Section 1 Introduction ........................................................................................4
1.1 Purpose...................................................................................................................... 4
1.2 Project Authority....................................................................................................... 4
1.3 Project Location ........................................................................................................ 5
1.3 Hydrologic and Hydraulic Methods.......................................................................... 5
1.4 Acknowledgment ...................................................................................................... 6
This study relied on assistance of RFCD GIS staff, who were integral to the
development of the models and maps............................................................................. 6
1.5 Study Results ............................................................................................................ 6
Section 2 FEMA Forms.....................................................................................10
2.1 Study Documentation Abstract for FEMA submittals............................................ 10
2.1.1 Date Study Accepted........................................................................................ 10
2.1.2 Study Contractor .............................................................................................. 10
2.1.3 FEMA Technical Review Contractor .............................................................. 10
2.1.4 FEMA Regional Reviewer............................................................................... 10
2.1.5 State Technical Reviewer ................................................................................ 10
2.1.6 Local Technical Reviewer ............................................................................... 10
2.1.7 Reach Description............................................................................................ 11
2.1.8 USGS Quad Sheets .......................................................................................... 11
2.1.9 Unique Conditions and Problems .................................................................... 11
2.1.10 Coordination of Peak Discharges................................................................... 11
2.2 FEMA Forms .......................................................................................................... 11
Section 3 Survey and Mapping Information ...................................................11
3.1 Field Survey Information........................................................................................ 11
3.2 Mapping .................................................................................................................. 11
Section 4 Hydrology .........................................................................................12
4.1 Method Description ................................................................................................ 12
4.2 Parameter Estimation .............................................................................................. 12
4.2.1 Drainage Area .................................................................................................. 12
4.2.2 Watershed Work Map ...................................................................................... 12
4.2.3 Gage Data......................................................................................................... 13
4.2.4 Spatial Parameters............................................................................................ 13
4.2.5 Precipitation ..................................................................................................... 13
4.2.6 Physical Parameters ......................................................................................... 13
4.3 Problems Encountered During the Study................................................................ 15
4.3.1 Special Problems and Solutions....................................................................... 15
4.3.2 Modeling Warning and Error Messages .......................................................... 15
4.4 Calibration............................................................................................................... 15
4.5 Final Results........................................................................................................ 15
4.5.1 Hydrologic Analysis Results........................................................................ 15
4.5.2 Verification results....................................................................................... 16
Section 5 Hydraulics.........................................................................................16
5.1 Method Description ................................................................................................ 16
5.2 Work Study Maps ................................................................................................... 17
5.3 Parameter Estimation .............................................................................................. 17

2

5.3.1 Roughness Coefficients ................................................................................... 17
5.3.2 Expansion and Contraction Coefficients ......................................................... 17
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
5.5.3 Levees and Dikes ............................................................................................. 18
5.5.4 Island and Flow Splits...................................................................................... 18
5.5.5 Ineffective Flow Areas..................................................................................... 18
5.6 Floodway Modeling ................................................................................................ 18
5.7 Problems Encountered ............................................................................................ 19
5.7.1 Special Problems and Solutions....................................................................... 19
5.7.2 Model Warnings and Errors............................................................................. 19
5.8 Calibration............................................................................................................... 19
5.9 Final Results............................................................................................................ 19
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 HEC-HMS analysis.............................................................. 13
Table 2 Physical Parameters for Sub-Basins .................................................................... 14
Table 3 Summary of the Hydrologic Analysis Results for Sub-Basins............................ 16
Table 4 Summary of the Hydrologic Analysis Results at the Concentration Points ........ 16
Table 5 Comparison of 100-yr discharges ........................................................................ 16
List of Figures
Figure 1 Watershed Map..................................................................................................... 7
Figure 2 Study Limit........................................................................................................... 8
Figure 3 Soil Map ............................................................................................................... 9
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 Map

3

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 Nanini Wash (NNI) located in Pima County,
Arizona. The objective of the TDN and LOMR submission is provide regulatory
discharge rates and floodplain limits along the Nanini 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

