the Via Entrada Wash is primarily
composed of sand and gravel channel. The overbank of the reach is covered with desert
brush.

2.1.5 USGS Quad Sheets
Not available for this study

2.1.6 Unique Conditions and Problems
None.

11

2.1.7 Coordination of Peak Discharges
The 100-year regulatory discharge rate at River Rd. was computed using PC-Hydro. 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 discharge rate was acceptable per Suzanne Shield,
Director of the Pima County Regional Flood Control District.

2.2 FEMA Forms
Not applicable.

Section 3 Survey and Mapping Information
3.1 Field Survey Information
None.

3.2 Mapping
The topographic data was obtained using HEC-GeoRas and ArcGIS. Digital Elevation
Model (DEM) derived from 2008 Light Detection and Ranging (LiDAR) data was used
to create 5-foot interval contour map. The documentation showing that this Lidar data set
is FEMA-compliant is included in Appendix C.
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 5 feet.

Section 4 Hydrology
4.1 Method Description
The 100-year peak discharges for the watershed outlet of the Via Entrada Wash ( Fig.
1.3) were calculated using PC-Hydro Version 5.4.2 (PC-Hydro). The PC-Hydro uses a
semi-empirical method, which is similar to the Rational Formula. The method is unique

12

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# 08-090473P) and it was approved by FEMA. The PC-Hydro method generally produces higher
discharge values compared to HEC-HMS or USGS Regression equations. Peak discharge
values produced by the PC-Hydro 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.

13

Figure 4.1 Flow Chart of Mapping Process
Topographic Data Preparation using ArcGIS with DEM

Hydrologic Analysis using PC-Hydro

Geometric Data Preparation using
ArcMap and Hec-GeoRAS
(stream network, stream centerlines,
cross sections, river banks, culverts,
and/or block obstruction)

Hydraulic Analysis using HEC-RAS
(Manually input the following data; Manning’s n-values,
culvert data, expansion and contraction coefficients,
normal depth boundary condition, ineffective flow areas,
adjustment of reach length if necessary)

Floodplain Delineation using Hec-GeoRAS

14

4.2 Parameter Estimation
4.2.1 Drainage Area
Subbasin boundaries were delineated using the hydrology function of ArcGIS with 2008
Lidar Data. A 5-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. A 100 year peak discharge was used for
HEC-RAS hydraulic analysis.

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 at River Rd.. The rainfall
intensity at the time of concentration for the Via Entrada Wash watershed is 2.83 inches.
No area reduction factor was applied.

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).

15

Table 1 Methods used for a PC-Hydro analysis

Rainfall Depth
Rainfall Loss
Time of Concentration

Selected Method
NOAA 14, upper 90% Confidence Interval
Adjusted SCS Curve number
Pima County Hydrology Procedure

Table 2 Watershed Characteristics
Sub basin
0
1
2
3
4
5
6

Area
(mi2)
0.27
0.13
0.21
0.08
0.44
0.32
0.19

Impervious Area
15
15
15
15
15
15
15

Vegetation Cover
20
20
20
20
20
20
20

4.3 Problems Encountered During the Study
4.3.1 Special Problems and Solutions
There were no problems with the hydrologic modeling.

4.3.2 Modeling Warning and Error Messages
None

4.4 Calibration
No calibration was conducted in this study.

4.5 Final Results
4.5.1 Hydrologic Analysis Results
The 100-year peak discharges at CPs were determined using the PC-Hydro. The results
are summarized Tables 3.

16

4.5.2 Verification of results
The estimated peak discharge at all CPs was also compared with the peak discharge
obtained from USGS Regression Equation 13 (Thomas et al., 1997) (Table 3).

