Table of Contents:
Section 1: Introduction ..........................................................................................4
1.1 Purpose .......................................................................................................4
1.2 Project Authority ..........................................................................................4
1.3 Project Location...........................................................................................5
1.4 Methodologies Used for Hydrology and Hydraulics.....................................5
1.5 Acknowledgements .....................................................................................5
1.6 Study Results ..............................................................................................5
Section 2 Summary of Key Facts..........................................................................9
2.1: General Information....................................................................................9
2.2: Mapping Information...................................................................................9
2.3: Hydrology ...................................................................................................9
2.4: Hydraulics...................................................................................................9
2.5: Additional Study Information:......................................................................9
Section 3: Survey and Mapping Information .......................................................10
3.1 Field Survey Information ...........................................................................10
3.2 Mapping ....................................................................................................10
Section 4: Hydrology...........................................................................................10
4.1 Method description. ...................................................................................10
4.2 Parameter estimation. ...............................................................................10
4.3 Problems encountered during the study. ...................................................15
4.4 Calibration .................................................................................................15
4.5 Final results ...............................................................................................15
Section 5: Hydraulics ..........................................................................................17
5.1 Method description. ...................................................................................17
5.2 Work study maps.......................................................................................17
5.3 Parameter estimation. ...............................................................................17
5.4 Cross section description. .........................................................................18
5.5 Modeling considerations............................................................................18
5.6 Floodway modeling ...................................................................................18
5.7 Problems encountered during the study. ...................................................18
5.8 Calibration. ................................................................................................19
5.9 Final results. ..............................................................................................19
Section 6: Erosion and Sediment Transport .......................................................19
Section 7: Ratio of the top width of 100-yr and 25-yr floodplain..........................20

2

List of Figures:
Figure 1.1 –Watershed Map .................................................................................6
Figure 1.2 – Study limit .........................................................................................7
Figure 1.3 – Soil Classification..............................................................................8
Figure 4.1 – Flow Chart of Mapping Process......................................................12
List of Tables:
Table 4.1 - Methods used for a HEC-HMS analysis............................................11
Table 4.2 - Sub-basin Characteristics .................................................................14
Table 4.3 – 100-yr Sub-basin discharges ...........................................................14
Table 4.4 – Summary of 100-yr Peak Discharge Values ....................................16
Table 4.5 – Summary of 25-yr Peak Discharge Values ......................................16
Table 4.6 – Summary of 500-yr Peak Discharge Values ....................................16
Table 4.7 – Comparison of 100-yr Peak Discharge Values ................................16
Exhibit
Exhibit 1 100-yr Floodplain Limit Map for the Canyon del Salto Wash
Exhibit 2 Annotated Flood Insurance Rate Map
Attached CD
Canyon del Salto Wash TDN with supporting models and GIS data.

3

Section 1: Introduction
1.1 Purpose
The purpose of this study is to provide flood and erosion hazard information for the
Canyon del Salto Wash for use by the Pima County Regional Flood Control District
(District) in floodplain use permitting and floodplain management. More specifically, it
provides:
 discharge values for sub-basins and important concentration points;
 hydrographs for use with floodplain mapping;
 floodplain mapping for channels with contributing areas greater than 1 square
mile, and channels with 100-yr discharges greater than 2000 cfs, which are treated
differently under the Pima County Ordinance.
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).
Section 16 of the Pima County Ordinance describes the provisions for floodplain
regulation in Pima County.