4

otherwise protected from flood damage, also contribute to the flood loss. (Ord.
2010).
Section 16 of the Pima County Ordinance describes the provisions for floodplain
regulation in Pima County.
This study has been prepared by the Pima County Regional Flood Control District
(RFCD):
Pima County Regional Flood Control District
97 East Congress, Tucson, AZ 85701
The project was prepared by:
Akitsu Kimoto, Ph.D., C.F.M., Principal Hydrologist.
Pima County Regional Flood Control District
97 East Congress, Tucson, AZ 85701

1.3 Project Location
The study reach of the Nanini Wash (NNI) is located within a Federal Emergency
Management Agency (FEMA)-designated “Zone A” and “Zone X-Shaded” flood-hazard
area, as depicted on FIRM Map Panel Numbers 04019C1660L (June 16, 2011). 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
is to provide regulatory discharge rates and floodplain limits along the Nanini Wash
using better topographic, hydrologic, and hydraulic data.
The study reach of the Nanini Wash is located in Sections 03, 09, and 10 of Township 13
South, Range 13 East, Pima County, Arizona (Figs. 1 and 2).

1.3 Hydrologic and Hydraulic Methods
Hydrologic analysis was preformed to determine proposed regulatory discharge rates at
concentration points along the Nanini Wash using U.S. Army Corps of Engineers
Computer Hydrologic Modeling System, HEC-HMS. The proposed regulatory discharges
are flow rates that have a 1-percent chance of being equaled or exceeded each year (“100year” discharge rates). Hydraulic analysis was performed to delineate floodplain limits
along the study reach of the Nanini Wash using U.S. Army Corps of Engineers Computer
Backwater Model, HEC-RAS. A floodplain for the Nanini Wash was mapped from Ina
Rd to La Cholla Blvd.

5

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 discharge rates were calculated at five concentration points along the
Nanini Wash (Fig. 3). Peak discharges at two concentration points (CP A, B) were used
for the hydraulic analysis in this study. The estimated regulatory discharge rates are 1831
cubic feet per second (cfs) with a drainage area of 1.04 square mile at the Concentration
Point B (CP B), and 1903 cfs at CP A with a drainage area of 1.78 square mile. A
floodplain for the Nanini Wash was mapped as a local floodplain.

6

RIVER

Fig.1
Watershed Map
Nanini Wash

OR ACL
EOR
ACLE

RIVER

LA CANADA

INA

!
(

CP B

RIVER

MAGEE

ORANGE GROVE

NNI B

NNI_subbasins

!
(

CP
Nanini Wash

NNI A

USGS Quad Map
Contour interval 20 ft

INA

Pima County Index Map

CP A
!
(

LA CHOLLA
Index Map Scale 1:5,250,000

MAGEE

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

0

1,000 2,000

4,000

6,000

Scale 1:61,000

8,000
Feet
mojo3/sourcedata/terrasw/aolt_hillshade4b_small.mxd hp4 jr

Fig.2
Study Limit
Nanini Wash

OR ACL
E

OR ACLE

NNI B

Legend

ORANGE GROVE

CP B

INA

!
(

Study Limit

NNI A

CP
Culvert
NNI_subbasins
Approved LOMR

LA CANADA

Existing FEMA Floodplain

FEMA Floodplain
ZONE A
ZONE AE

B

ge
d
i
r

#1

CP A

RIVER

LA CHOLLA

Pima County Index Map

!
(

INA

Culvert #1

Study Limit

Index Map Scale 1:5,250,000

MAGEE

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.

Scale 1:61,000

R

Pima County Regional Flood Control District

RI
VE

MAGEE

!
(

0

1,000 2,000

4,000

6,000

8,000
Feet
mojo3/sourcedata/terrasw/aolt_hillshade4b_small.mxd hp4 jr

Fig.3
Soil Map
Nanini Wash

OR ACL
E

OR ACL
E

NNI B
RIVER

NNI_Hydrologic Soil Group

MAPTIP_1
Soil Group: A (100%)
Soil Group: B (100%)

RIVER

MAGEE

ORANGE GROVE

NNI_subbasins

INA

LA CANADA

Soil Group: B (50%) C (50%)
Soil Group: B (82%) C (18%)
Soil Group: C (100%)