Table 3 Comparison of a peak discharge
Concentration
Point

Reach

Location

Area
2
(mi )

Q100 PCHydro(cfs)

Q100 RRE
(cfs)

6
5
4

West
East
West

0.19
0.54
0.67

485
944
1630

368
821
957

3

West

0.08

300

175

2

East

0.21

672

400

1
0

West
West

Via Entrada/Entrada Sexta
At River Rd/Via Entrada
At River Rd/Via Entrada
Camino Miraval/Camino
Escalante
Camino El Ganado/Mina
Vista
Avenida de Posada/Calle
del Caballo
Campbell/Table Mountain

0.40
0.27

1140
1010

659
488

RRE: USGS Regression Equation 13

Section 5 Hydraulics
5.1 Method Description
The hydraulic modeling for the Via Entrada Wash was performed using Hec-Ras,
Version 4.1 (HEC-RAS), HEC-GeoRAS, Version 4.2.93 (HEC-GeoRAS), and ArcGIS,
Version 9.3.1. Corrected model is proposed in this study. The model name is VE, and the
plan name is Plan 01.
As previously mentioned, DEM derived from 2008 LiDAR data was used to create a 5foot contour map. The locations of the stream centerline, cross-sections, and bank of the
Via Entrada Wash were determined using the contour map and 2008 PAG aerial photos.
The physical attributes of the wash were digitized in ArcGIS using the HEC-GeoRAS
extension and then exported to HEC-RAS to create geospatially referenced geometric
data (cross section, reach profile). Other parameters for the steady-state analysis, such as
Manning’s n-values, expansion and contraction coefficients, boundary condition, and
ineffective flow areas were manually added in the HEC-RAS model. The hydraulic data
obtained from HEC-RAS were then imported into HEC-GeoRAS to delineate a
floodplain boundary of the Via Entrada Wash.
Hydraulic analysis was performed in the area currently mapped as FEMA Zone X. Steady
flow analysis was performed to determine 100-year water surface elevations in the study
area by using HEC-RAS. As described above, geometric data for HEC-RAS including
stream centerline, flow paths and cross-sections were obtained using HEC-GeoRAS.

17

Normal-depth with a slope of 0.026-0.031 was assumed for the upstream boundary
condition.

5.2 Work Study Maps
No work map is included in this study.

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. Manning’s n value of 0.055 was assigned for the overbank with desert brush
along the Via Entrada Wash. The value of 0.035 was assigned to a channel.

5.3.2 Expansion and Contraction Coefficients
The channel of the Via Entrada Wash 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 entire study reach.

5.4 Cross-Section Description
A 5-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
Five culverts were modeled with HEC-RAS for the right channel, while one culvert was
modeled for the left channel.

18

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

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

5.5.5 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.

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

5.7 Problems Encountered
5.7.1 Special Problems and Solutions
There are no special problems in the study limit.

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.

19

5.8 Calibration
The model was not calibrated in this study.

5.9 Final Results
5.9.1 Hydraulic Analysis Results
The HEC-RAS model is included in Appendix E.

5.9.2 Verification of Results
The proposed floodplain limit tends to follow the existing floodplain limit. The results
suggest that the proposed floodplain limit is reasonable based on the topography.

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

Section 7 Draft FIS Report Data
7.1 Summary of Discharges
Peak discharges used for the hydraulic analysis in this study were summarized in Table 3.

7.2 Floodway Data
Not applicable.

7.3 Annotated Flood Insurance Rate Map
An annotated Flood Insurance Rate Map (FIRM) is not included in this study.

7.4 Flood Profiles
Flood profiles are included in the HEC-RAS model in Appendix E.
20

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

29
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This product is subject to the Department of Transportation
Technical Services Division's Disclaimer and Use Restrictions.
Pima County Regional Flood Control District

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The information depicted on this display is the result
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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 Department of
Transportation Technical Services Division makes no
claims regarding the accuracy of the information depicted
herein.