4

1.3 Project Location
The study was performed to provide drainage information for the Canyon del Salto Wash.
The site includes Sections 13, 24, 25, 26, 35, and 36 of Township 13 South, Range 16
East, Sections 16, 17, 18, 19, 20, and 30 of Township 13 South, Range 17 East, Sections
02 of Township 14 South, Range 16 East, Pima County, Arizona. The Canyon del Salto
Wash watershed is in FEMA Zone X and Zone D, as shown on the current Flood
Insurance Rate Map (FIRM) number 04019C-1667L.
The watershed is 8.18 square mile. The study watershed was divided into seven subbasins (Fig.1.1). The study limits for the Canyon del Salto Wash extends from a
confluence with Tanque Verde Creek to the downstream end of Zone D (Fig.1.2).
1.4 Methodologies Used for Hydrology and Hydraulics
Topographic, hydrologic and hydraulic analyses were performed to determine drainage
conditions in the Canyon del Salto Wash. ArcGIS, Version 9.3.1, HEC-HMS Version 3.4
(HEC-HMS), HEC-RAS Version 4.0 (HEC-RAS), and HEC-GeoRAS, Version 4.1.1
(HEC-GeoRAS) were used for the analyses.
1.5 Acknowledgements
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 modeled discharge for the Canyon del Salto Wash at the confluence with the Tanque
Verde Creek is 4743 cfs, where the area is 8.18 square miles.
The Canyon del Salto Wash watershed is partially located within Federal land (national
forest, FEMA Zone D). The floodplain was mapped downstream of the Zone D on the
Canyon del Salto Wash.

5

Figure 1.1
Watershed Map
Canyon Del Salto Wash

(
!

Discharge Point

RE

DI
NG

TO

N

Contour 50 foot

CP F CP G

!!
(
(

Streets
Subbasins
CDS A
CDS B
CDS C
CDS D

CP D

(
!

CDS E
CSD F

CP E

(
!

CSD G
Aerial : 2006 Pima Association of Governments
Topo: 2008 Pima Association of Governments
Datum: NAVD 1988

Pima County Index Map

CP B CP C

!
(
(
!

RE D

Index Map Scale 1:5,250,000

ING
TON
CP A

(
!

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

600 300

0

11/2010
\\gislib\rfcd\projects\imd\xavi\mxd\AKITSU\Canyon_Del_Salto_wash_Fig1.1.mxd

600 Feet

Figure 1.3
Soil Classification Map
Canyon Del Salto Wash

CSD G
Subbasins

CSD F

RE

DI
NG

TO

N

Soil Classificaton
Soil Group: A (100%), ARIZO-RIVERWASH COMPLEX,
0 TO 3 PERCENT SLOPES
Soil Group: B (100%),
Soil Group: B (50%) C (50%), PALOS VERDESSAHUARITA COMPLEX, 2 TO 8 PERCENT SLOPES
Soil Group: C (50%), D (50%)
Soil Group: D (100%), CELLAR-LAMPSHIRE-ROCK
OUTCROP COMPLEX, 15 TO 60 PERCENT SLOPES
Soil Group: D (100%), CELLAR-LEHMANS COMPLEX,
5 TO 25 PERCENT SLOPES

Aerial : 2006 Pima Association of Governments

CDS E
CDS D

CDS B

CDS C

Pima County Index Map

CDS A
REDINGTON

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.
600 300

0

Pima County Regional Flood Control District

11/2010
\\gislib\rfcd\projects\imd\xavi\mxd\AKITSU\Canyon_Del_Salto_wash_Fig1_3.mxd

600 Feet

Figure 1.2
Study Limit Map
Canyon Del Salto Wash

CSD G
!
(

RE

DI
NG

TO

N

CSD F

CP F CP G

!
(!
(

Discharge Point
River
Streets
Subbasins

Existing FEMA Floodplain
ZONE A
CDS E

CDS D

CP D

!
(

ZONE AE
ZONE X - SHADED
Aerial : 2006 Pima Association of Governments

CP E

!
(

CDS B

CDS C

CDS A

Pima County Index Map

CP B CP C

!
(!
(

Index Map Scale 1:5,250,000

REDINGTON

Study Limit

CP A

!
(

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
590 295 0

11/2010
\\gislib\rfcd\projects\imd\xavi\mxd\AKITSU\Canyon_Del_Salto_wash_Fig1.2.mxd

