Section 1 Introduction ........................................................................................4
1.1
Purpose.............................................................................................................. 4
1.2 Project Authority....................................................................................................... 4
1.3 Project Location ........................................................................................................ 5
1.4 Hydrologic and Hydraulic Methods.......................................................................... 5
1.4 Acknowledgments..................................................................................................... 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 Local Technical Reviewer: ............................................................................. 10
2.1.4 Reach Description............................................................................................ 10
2.1.5 USGS Quad Sheets .......................................................................................... 10
2.1.6 Unique Conditions and Problems .................................................................... 11
2.1.7 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......................................................................................................... 12
4.2.4 Statistical Parameters ....................................................................................... 12
4.2.5 Precipitation ..................................................................................................... 12
4.2.6 Physical Parameters ......................................................................................... 13
4.3 Problems Encountered During the Study................................................................ 14
4.3.1 Special Problems and Solutions....................................................................... 14
4.3.2 Modeling Warning and Error Messages .......................................................... 14
4.4 Calibration............................................................................................................... 15
4.5 Final Results........................................................................................................ 15
4.5.1 Hydrologic Analysis Results........................................................................ 15
4.5.2 Verification of Results ................................................................................. 15
Section 5 Hydraulics.........................................................................................16
5.1 Method Description ................................................................................................ 16
5.2 Work Study Maps ................................................................................................... 16
5.3 Parameter Estimation .............................................................................................. 16
5.3.1 Roughness Coefficients ................................................................................... 16
5.3.2 Expansion and Contraction Coefficients ......................................................... 18
5.4 Cross-Section Description ...................................................................................... 18
5.5 Modeling Consideration.......................................................................................... 18
5.5.1 Hydraulic Jump and Drop Analysis................................................................. 18
5.5.2. Bridges and Culverts....................................................................................... 18

1

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 ................................................................................................ 19
5.7 Problems Encountered ............................................................................................ 19
5.7.1 Special Problems and Solutions....................................................................... 19
5.7.2 Model Warnings and Errors............................................................................. 19
5.8 Calibration............................................................................................................... 19
5.9 Final Results............................................................................................................ 19
5.9.1 Hydraulic Analysis Results.............................................................................. 19
5.9.2 Verification of Results ..................................................................................... 19
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 4. 1. Methods used for the HEC-HMS analysis...................................................... 13
Table 4. 2. Physical Parameters for the Sub-Basins. ........................................................ 14
Table 4.3. Summary of the Hydrologic Analysis Results for Sub-Basins........................ 15
Table 4. 4. Summary of the Hydrologic Analysis Results at the Concentration Points. .. 15
Table 4.5. Comparison of modeled peak discharge to the Regional Regression Equation
13 peak discharge.............................................................................................................. 15
List of Figures
Figure 1. 1. Sub-basins for the Del Cerro Wash ................................................................. 7
Figure 1.2. Study limits of the Del Cerro Wash LOMR study ........................................... 8
Figure 1. 3. Hydrologic Soil Group .................................................................................... 9
Figure 5. 1. Del Cerro Wash Photo 1. The center of the flow path of the Del Cerro Wash
immediately upstream of Silverbell Rd. ........................................................................... 17
Figure 5.2. Del Cerro Wash Photo 2. The center of the flow path of the Del Cerro Wash
immediately downstream of Silverbell Rd. ...................................................................... 17

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

2

Exhibit
Exhibit 1 100-yr floodplain limits for the Del Cerro Wash
Exhibit 2 Annotated Flood Insurance Rate Map for the Del Cerro Wash
Attached CD Del Cerro Wash TDN with supporting models and GIS data.

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

1.2 Project Authority
The State of Arizona has delegated the responsibility to each county flood control district
to adopt floodplain regulations designed to promote the public health, safety and general
welfare of its citizenry as provided under the Arizona Revised Statutes, Title 48, Chapter
21, Article 1, Sections 48-3601 through 3627. More specifically, A.R.S. 3609 directs
county flood control districts to adopt floodplain regulations that:
A. Regulate all development of land, construction of residential, commercial or
industrial structures or uses of any kind which may divert, retard or obstruct flood
water and threaten public health or safety or the general welfare; and
B. Establish minimum flood protection elevations and flood damage prevention
requirements for uses, structures and facilities which are vulnerable to flood
damage; and
C. Comply with state and local land use plans and ordinances, if any.
In conformance with A.R.S. 3609, this ordinance provides for protection of the
public health safety and welfare by regulation of flood and erosion hazard areas to
control flood hazards and prevent repetitive loss from flood damage.
D. The flood hazard areas of Pima County are subject to periodic inundation which
may result in loss of life and property, create health and safety hazards, disrupt
commerce and governmental services, require extraordinary public expenditures for
flood protection and relief, and impair the tax base, all of which adversely affect the
public health, safety, and general welfare.
E. These flood losses are caused by the cumulative effect of obstructions in areas of
special flood hazards which increase flood heights, flow velocities, and cause flood
and erosion damage. Uses that are inadequately flood-proofed, elevated, or
otherwise protected from flood damage, also contribute to the flood loss. (Ord. 2005
FC-2 § 2 (part), 2005).
4