NNI A

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

INA

Pima County Index Map

LA CHOLLA

Index Map Scale 1:5,250,000

MAGEE

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

0

1,000 2,000

4,000

6,000

Scale 1:61,000

8,000
Feet
mojo3/sourcedata/terrasw/aolt_hillshade4b_small.mxd hp4 jr

Section 2 FEMA Forms
2.1 Study Documentation Abstract for FEMA submittals
2.1.1 Date Study Accepted: ___________________
2.1.2 Study Contractor:
Akitsu Kimoto, Ph.D, C.F.M., Principal Hydrologist.
Planning and Development Division,
Pima County Regional Flood Control District
97 East Congress, Tucson, AZ 85701
(520) 243-1800

2.1.3 FEMA Technical Review Contractor: _________________________

2.1.4 FEMA Regional Reviewer: __________________________________

2.1.5 State Technical Reviewer: ____________________________________

2.1.6 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

10

2.1.7 Reach Description
The study reach of the Nanini Wash is located within a Federal Emergency Management
Agency (FEMA)-designated “Zone A” and “Zone X-Shaded” flood-hazard area, as
depicted on FIRM Map Panel Numbers 04019C1660L (June 16, 2011). The study limit
for the Nanini Wash is from Ina Rd. to La Cholla Blvd (Fig. 2).
The study reach is primarily composed of sand channels and the bottom of the reach is
clean with no significant vegetation cover. The overbank of the reach is covered with
scattered desert brush.

2.1.8 USGS Quad Sheets
Not available for this study

2.1.9 Unique Conditions and Problems
No unique conditions or problems in the study limit.

2.1.10 Coordination of Peak Discharges
The 100-year regulatory discharge rates at the concentration points along the study reach
were computed using HEC-HMS, assuming no base flow in the watersheds and no
transmission loss within the reaches. All reaches were modeled with HEC-RAS.

2.2 FEMA Forms
The FEMA MT-2 forms are included in this section.

Section 3 Survey and Mapping Information
3.1 Field Survey Information
No field survey was conducted.

3.2 Mapping

11

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

Section 4 Hydrology
4.1 Method Description
The 100-year peak discharges for the three sub-basins of the Nanini Wash (NNI-A, NNIB; Fig. 3) were calculated using U.S. Army Corps of Engineers Computer Hydrologic
Modeling System (HEC-HMS), version 3.1.0. The HEC-HMS morel 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.

4.2 Parameter Estimation
4.2.1 Drainage Area
As mentioned in 3.2, topographic data was derived from DEM (5-ft cell size) created
from 2008 LiDAR data. ArcGIS was used to create a 2-ft interval contour map. The
limits of the upstream watersheds contributing to the study reaches were determined
using the contour map. The watershed map is included in Fig. 1.

4.2.2 Watershed Work Map
As mentioned above, a 2-foot interval contour map was created using ArcGIS. The 2-foot
interval contour map was used to determine contributing watershed areas. A watershed
work map is included in Exhibit 1. Three sub-basins were delineated for HEC-HMS
hydrologic analysis. Three concentration points were included in the study watershed (CP
A, B), and the 100-year peak discharges at the three concentration points were used for
HEC-RAS hydraulic analysis.

12

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 Tech-018, the 3-hour storm shall be used as rainfall data in the HEC-HMS
model in the case that a time of concentration (Tc) is equal or less than three hours. A 3hour storm was selected, since Tc was less than 3 hours in all the sub-basins.
NOAA Atlas 14, upper 90% confidence interval precipitation frequency estimate values
(NOAA 14 rainfall) were used to determine point 3-hour rainfall depth for the Naini
Wash watershed. The point rainfall depth for the 3-hour storm was obtained, based on the
coordinates of the centroid of the watershed. Areal reduction factor was applied to
watersheds larger than 1 square mile as noted in Tech-018. The 3-hour rainfall depth is
3.12 inches for CP B, and 3.05 inches for CP A.

4.2.6 Physical Parameters
The physical parameters for the sub-basins 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
determined based on Tech-018. Table 1 summarizes the method used for a HEC-HMS
analysis.