590 Feet

Section 2 Summary of Key Facts
2.1: General Information
2.1.1 Community: Pima County Regional Flood Control
2.1.2 Community Number: NFIP Community Number 04019C
2.1.3 County: Pima
2.1.4 State: Arizona
2.1.5 Date Study Accepted: Not Accepted
2.1.6 Study Contractor: Pima County Regional Flood Control District – Akitsu Kimoto
2.1.7 State Technical Reviewer: Not Applicable
2.1.8 Local Technical Reviewer: Suzanne Shields
2.1.9 River or Stream Name: Canyon del Salto Wash
2.1.10 Reach Description: Canyon del Salto Wash
2.1.11 Study Type: Hydrology and Hydraulics study of a Riverene System
2.2: Mapping Information
2.2.1 FIRM Panels: 04019C-1667L
2.2.2 Mapping for Hydrologic Study: Lidar based on 2008 flight used to derive 10’
contour interval maps using ARC-GIS 9.3.1
2.2.3 Mapping for Hydraulic Study: Lidar based on 2008 flight used to derive a DEM
(5-ft cell size) for use with GeoRAS
2.3: Hydrology
2.3.1 Model or Method Used: HEC-HMS (v. 3.4) model parameterized using methods
of RFCD Draft Tech Policy 018
2.3.2 Storm Duration: 3-hr
2.3.3 Hydrograph Type: SCS Unit Hydrograph
2.3.4 Frequencies Determined: 100 yr
2.3.5 List of Gages used in Frequency Analysis or Calibration: None
2.3.6 Rainfall Amounts and Reference: SCS Type II, NOAA 14 Upper 90%
Confidence Interval
2.3.7 Unique Conditions and Problems: None
2.3.8 Coordination of Q’s: Comparison with previous studies on file with RFCD and
discharge estimates
2.4: Hydraulics
2.4.1 Model or Method Used: HEC-RAS 4.0, GeoRAS to parameterize
2.4.2 Regime: Modeled as subcritical
2.4.3 Frequencies for which Profiles were computed: 100 yr
2.4.4 Method of Floodway Calculation: No Floodway
2.4.5 Unique Conditions and Problems: Boundary set at normal depth.
2.5: Additional Study Information:
None

9

Section 3: Survey and Mapping Information
3.1 Field Survey Information
No field survey was used.
3.2 Mapping
The 2008 Light Detection and Ranging (LiDAR) data was used for the analysis.
Coordinates were in Pima County projection:
Projection = State Plane, Arizona Central Zone
Datum = NAD83 HARN
Units = International Feet
North American Vertical Datum of 1988 (NAVD, 1988)
The LiDAR was used to derive a Digital Elevation Model (DEM) and a contour map.
DEM derived on 5’ centers provided the basis for delineating the watershed and subbasins. DEM was also used to characterize the topography along channels used for the
floodplain mapping process. Contour maps derived from the DEM allowed modelers to
visualize topographic differences in making decisions on how to model different areas.

Section 4: Hydrology
4.1 Method description.
For the floodplain mapping, a 100-yr discharge is required. The 100-year peak discharges
for the sub-basins of the Canyon del Salto Wash (CDS A, B, C, D, E, F and G; Figure
1.1) 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.
4.2 Parameter estimation.
Methods are summarized in Table 4.1. The data processing methods are summarized in
Fig. 4.
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, 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). An areal reduction factor was applied to watersheds larger than 1
square mile, as described in Tech-018.
10

Table 4.1 - Methods used for a HEC-HMS analysis

Rainfall Depth
Rainfall Distribution
Rainfall Loss
Time of Concentration
Transform
Routing

Selected Method
NOAA 14, upper 90% Confidence Interval
3-hr SCS Type II Storm
SCS Curve number
SCS Segmental Method
SCS Unit Hydrograph
Modified-Puls and Kinematic Wave