Section 16 of the Pima County Ordinance describes the provisions for floodplain
regulation in Pima County.
This study has been prepared by the Pima County Regional Flood Control District
(RFCD):
Pima County Regional Flood Control District
97 East Congress, Tucson, AZ 85701
The project was prepared by:
Dave Stewart, EIT, Civil Engineering Assistant.
Pima County Regional Flood Control District
97 East Congress, Tucson, AZ 85701

1.3 Project Location
The study reach of the Del Cerro Wash (DCR) contains Federal Emergency Management
Agency (FEMA)-designated “Zone A” flood-hazard areas, as depicted on FIRM Map
Panel Numbers 04019C1616K (February 8, 1999). The existing “Zone A” flood hazard
area is not consistent with current topographic data. The objective of the TDN and
LOMR submission is to provide regulatory discharge rates and floodplain limits along the
Del Cerro Wash using better topographic, hydrologic, and hydraulic data.
The study reach of the DCR is located primarily west of N. Silverbell Rd. in Sections 17,
18, 19, and 20 of Township 13 South, Range 13 East in Pima County, Arizona (Fig. 1).

1.4 Hydrologic and Hydraulic Methods
The hydrologic analysis was performed to determine proposed regulatory discharge rates
at concentration points along the DCR using the U.S. Army Corps of Engineers
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 (“100-year”
discharge rates). Hydraulic analysis was performed to delineate floodplain limits along
the study reach of the Del Cerro Wash using the Hydrologic Engineering Center’s River
Analysis System.
No duplicate effective model is being provided because the proposed map revision
represents a complete replacement of the Del Cerro wash based on better topographical
data and revised hydrology. The revised hydrology is based on newer rainfall values
from NOAA Atlas 14.

5

The annotated FIRM panel data was generated digitally. All shape files for the Flood
Hazard Zones, Cross Sections, LOMR boundary boxes came from FEMA digital data.
The digitally produced annotated FIRM panels were generated based on discussions
between Terry Hendricks, Chief Hydrologist at Pima County Flood Control, and Joe
Kuechenmeister, MT-2 Revisions Manager at Michael Baker Jr, Inc., about the problems
with pasting paper LOMRs

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

1.5 Study Results
The regulatory discharge for floodplain mapping was calculated at Silverbell Rd. for the
Del Cerro Wash (DCR A). The 100-yr discharge of the Del Cerro Wash at N. Silverbell
Rd. (DCR A) was found to be 1182.0 cfs with a drainage area of 1.232 mi2.

6

Figure 1.1
Watershed Map
Del Cerro Wash
CP A
CAMINO DE OESTE

(
!
(
!

Del Cerro CP
10ft Contour
Del Cerro Stream

EL CAMINO DEL CERRO
L
EL
RB
VE
SIL

Del Cerro subbasin
DCR A
DCR B
DCR C
DCR D
Aerial Photo: 2008 Pima Association of Governments

Pima County Index Map

Index Map Scale 1:5,250,000

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

Scale 1:1000

SW

EE
TW
AT
E

R

EL MORAGA

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.

400

200

0

400 Feet

03/2010
\\gislib\rfcd\projects\imd\xavi\mxd\AKITSU\Del_Cerro_wash_Watershed_Fig1_1.mxd

I10

RI
VE
R

EX
IT
25
N
1O

CAMINO DE OESTE

Figure 1.2
Study Limit
Del Cerro Wash

RIVER

MP
RA
SA
CA
DE
AN
GR

Study Limit

!
(

CP A
0
I1

!
(
0
I1

EL CAMINO DEL CERRO

Del Cerro Stream

RUTHRAUFF RUTHRAUFF

Study Limit

Del Cerro subbasins

0
I1
EX
IT

DCR A

Del Cerro CP

25
2

Existing FEMA Floodplain

ON
M
RA
P

ZONE A

I10
GE
NT
TA
CE
ON
SS
FR
NE
SI
BU

L
EL
RB
VE
SIL

DCR C

ZONE AE

ER

ZONE X - SHADED
Aerial Photo: 2008 Pima Association of Governments

DCR D

DCR B

CAMINO DE OESTE

EL MORAGA

SWEETWATER

Pima County Index Map

GORET
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

2,000

1,000

0

2,000 Feet

Scale 1:2000

03/2010
\\gislib\rfcd\projects\imd\xavi\mxd\AKITSU\Del_Cerro_wash_Watershed_Fig1_2.mxd

Figure 1.3
Soil Classification
Del Cerro Wash

CP A
CAMINO DE OESTE

!
(

!
(

Del Cerro CP
Del Cerro Stream

EL CAMINO DEL CERRO

Del Cerro subbasins
L
EL
RB
VE
SIL

DCR A

Del Cerro Soil Classification
Soil Group: B (100%), ANTHONY FINE
SANDY LOAM, 0 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: B (82%) C (18%), PINALENOSTAGECOACH-PALOS VERDES COMPLEX,
10 TO 35 PERCENT SLOPES

Aerial Photo: 2008 Pima Association of Governments

DCR C

Pima County Index Map

DCR B
DCR D
SWEETWATER

EL MORAGA

Index Map Scale 1:5,250,000

1,000

500

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 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 1:1000

1,000 Feet
03/2010
\\gislib\rfcd\projects\imd\xavi\mxd\AKITSU\Del_Cerro_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 Dave Stewart, Civil Engineering Assistant.