Table 1 Methods used for a HEC-HMS analysis

13

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 tables and Hydrologic
Soils Group maps associated with the PC Hydro User Guide (Arroyo Engineering, 2007).
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 2008 PAG aerial photograph. The combination of the kinematic wave
time of concentration method and the U.S. Natural Resources Conservation Service
(NRCS) segmented Time of Concentration (Tc) calculation (USDA-NRCS, 1986) was
used to determine Tc, based on the recommendation on Tech-018. The Tc was calculated
by summing the travel time for overland flow, shallow concentrated flow and channel
flow. The Tc for overlandflow 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).
The detail of the Tc calculation is included in Appendix D.

Table 2 Physical Parameters for Sub-Basins
Sub-Basin
NNI A
NNI B

Area
(sq mi)
0.74
1.04

CN
89.5
89.3

Impervious Area
(%)
15.0
15.0

Vegetation Cover
(%)
25
25

Lag Time
(min)
38.6
20.0

Runoff from sub-basins was routed using the Modified-Puls method. A storage discharge
table for the channel routing was developed using the cross sections and slopes derived
from HEC-HMS. 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
t

14

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.
The following warnings were produced in the HEC-HMS;


Warning: Gage “For CP A, B” with data interval 5 minutes was interpolated to
simulation time interval 1 minute.

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 the concentration points along the Nanini Wash were
determined using the HEC-HMS. Calculations were performed on one-minute time step
over six hours. Rainfall occurred on a 5 minute time step with rainfall occurring in the
first three hours. In general, the discharge from the downstream point was used for the hydraulic
analysis. The results are summarized in Tables 3 and 4.

15

Table 3 Summary of the Hydrologic Analysis Results for Sub-Basins
Sub-Basin
NNI A
NNI B

Area
(sq mi)
0.74
1.04

Rainfall Depth
(in)
3.21
3.21

Runoff Volume
(in)
2.14
2.12

Peak Discharge
(cfs)
859.2
1905.7

Table 4 Summary of the Hydrologic Analysis Results at the Concentration Points
Concentration
Point

Location

CP A
CP B

at La Cholla Bl.
at La Canada Dr.

Area (sq Rainfall
Runoff
Q100
mile)
Depth (in) Volume HMS (cfs)
(in)
1.78
3.05
1.98
1903
1.04
3.12
2.03
1831

Time to
Peak
2:28
1:43

4.5.2 Verification results
The calculated 100-year 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 peak discharge from the HMS-derived peak discharges were
higher than the ones derived from USGS Eq 13.
Table 5 Comparison of 100-yr discharges
Concentration
Point

Location

CP A
CP B

at La Cholla Bl.
at La Canada Dr.

Area (sq
Q100
Q100
mile)
HMS (cfs) RRE (cfs)
1.78
1.04

1903
1831

1827
1292

RRE: USGS Regression Equation 13

Section 5 Hydraulics
5.1 Method Description
The hydraulic modeling for the Nanini Wash was performed using Hec-Ras, Version
4.1.0 (HEC-RAS), HEC-GeoRAS, Version 4.1.1 (HEC-GeoRAS), and ArcGIS, Version
9.2.
As previously mentioned, 2008 LiDAR data was used to create DEM and a 2-foot
contour map. The locations of the stream centerline, cross-sections, and bank of the CBW
were determined using the topographic 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
16

n-values, culvert data, expansion and contraction coefficients, normal depth 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 in the study area.
Hydraulic analysis was performed in the area currently mapped as FEMA Zone A. 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, cross-sections, and culverts were obtained using HEC-GeoRAS. The
HEC-RAS data and shape files (contour lines, flowpath, cross section lines, study
watersheds, concentration points, subbasins, hydrologic soil groups, proposed floodplain
limit) used in the analysis are included in an attached CD. Normal-depth with a slope of
0.01 was assumed for the downstream boundary condition.

5.2 Work Study Maps
The work study map utilized to digitize the stream centerline and cross-sections of the
Ninini Wash is included in Exhibit 1.

5.3 Parameter Estimation
5.3.1 Roughness Coefficients
Manning’s n values were determined using 2008 PAG aerial photo. The assigned
Manning’s n value ranges from 0.035 to 0.04 for the channel of the Nanini Wash, while it
was 0.055 for the overbank with scattered desert brush. Differentiation of channel and
overbank ‘n’ values was done only when channel flow is at least twice as deep as
overbank flow (Phillips and Tadayon, 2006). For cross sections with the channel flow is
less than twice as deep as overbank flow, an average n for the whole cross-section of
0.045 was assigned rather than assign a channel and overbank Manning’s n,.

