Section 1 Introduction..................................... 5
1.1 Purpose...................................................................................................................... 5
1.2 Project Authority....................................................................................................... 5
1.3 Project Location ........................................................................................................ 6
1.4 Hydrologic and Hydraulic Methods.......................................................................... 6
1.5 Acknowledgment ...................................................................................................... 7
1.6 Study Results ............................................................................................................ 7

Section 2 FEMA Forms ................................. 11
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 Unique Conditions and Problems .................................................................... 11
2.1.6 Coordination of Peak Discharges..................................................................... 11
2.2 FEMA Forms .......................................................................................................... 12

Section 3 Survey and Mapping Information 13
3.1 Field Survey Information........................................................................................ 13
3.2 Mapping .................................................................................................................. 13

Section 4 Hydrology...................................... 13
4.1 Method Description ................................................................................................ 13
4.2 Parameter Estimation .............................................................................................. 14
4.2.1 Drainage Area .................................................................................................. 14
4.2.2 Watershed Work Map ...................................................................................... 14
4.2.3 Gage Data......................................................................................................... 14
4.2.4 Spatial Parameters............................................................................................ 14
4.2.5 Precipitation ..................................................................................................... 14
4.2.6 Physical Parameters ......................................................................................... 14
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 ..................................... 18
5.1 Method Description ................................................................................................ 18
5.2 Work Study Maps ................................................................................................... 19
5.3 Parameter Estimation .............................................................................................. 19
5.3.1 Roughness Coefficients ................................................................................... 19
5.3.2 Expansion and Contraction Coefficients ......................................................... 19
5.4 Cross-Section Description ...................................................................................... 19
5.5 Modeling Consideration.......................................................................................... 19

2

5.5.1 Hydraulic Jump and Drop Analysis................................................................. 20
5.5.2. Bridges and Culverts....................................................................................... 20
5.5.3 Levees and Dikes ............................................................................................. 20
5.5.4 Island and Flow Splits...................................................................................... 20
5.5.5 Ineffective Flow Areas..................................................................................... 20
5.6 Floodway Modeling ................................................................................................ 20
5.7 Problems Encountered ............................................................................................ 20
5.7.1 Special Problems and Solutions....................................................................... 20
5.7.2 Model Warnings and Errors............................................................................. 20
5.8 Calibration............................................................................................................... 21
5.9 Final Results............................................................................................................ 21
5.9.1 Hydraulic Analysis Results.............................................................................. 21
5.9.2 Verification of Results ..................................................................................... 21

Section 6 Erosion and Sediment Transport 23
Section 7 Draft FIS Report Data ................... 23
7.1 Summary of Discharges.......................................................................................... 23
7.2 Floodway Data ........................................................................................................ 23
7.3 Annotated Flood Insurance Rate Map .................................................................... 23
7.4 Flood Profiles.......................................................................................................... 23
List of Tables
Table 1 Methods used for a HEC-HMS analysis.............................................................. 15
Table 2 Physical Parameters for the Sub-Basins .............................................................. 15
Table 3 Summary of the Hydrologic Analysis Results for Sub-Basins............................ 17
Table 4. Summary of Discharges at Relevant Concentration Points ................................ 17
Table 5 Comparison of a peak discharge.......................................................................... 17
List of Figures
Figure 1.1 Sub-basins for the Camino De Oeste Wash ...................................................... 8
Figure 1.2 Study limits of the Camino De Oeste LOMR Study ......................................... 9
Figure 1.3 Hydrologic Soil Group .................................................................................... 10
Figure 5.1 Comparison of FLO-2D and HEC-RAS Floodplains…………………… …22
Appendices
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

3

Exhibit
Exhibit 1 100-yr Floodplain limits for the Camino De Oeste Wash
Exhibit 2 Annotated Flood Insurance Rate Map for the Camino De Oeste Wash

4

Section 1 Introduction
1.1 Purpose
This Technical Data notebook (TDN) has been prepared for a Letter of Map Revision
(LOMR) application for a portion of the Camino De Oeste Wash (CMNO) located in
Pima County, Arizona. The objective of the TDN and LOMR submission is provide
regulatory discharge rates and floodplain limits along the Camino De Oeste 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).

5

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 Canfield, PE, Chief Hydrologist
Planning & Development Division
Pima County Regional Flood Control District
97 East Congress, Tucson, AZ 85701

1.3 Project Location
The study reach of the Camino De Oeste Wash (CMNO) is located within a Federal
Emergency Management Agency (FEMA)-designated “Zone A” flood-hazard area, as
depicted on FIRM Map Panel Numbers 04019C1618K, and 1619K (February 8, 1999).
No documented hydraulic analyses were found to determine the “Zone A”, and the
existing “Zone A” depiction is not consistent with current topography. The objective of
the TDN and LOMR submission is to provide regulatory discharge rates and floodplain
limits along the Camino De Oeste Wash using better topographic, hydrologic, and
hydraulic data.
The study reach of the Camino De Oeste Wash is located primarily west of Silverbell Rd.
and extends to Sections 28, 29, 32 & 33, Township 13 South, Range 13 East, Pima
County, Arizona (Fig. 1.1). The upstream study limit for the Camino De Oeste Wash
begins immediately downstream of West Goret Rd. The Camino De Oeste Wash enters
study limit from the west, where it is mapped as an AE Zone and flows east until it
converges with the Santa Cruz River.

1.4 Hydrologic and Hydraulic Methods
Hydrologic analysis was preformed to determine proposed regulatory discharge rate at
Silverbell Rd using U.S. Army Corps of Engineers Computer Hydrologic Modeling
System, HEC-HMS. Parameterization followed guidelines developed by Pima County
Regional Flood Control District and described in technical Policy 018 (Tech 018,
Appendix A). The proposed regulatory discharges are flow rates that have a 1-percent
chance of being equaled or exceeded each year (“100-year” discharge rates). Hydraulic
analysis was performed to delineate floodplain limit along the study reach of the Camino
De Oeste Wash using U.S. Army Corps of Engineers Computer Backwater Model, HEC-

6

RAS. Because the floodplain of the Camino De Oeste Wash is not confined when it
enters the geologic floodplain of the Santa Cruz River, the FLO-2D model was used to
determine the direction of flow east of Silverbell Rd.
.