4.2.1 Drainage area boundaries.
The limits of this study are shown in Fig.1.2. The Canyon del Salto Wash watershed is
partially located within Federal land (national forest, FEMA Zone D), as shown on the
current Flood Insurance Rate Map (FIRM) number 04019C-1700 and 2285 K. The
floodplain was mapped in the downstream area of the Canyon del Salto wash.
The watershed is 8.18 square mile. The study watershed was divided into seven subbasins (Fig.1.1). The upstream study limits is the upstream limit of Zone D along the
Canyon del Salto wash, while the downstream limit is the confluence with the Tanque
Verde Wash (Fig.1.2).
4.2.2 Watershed work maps
Watershed work map is shown in Exhibit 1. The boundary of the watershed and internal
sub-basins were determined using Hydrology function in ArcGIS with DEM derived
from the 2008 Lidar. The sub-basins reflected predominant topographic, soils, cover and
development conditions, so that the sub-basins would represent hydrologic response from
the sub-basin. The locations of the stream centerline, cross-sections, culverts, and other
physical attributes of the wash were determined by using the 10-ft interval contour map
and 2002 aerial photo.

11

Figure 4.1 – Flow Chart of Mapping Process

Topographic Data Preparation using ArcGIS with
DEM

Hydrologic Analysis using HECHMS

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

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

Floodplain Delineation using HECGeoRAS

12

4.2.3 Gage Data.
None Available
4.2.4 Statistical parameters
None Available
4.2.5 Precipitation.
Rainfall depth was selected from the NOAA 14 Upper 90% rainfall data used in PC
Hydro. The point rainfall depth for the 3-hour storm was obtained, based on the
coordinates of the centroid of the watershed (Latitude: 32.278, Longitude: 110.65). Areal
reduction factor was applied to watersheds larger than 1 square mile as noted in Tech018. The 3-hr, SCS Type II rainfall distribution described in Haan et al (1994) was used.
4.2.6 Physical parameters.
A hydrologic soils group map for the study watershed is presented in Fig.1.3. The study
watershed is mostly covered with Desert brush. Hydrologic Soil Group C and D are the
dominant soil types in the Canyon del Salto Wash watershed. The SCS Curve Number
was determined using maps obtained from NRCS (http://soildatamart.nrcs.usda.gov/) as a
basis for preparing a Hydrologic Soil Group Map for Pima County. The CN charts in the
PC Hydro Manual (Arroyo Engineering, 2007) were the basis for CN selection. A
vegetation cover density of 30% was used to select the SCS Curve Number for the
hydrologic calculation of the mountainous watersheds. Impervious cover percentage
from 5-7%, were selected based on lot size, the fraction of the sub-basin that is developed
and the tables in the PC Hydro manual. Sub-basin characteristics are summarized in
Table 4.2 The detail of the CN calculation is included in Appendix D.

13

Table 4.2 - Sub-basin Characteristics
Sub-Basin
CDS A
CDS B
CDS C
CDS D
CDS E
CDS F
CDS G

Area
(sq mi)
0.53
1.34
1.08
1.24
0.98
1.42
1.59

CN
90.4
87.0
89.1
86.2
86.6
86.2
84.5

Impervious Area
(%)
7
5
5
5
5
5
5

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

Lag Time
(min)
12.1
14.1
18.7
11.4
17.8
11.2
31.7

The SCS TR-55 segmental Time of Concentration (Tc) method with a combination of
kinematic wave method was used. The hydraulically most distant point on the sub-basin
was identified. The length of sheetflow was estimated at 100 feet, the distance from the
end of the sheetflow to a well-defined channel was selected as the shallow concentrated
portion of the flow path, and the channel portion was the path from the well-defined
channel to the sub-basin outlet was the ‘channel flow’ portion of the flow path.
Tc is the sum of the travel time for sheetflow, shallow concentrated flow and channel
flow. The travel time for sheetflow was calculated using kinematic wave method. The
travel time for shallow concentrated flow was calculated using the methods described in
the TR-55 manual (USDA-1986). The travel time for channels used estimates from a
HEC-RAS model. The lag time was calculated as 0.6 Tc. The detail of the Tc calculation
is included in Appendix D.
The SCS unit hydrograph method was used to produce hydrographs at the outlet of the
sub-basin in HEC-HMS. 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. Modified Puls routing employed the
methods described in the HMS manual. The detail of the calculation of the number of
subreach is included in Appendix D. Sub-basin discharges are summarized on Table 4.3.
Table 4.3 – 100-yr Sub-basin discharges
Sub-Basin
CDS A
CDS B
CDS C
CDS D
CDS E
CDS F
CDS G