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 Del Cerro Wash (DCR) is located within a Federal Emergency
Management Agency (FEMA)-designated “Zone A” flood-hazard area, as depicted on
FIRM Map Panel Numbers 04019C1616K (February 8, 1999). The study reach of the Del
Cerro Wash is located primarily west of N. Silverbell Rd. in Sections 17, 18, 19, and 20
of Township 13 South, Range 13 East in Pima County, Arizona (Fig. 1).
The study reaches of the DCR contain coarse sand and cobble beds. Small shrubs and
trees grow in some areas of the channel bed, and desert brush covers the overbanks.

2.1.5 USGS Quad Sheets
The study area is better described by the FEMA maps, which are referenced in Section
2.1.7.

10

2.1.6 Unique Conditions and Problems
There were no unique conditions or problems.

2.1.7 Coordination of Peak Discharges
The 100-year regulatory discharge rate at the concentration point was 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. The discharge rates were acceptable
per Suzanne Shields, Director of the Pima County Regional Flood Control District, and
Andrew Dinauer, Engineering Administrator of the City of Tucson.

2.2 FEMA Forms
The FEMA MT-2 forms are included at the end of this TDN.

Section 3 Survey and Mapping Information
3.1 Field Survey Information
No field survey was performed for this study.

3.2 Mapping
The topographic data for the hydrology was obtained using 2008 Pima Associations of
Governments (PAG) Light Detection and Ranging (LiDAR) data in Geo-RAS and
ArcGIS. A raster was created from the 2008 LiDAR data with 5’ cells and used with
Geo-RAS.
For the hydraulic analysis, the triangular irregular network (TIN) developed by HDR in
the Silverbell Road, Grant Road to Ina Road Design Concept Report (2009) was used.
The TIN was developed from 2005 Lidar and supplemented with field survey methods
that provide equal or better precision and accuracy to the Lidar data (Appendix C).
The following data was used in this TDN;
The aerial photo: 2008 PAG aerial photo
Projection: UTM, Zone 12
Units: International feet
The contour interval of the topographic map is 2 feet.
Vertical Datum: NAVD 1988

11

Section 4 Hydrology
4.1 Method Description
The 100-year peak discharges for the Del Cerro Wash were modeled using the U.S. Army
Corps of Engineers Computer Hydrologic Modeling System, (HEC-HMS) version 3.2.
The HEC-HMS model requires parameters for 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
The topographic data was obtained from a 5’ cell raster created from 2008 PAG LiDAR
data. ArcGIS was used to delineate watersheds from the raster and determine the drainage
areas of each sub-basin. The composite watershed map is included in Figure 1.1.

4.2.2 Watershed Work Map
Four sub-basins were delineated for the Del Cerro Wash basin. The 100-year peak
discharge was calculated for DCR A and used in the HEC-RAS hydraulic analysis for the
floodplain maps.

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

4.2.4 Statistical Parameters
No data record was available for the Del Cerro Wash and therefore no Bulletin 17B
analysis was used for this TDN.

4.2.5 Precipitation

12

According to Tech-018, the design storm should be used that produces the higher
discharge between the 100-yr 3-hour SCS Type II distribution and the 100-yr 24-hr SCS
Type I distribution. The 100-yr 3-hour SCS Type II distribution was found to produce the
higher discharge on the Del Cerro Wash.
NOAA Atlas 14, upper 90% confidence interval precipitation frequency estimate values
(NOAA 14 rainfall) were used to determine 3-hour and 24-hour point rainfall depths for
the watershed. The point rainfall depth for the 3-hour storm was obtained for the
coordinates of the watershed centroid. An areal reduction factor was applied to
watersheds larger than 1 square mile as noted in Tech-018.

4.2.6 Physical Parameters
The physical parameters for the sub-basins and reaches of the HEC-HMS model are
summarized in Tables 4.1 and 4.2. As mentioned in Section 4.1, all the methods and
parameters were determined based on Tech-018. Table 4.1 summarizes the method used
for the HEC-HMS analysis.
Table 4. 1. Methods used for the 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

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 photographs. 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 sheet flow, shallow concentrated flow and channel flow.
The Tc for sheet flow was estimated using the kinematic wave equation. The 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 channel velocity
was calculated using Manning’s equation. The Tc calculations are included in Appendix
D.