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 rate was calculated at Silverbell Rd (CP_A; Fig. 1.3). The
estimated regulatory discharge rate is 6432 cubic feet per second (cfs) with a drainage
area of 5.69 square mile at CP_A where the watercourse crosses Silverbell Rd. The new
mapping removed some structures from the floodplain west of Silverbell Rd, but did not
add any structures. To the east of Silverbell Rd, the flow is basically unconfined and the
floodplain expands greatly. Fortunately, most of this land is golf course.

7

SWEETWATER

EL MORAGA

0
I1

PRINCE
E
FR
EW
AY

CP-A

Figure 1.1
Watershed Map
Camino De Oeste Wash

(
!

I1 0

(
!

V
SIL

GORET

Discharge Points

ER
BE

20 Foot Contour

LL

Subbasins

Name
CMN_A
CMN_B
GRANT GRANT

IRONWOOD HILL

CMN_C
CMN_D

CAMINO DE OESTE

CMN_E

CP-B

CMN_F

(
!

CMN_G

CP-D

CMN_H

(
!

CMN_I
TE
GA

S

PA

SPEEDWAY

CP-J

SS

CMN_J

(
!

Aerial : 2008 Pima Association of Governments
Topo : 2008 Pima Association of Governments

CP-I
(
!
ANKLAM

CP-H

Pima County Index Map

GREASEWOOD

(
!

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.

STARR PASS

STARR PASS

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

K

IN

N

3,000

EY

1,500

0

3,000 Feet

Scale 1:3000

06/2010
\\gislib\rfcd\projects\imd\xavi\mxd\AKITSU\Camino_De_Oeste_wash_Watershed_Fig1_1.mxd

SS

0
I1

NE
SI
BU

NT

I10

CE

Study Limit

FR

ER

G
TA
ON
E

I10

EL MORAGA

Figure 1.2
Study Limit Map
Camino De Oeste Wash

FR
G
TA
ON
E

IN
PR

PRINCE

CE

EW

E
FR

I10

AY

Discharge Points
Existing Floodplain
ZONE A
ZONE AE
ZONE X - SHADED
(
!

CP-A

(
!

VE
SIL

GORET

LL

E
RB

Aerial: 2008 Pima Arizona Government

Pima County Index Map

Index Map Scale 1:5,250,000

Study Limit

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

1,000

500

IRONWOOD HILL

0

Scale 1:1000'

1,000 Feet

GRANT GRANT
06/2010
\\gislib\rfcd\projects\imd\xavi\mxd\AKITSU\CaminoDeOeste\Camino_De_Oeste_wash_Watershed_Fig1_2.mxd

E
FR

SW

EL MORAGA

0
I1

EE
TW
AT
ER

I10

Figure 1.3
Soil Classification
Camino De Oeste Wash
EW

CP-A

VE
SI L

GORET

AY

(
!

E
RB
LL

(
!

Discharge Point
Subbasins

Soil Classification

CMN_A
GRANT

IRONWOOD HILL

Soil Group: A (100%), ARIZO-RIVERWASH COMPLEX,
0 TO 3 PERCENT SLOPES
Soil Group: B (100%), GLENDALE SILT LOAM,
0 TO 3 PERCENT SLOPES
Soil Group: B (100%), GRABE GRAVELLY LOAM,
1 TO 3 PERCENT SLOPES
Soil Group: B (100%), PINALENO VERY COBBLY SANDY LOAM,
1 TO 8 PERCENT SLOPES
Soil Group: B (100%), PINALENO-STAGECOACH COMPLEX,
5 TO 16 PERCENT SLOPES
Soil Group: C (47%) D (53%), PANTANO-GRANOLITE COMPLEX,
5 TO 25 PERCENT SLOPES
Soil Group: D (100%), ANKLAM-CELLAR-ROCK OUTCROP COMPLEX,
15 TO 55 PERCENT SLOPES

CP-B

(
!

Aerial: 2008 Pima Arizona Government
CP-D

CMN_G

(
!

CMN_B

SPEEDWAY

CMN_F
CMN_D

(
!

CMN_C

CP-J

CP-I

CMN_I

T
GA

PA
ES

SS

( CMN_E
!
CMN_J

Pima County Index Map
GREASEWOOD

(
!

ANKLAM

CP-H

CMN_H

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.

STARR PASS

STARR PASS

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

KIN
NEY

3,000

1,500

0

Scale 1:3000'

3,000 Feet

06/2010
\\gislib\rfcd\projects\imd\xavi\mxd\AKITSU\CaminoDeOeste\Camino_De_Oeste_wash_Watershed_Fig1_3.mxd

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 Canfield, PE, Chief Hydrologist

2.1.3 Local Technical Reviewer:
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 Camino De Oeste Wash is located within a Federal Emergency
Management Agency (FEMA)-designated “Zone A”, as depicted on FIRM Map Panel
Numbers 04019C1618K, and 1619K (February 8, 1999). The study reach of the Camino
De Oeste Wash is located primarily west of Silverbell Rd., Pima County, Arizona (Fig.
1.1). The study reach of the Camino De Oeste Wash is primarily composed of sand
channel and the bottom of the reach is relatively clean with vegetation cover. The
overbank of the reach is covered with desert brush.

2.1.5 Unique Conditions and Problems
None.

2.1.6 Coordination of Peak Discharges
The 100-year regulatory discharge rate at the Silverbell Rd. was computed using HECHMS, assuming no base flow in the watersheds and no transmission loss within the

11

reaches. The hydraulic data used to derive parameters for HEC-HMS was obtained using
HEC-RAS. The discharge rate was acceptable per Suzanne Shields, Director of the Pima
County Regional Flood Control District and Andy Dinauer of the City of Tucson

2.2 FEMA Forms
The FEMA MT-2 forms are included in Appendix B of this TDN.

12

Section 3 Survey and Mapping Information
3.1 Field Survey Information
Field Survey was done to supplement the topographic mapping in areas of known change
since the topographic data were collected in 2005. These data were prepared by a
Registered Land Surveyor. Notes on this data are included in Appendix C.

3.2 Mapping
The topographic data was obtained using HEC-GeoRas and ArcGIS. Digital Terrain
Model (DTM) derived from 2005 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: 2005 PAG aerial photo
Projection: UTM, Zone 12
Units: International feet
The contour interval of the topographic map is 2 feet.
This data set has been shown to be FEMA-compliant in an area of similar cover and
topography. Notes are included in Appendix C.
In addition, the field survey described in section 3.1 was used to replace topography in
these areas of change, so that both 2005 LiDAR and field survey were used to
characterize the topographic surface.