5.3.2 Expansion and Contraction Coefficients
The channel of the Nanini Wash is assumed to have generally gradual transitions with
minimum curvature, except for the upstream and downstream of the culverts. The
expansion coefficient of 0.30 and contraction coefficient of 0.10 were used for the entire
study reaches of the Nanini Wash I except the upstream and downstream of the culverts.
The expansion coefficient of 0.50 and contraction coefficient of 0.30 were used for the
upstream and downstream of the culverts.

17

5.4 Cross-Section Description
A 2-foot interval contour map created using DEM with 2-ft cell size was used to select
the location of cross sections. Cross-section locations were determined primarily based
on the channel topography. The cross-section lines were drawn to be perpendicular to
flow paths in GeoRAS and ArcGIS.

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

5.5.2. Bridges and Culverts
There is one culvert in the study limit. A 3-cell, 12-ft wide by 7-ft high reinforced
concrete box (RCB) is located on Orange Grove.

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 following situations;
 Floodplain areas are not hydraulically connected
 A contraction and expansion of flow through the culvert or bridge openings
occurs at the upstream and downstream of the culvert or bridge. 4:1 expansion
and 1:1 contraction ratios were used.

5.6 Floodway Modeling

18

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
The FEMA guidelines state that it is required to run hydraulic models under subcritical
flow conditions. Since the Nanini Wash watershed has steep slopes, the flow regime of
the Nanini Wash is expected to be critical or supercritical. The HEC-RAS modeling
produced warnings stating “During the standard step iterations, when the assumed water
surface was set equal to critical depth, the calculated water surface came back below
critical depth”. This indicates that there is not a valid subcritical answer. The program
defaulted to critical depth at many cross-sections along the Nanini Wash. Most of the
errors force a critical solution which is reasonable for these steep watercourses.
Flow divides occur along the Nanini Wash. At the cross-sections where there is divided
flow, the flow depth typically defaults to critical due to the subcritical run. Subcritical
condition creates higher water surface elevations at those cross sections.
The warnings stating that “The energy equation could not be balanced within the
specified number of iterations. The program used critical depth for the water surface and
continued on with the calculations”, “The energy loss was greater than 1.0 ft (0.3 m)
between the current and previous cross section. This may indicate the need for additional
cross sections”, and “The conveyance ratio (upstream conveyance divided by
downstream conveyance) is less than 0.7 or greater than 1.4. This may indicate the need
for additional cross sections” are produced at many cross sections through the Nanini
Wash. These warming messages were produced mainly due to the steepness of the slope
of the Nanini Wash and the subcritical flow requirement of FEMA. All the warning
messages in the HEC-RAS modeling are included in Appendix E.

5.8 Calibration
The model was not calibrated in this study.

5.9 Final Results

19

5.9.1 Hydraulic Analysis Results
The HEC-RAS modeling results are summarized in Appendix E.

5.9.2 Verification of Results
The floodplain limit of this study was extended to La Cholla Blvd. The proposed
floodplain limit is reasonable based on the topography of the Nanini Wash.

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 at three concentration points (CP A, B) were used for the hydraulic
analysis in this study. The estimated regulatory discharge rates are 1831 cubic feet per
second (cfs) with a drainage area of 1.04 square mile at the Concentration Point B (CP
B), and 1903 cfs at CP A with a drainage area of 1.78 square mile.

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 TDN.