13

Table 4. 2. Physical Parameters for the Sub-Basins.
Impervious Vegetation
Sub-basin Area (sq mi)
CN
Area (%) Cover (%)
DCR A
0.393
85.7
16.7
20
DCR B
0.295
85.5
12.9
20
DCR C
0.414
85.9
16.5
20
DCR D
0.129
86.4
16.8
20

Lag Time
(min)
18.6
26.5
18.3
13.9

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 sub-reaches 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 the average flow velocity, L is the reach length, Vw is the velocity of the
flood wave (a conversion factor of 1.5 is used for natural channels), K is the 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 sub-reach 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 HEC-HMS;

14

•

The “3-hr SCS Type II” gage with data interval of 5 minutes was interpolated to a
simulation time interval of 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 DCR were determined
using HEC-HMS. The results are summarized in Tables 4.3 and 4.4.
Table 4.3. Summary of the Hydrologic Analysis Results for Sub-Basins.
Rainfall Runoff Volume Peak Discharge
Sub-basin Area (Sq mi)
Depth (in)
(in)
(cfs)
DCR A
0.393
1.62
576.8
2.98
DCR B
0.295
2.98
1.61
335.7
DCR C
0.414
2.98
1.64
620.1
DCR D
0.129
2.98
1.68
235.0

Table 4. 4. Summary of the Hydrologic Analysis Results at the Concentration Points.
Drainage Rainfall
Runoff
Time to
CP
Location
Qp (cfs)
2
(in)
Volume
(in)
Peak
Area (mi )
Del Cerro Wash
DCR A
1.23
2.98
1.62
1182.0
1:43
at Silverbell Rd.
4.5.2 Verification of Results
The modeled 100-yr peak discharge was found to be lower than the Regional Regression
Equation 13 (Thomas et al., 1997) peak discharge (Table 5).
Table 4.5. Comparison of modeled peak discharge to the Regional Regression Equation
13 peak discharge.
Qp100 HMS
Qp100 RRE (cfs)
CP
Location
Area (mi2)
(cfs)

DCR A

Del Cerro Wash
at Silverbell Rd.

1.23

1182.0

1443.4

15

Section 5 Hydraulics
5.1 Method Description
The hydraulic modeling for the DCR was performed using HEC-RAS, Version 4.0,
HEC-GeoRAS, Version 4.1.1, and ArcGIS, Version 9.2.
The topographic data was obtained using a triangular irregular network (TIN) developed
by HDR from 2005 Lidar and supplemented with survey (Appendix C). The locations of
the stream centerlines were determined using ArcGIS with the contour lines from the
topographic data 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 sections, reach lengths). Other parameters for the steady-state analysis, such
as the Manning’s n-values, obstructions, and ineffective flow areas were manually
entered into HEC-RAS. The hydraulic data obtained from HEC-RAS were exported to
ArcGIS to delineate the floodplain in the study area.
The hydraulic analysis was performed in the area currently mapped as FEMA Zone A. A
steady flow analysis was performed to determine 100-year water surface elevations in the
study area by using HEC-RAS. The HEC-RAS data and shape files (contour lines, flow
path, cross section lines, study watersheds, concentration points, sub-watersheds,
hydrologic soil groups, proposed floodplain limit) used in the analysis are included in
Appendix D with an attached CD.
A normal depth downstream boundary condition was assumed using the average bed
slope calculated from the two most downstream cross sections.

5.2 Work Study Maps
The work study map for the Del Cerro Wash is included in Exhibit 1.

5.3 Parameter Estimation
5.3.1 Roughness Coefficients
Manning’s n values were determined in the field and using 2008 PAG aerial photo based
on USGS publications for Manning’s n values in southern Arizona (Phillips and
Tadayon, 2006). The channel bank stations were assigned in HEC-RAS to be wide
enough to provide an accurate hydraulic radius for the channel. Therefore, overbank
vegetation outside of the sand bed is included in the HEC-RAS channel flow path for the
100-yr flood and is included in the Manning’s n value assigned for the channel.

16

A Manning’s n value of 0.045 was assigned for the sand bed and channel due to the dense
vegetation in the flow path, and a value of 0.060 was assigned for the overbank areas due
to the desert brush and shallow flow depth (Figures 5.1 and 5.2).

Figure 5. 1. Del Cerro Wash Photo 1. The center of the flow path of the Del Cerro Wash
immediately upstream of Silverbell Rd.

Figure 5.2. Del Cerro Wash Photo 2. The center of the flow path of the Del Cerro Wash
immediately downstream of Silverbell Rd.

17

5.3.2 Expansion and Contraction Coefficients
The Del Cerro Wash is assumed to have relatively gradual transitions, and the default
values for the expansion and contraction coefficient of 0.30 and 0.10 were used
respectively.

5.4 Cross-Section Description
Cross-section locations were determined primarily based on the channel topography from
the TIN and 2008 PAG LiDAR data. Cross sections were placed at a spacing of
approximately 100 ft or less. The cross-section lines were drawn to be perpendicular to
flow paths in ArcGIS.

5.5 Modeling Consideration
5.5.1 Hydraulic Jump and Drop Analysis
No hydraulic jumps or hydraulic drops were modeled in this study.

5.5.2. Bridges and Culverts
There are no bridges located in the floodplain study reach of the Del Cerro Wash.

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

5.5.4 Island and Flow Splits
No islands or split flows were modeled in the study.

5.5.5 Ineffective Flow Areas
The ineffective flow areas were used in situations where:
• The floodplain areas are not hydraulically connected
• There is a contraction or expansion of the effective flow area either from an
obstruction in the flowpath or from the channel banks.