Section 4 Hydrology
4.1 Method Description
The 100-year peak discharges for the ten subbasins of the Camino De Oeste Wash
(CMNO A, to J; Fig. 1.3) were calculated using U.S. Army Corps of Engineers Computer
Hydrologic Modeling System, (HEC-HMS) version 3.4. The HEC-HMS model requires
the parameters regarding rainfall, topography, soil, vegetation, and channel
characteristics to determine runoff volume and peak discharge. Those parameters were
determined according to the Pima County Regional Flood Control District Technical
Policy 018 (Tech-018). Tech-018 is included in Appendix A. The HEC-HMS model is
included in Appendix D.

13

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 that the subbasin delineation was
reasonable.

4.2.2 Watershed Work Map
A watershed work map is included in Exhibit 1. Ten subbasins were delineated for HECHMS hydrologic analysis. Five concentration points were included in the study watershed
(CP_A, CP_B, CP_H, CP_J, CP_I). A 100-year peak discharge at Silverbell Rd. (CP A)
was used for HEC-RAS and FLO-2D 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
According to the Tech-018, the 3-hour storm shall be used as rainfall data in the HECHMS model in the case that a time of concentration (Tc) is equal or less than three hours.
A 3-hour storm was selected for a peak discharge calculation for the Camino De Oeste
Wash, since Tc was less than 3 hours in all the sub-basins.
A point 3-hour rainfall depth at the coordinates of the centroid of the watershed was
obtained from NOAA Atlas 14, upper 90% confidence interval precipitation frequency
estimate (NOAA 14 rainfall). Areal reduction factor was applied to watersheds larger
than 1 square mile, as described in Tech-018. The 3-hour rainfall depth for the Camino
De Oeste Wash watershed is 3.23 inches at the upper part of the watershed and 3.14
inches in the lower part of the watershed. The aerial reduction factor of 0.85 was applied
to CP_A.

4.2.6 Physical Parameters
The physical parameters for the subbasins and reaches of the HEC-HMS model were
summarized in Tables 1 and 2. As mentioned in 4.1, all the methods and parameters were

14

determined following Tech-018. Table 1 summarizes the method used for a HEC-HMS
analysis.
Table 1 Methods used for a HEC-HMS analysis
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

Rainfall Depth
Rainfall Distribution
Rainfall Loss
Time of Concentration
Transform
Routing

The SCS Curve Number (CN) method was utilized as a rainfall loss method in the HECHMS model. The CN was determined using the Curve Number table associated with the
PC Hydro User Guide (Arroyo Engineering, 2007) and a Hydrologic Soils Group map.
The CN was not adjusted for rainfall intensity or antecedent moisture conditions. The
SCS Unit Hydrograph method was used as a transform method. Impervious cover was
determined using the 2008 PAG aerial photograph and Table 3 in the PC Hydro User
Guide (Arroyo Engineering, 2007). The combination of the kinematic wave method and
the U.S. Natural Resources Conservation Service (NRCS) segmented Time of
Concentration (Tc) calculation method (USDA-NRCS, 1986) was used to determine Tc,
following the recommendation on Tech-018. The Tc was calculated by summing the
travel time for sheet flow, shallow concentrated flow and channel flow. The Tc for sheet
flow was estimated using the kinematic wave equation. Manning’s roughness coefficient
for sheet flow was obtained using Table 3-1 in Technical Release 55, Urban Hydrology
for Small Watersheds (USDA-NRCS, 1986). HEC-GeoRAS and HEC RAS were used to
estimate average velocity of channels. The detail of the Tc calculation is included in
Appendix D.
Table 2 Physical Parameters for the Sub-Basins
SubBasin
CMN_A
CMN_B
CMN_C
CMN_D
CMN_E
CMN_F
CMN_G
CMN_H
CMN_I
CMN_J

Area
(sq mi)
0.7
0.16
0.13
0.7
0.19
0.05
0.1
2.1
0.8
0.76

CN
72.6
90.2
89.6
89.8
89.9
91.7
89.1
89.7
90.1
90.0

Impervious Area
(%)
10.0
15.0
10.0
5.0
5.0
30.0
5.0
0.0
5.0
5.0

Vegetation Cover
(%)
30
30
30
30
30
30
30
30
30
30

Lag Time
(min)
29.4
14.3
12.1
16.0
10.8
8.1
6.1
17.3
14.8
10.0

15

Runoff from subbasins was routed using the Modified-Puls method. Storage discharge
tables for the channel routing were developed using HEC-GeoRAS and HEC-RAS. Six
different discharges were used for storage-discharge relations. The number of subreaches
was calculated using the following method:
Vw = 1.5 * Vave .........eq.1
K=

L
...................eq.2
Vw

Therefore,
K
N = ..................eq.3
Δt
where Vave is average flow velocity, L is reach length, Vw is velocity of flood wave (a
conversion factor of 1.5 is used for natural channels), K is hydrograph travel time, Δt is
the time interval for computations in the model, and N is the number of steps in the reach
routing. Eq.4 was obtained from eq.1, 2, and 3. The detail of the calculation of the
number of subreach is included in Appendix D.

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
The time interval of the rainfall data used in this study is 5 minutes, while the simulation
time interval is 1 minute. The HEC-HMS model interpolated the 5-minute time interval
of the rainfall data to 1-minute time interval.

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 for the Camino De Oeste Wash subbasins and at CP A
were determined using the HEC-HMS. The results are summarized Tables 3 and 4.