Area
(sq mi)
0.53
1.34
1.08
1.24
0.98
1.42
1.59

Rainfall Depth
(in)
3.57
3.57
3.57
3.57
3.57
3.57
3.57

Runoff Volume
(in)
2.55
2.25
2.43
2.18
2.21
2.18
2.04

Peak Discharge
(cfs)
1557
3229
2377
3237
2025
3729
2017

14

4.3 Problems encountered during the study.
None
4.3.1 Special problems and solutions
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
4.5 Final results
4.5.1 Hydrologic analysis results
As described above, this study mainly focuses on drainage information in the
downstream of the Canyon del Salto wash (Subbasins A and B). The 100-year peak
discharge at CPs A and B were determined using the HEC-HMS. Six hours were
simulated on a 1 minute time step with rainfall occurring in the first three hours. The
following discharges were obtained from the hydrologic analysis:

15

Table 4.4 – Summary of 100-yr Peak Discharge Values
Concentration
Point

Location

CP A
CP B
CP C

Confluence with Tanque Verde Creek
Southwest of the National Forest
Southwest of the National Forest

Area (sq Rainfall
Runoff
Q100
Time to
mile)
Depth (in) Volume HMS (cfs)
Peak
(in)
8.18
2.93
1.66
4743
1:47
6.57
3.00
1.67
2695
1:57
1.08
3.57
2.43
2377
1:42

Table 4.5 – Summary of 25-yr Peak Discharge Values
Concentration
Point

Location

CP A
CP B
CP C

Confluence with Tanque Verde Creek
Southwest of the National Forest
Southwest of the National Forest

Area (sq Rainfall
Runoff
mile)
Depth (in) Volume
(in)
8.18
2.29
1.1
6.57
2.34
1.11
2.43
1.71
1.08

Q25 HMS Q25 RRE
(cfs)
(cfs)
3224
1752
1673

2438
2173
761

Time to
Peak
1:47
1:38
1:42

Table 4.6 – Summary of 500-yr Peak Discharge Values
Concentration
Point

Location

CP A
CP B
CP C

Confluence with Tanque Verde Creek
Southwest of the National Forest
Southwest of the National Forest

Area (sq Rainfall
Runoff
Q500
Time to
mile)
Depth (in) Volume HMS (cfs)
Peak
(in)
8.18
3.81
2.43
7182
1:45
6.57
3.90
2.45
4379
1:53
1.08
3.57
2.92
3317
1:42

4.5.2 Verification of results.
Results are reasonable when compared with USGS Regression Equation 13 (Thomas et
al, 1997, Table 4.7). The equation 13 results were generally lower than the HMS results,
which would be expected, because these steep watersheds could be expected to produce
higher than average discharge on average. A 25-yr peak discharge for CP B derived from
the Regression Equation 13 is higher than the one derived from HEC-RAS. No regulatory
discharge point data is available along the Canyon del Salto Wash.
Table 4.7 – Comparison of 100-yr Peak Discharge Values
Concentration
Point

Location

CP A
CP B
CP C

Confluence with Tanque Verde Creek
Southwest of the National Forest
Southwest of the National Forest

