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 .......................................................................................... 11
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 ...................................................12
3.1 Field Survey Information........................................................................................ 12
3.2 Mapping .................................................................................................................. 12
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 ...................................................................................... 13
4.2.3 Gage Data......................................................................................................... 13
4.2.4 Statistical Parameters ....................................................................................... 13
4.2.5 Precipitation ..................................................................................................... 13
4.2.6 Physical Parameters ......................................................................................... 13
4.3 Problems Encountered During the Study................................................................ 16
4.3.1 Special Problems and Solutions....................................................................... 16
4.3.2 Modeling Warning and Error Messages .......................................................... 16
4.4 Calibration............................................................................................................... 16
4.5 Final Results........................................................................................................ 16
4.5.1 Hydrologic Analysis Results........................................................................ 16
4.5.2 Verification results....................................................................................... 17
Section 5 Hydraulics.........................................................................................18
5.1 Method Description ................................................................................................ 18
5.2 Work Study Maps ................................................................................................... 18
5.3 Parameter Estimation .............................................................................................. 18
5.3.1 Roughness Coefficients ................................................................................... 18
5.3.2 Expansion and Contraction Coefficients ......................................................... 20
5.4 Cross-Section Description ...................................................................................... 20
5.5 Modeling Consideration.......................................................................................... 20
5.5.1 Hydraulic Jump and Drop Analysis................................................................. 20
5.5.2. Bridges and Culverts....................................................................................... 20

1

5.5.3 Levees and Dikes ............................................................................................. 20
5.5.4 Island and Flow Splits...................................................................................... 20
5.5.5 Ineffective Flow Areas..................................................................................... 20
5.6 Floodway Modeling ................................................................................................ 21
5.7 Problems Encountered ............................................................................................ 21
5.7.1 Special Problems and Solutions....................................................................... 21
5.7.2 Model Warnings and Errors............................................................................. 22
5.8 Calibration............................................................................................................... 22
5.9 Final Results............................................................................................................ 22
5.9.1 Hydraulic Analysis Results.............................................................................. 22
5.9.2 Verification of Results ..................................................................................... 22
Section 6 Erosion and Sediment Transport ...................................................23
Section 7 Draft FIS Report Data.......................................................................23
7.1 Summary of Discharges.......................................................................................... 23
7.2 Floodway Data ........................................................................................................ 23
7.3 Annotated Flood Insurance Rate Map .................................................................... 23
7.4 Flood Profiles.......................................................................................................... 23
List of Tables
Table 1 Methods used for the HEC-HMS analysis........................................................... 14
Table 2 Physical Parameters for the Sub-Basins .............................................................. 14
Table 3. Summary of the Hydrologic Analysis Results for Sub-Basins........................... 17
Table 4 Summary of the Hydrologic Analysis Results at the Concentration Points ........ 17
Table 5. Comparison of modeled 100-yr peak discharges to Regional Regression
Equation 13 peak discharges............................................................................................. 17
Table 6. Stage-storage relationship for overbank ponding located at River Station
1430.................................................................................................................................. 21
List of Figures
Figure 1.1 Sub-basins for the Trails End Wash .................................................................. 7
Figure 1.2 Study limits of the Trails End Wash LOMR study ........................................... 8
Figure 1.3 Hydrologic soil groups for the Trails End Wash watershed.............................. 9
Figure 4.2 Soil Classification Map ....................................................................................15
Figure 5.1. Trails End Wash Photo 1............................................................................... 19
Figure 5.2. Trails End Wash Photo 2............................................................................... 19
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 Trails End Wash
Exhibit 2 Annotated Flood Insurance Rate Map for the Trails End Wash
Attached CD Trails End 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 Trails End Wash (TRA) located in Pima County,
Arizona. The objective of the TDN and LOMR submission is to provide regulatory
discharge rates and floodplain limits along the Trails End Wash using better topographic,
hydrologic, and hydraulic data.
This TDN was prepared in accordance with the “Instructions for Organizing and
Submitting Technical Documentation for Flood Studies” prepared by the Arizona
Department of Water Resources, Flood Mitigation Section (Arizona State Standard, SSA
1-97) and FEMA Guideline. FEMA LOMR forms are included in this TDN.

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

Section 16 of the Pima County Ordinance describes the provisions for floodplain
regulation in Pima County.
This study has been prepared by the Pima County Regional Flood Control District
(RFCD):
Pima County Regional Flood Control District
97 East Congress, Tucson, AZ 85701
The project was prepared by:
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 Trails End Wash (TRA) is located within a Federal Emergency
Management Agency (FEMA)-designated “Zone A” flood-hazard area, as depicted on
FIRM Map Panel Numbers 04019C1618K and 04019C1619K (February 8, 1999). The
objective of the TDN and LOMR submission is to provide regulatory discharge rates and
floodplain limits along the Trails End Wash using better topographic, hydrologic, and
hydraulic data.
The study reach of the Trails End Wash is located primarily west of N. Silverbell Rd. and
extends from Section 20 of Township 13 South, Range 13 East into Section 29 of
Township 13 South, Range 13 East, in Pima County, Arizona.