7.4 Flood Profiles
Flood profiles are included 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

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

LA

BA
N

SAN PASQUALE

NT
AL
O

2440

2440

LEONARDO DA VINCI

O

244
0

PALER
M

243
0

2430

POMONA

KENANNA

PENNY
E
AM
SE
S

241
0

2410
24
10

24
40

LA
S
CO
NI
SA
N

MONTEBELLA

DE S A N

10163

U
V

PLAC IT
A

24
10

SAN IGNACIO

2372.536

2400

23
90

VIA RANCHERO

23
80

IA
EL
ME
D

23
70

CA

LL

ED

23
60

CAMINO DE COROZAL

MONTEBELLA

23
80

SAFARI

VIA CABALLO

O
EL

R

O

N

23
50

AN

G

CORONA

233
0

FOUNTAINS

U
TI
B

ESCONDIDO

LE
AL
C

MONTEBELLA

2340

FOUNTAIN PLAZA

PANORAMA

RUDASILL

2350

Pima County Index Map

23
30

60
23

2310

CA

LL

IN
EK

O

ST
AT
IO

N

U
TIB
E
L
L

R

ON

LAS PALMAS

23
20

ES

23
00

22
70

SAN JOAQUIN

2390

23
20

230
0
230
0

LI S A

SU MAYA

2370

235
0

TI
N
US
AG
SA
N

2330

20
23
10

0
234

ES

MON
A

VIA TIERRA

SAHARA PALMS

LAS LOMITAS

LOS ALAMOS

IA
M
NA
KA
TA
VI
S
90
22

EZYBROOK

SUNSET

N

ALDER GROVE

SAHARA

OW
CK

TYLER RIVER

I
TH

50
22

ET

CROWLEY

ILL

50
22

22
50

W

WATERWAY

RO

AN

OK
E

AF
WATER LE

KLAMATH

POMONA

HUDSON

N

COACHWHIP

PAINTBRU SH

E
TH
R
O

RN

HI

LL

S

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

0

200 400

800
Feet

ESCONDIDO

O

HOPBUSH

M

ST
AT
I

M

FLINT

ES

CU

A

BRAMBLE BROOK

2260

EA

JA
YN

BE

ON

ST
R

E

PO
M

R

CL

D
AN
L
R

KENN
EBEC

SI
LV
E

RA

TRINITY

O

LA CHOLLA

MORNING SPRING

QUIET DREAM

KAIN

22
50

2250

2250

O

E

A
VI

TIG
LA

D

226
0

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.