Area (sq
Q100
Q100
mile)
HMS (cfs) RRE (cfs)
8.18
6.57
1.08

4743
2695
2377

4360
3884
1325

16

Section 5: Hydraulics
5.1 Method description.
Steady flow analysis was performed to determine 100-year water surface elevations in the
study area by using HEC-RAS with the discharge obtained from HEC-HMS. Floodplain
boundary within subbasins A and B is shown in this study.
5.2 Work study maps
As described above, geometric data for HEC-RAS including stream centerline, crosssections, and culverts, were obtained from HEC-GeoRAS. The locations of cross sections
and channels used for the 100-yr floodplain analysis are show in Exhibit 1. The 100-yr
floodplain limit is also shown in Exhibit 1.
5.3 Parameter estimation.
The watershed was modeled using methods consistent with District Tech Policy 019.
5.3.1 Roughness coefficients.
Manning’s roughness coefficients for the channel and the over-bank areas were
determined by using a 2002 aerial photo. Differentiation of channel and overbank ‘n’
values should be done only when channel flow is at least twice as deep as overbank flow
(Phillips and Tadayon, 2006). The reach within Subbasin A is wide with several flow
paths. Rather than assign a channel and overbank Manning’s n, an average n for the
whole cross-section of 0.045 was assigned.
5.3.2 Expansion and contraction coefficients.
Default HEC RAS expansion (0.3) and contraction (0.1) coefficients were used for the
most cross sections.

17

5.4 Cross section description.
A 10-foot interval contour map derived from 2008 LiDAR data 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 Geo-RAS and ArcGIS.
5.5 Modeling considerations.
5.5.1 Hydraulic Jump and drop analysis.
No hydraulic jumps were encountered.
5.5.2 Bridges and culverts.
There are no culverts along the study reaches of the Canyon del Salto Wash.
5.5.3 Levees and dikes.
None.
5.5.4 Islands and flow splits.
None.
5.5.5 Ineffective flow areas.
Ineffective flow areas were noted on the study reach of the Canyon del Salto Wash.
In general these ineffective flow areas were disconnected overbank areas that would not
convey flow to the next downstream cross-section.
5.5.6 Supercritical flow.
No supercritical reaches.
5.6 Floodway modeling
No encroachment calculations were performed.
5.7 Problems encountered during the study.
5.7.1 Special problems and solutions.

18

None.
5.7.2 Modeling warning and error messages.
No errors occurred. The following warning messages occurred:
Divided flow
Energy loss greater than 1.0
Energy equation could not be balanced and defaulted to critical.
Cross-section extended vertically.
Multiple critical depths calculated.
Conveyance ratio is less than 0.7 or greater than 1.4.
Inspection indicated that the modeling is accurate given the steep channel conditions.
Most of these errors force a critical solution which is reasonable for these steep
watercourses. A summary of errors is available in Appendix E.
5.8 Calibration.
None.
5.9 Final results.
5.9.1 Hydraulic analysis results.
The HEC-RAS modeling results were summarized in Appendix E.
5.9.2 Verification of results.
Existing floodplain maps are not available along the Canyon del Salto Wash. The new
map tends to follow the floodplain topography. The results suggest that the mapping is
reasonable.
Section 6: Erosion and Sediment Transport
6.1 Method description.
None – not applicable
6.2 Parameter estimation.
None – not applicable
6.4 Modeling considerations.
None – not applicable
6.5 Problems encountered during the study.
6.5.1 Special problems and solutions.
None – not applicable
6.5.2 Modeling warning and error messages.

19

None – not applicable
6.6 Calibration.
None – not applicable.
6.7 Final results.
6.7.1 Erosion and sediment transport analysis results.
None – not applicable
6.7.2 Verification of results.
None – not applicable
Section 7: Ratio of the top width of 100-yr and 25-yr floodplain
A map showing the cross sections with the ratio of the topwidth less than 1.25 is included
in Addendum 1. The average ration of 100-yr to 25-yr floodplain topwidth for the study
reaches are 1.11 for the Reach A (the reach runs through subbasin A) and 1.27 for the
Reach B.