16

Table 3 Summary of the Hydrologic Analysis Results for Sub-Basins
SubBasin

CMN_A
CMN_B
CMN_C
CMN_D
CMN_E
CMN_F
CMN_G
CMN_H
CMN_I
CMN_J

Area
(sq mi)

Rainfall Depth
(in)

Runoff
Volume
(in)

Peak Discharge
(cfs)

0.70
0.16
0.13
0.70
0.19
0.05
0.10
2.10
0.80
0.76

3.14
3.23
3.23
3.23
3.23
3.23
3.23
3.23
3.23
3.23

0.92
2.21
2.16
2.18
2.19
2.35
2.12
2.17
2.21
2.20

395.7
375.4
325.0
1519.6
506.5
158.0
314.7
4329.4
1837.6
2102.5

Table 4. Summary of Discharges at Relevant Concentration Points
Concentration
Point

Location

Area
(sq
mile)

Rainfall
Depth
(in)

Runoff
Volume
(in)

Q100
HMS
(cfs)

CP_A

at Silverbell Rd

5.69

2.74

1.6

6,432

4.5.2 Verification of results
The existing 100-year regulatory discharge for Camino De Oeste Wash in the AE zone
immediately upstream is 6,418 cfs (99-09-434P), which is nearly the same as the
discharge determined in this study (6,432 cfs) shown in Table 5. The comparison shows
that the 100-year peak discharges estimated in this study is very close to the existing
value. The peak discharge was also compared with the peak discharge obtained from
USGS Regression Equation 13 (Thomas et al., 1997) (Table 5). The comparison showed
that the HMS-derived peak discharge was much higher than the ones derived from the
Regression Equation. This is to be expected, because the watershed is steep, and has a
shape that is conducive to routing sub-basins with similar travel times to the same
downstream location.
Table 5 Comparison of a peak discharge
Concentration
Point

Location

Area
(sq
mile)

Rainfall
Depth
(in)

Runoff
Volume
(in)

Q100
HMS
(cfs)

Q100
RRE
(cfs)

Time
to
Peak

CP_A

at Silverbell Rd
at Speedway
Blvd

5.69

2.74

1.6

6,432

3,595

2:18

4.99

2.74

1.73

6,606

3,347

1:48

CP_B

17

Section 5 Hydraulics
5.1 Method Description
The hydraulic modeling for the Sweetwater was performed using FLO-2D (version
2007.06), and compared to the results of Hec-Ras, Version 4.1 (HEC-RAS), which also
used HEC-GeoRAS, Version 4.1.1 (HEC-GeoRAS), and ArcGIS, Version 9.3. Hydraulic
analysis was performed in the area currently mapped as FEMA Zone A.
The DTM derived was from 2005 LiDAR data, which was augmented with field survey
data in areas where topography had changed since 2005. Two earthen pads have been
started on the eastern side of Silverbell Rd on either side of the excavated channel of the
Camino De Oeste wash in preparation for a subdivision that is currently on hold. The
field survey data in the area of the pad was used to replace the data in the 2005 LiDAR
dataset, so that the topographic dataset in this analysis more accurately reflected existing
conditions.
Both the HEC-RAS and FLO-2D model were used to determine the limits of the
floodplain. In the confined portions of the wash the two model can be expected to
produce similar floodplains, but as the flow crosses Silverbell, it enters the geologic
floodplain of the Santa Cruz River the constructed channel is too small to contain the
100-yr discharge. For this reason, FLO-2D is more useful in determining flow patterns in
this area where flow direction is undefined.
FLO-2D was used throughout the mapping area in order to provide a single model for the
study area. However, the model is most important in the downstream distributary area
east of Silverbell Rd to a confluence with the Santa Cruz River. The HEC-RAS model is
used to validate the results of the FLO-2D model in the reach west of Silverbell Rd,
where flow is confined, and flow can be approximated as one-dimensional and modeled
with HEC-RAS.
Geometric data for the FLO-2D model were derived from the 2005 Lidar data. Grid cell
size of 20 feet was used to map a floodplain in the distributary area. The time interval
used for the computation was 5 minutes. The FLO-2D model includes floodplain cross
sections at immediately upstream of Silverbell Rd to estimate discharge crossing the
road. The model does not include infiltration or rainfall. A hydrograph from the HMS at
CP A (at Silverbell Rd.) was used as inflow data at a cell located at the upstream limits of
the mapping at Goret Rd.
For the HEC-RAS mapping, the locations of the stream centerline, cross-sections, and
bank of the Camino De Oeste Wash were determined using the contour map and 2005
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-

18

state analysis, 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 then imported into HEC-GeoRAS to
delineate a floodplain boundary in the study area.
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 HECGeoRAS.

5.2 Work Study Maps
The work study map for the Camino De Oeste Wash is included in Exhibit 1.

5.3 Parameter Estimation
5.3.1 Roughness Coefficients
Within FLO-2D, Manning’s n values were determined by a combination of a site visit
and 2008 PAG aerial photo. Manning’s n value of 0.06 was assigned for the overbank
with desert brush along the Camino De Oeste Wash. A value of 0.035 was used in the
unvegetated portion of channels and in the constructed reach downstream of Silverbell
Rd.

5.3.2 Expansion and Contraction Coefficients
The channel of the Camino De Oeste 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
The FLO-2D model is a grid-based model. Upstream of Silverbell the watercourse is
riverine and the HEC-RAS model can also be used as a basis for comparing mapping. 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

19

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
No bridges and culverts are found in the mapping area.

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
In general these ineffective flow areas were disconnected overbank areas that 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 in FLO-2D. In HEC-RAS 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.
20

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 channel conditions. In most
cases, a subcritical solution was found. However, in some cases the errors require a
critical solution which is reasonable in steeper portions of this watercourse. A summary
of errors is available in Appendix E.

5.8 Calibration
The model was not calibrated in this study.

5.9 Final Results
5.9.1 Hydraulic Analysis Results
The FLO-2D and HEC-RAS modeling results are summarized in Appendix E.

5.9.2 Verification of Results
The floodplain limit produced in this Camino De Oeste Wash LOMR study was
compared to the results of the HEC-RAS 4.1 simulation (Figure 5.1). Where the flow is
confined in the area west of Silverbell Rd, the proposed floodplain limit tends to follow
the existing floodplain limit. The results suggest that the proposed floodplain limit
created in FLO-2D is reasonable compared to the more commonly-used one dimensional
hydraulic model. East of Silverbell, where the flow enters the geologic floodplain of the
Santa Cruz River, the results are very different. The FLO-2D model shows great
divergence indicating the dominance of two-dimensional flow, which could not be
adequately be simulated with HEC-RAS.