18

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

5.7 Problems Encountered
5.7.1 Special Problems and Solutions
There were no special problems encountered in this study.

5.7.2 Model Warnings and Errors
The FEMA guidelines require hydraulic models to simulate subcritical flow conditions.
The HEC-RAS modeling produced warnings at some cross sections stating that:
• The energy equation could not be balanced within the specified number of
iterations
• The energy loss was greater than 1.0 ft between cross sections
• The conveyance ratio is less than 0.7 or greater than 1.4
• Multiple critical depths were found
• Divided flow was computed and
• The program defaulted to critical depth when the water surface was
calculated below critical depth at some locations.”
A summary of warnings 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 HEC-RAS modeling results are summarized in Appendix E.

5.9.2 Verification of Results

19

The floodplain limit produced in this LOMR study was compared to the existing FEMA
floodplain limit. The proposed floodplain limit is reasonable based on the existing
FEMA floodplain limit and provides greater accuracy based on contour lines from the
updated topographic data.

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 peak discharge at DCR A was calculated as 1182.0 cfs.

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.

20

22
20
22

2220

Exhibit 1
100-year Floodplain
with cross sections
Del Cerro Wash

10
22

22

0

50 2260

4
22

22

20

20

22

Study Limit
10

2280

2210
2210

47

22
22

19

222 6

V
U

22

. 697

25

. 07

424

22

72
7

222

8. 9

22
7. 9

31

8

5

0

225

60

22

0
22

80

22
22

22

30

4527

4432

3976

4076

4176

4275

437
4

U
V
V
U
V
VU
U
V
U
V
U

V
U

29

22
37

22
21

23
56

74

. 042

22

226

69

7. 18

5

V
U

303
5

4

228 7

. 31

22

70

8. 4

L
EL

228 7

. 474

4582

V
U

V
U

50

RB

3

22

VE
SIL

U
V
V
U
V
U

21
48

V
U

226

7

228 9.22

V
U

47

4621

209
0

.6

10

V
U

7

38
24

. 15

2289.503

4

. 18

55

23

54

75
. 25

V
U

31
36

4

22

2279.697

2
228 1.20

228 2.519

43
228 3. 4

. 861

228

V
U

22
2280

50

2270

V
U

38
33

92

.9
94

23

V
U

03

06
34

23

2280.48

80

32
37

69

18

.8

8

8

447
6

.4

.6

73

69

3

V
U

71

72

22

5. 6

. 14

227 7.94

229 1. 7

01

172

228 4

6. 45

4

70

22

7

227

6. 04

8

23

V
U

97
54

2278.996

2

8

6

35

228 8.

22

227

3. 88

5. 55

6. 31

.2

7. 84

03

2350

. 90

22

23

22
54

22

80

198
4

27
.6

8

1

.6
60

71
34

229

229

23

36

58

22
. 533

U
V
V
U

5
229

229

23

2390

2. 70

22

225 1. 1

2

58

84

4

67

00

05

2280

16
35

3829

44

3876

3926

3747

13

V
U
V
U
V
U
U
V

.6

3
366

48

5
355

.0

1
361

06

07

V
U
V
U
V
U
U
V

11
.1

23

2260

Pima County Index Map
2250

36
09
.7

2

54

2290

8

66

23

14

.
11
35

0

.1

Aerial Photo: 2008 Pima Association of Governments
Topo: 2005 Pima Association of Governments
with Supplemental Survey
Vertical Datum: NAVD 1988

.5

.
11

.0

236

13

70

72

. 86

.8

23

10

23
23
23

23

5. 0

.9

226

4. 4

2290

.3

75

23

.5

9

56

226

226 5

09

13

55

47

V
U

2290.486

2. 85
5. 05

98

02
23

23

23

0

. 19

22

52

22

23

97
55

V
U
97
58

V
U
V
V U
U
V
U
VU
U
V
U
V

8
23

63

.1

.2

51

22

4690

V
U

4795

229

22

30
55

V
U
U
V

V
U

97
56

97
57

0

41
60
97
59
46
61
97
60 46
61 7
9
61

V
U

97
62

63
37

229

1
495

20

70

V
U

7
483

7
489

7
499

7
509

7
519

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

3
528

V
U
97
53

V
U

23

23

4
23

62

61

.0

1759

1859

1. 48

225

Proposed 100yr Floodplain

V
U

969

225

60

1659

22

289
4

2935

50

22

Existing Zone AE

1559

29
224 9.93

225 0.

2280

226

V
U

85
25

25
40

27
36

U
V
V
U
V
U

219
6

2280

283
5

23

224 9. 6

2036

V
U

1513

73

2260

2290

U
V
V
U
V
U

2340

00

224 5.8

224 9.069

Contour 10 foot

1459

2248.531

1938

2350

23

. 251

4.

1408

224 6.367
2247.052
2247.951

98
11

1821

26
78

2330

224 5

1708

26
24

EL CAMINO DEL CERRO

224

607

Stream
Contours 2 foot

2260

2280
90
22

2

3

1614

0
230

0
31

4
22

2

5
. 46

22

0
233
0
233

2

2
. 16 34
2
4
.7
4
22
42
04
22 24 4.
2

58
11

0
32

22

09

20

0
28

1. 8

.
42

Cross Sections
22

2

1
110

4
22

23

30

9
104

22

U
V
V
VU
U
VU
U
V
V
U
V
U
V
U
V
U

1
123
0 313
126 1
1357

1002

90

247

04

V
U

1. 1

352

224

0

469

63

364

223

V
U

9. 9

.
223 9

601

223

3

V
U

.0
223 9

V
U

2238.558

967

22

2230
6

2270

29

. 16

223 8.045

913

0

. 684

.9

20

857

29

(
!