20

91

288

. 52 8

2. 80

40
29

8

9

!
(

2920

80
29

4. 1

24

V
U

3030

285
0

3170

2830

28

31
60

78

27

10
28

2

84

298 4

V
U

2790

2860

10

V
U

3. 5

20

.9

99

281

47

2
291
1 . 04
0

321

V
U

Datum: NAVD 1988

2

57

933

V
U
10

V
U

20
29

51
1

8. 0

0
288

92

3130

4. 8

87

. 14

V
U
19

V
UU
V
28

36

1

5

7

3

. 52

3120

10
30

04

20
30

3

7

76

.9

62

278

0. 03

00
29

291
0

V
U
40

58

2900

Pima County Index Map

2920

285
0

2756.029

2860
50
28

28
40

28
30

28
80

2761.573

80
27

2930

282
0

2758.116
2760

6

2940

3144

29
90

28
90

2873

V
U

77

2810

70
28
2780

2850

0
284

Index Map Scale 1:1,500,000

2810

46

1

8
2950

5

2940

4

. 84
2760

2740
2740

90
27

8

27
60

2720

2760

50
27

2760

60
29

40
27

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

2760

. 14

3120

3140

16

89

2

20

29
20

2890.934
2829

V
U

Topo: 2008 Pima Association of Governments

22

80
28

27
80

Aerial : 2009 Landiscor Aerial Imagery

70
29

0

100 200

2750

88

20
27

U
V
V
U
40

3

32

27
20

. 51

9

2710

27
10

CP A
!
(

6. 1

52

2930

30
28

271

17

74

10
28

27

V
U
14

16

6

2720

278

68

5

27

Proposed 100-yr Floodplain

97

. 65

2760

0
272

44

. 51

. 61

.2

42

1

74

21

. 00

. 27

92

41

27

23

1. 2

9

3. 3

27

277

27

V
U

24

8

2

. 54

34

6

28

CP C
!
( CP B

2850

8. 94

27

26

276

27

0

. 10

4

Contour 10ft

26

80
29

V
U

2780

29
00

38

V
U

5

28

. 34

83 4

27

29

. 37

27

20

River

3

4

. 91

09

V
U

U
V
V
U
11
5

4

1

.7

28

2790

27

31

1

0
280

70

.3

13

00
28
10
28
20
28

27

37

18

281

51

2763.5

23

U
V
V
U

7. 18

.9

85

32

2

U
V
V
U
95

2751.29

274

42

U
V
V
U

276 5.