21

0

22
7

0
0

0
22 7

22 60

33

7
22

0

0

0

RB
L

0

37 9

0

22 7 0

2
23

23
0

0

562

Figure 5.1
Comparison of
FLO-2D and HEC-RAS
Camino De Oeste Wash

0
228

U
V
V
U
V
U
V
U
V
U

7
22

EL

1
23

0

7
22

163

0
227

E
LV
SI

22 8 0

V
U
228
0

2320

V
U

7
22

9
22

23 20

231

0

0

22
6

22
7

2270

0
22
8

22
9

22 9 0

0

0

22 70

2290

8
22

22
7

0

2270

0

23 3 0

0

8
22

869

7
22

2270

738

(
!

1004

229 0

23
1

23
0

0

0

0

U
V
V
U
V
U

2280

XS Cutlines
228 0

13
3

4

23 40

23 4 0

0
22
8

6

V
U

7

2280

ZONE AE

0
228

22
8

0
267

V
U
U
V

1
15

9
17

7
189

20 2 1

2
22 0

21 2 8

4
23 4

22 6 3

20

HECRAS AZone for Comparison

2280

22 80

0
258

8
251

2690

V
U

22
8

ZONE A

0

0

Aerial : 2008 Pima Association of Governments
Topo : 2008 Pima Association of Governments

30 0
2

0

32
5

32
0

22
8

0

0

2

2

1

22
8

8

6

0

22 8 0

9

8
22
0

0

42
7

U
VV
VU
U

9

40
9

1
38

U
V
V
U
V
U
V
U
V
U

3
34 5

V
U
V
U
U
V

5
33

10
23

31
2

227

306
3

2310

23
5

23

229 0

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

(
!

River
Proposed FLO-2D AZone

0
228

CP-A

Discharge Points
10 Foot Contour

123 4

22 7 0

0

0

229

23 20

234
0

22
9

0

111 0

9
22

231
0

228

23
2

44 0 8

22 80

451 8

22
8

23 2 0

45 8 8

2280
9
22

23 30

22
8

0

0

228 0

228 0

U
V
V
U
477

0

22
8

0

22 80

2

48 7 7

0

Pima County Index Map

23
3

V
U
0

50 0
1

23
4

23 7
0

51
7

5

0

0
23

23 3 0

23 60

2

5

23 5 0

8

2370

0

5
55

6

23 1 0

V
U

4

7
63

8
62

66
0

Index Map Scale 1:5,250,000

22 9 0

2
58

6

T

U
V
V
U

1

U
V
V
U

1
54

4

RE

9
61

V
U
57
0

0
61

V
U
U
V
U
V
V
U

GO

23 7 0

238
0

V
U

23 30

52
9

234 0

V
U

22 90
22 9 0

0
23
2

0
23
6

0
23
6

0

500

250

0

06/2010

500 Feet
0

0

3
23
0

7
23

23
4

6
23

0
23 00

23 7 0

0

3
23

8

23 9
0
23
8

Scale 1:500

22 90

Pima County Regional Flood Control District

V
U
69
7

This product is subject to the Department of Transportation
Technical Services Division's Use Restriction Agreement.

9

68 0 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.

4
23

0

\\gislib\rfcd\projects\imd\xavi\mxd\AKITSU\Camino_De_Oeste_wash_Watershed_Fig5_1.mxd

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
The estimated regulatory discharge rate is 6432 cubic feet per second (cfs) with a
drainage area of 5.69 square mile at CMN_Outlet.

7.2 Floodway Data
Not applicable.

7.3 Annotated Flood Insurance Rate Map
An annotated Flood Insurance Rate Map (FIRM) is included in Exhibit 2.

7.4 Flood Profiles
Flood profiles are included in Appendix E.

23

2270

0

0
50

22

50

50

22

50

0

0

22

70

Exhibit 1
100-year Floodplain
Camino De Oeste Wash

225

22

2250

22

0

2260

5
22

0

2250

225

22

225

90

225

2250

22

90

2250

229

2250
2260

22

60
2270

60

2270

23

00

22

226

2250

0

2270

10

22

2260

23

00

90

22

70

227
227

E
LV
SI

10 Foot Contour

0

2270

22

60

70

L
EL

90

Proposed Floodplain FLO 2D AZone

70

0

2280

227

22

0

Existing ZONE AE

70

228

22

310

22

2330

80

228

00
23

10
23

=>0.200

0

=> 0.500

90

=>1.000

2270

90

90

2320

22

70

2280

22

22

2270

80
22

0

Feet

2270

2320

22

80

2300

Flow Depth at Cell

22

2270

0

231

Discharge Point
2 Foot Contour

70

22

RB

22

231

0
233

!
(

2270

2320

22

22

2

2340

70

2270

0

23

2290

2340

=>2.000
22

!
(

80

2280

CP-A

2

2350

228

0
232

2280

280

228

0

228

23

Aerial : 2008 Pima Association of Governments

2280

2290

Topo: 2008 Pima Association of Governments

0

Datum: NAVD 1988

0

50

23

10

70
22

23

10

2310

22

2280

2320

80

22

23

20

2280

80

2280

0

90

22

22

2280

2280

228

0

2280

2320

2280

80

228

Pima County Index Map

23

30

23

60

GORET

0

23

2340

229

233

0

70

23

Index Map Scale 1:1,500,000

00

2390

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 Department of
Transportation Technical Services Division makes no
claims regarding the accuracy of the information depicted
herein.

2310

2360

2350

2340

2370

2290

22

90

80

23

232

2340

2410

100

0

200 Feet

Pima County Regional Flood Control District

00

0

24

00

2390

23

200

2290

0

60

230

23

23

2300

70

2290

This product is subject to the Department of Transportation
Technical Services Division's Disclaimer and Use Restrictions.

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

05/2010

\\gislib\rfcd\projects\imd\xavi\mxd\AKITSU\CaminoDeOeste\CaminoDeOeste_watershed_100yr_exh1.mxd

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.