07

Discharge Point

22

223 7

.5

22

CP A

31

0

2280

36

22

0
23

6
22

2270

22

(
!

30

.0

U
V
V
U
V
U
V
U
V
U
V
U
V
U
V
U
V
U
V
U
V
U
V
U
V
U
V
VU
U
806

20

22

34
3 0 22

V
U

2

30

V
U

0
64

222

20

30

134

80

30

22

22

U
V
V
U

222 6.1

Study Limit

23

00

2280

231

0

Index Map Scale 1:1,500,000
229

0

23

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.

30
30

23

20

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

0

100 200

400
Feet

2350

2350

23

23

70

23

24

00

2390

2360

2380

23

30

60

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

09/2010

\\gislib\rfcd\projects\imd\xavi\mdx\AKITSU\Del_Cerro_watershed_100yrFINALexh1.mxd

ççççççç
ç

çç

ç ççç

ççç çç

ççç
ç ççç ç

7

2229

222

ç ççç ç

CAMINO DE LA TIERRA çççç 22
ççç çç 2 6
ç

4

22
2

ççççç2225
ççç çç
ç çççç

3
22
2

E

P
AM

PIMA COUNTY

LOMR Case Studies

SAHARA

I10

FIRM - Flood Insurance Rate Map
GH
HI

I10

çç
çççççç
ç
ç
ç
ç
ç
çççç

EMERALD

RT
SE
DE

G

F

R
FF

AY
W

CA

Floodways
PALMYRA

Sections

ZONE X

SA
GR

ZONE X

çç
ççççç
ç
ç
ç
ç
ç
ççç
çççççç

Jurisdictions

AN

ç ç ççç

ç ççç

ççç ççççç ç

çççç

ççç

ççççç ççççç

ç

çççççççç

ç ç çç
çççç223
çççç0
ççç

"
)

çççççççç

1 çç
22ç3ç çç çç

çç
çççççç

çç

ZONE X - SHADED

"
)
EK

çççççççççççççççççç
2232

PIMA COUNTY

"
) ççççççççççççççççç EL CAMINO DEL CERRO
EL

EL

"
)
EM

B OW

çç

ç
36 ççç
22ççççç

Pima County Index Map

çççç

GO

LD

RAIN

D
DA

EL

DO

çççç
çççç2247
çççç
çççç
ç

çççç

ççç

ççççç
ççççç

çççç
çççç
ç

ççççç
ççççç

NZ
A

"
)

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

DE

ZONE X - SHADED

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.

INO
B

CA

CAM

REV

E

ZONE X

CA

24

LLE

C AM

INO
P

INTO

çççç

RES

CO

ççç2çç245
ççççç
çç

20

çççç
çççç
çççç
ç

ZONE X-(SHADED)

ççççç
ç

RK

ççç224
ççç 1
ççç

YO

ççççç

W
NE

ç

çççç

SA

NEWLAND

INU O

VIA S

ççç

çç

)"

HIL
LS

ç
39ççç
22çççç

EN

OF

ZONE A

çç

O

SUNSET

ZONE A

ç

LOST HORIZON

ZONE X

CERRITOS

2234

ç
ççççç
çç ççç

L

RIC

ZONE A

ççç

çç
3 5 ççç
22ççççç

CITA

SUNSET HILLS

TE

RB

PASEO DE LOS CERRITOS

MON

VE
SIL

PLA

DEL
CITA

PLA

BARGHOUT

WILD LIFE

EL CAMINO DEL CERRO

19

VER

X - (SHADED)

DIAMOND

çççç
ç

çççç
ç

ççç çççççç

çççç
çççç
ç

ççç2ç2çç2ç9çç

çç çç

ççççç çççç

ççççç 2
çççç231
ççççç
çççç

çççççççç

çç ççççççç

ç 2227

ççççççççç
ç

EI

VISTA DEL CERRO RANCH

P
M
RA
N
O
2
P
25
AM
IT
FR
EX OF
0
I1 252
T
XI

"
)

EJ

TUCSON
ZONE X

X

P
M
RA
N
O
MP
2
RA
25
FF
IT
2O
EX
0
25
I1
IT
EX
I10

PETRANEK

E
I10

CAMINO DE OESTE

AO

DE

Proposed
100 year
Floodplain

AE

AN

CAMINO DE OESTE

"
)

EH

JAD E

GR

çç
ççç
ç
ç
ç
ZONE AEççç
çç
26çççç
2
ç
2 çç
çççç
ç
ç
ç
çççç
ç
ç
ç
çç
çççç
ç
ç
ç
çç