9
27

47

27

27

35

3. 7

2810 2820

V
U

V
U

. 70

.0

92

.2

278

3253

19

44

40

12

2754.112

274 9. 2

27

27

V
U

35

86

97

3

27

V
U

24

89

27

. 42

355

266 0

V
U

53

V
U

30

V
U
13

2750

70
27

63

88

48

27

21

69

V
U
16

16

15

2710

2710

2730

27
10
27

27

12

. 04

13

.5

11

9

2960

V U
U
V
27
20

11
9

2710

51

V
U

2790

V
U

22

19

V
U

18

V
U

V
U

63

337 0

277 6

4

V
U

V
U

257 8

V
U

241

20
28

RE

27

V
U
41

34

71

10
30

V
U

34

50
31

27

90

27

5

V
U

374

0
284

62

01

Cross Sections C

2830

10
28

430

.4

17

13

8

V
U
45

95

71

27

V
U

0
284

297
0

97

!
(

.2

.9

V
U

V
U

60
30

44

27

2

V
U
46

V
U

2890

7

. 30

2800

V
U
485

. 33

26

35

38

U
V
V
U
21

11

29

26

36

13

78

70

06

12

95

29

45

U
V
V
U
V
U
V
U

.7

73

2700

28

28

3

17

19

2

5

28

6

9

22

6

2850

62

49

291
0

N
O
T
G
N
DI

55

V
U

30
60

2820

. 23

55
37
. 80

V U
U
V

V
U

V
U

4

V
U

30
00

296
0

72

U
V
V
U

23

.9

.6

50

.9

2940

2910

2890

285
0

334
0

332
0

3100

2821.848

5. 2

1. 2

52

5
09

293
0

31
30
10
90

33
30

33
00

3270

331
0

33
40

319
0

283

2827.428

567 7

V
U
54

10

283

3

58

. 99

29

.
06

40

49

Cross Sections AB

9

2770

3340
31
20

. 73

28

. 96 5

245 1

66

5

2830

3400

29
20

3400

341
0

337
0
32
50

32
20

322
0

318
0

2870

0
0
324 323

3220

3250

283 3

5. 8

. 36

1. 3
28

282

0
306

11
6

53

. 55

. 36

49

.7

4

29

. 72

330 6

3070

3360

9. 2

40

43

28

61

.7

. 47

6

2
.5

58

60

V
U

0
295

10
33

284

283

577 5

2780

28

9

6079

3130

28
00

39

V
U

V
U

2820

3. 2

28

V
U

0
316

2890

6

28

5925

28
90

28

63

67

81

9
28

29

2920.522

6

V
U

30
50

3

2900

284

283

3010

. 10

4

7. 9

624 4

0
302

85

284

V
U
663

. 39 5

28

V
U
681

28

9

322
0

00
32

29

29

V
U

28

10
29

285 3

90
32

60
33

0
335
3210

287 5

7115

646

50
33

7

05

U
V
V
U
V
U

90
33

3330

0

2859.608

7286

80
30

80
28

3240

371

V
U
258

28

696

0
326
3240

V
U

V
U

3430

V
U

341
0

0
332

. 25 9

2864.248

7450

50
33

3230

286 7

27

0
342

333
0

759 8

90
31

Discharge Point

2910

3380
33

90

287

29
30

60
33

3280

3160

3040

2940

2930

90
32

2892.142

288 7

V
U
775

3150

34 5

Exhibit 1
100-year Floodplain
with cross sections
Canyon Del Salto Wash

2896.246

801 4
1

20
33

290 0.

8117

792

3140

96

320
0

820 5

319
0

20
32

290 1. 8

829 9

3200

3170

. 66

33
40

90
31

843 1

00
33

06

80
90 32
32
60
32

29

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

3230

3
3180

40
30

60
31

. 06

. 75

33
90

33
60

70
32

19

3250

40
32

3150

16

61

10
32

V
U
86

29

26

V
U

30
32

2990

3140

29

70

29
80

87

45

. 93
90

10
33

V
U

2. 6

39

30
33

293

3400

29
40

3

33
00

0
70 460
34
43
3
40 3 410
80
3
0 34
33
345
20
34
70
33

88

29

3350

V
UU
V
897

20

1

295
0

2970

3170

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

08/2011

gislib\rfcd\projects\imd\xavi\mdx\AKITSU\Canyon_Del_Salto\Canyon_Del_Salto_Exhibit_1.mxd

400
Feet

Appendix A: References
A.1 Data collection summary.
Include a list of previous studies, other applicable studies, published and unpublished
historical
flood information, and research contacts.
A.2 Referenced documents.
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
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
NOAA, 2006. NOAA Atlas 14, Precipitation Frequency Atlas for the United States:
Volume 1 - Version 4.0 The Semiarid Southwest. National Weather Service,
Hydrometeorological Design Studies Center. Available on the internet at:
http://hdsc.nws.noaa.gov/ hdsc/pfds/sa/az_pfds.html
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.
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). 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.

Appendix B: General Documentation & Correspondence
B.1 Special Problem Reports.
B.2 Contact (telephone) reports.
Provide copies of correspondence documenting notification of the client and the methods
of addressing any special problems described in Sections 4.4.1, 5.5 and 6.5.
B.3 Meeting minutes or reports.
B.4 General Correspondence.
B.5 Contract Documents.
Provide a copy of the contract Scope of Work, not financial documents.

Appendix C: Survey Field Notes
C.1 Survey field notes for aerial mapping control.
C.2 Survey field notes for hydrologic modeling.
C.3 Survey field notes for hydraulic modeling.

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)