AN

ER

L

TERNERO

A

RI

10
23

CHEYENNE

TRISHA

LA CHOLLA

SUNSET

A
TA
S
I
V

H
ES

R

BAYBROOK

Index Map Scale 1:1,500,000

G

2250

PLAC ITA
MALAGA

PLACITA DEL LOBO

JA
YN
2250

2360

2350

2330

2340
2330

PL
AC
IT
A
23

2340

LITTLE RIVER

PALMETTO

2250

2360

MONTROSE
2310

MONA LISA

2290

NCA

N

EDENBROOK

2390

2390
23
80
23
50

23
40

23
00

VIA HACIENDA

O

SUNBROOK

INADA

R

2250

2360

MONA LISA

CALLE DE ONA

ITA B
AR R
A

U

MOONBROOK

PLA
C

B
TI

ORANGETIP

PLAC ITA A
L

2370

A
IT

DARTWHITE

2430

24
30

MONTEBELLA

AMAHL

2390

MEDICI

PLAC ITA HACIEND A
CARAPAN

Aerial Photo: 2010 Pictometry

CARAVAN

PLAC ITA DE OCAMPO

AC
PL

CLOUDWING

100-yr Floodplain

APPIAN

24
20

0
241

CARAPAN

00
24

60
23

2260

SHANNON

Contour 10ft

24
40

0
237

LINKHART

50
24

ORANGE GROVE

UE

PLACITA ARIEL

GI N A

0
239

0
236

ILENE

0
242

Contour 2ft

2410

2400

MESQU ITE BO
SQ

PERU GIA

O IVAN
CAMIN

A
N
O
VE
R

TI
A

10
24

7

5

8

PARSLEY

110
8

1076

POSITANO

.10
4

2360

0
234

NIGHT AIR

DISTANT SONG

RIV

EMERALD

92

61

1065

54

TEALEAF

S

2410

.5
80
23

88

.7
2377

99

0
236

SEBBA

238
2

CA

TERNERO

2250

PALMYRA

L

O
FIL
OS

60
22

ROYAL PALM

2250

River

SAN NICOLAS

30
23

22
50

CARNAUBA

Cross Sections

9

.734

Concentration Point

MIDDLETON

MONTENEGRO

2384
.2

.2
79
23

77

MORNING DREAM

225
0

24

6

JA
YN

2250

2240

17

2270

2250
225
0

1029

LE

PLACITA ALGODON

K

02
2374.4

O

0

RO

1002

WHISBROOK

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6

12

00
23

RI
VE
R

23
34
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57

2320

AC

PLACITA DE RAMO

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B

TARANTULA RANCH

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(

LAS LOMITAS

K

LA

0
246

00
23

FANBROOK

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23
95
.9

35

MEDICAL

2350

O

79
2360

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ORACLE JAYN

2240

FALBROOK

CHULA VISTA

DESERT HARBOR

5

4

EB
RO

TENBROOK

24
03
.5
89

2470

2260

2240

ER

GLENBROOK

FIELDBROOK

SANDBROOK

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7

VISTA LEJOS

69

LOS ALAMOS

FI
R

24
05
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65

07

DOLBROOK

BENSBROOK

GRANDBROOK

OR

IAN

8

0

2386.684

2335.275

76

LEAFWING

LAS LOMITAS

9

925

2336.849

2280

MASTER PIECES

BELBROOK

LAS LOMITAS

FLAMEBROOK

935

RUDASILL

2250

DUSKYW ING

2320

2320

00
23

RUDASILL

81

7987

8 7
.85
32
1
23
.60
30
23

CORIANDER

BARTLETT

1

24
06
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ORANGE GROVE

2340
.502
233
9.4
98
2338.236

HOSPITAL

2320

CALLE OCIO

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2320

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2310

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15
23
61
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62
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59
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23
3
57
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26

2342.504

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62
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30
8
23
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3
28
6
23
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27
5
23
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26
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23
30

2330

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BARTLETT

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05

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8

246
0

2348.189

!
(

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SHUMAKER

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236
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8082

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NT
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67
23

2340

U
V
U
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U
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WATERCRESS

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U
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U
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U
V

2350

M
THY
CINNAMON

23
54
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04

23
62
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52
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1

8527

10
23

10

VIA PICCOLINA

2320

0
231

CELERY

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LE

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23

29

23
65
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7

85

70
23

U
V
88

U
V
U
V

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98

V
U
U
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2380

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23

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238

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99
23
99
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U
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109

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2360

2380

CHOLLA ESTATE

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36

78

2430

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238
9

A

23
60

DR

0
236

TANIA

DA
VIA HACIEN

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MAXIMILIAN

14529

.10
8

Exhibit 1
100-year Floodplain
with cross sections
Nanini Wash

02

36

C
FELI

TREELINE

BASIL

12

24
30
.2

24
32
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3

24
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.8

11487

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23

DE

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6

2429
.218

24
34
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137

2370

LABR IEGO

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PA

TREELINE

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9

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GREENRIDGE

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2411.9

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239

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SIM
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KHAIBAR

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O
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PR

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1

TAS

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PU
C

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AL
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242
1

.509

SHANNON SHANNON

AG
M

RA

CORTE MADELENA

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139

242
4

!
(

CP B

4

2427
.887

33

24
36
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07

3

36

1476

81

9
240

DA

D

AN

141

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CIN

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U
V
1464

U
V
U
V
U
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08
24

LU

10
24

E
NT

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NA

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00
24

DA

CA

AVENIDA ADELLA

TE O
L

KHAIBAR

Study Limit

13200

C OR

AR

O

R
CI

CO

O

M

LL
TE
NA

D

N

O
O

DO

GIACONDA

L
EL
T
A

149

l

NIONA

MAXIMILIAN

12

LA CANADA

24
20

PA
S
2420

2440

15

58
.3
38
24

U
V
V
U

2470

2450

9

SHALIMAR

2420

38

INA

INA

WANDA VISTA

CERRADA VERACRUZ

U
V

INA

EL

N

15

CRYSTAL CAVE

EO

M

A NNA

O
LIS

LA CANADA

SA
B
CA

245
0

MAGIC

SOLERO

LAS QUINTAS

NC

A

O
TE
R
MO
N

SHAMA WING

IA

AS

SAN

AR

50
24

SCHOONER
ALTERO

M

BL

ME

SA
N

N
SA

E
CL

A
NT

WHISPERING HILLS

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

09/2011

gislib\rfcd\projects\imd\xavi\mdx\akitsu\Nanini Wash_100yr_exh1.mxd