ççç
ççç
ç
ç
çç

ççççççççç

ç

A

SA

ççç

çççç

CURTIS

CURTIS

17

CA

çç
çççç

ççç
ç çç ç

ççç
ççç ç

çç
2 3 ççç
22ççç ç

Existing Floodplain Zone

I10

"
)
EG

çç

I10

DE

18

ç çç
ç ççç

çççç

Base Flood Elevations
Proposed Floodplain

MP

çççç
çççççç

1O
25

RA

EF

çççççççççççççççç

ZONE X
2 çç
22ç2ççççç

FIRM X-Sections

XIT

ç

ç

"
)

JUSNIC

E
I10

ççç çç

çççç

MP N
RA O
N 1
25

ç çç
ççççç

8 ççç
22ç1ççççç

ç
çççç
çç çççç

O
51

çç çç

ZONE X-(SHADED)
çç
çççç

çç çç ç

T
XI

ç
çç çç çç
ç
ç
ç
ç
ç
çç

8 ç çç ç
22çç1çç çç ç

ç
ç çç çç ç

Streets

"
)

"
)

ç
ççç
ççç
ççç
ççç221
ççç 3
ç ççç
ççç
ççç
ççç
çççç

RO
UA
G

ZONE X-(SHADED)

T2
XI

SA

çççç

0E

ççç

"
)

7
22
0
EB

"
)

TS
SU
N

IST
A
EV
RD
VE

ççç
çççç
ç
ç
ç
ççç
çççç
ç
ç
ç
ççç
çççç
ç
ç
ç
ç
16 ç ç
22ççççç
ç
ç
çççç

SUNSET

çç ççç ççç çççç

SUNSET

RIVER

çç ççç ççç ççç ç

çç çç

HE
IGH

ZONE X - SHADED

çç çççç
ççççç

SET

ER

E
AG
NT

ç
çççç
ç
ç
ç
ç
çççç
çççç

TRES NOGALES

I1 E
I10

PA
LO

RIV

RO

D

ççç
çççç
ç
ç
ç
çççç
çç

"
)

EE

F
I10

T W OO

çç
ççç

çç

çç

E
AG
NT

"
)
ED

DESER

çç
ççç
ççç
çç
ççç
ççç

ççç
ç
ççç
çç

E

ççççç

ççççç

RO

ç

ç
çç çç ç
çç çççç

ç
ç çççç
ç
ç
ç
ç
çç

Exhibit 2
Annotated Flood
Insurance Rate Map
04019C1616 K
Del Cerro Wash

ER

LOMR Case 04-09-0465X Effective Date4/22/2004

SUNSET

HIDDEN WOOD

RIV

P

08

F
I10

SUNSET

AMG
TRA
ON
N
51
RO

0
221çççççç

çç
ççççççç
ç
ç
ç
ç
ç
ç
ççç

ççççç
ççççççç

2
IT

"
)
EC

F
EX
I1I100

AZ
A

çç
çç ç

ççç

B

07 MARANA

PL

çççç
çç ççç

ççç
çç ççç

"
)

ç

NS

ET

çç çç
ççç
ç

çççç

ççç
ç

çç
çç

SU

ç
çççç

ççç

çççç

ç
ççççççç
ç
ç
ç
ç
ç
ç
ç
ççççççç

ç

ç ç ç ç ç ç çç çç ç ç

ççç
ççç
ççç
ççç
ççç

SUNSET DUNES

çç
ççççççç
ç
ç
ç
ç
ç
ç
çç

çççç

ççççççç
ççççççç
ççççççç

çççç
ç
ççç
ççç
ççç
ççç
ççç
çç
çç
ç
ç
ççç
ç
08 ç ç
22ççççç

çççç
çççç

ç
ççççç
ç
ç
ç
ç
çç

çç
ç ç çç

ç
çç çç

VE

NA

"
)
EO

A

ZONE A

EP

B
OX
O

500

W
R
ST

M
CA

O
IN

"
)
EQ

O

E
NU

DR

ISC

OL

250

0

2250ç çççç çççç çç

çç ççç
çç çççç çççç ç

ç
22ç5ç1ç ççççç çççç ç

çççççççç

ççç çççç ççç

ç çççç çççç
çç çççç çççç

çççç ççç çççç

çççç çç

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

gislib\rfcd\projects\imd\xavi\mdx\AKITSU\Del_Cerro\Del_Cerro_watershed_Anno_FIRM28x40.mxd

500 Feet

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
“Requirements for Flood Study Technical Documentation” SS1-97, November 1997
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). 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
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 General Documentation and
Correspondence

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

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

OVERVIEW & CONCURRENCE FORM
PAPERWORK BURDEN DISCLOSURE NOTICE

Public reporting burden for this form is estimated to average 1 hour 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.

A. REQUESTED RESPONSE FROM DHS-FEMA
This request is for a (check one):
CLOMR:

A letter from DHS-FEMA commenting on whether a proposed project, if built as proposed, would justify a map revision, or
proposed hydrology changes (See 44 CFR Ch. 1, Parts 60, 65 & 72).