PIMA COUNTY REGIONAL FLOOD CONTROL DISTRICT
TECHNICAL POLICY

POLICY NAME:

Acceptable Model Parameterization for Determining Peak
Discharges

POLICY NUMBER:

Technical Policy, TECH-018

EFFECTIVE DATE:

July 1, 2010

PURPOSE
The purpose of this technical policy is to standardize the parameterization of hydrologic
models.
BACKGROUND
When determining peak discharges, a computer-based hydrologic model or previouslyaccepted discharge value may be used. Technical Policy TECH-015, Hydrologic Model
Selection for Peak Discharge Determination, describes which models are acceptable for
determining peak discharges. Pima County Hydrology Procedures (PC-Hydro) shall be
used for riverine watersheds with an area less than 1 square mile, and it may be used for
watersheds up to 10 square miles. However, the use of PC-Hydro shall be limited to
riverine watersheds with little impact of detention basins, reservoirs, or channel storage
and attenuation. HEC-HMS or HEC-1 may be applied to riverine watersheds with an area
larger than 1 square mile, and is useful for evaluating watersheds that have detention
basins and where channel routing or storage is important. This policy describes which
parameterization shall be used for submittals to the Pima County Regional Flood Control
District (District).
POLICY
A. Watershed Delineation: The accuracy of watershed delineation and flow path
identification is critical in hydrologic modeling. The District requires the use of
2-foot contour interval (or finer where available) maps, such as the Pima
Association of Governments (PAG) contour maps for delineation of basin
boundaries and flow paths in all areas other than steep terrain. In areas of steep
terrain, or where 2-foot or finer contour interval maps are not available, U.S.
Geologic Survey (USGS) contour maps (7.5 minute series) may be accepted. At
the discretion of the District, it may be a requirement that topographic data be
sealed by an Arizona registered civil engineer (PE), or land surveyor (RLS). In
regulatory sheetflood areas, both 2-foot or finer contour interval maps and aerial
photos shall be used with a resolution sufficient to determine flow paths and
watershed boundaries. If Geo-HMS (COE, 2003) is used, Digital Elevation

Models (DEMs) or Digital Terrain Models (DTMs) or DEMs derived from Lidar
data from PAG or other reputable vendors, may be used. With the approval of the
District, alternative topographic data, such as stereo photography, may be used.
B. Pima County Hydrology Procedures: Peak-discharge calculations performed
using the Pima County Hydrology Procedures (PC-Hydro) shall follow the
guidance for parameterization provided in the PC- Hydro User Guide (Arroyo
Engineering, 2007).
C. HEC-1 and HEC-HMS: Peak discharges calculated using HEC-HMS (COE,
2006) or HEC-1 (COE, 1998) shall employ the following parameterization:
a. Rainfall Loss Method: Models shall employ the U.S Soil Conservation
Service (SCS) Curve Number method using the Curve Number tables,
Vegetation map and Hydrologic Soils Group map associated with the PC
Hydro User Guide (Arroyo Engineering, 2007), shall be used. The default
vegetation cover percent provided in the PC- Hydro User Guide (Arroyo
Engineering, 2007) shall be used unless additional justification is
provided. The Curve Number shall not be adjusted for rainfall intensity or
antecedent moisture conditions.
b. Time of Concentration Calculation: The modified U.S. Natural
Resources Conservation Service (NRCS) segmented Time of
Concentration (Tc) calculation shall be employed (USDA-NRCS, 1986).
The Tc shall be calculated by summing the travel time for sheet flow,
shallow concentrated flow and channel flow, along the primary flow path.
i. For sheet flow segment:
1. Manning’s roughness coefficient for sheet flow shall be
obtained using Table 3-1 in Technical Release 55, Urban
Hydrology for Small Watersheds (USDA-NRCS, 1986).
2. Maximum slope length for sheet flow shall be 100 feet
unless additional justification is provided.
3. The Kinematic wave method shall be used to estimate the
travel time for sheet flow.
ii. For shallow concentrated flow segment:
1. The travel time for shallow concentrated flow shall be
obtained using the velocity determined from Figure 3-1 of
Technical Release 55, Urban Hydrology for Small
Watersheds (USDA-NRCS, 1986).
iii. For channel flow
1. Manning’s roughness coefficient for channel flow shall be
determined using the method described in the District’s

Technical Policy TECH-019, Standards for Floodplain
Hydraulic Modeling.
2. HEC-RAS velocity or the Manning’s equation may be used
to estimate the travel time for channel flow.
3. The discharge for upstream sub-basins shall be 2/3 times
the 100-yr discharge value calculated with Regional
Regression Equation 13 (Thomas et al., 1997). Sub-basins
with channel flow from an upstream basin shall use the
100-yr discharge value calculated with Regional
Regression Equation 13.
c. Transform: The SCS Unit Hydrograph method shall be used.
d. Channel Routing:
1.) Routing in Natural Channels: Runoff shall be routed using the
Modified-Puls method for natural channels with the slope less than
1.5%. It may also be used for steeper channels. A storage discharge
table is required if HEC-HMS is used. Such a table can be developed
using cross-sections and slopes derived from a Manning normal depth
analysis or HEC-RAS (COE, 2001). The number of sub-reaches shall
be calculated using the methods described in the HEC-HMS User’s
Manual. Initial discharge to estimate HEC-RAS velocity for channel
flow should be determined using discharge calculated with USGS
Regression Equation 13 (Thomas et al., 1997).
2.) Routing in Constructed Channels and Steep Channel: The
Kinematic Wave Method may be used for constructed channels and
natural channels with slopes greater than 1%. Reach length, slope,
bottom width and side slope may be obtained using the data utilized
for watershed delineation (e.g. 2-foot contour interval contour maps,
Digital Elevation Models (DEMs) or Digital Terrain Models (DTMs),
or DEMs). Selection of Manning’s n values shall conform to the
guidance in Technical Policy TECH-019, Standards for Floodplain
Hydraulic Modeling.. The number of sub-reaches shall be calculated
using the methods described in the HEC-HMS User’s Manuals.
e. Rainfall: The NOAA 14 Upper 90% rainfall shall be used as described in
the District’s Technical Policy TECH-010, Rainfall Input for Hydrologic
Modeling. Point rainfall depth shall be evaluated for a watershed, based
on the latitude and longitude of the centroid of the watershed. If
appreciable elevation change occurs on a watershed, users should use
different values for higher and lower elevations.
f. Rainfall Aereal Reduction: Aereal reduction shall be applied to
watersheds larger than 1 square mile. Aereal reduction shall be estimated

using Hydro-40 (National Weather Service, 1984) for the watershed and
event of interest (i.e. same tables as contained in Arizona State Standard
[SS10-07]).
g. Rainfall Distribution: The following rainfall distributions shall be used,
with the highest peak discharge selected in order to determine the critical
storm (i.e. the storm that produces the highest discharge) :
1. SCS Type II 3-hr Storm: The 3-hr distribution shall be used
as the local storm. In general, this includes watersheds with a
time of concentration (Tc) equal to or less than three hours
(Haan et al 1994).
3. SCS Type I (24 hr): The SCS Type I rainfall (NRCS, 1986)
may apply for general storms on watersheds with times of
concentration (Tc) greater than three hours.
D. Comparison of peak discharge: Peak discharges shall be compared with the peak
discharges obtained from USGS Regression Equation 13 (Thomas et al., 1997) and/or
the equations (both urban and rural) developed by Eychaner (1984) (See Appendix),
and existing regulatory discharge estimates. Appropriate Basin Development Factors
(BDFs) shall be used for urban areas.