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V
V
UU
V
V
U
V
VU
U

26
4

3
1135

10
72
6

10
22
2

0
255

65
111

2580

0

11
03
7

2565

5
250

V
U
U
V

7
25

V
VU
U
10876

2705

V
U

11
03
7

11
56
5

2655

116
82

11
66
0

2735

5

2665

11536

RiverWest

40
27

0

11
49
9
11
40
4

8
26

1177
0

118
52

2765

5

271
0

5
26

2580

5

18320

2595

5

2695

16158
26 81

119
68

11
74
6

2725

8
1201

122
55

Cross Section

0

SKYLINE

27
2

1240
6

12147

U
V
U
V
V
U
V
U
V
U
V
U
V
U
V
U
V
VU
U
12135

0

125
96

12291

V
U

27
1

5

2660

5

2720

4
27

1277
7

12516

265
0

12
39
4

6
27

7
38
15

12848

0

5

5

1268
1

V
U

5

13
13
130
48
9
12848

2740

2730

U U
V
V
U
V
V
U
U
U V
V
U
V
V
U
V
U
V
U
V
U
V
U
U
V
V
U
V
U
V
U
V
U
V
U

12049

5

5

2725

0
27

RiverEast

275
5

2725

14
69
6

26
8

5
64
13

0
26

5
255

V
U
U
V
V
U
12
53
0

2565

RI
V

4
45
15

137
57

U
V
V
U
V
U
V
U

1597
5

15
58
3

V
V U
U
V
U
U
V

138
66

129
25

V
U

27
4

V
U

273
0
2730

2
51
14

139
60

U
V
V
U

25
9

07
144

1
29
14
9
14
14

U
V
V
U
V
U

0

13
36
1
132
74

5
25

4
24

V
U
V
U
V
U
V
U
U
V

140
44

1
61
14

U
V

2600

2540

25
4

5
27
15
4
20
15

2640
2595

2585

9
24

V
UU
V
V
U

!
( 1483314951

12738

RIVER

157
39

1

2605

2495

160
27302
5

V
U

5

V
U

0

26
1

2
25

V
U

2730

26
9

40
26

6
27

5

271
0

9
09
15

2570

25
8

8
27

2755

0

5

25

2780 2790

2775

1634
3

6
26

2595

2615

95

0

164
50

5

27
1

2605

2595

2595

20
25

2785

Discharge Point

2810

5
280

1
26
17

165
89

65
25
0

46
171
47
170
1
89
1 16
89
16

U
V
V
U
V
U

90
26

!
(

2800

2820

2
28

V
U
V
U
V
U
V
UU
V

269
5

2685

5
26

5

5

2640
26
5

6
25

18207

2675

5

0

2770

V
U
V
U
U
V

V
VU
U

17
66
17
0
55
9

8
89
17

2765

1
51
18

2760

2580
7
25

26
9

27
8

V
U

2795

2770

0

6
27

2775

3
84
18

279
0

0
283

!
(

V
U

90
26

5
259

0
26

0

28
8

0

28
1

2805

18100

2695

0

05

2810

279
0

28

5

75
27

5

2730

0

2
28

2785

2700

5

29
4

5
28
8
0
29
1

2780

2740
5
27
3

2705

28
3

5
260

8
25

28
7

283
5

0
27
4
2720

0

27
1

5

29
0

5

287
5

2900

5
27
3
5
27
0
5
26

0

2640

2610

5
28

2715

2680

5

2845

2
27

2600

2845

281
5

5
27
4

0

26
2

5

0
261

Exhibit 1
100-year Floodplain
with cross sections
Via Entrada Wash

5
287

2850

2
27

0

5

2970

0
27
5

24

0

293
0

2865

2860

2795

27
1

2710

5
27
0

26
5

5

29
5

2850

27
4

5

85
29

5

5

5

2
27

1
26

6
29

30
2950
29
2925

5

9
28

5

0
6
26

279
0

2765

2735

10
27

0
297

0
295

0

0
29
0

2765

27
6

5

2630

0
277

5

0
261

2
29

0
280

7
26

2
26

ORANGE GROVE

2935

0
29
0

2820

5

5

2635

27
3

5

299
5

5
29
0

0
28
2

28
4

2700

5

265
0

264
5

5
291

29
2

0
293

0
295

2955

0

0
29

0

2975

0

0

29
5

5
285

6
29

2895

0
276

27
2

2975

298
5

5

0

5

5

0

29
7

0

287

299

2965

29
9

29
8

2960

2965

292
5
294
5

2980

29
3

5

28
3

2795

273
0

0
26
7

3
28

3005

3000

55
29
2950

5
276

0

5

266
0

0

27
4

2850

274
5

276
0

5
273

2785
278
5

5
26
6

3
27

273
5

2970

INA

2660

Pima County Regional Flood Control
97 East Congress Street - 3rd Floor
Tucson. Arizona 85701-1207
(520)243-1800 - FAX (520)243-1821
http://www.rfcd.pima.gov

gislib\rfcd\projects\imd\xavi\mdx\AKITSU\Via_Entrada\Via_Entrada _Exhibit_1.mxd

03/2012

1,000
Feet