LOMR:

A letter from DHS-FEMA officially revising the current NFIP map to show the changes to floodplains, regulatory floodway or
flood elevations. (See 44 CFR Ch. 1, Parts 60, 65 & 72)

B. OVERVIEW
1.

The NFIP map panel(s) affected for all impacted communities is (are):

Community No.
Ex: 480301
480287
040073

Community Name
City of Katy
Harris County
Pima County

State
TX
TX
AZ

Map No.
480301
48201C
04019C

Panel No.
0005D
0220G
1616K

Effective Date
02/08/83
09/28/90
02/08/99

040078

City of Tucson

AZ

04019C

1616K

02/08/99

2.

a. Flooding Source: Del Cerro Wash
b. Types of Flooding:

Riverine

Coastal

Alluvial fan

Shallow Flooding (e.g., Zones AO and AH)

Lakes

Other (Attach Description)

3.

Project Name/Identifier: Del Cerro Wash

4.

FEMA zone designations affected: A (choices: A, AH, AO, A1-A30, A99, AE, AR, V, V1-V30, VE, B, C, D, X)

5.

Basis for Request and Type of Revision:
a.

The basis for this revision request is (check all that apply)
Physical Change

Improved Methodology/Data

Regulatory Floodway Revision

Coastal Analysis

Hydraulic Analysis

Hydrologic Analysis

Weir-Dam Changes

Levee Certification

Alluvial Fan Analysis

New Topographic Data

Other (Attach Description)

Base Map Changes
Corrections
Natural Changes

Note: A photograph and narrative description of the area of concern is not required, but is very helpful during review.
b. The area of revision encompasses the following structures (check all that apply)
Structures:

DHS- FEMA Form 81-89,DEC 07

Channelization

Levee/Floodwall

Bridge/Culvert

Dam

Fill

Other (Attach Description)

Overview & Concurrence Form

MT-2 Form 1 Page 1 of 2

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

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

OVERVIEW & CONCURRENCE FORM
PAPERWORK BURDEN DISCLOSURE NOTICE

Public reporting burden for this form is estimated to average 1 hour 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.

A. REQUESTED RESPONSE FROM DHS-FEMA
This request is for a (check one):
CLOMR:

A letter from DHS-FEMA commenting on whether a proposed project, if built as proposed, would justify a map revision, or
proposed hydrology changes (See 44 CFR Ch. 1, Parts 60, 65 & 72).

LOMR:

A letter from DHS-FEMA officially revising the current NFIP map to show the changes to floodplains, regulatory floodway or
flood elevations. (See 44 CFR Ch. 1, Parts 60, 65 & 72)

B. OVERVIEW
1.

The NFIP map panel(s) affected for all impacted communities is (are):

Community No.
Ex: 480301
480287
040073

Community Name
City of Katy
Harris County
Pima County

State
TX
TX
AZ

Map No.
480301
48201C
04019C

Panel No.
0005D
0220G
1616K

Effective Date
02/08/83
09/28/90
02/08/99

040078

City of Tucson

AZ

04019C

1616K

02/08/99

2.

a. Flooding Source: Del Cerro Wash
b. Types of Flooding:

Riverine

Coastal

Alluvial fan

Shallow Flooding (e.g., Zones AO and AH)

Lakes

Other (Attach Description)

3.

Project Name/Identifier: Del Cerro Wash

4.

FEMA zone designations affected: A (choices: A, AH, AO, A1-A30, A99, AE, AR, V, V1-V30, VE, B, C, D, X)

5.

Basis for Request and Type of Revision:
a.

The basis for this revision request is (check all that apply)
Physical Change

Improved Methodology/Data

Regulatory Floodway Revision

Coastal Analysis

Hydraulic Analysis

Hydrologic Analysis

Weir-Dam Changes

Levee Certification

Alluvial Fan Analysis

New Topographic Data

Other (Attach Description)

Base Map Changes
Corrections
Natural Changes

Note: A photograph and narrative description of the area of concern is not required, but is very helpful during review.
b. The area of revision encompasses the following structures (check all that apply)
Structures:

DHS- FEMA Form 81-89,DEC 07

Channelization

Levee/Floodwall

Bridge/Culvert

Dam

Fill

Other (Attach Description)

Overview & Concurrence Form

MT-2 Form 1 Page 1 of 2

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: Del Cerro 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
Silverbell Rd.

Drainage Area (Sq. Mi.)
1.23

Effective/FIS (cfs)
N/A

.

Revised (cfs)
1182.0

N/A
N/A

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

Precipitation/Runoff Model
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

Confluence with the Santa Cruz
River

St#93.58

Upstream Limit

N. Via Sinuosa Rd..

St# 6337.23

Proposed/Revised

2. Hydraulic Method/Model Used
HEC-RAS

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:

Floodway Run

Datum

N/A
Plan Name: N/A
File Name:
N/A Plan Name:
DelCerroWash Plan Name: Plan 1
File Name:
Plan Name:
N/A
Plan Name:
File Name:
Plan Name:
N/A
Plan Name:
File Name:
Plan Name:
N/A
Plan Name:
File Name:
Plan Name:

NAVD 88

* 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

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

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

Appendix D: Hydrology
Supporting documentation is included as digital data on the CD.

Appendix E: Hydraulics
Supporting documentation is included as digital data on the CD.

Appendix F: Erosion and Sediment Transport Analysis
Supporting Documentation
None