REFERENCES
Aldridge, B. and J. Garrett. 1973. Roughness Coefficients for Stream Channels in
Arizona. US Department of the Interior Geological Survey. Tucson, AZ.
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.
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.
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.
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. 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.

APPROVED BY:

________________________________________
Suzanne Shields, P.E.
Director and Chief Engineer

______________________________
Date

Appendix
1.) USGS Regression Equation 13: The current regional regression relationship for
southern Arizona is Regression Equation 13 from Thomas et al (1997). This
method predicts peak discharge in cfs (Qp) as a function of watershed Area
(square miles) only. It has the form:

Q p100 = 10 ( 5.52− 2.42* A

−0.12

)

2.) Eychaner 1984 (rural): This is a USGS publication that was prepared in
cooperation with the City of Tucson and Pima County. It presents a series of
regression equations that rely on watershed area (sq. miles), main channel slope
(%), channel length (miles) and a shape factor to account for the differences in
runoff noted between long watersheds and more traditionally-shaped watersheds.
The equation for the 100 year peak discharge is:
Q p100 rural = 10 ( 3.044+ 0.646 (log A)−0.49 (log A)

2

+ 0.706 (log S ) − 0.367 (log S ) 2 − 0.614 (log S )( LogSh ))

The shape factor (Sh) is calculated as the channel length squared divided by the
contributing watershed area (i.e. L2/A).
3.) Eychaner 1984 (urban): This equation adjusts Eychaner’s rural equation to
account for the amount of impervious area, channel lining and channel
modification. It is:
Q p100 urban = 7.7 A 0.15 (13 − BDF ) −0.32 Q p100 rural 0.82

The Basin Development Factor (BDF) is a scoring factor to account for the degree
of urbanization within a watershed. The specific scoring is based on four factors
described in pages 10-13 of the USGS publication by Eychaner. The lower,
middle and upper portions of a watershed are scored separately, and the results are
summed. The maximum BDF score is 12, and a score of 0 indicates that the rural
equation should be used. (The Qp100 rural in the equation is the value calculated
using Eychaner’s rural method described in section 2 above.)

Appendix B General Documentation and
Correspondence

U.S. DEPARTMENT OF HOMELAND SECURITY - FEDERAL EMERGENCY MANAGEMENT AGENCY

RIVERINE HYDROLOGY & HYDRAULICS FORM

O.M.B No. 1660-0016
Expires: 12/31/2010

PAPERWORK REDUCTION ACT
Public reporting burden for this form is estimated to average 3.25 hours per response. The burden estimate includes the time for reviewing
instructions, searching existing data sources, gathering and maintaining the needed data, and completing, reviewing, and submitting the form. You
are not required to respond to this collection of information unless a valid OMB control number appears in the upper right corner of this form. Send
comments regarding the accuracy of the burden estimate and any suggestions for reducing this burden to: Information Collections Management, U.S.
Department of Homeland Security, Federal Emergency Management Agency, 500 C Street, SW, Washington DC 20472, Paperwork Reduction
Project (1660-0016). Submission of the form is required to obtain or retain benefits under the National Flood Insurance Program. Please do not
send your completed survey to the above address.

Flooding Source: Camino De Oeste Wash
Note: Fill out one form for each flooding source studied

A. HYDROLOGY
1. Reason for New Hydrologic Analysis (check all that apply)
Not revised (skip to section B)

No existing analysis

Improved data

Alternative methodology

Proposed Conditions (CLOMR)

Changed physical condition of watershed

2. Comparison of Representative 1%-Annual-Chance Discharges
Location
at Silverbell Rdi

Drainage Area (Sq. Mi.)
5.69

Effective/FIS (cfs)
6418 (upstream AE)

Revised (cfs)
6432

3. Methodology for New Hydrologic Analysis (check all that apply)
Statistical Analysis of Gage Records
Regional Regression Equations

Precipitation/Runoff Model HEC-HMS
Other (please attach description)

Please enclose all relevant models in digital format, maps, computations (including computation of parameters) and documentation to support the
new analysis.
4. Review/Approval of Analysis
If your community requires a regional, state, or federal agency to review the hydrologic analysis, please attach evidence of approval/review.
5. Impacts of Sediment Transport on Hydrology
Yes
No If yes, then fill out Section F (Sediment Transport) of Form 3. If No, then attach your
Was sediment transport considered?
explanation for why sediment transport was not considered.

B. HYDRAULICS
1. Reach to be Revised
Description

Cross Section

Water-Surface Elevations (ft.)
Effective

Downstream Limit

Atthe confluence with the Santa
Cruz Riv

Upstream Limit

Goret Rd at transition to upstream
AE

Proposed/Revised

2. Hydraulic Method/Model Used
FLO-2D (v 2007- 06)

DHS - FEMA Form 81-89A, DEC 07

Riverine Hydrology & Hydraulics Form

MT-2 Form 2 Page 1 of 2

B. HYDRAULICS (CONTINUED)
3. Pre-Submittal Review of Hydraulic Models
DHS-FEMA has developed two review programs, CHECK-2 and CHECK-RAS, to aid in the review of HEC-2 and HEC-RAS hydraulic models,
respectively. These review programs may help verify that the hydraulic estimates and assumptions in the model data are in accordance with NFIP
requirements, and that the data are comparable with the assumptions and limitations of HEC-2/HEC-RAS. CHECK-2 and CHECK-RAS identify
areas of potential error or concern. These tools do not replace engineering judgment. CHECK-2 and CHECK-RAS can be downloaded from
http://www.fema.gov/plan/prevent/fhm/frm_soft.shtm. We recommend that you review your HEC-2 and HEC-RAS models with CHECK-2 and
CHECK-RAS. Review of your submittal and resolution of valid modeling discrepancies may result in reduced review time.
4.

Natural Run

Models Submitted
Duplicate Effective Model*
Corrected Effective Model*
Existing or Pre-Project Conditions Model
Revised or Post-Project Conditions Model
Other - (attach description)

File Name:
File Name:
File Name:
File Name:
File Name:

N/A
N/A
N/A
N/A
N/A

Plan Name: N/A
Plan Name:
Plan Name:
Plan Name:
Plan Name:

Floodway Run
File Name:
File Name:
File Name:
File Name:
File Name:

N/A

Datum

Plan Name:
Plan Name:
Plan Name:
Plan Name:
Plan Name:

* For details, refer to the corresponding section of the instructions.
Digital Models Submitted? (Required)

C. MAPPING REQUIREMENTS
A certified topographic map must be submitted showing the following information (where applicable): the boundaries of the effective, existing, and
proposed conditions 1%-annual-chance floodplain (for approximate Zone A revisions) or the boundaries of the 1%- and 0.2%-annual-chance
floodplains and regulatory floodway (for detailed Zone AE, AO, and AH revisions); location and alignment of all cross sections with stationing control
indicated; stream, road, and other alignments (e.g., dams, levees, etc.); current community easements and boundaries; boundaries of the requester's
property; certification of a registered professional engineer registered in the subject State; location and description of reference marks; and the
referenced vertical datum (NGVD, NAVD, etc.).
Digital Mapping (GIS/CADD) Data Submitted
Note that the boundaries of the existing or proposed conditions floodplains and regulatory floodway to be shown on the revised FIRM and/or FBFM
must tie-in with the effective floodplain and regulatory floodway boundaries. Please attach a copy of the effective FIRM and/or FBFM, annotated to
show the boundaries of the revised 1%- and 0.2%-annual-chance floodplains and regulatory floodway that tie-in with the boundaries of the effective
1%- and 0.2%-annual-chance floodplain and regulatory floodway at the upstream and downstream limits of the area of revision.
Annotated FIRM and/or FBFM (Required)

D. COMMON REGULATORY REQUIREMENTS*
1.

For LOMR/CLOMR requests, do Base Flood Elevations (BFEs) increase?

Yes

No

a. For CLOMR requests, if either of the following is true, please submit evidence of compliance with Section 65.12 of the NFIP regulations:
•
The proposed project encroaches upon a regulatory floodway and would result in increases above 0.00 foot.
•
The proposed project encroaches upon a SFHA with or without BFEs established and would result in increases above 1.00 foot.
b.

2.

Yes
No
For LOMR requests, does this request require property owner notification and acceptance of BFE increases?
If Yes, please attach proof of property owner notification and acceptance (if available). Elements of and examples of property owner
notification can be found in the MT-2 Form 2 Instructions.

Does the request involve the placement or proposed placement of fill?

Yes

No

If Yes, the community must be able to certify that the area to be removed from the special flood hazard area, to include any structures or
proposed structures, meets all of the standards of the local floodplain ordinances, and is reasonably safe from flooding in accordance with the
NFIP regulations set forth at 44 CFR 60.3(a)(3), 65.5(a)(4), and 65.6(a)(14). Please see the MT-2 instructions for more information.
3.

For LOMR requests, is the regulatory floodway being revised?

Yes

No

If Yes, attach evidence of regulatory floodway revision notification. As per Paragraph 65.7(b)(1) of the NFIP Regulations, notification is
required for requests involving revisions to the regulatory floodway. (Not required for revisions to approximate 1%-annual-chance floodplains
[studied Zone A designation] unless a regulatory floodway is being added. Elements and examples of regulatory floodway revision notification
can be found in the MT-2 Form 2 Instructions.)
4.

For LOMR/CLOMR requests, does this request have the potential to impact an endangered species?

Yes

No

If Yes, please submit documentation to the community to show that you have complied with Sections 9 and 10 of the Endangered Species Act
(ESA). Section 9 of the ESA prohibits anyone from “taking” or harming an endangered species. If an action might harm an endangered species,
a permit is required from U.S. Fish and Wildlife Service or National Marine Fisheries Service under Section 10 of the ESA.
For actions authorized, funded, or being carried out by Federal or State agencies, please submit documentation from the agency showing its
compliance with Section 7(a)(2) of the ESA.

* Not inclusive of all applicable regulatory requirements. For details, see 44 CFR parts 60 and 65.
DHS - FEMA Form 81-89A, DEC 07

Riverine Hydrology & Hydraulics Form

MT-2 Form 2 Page 2 of 2

Appendix C: Survey Field Notes

Exhibit 1:
2008 LiDAR Coverage and
FEMA Special Flood Hazard
Areas
2008 LiDAR Coverage
FEMA Floodplains
Major Streets
Jurisdiction Lines
Not Shown: Western Pima County, including
Ajo and LiDAR coverage on Tohono O'dham
Nation.

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.
Pima County Regional Flood Control District

Scale 1:415,000

\\gislib\rfcd\projects\imd\ken\lidar08\fema_08cov.mxd km

Page 1 of 2

Evan Canfield
From:

Kenneth Maits

Sent:

Monday, May 03, 2010 12:20 PM

To:

Evan Canfield

Subject: FW: PAG 2008 Orthos/Lidar
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
From: Manny M. Rosas [mailto:MRosas@pagnet.org]
Sent: Tuesday, November 10, 2009 7:29 AM
To: 'Lucero, Andrew'; 'Caldwell, Jason'
Cc: 'Terry Hendricks'; Curtis, Edward
Subject: PAG 2008 Orthos/Lidar

Hi Andy,
I resent Sanborn’s Version 3 document produced in July 2009 and yet to receive any
comments from FEMA, Pima County and Michael Baker Inc. therefore
please proceed with direct communications with Michael Baker Inc (Pascal Akl) to resolve all
issues regarding the FEMA guidelines
Thank You
Manny

5/6/2010

Page 2 of 2

Manny M. Rosas Jr.
GIS Administrator

177 N Church Ave. Suite 405
Tucson, Arizona 85701
520-792-1093 (tel)
520-620-6981 (fax)

5/6/2010

Appendix D: Hydrologic Analysis
(in digital form on DVD)

Appendix E: Hydraulic Analysis
(in digital form on DVD)

Appendix F: Erosion and Sediment Transport Analysis
Supporting Documentation
None