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

5

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 discharges were calculated for floodplain mapping at three concentration
points along the Trails End Wash (TRA A, B, and C). The 100-yr discharge of the Trails
End Wash at N. Silverbell Rd. (TRA A) was found to be 2546.0 cfs with a drainage area
of 2.84 mi2.

6

VE
SIL
RB

Figure 1.1
Watershed Map
Trails End Wash

EL
L

SWEETWATER

CP_A

EL MORAGA

(
!
CP_B

(
!

TrailsEnd_ConcPoints
TrailsEnd_MainStream
TRE_contour20ft
Trails End_subbasins
TRA A
TRA B
TRA C
TRA D
TRA E
TRA F
TRA G
TRA H
(
!

CP_C

(
!
GORET

2008PAGclr01ft.ecw
IRONWOOD HILL

CAMINO DE OESTE

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.

SPEEDWAY
S

TE
GA

SS
PA

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

Scale 1:2000'

ANK

LAM
03/2010
\\gislib\rfcd\projects\imd\xavi\mxd\AKITSU\Trails_End_wash_Watershed_Fig1_1.mxd

VE
SIL
RB

EL MORAGA

ShadedX

L

SWEETWATER

EL

Study Limit

Figure 1.2
Study Limit Map
Trails End Wash

A

CP_A
ShadedX A
(
!
A

TRA A

CP_B

(
!

TrailsEnd_ConcPoints
TrailsEnd_MainStream
Subbasin
Existing Floodplain
ZONE A
ZONE AE
ZONE X - SHADED
(
!

TRA B
CP_C

(
!
GORET

TRA E

TRA C

2008PAGclr01ft.ecw

TRA F
TRA D

IRONWOOD HILL

Pima County Index Map

CAMINO DE OESTE

TRA G

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.

TRA H
SPEEDWAY
S

TE
GA

SS
PA

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

Scale 1:2000'

ANK

LAM
03/2010
\\gislib\rfcd\projects\imd\xavi\mxd\AKITSU\Trails_End_wash_Watershed_Fig1_2.mxd

VE
SIL
RB

Figure 1.3
Zoning Classification Map
Trails End Wash

EL
L

EL MORAGA

SWEETWATER

TRA A

Subbasin
Pima County Zoning
CB-1
CR-1
CR-2
CR-3
IR
SR
TUC
2008PAGclr01ft.ecw

TRA B

GORET

TRA E

TRA C

TRA F
TRA D

IRONWOOD HILL

Pima County Index Map

CAMINO DE OESTE

TRA G

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.

TRA H
SPEEDWAY
S

TE
GA

SS
PA

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

Scale 1:2000'

ANK

LAM
03/2010
\\gislib\rfcd\projects\imd\xavi\mxd\AKITSU\Trails_End_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 Trails End Wash (TRA) is located within a Federal Emergency
Management Agency (FEMA)-designated “Zone A” flood-hazard area, as depicted on
FIRM Map Panel Numbers 04019C1618K and 04019C1619K (February 8, 1999). The
study reach of the TRA is located primarily west of N. Silverbell Rd. and extends from
Section 20 of Township 13 South, Range 13 East into Section 29 of Township 13 South,
Range 13 East, in Pima County, Arizona.
The study reaches of the Trails End Wash contain coarse sand and cobble beds. Small
shrubs and trees grow in some areas of the channel bed, and desert brush dominates the
overbanks.

10

2.1.5 USGS Quad Sheets
Not available for this study.

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 rates at the concentration points along the study reach
were computed using HEC-HMS, assuming no base flow in the watersheds and no
transmission loss within the reaches. All reaches were modeled with HEC-RAS. 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 in Appendix B at the end of this TDN.

11

Section 3 Survey and Mapping Information
3.1 Field Survey Information
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 (Appendix C) and supplemented with field
survey methods that provide equal or better precision and accuracy to the Lidar data.
The following data was used in this TDN;
The aerial photo: 2008 PAG aerial photo
Projection: UTM, Zone 12
Units: International feet
The contour interval of the topographic map is 5 feet.

Section 4 Hydrology
4.1 Method Description
The 100-year peak discharges for the Trails End Wash were modeled using the U.S.
Army Corps of Engineers Computer Hydrologic Modeling System, (HEC-HMS) version
3.2. The Trails End Wash basin upstream of N. Silverbell Rd. was split into eight subbasins.
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

12

The topographic data was obtained from a 5-ft 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 Exhibit A.

4.2.2 Watershed Work Map
Eight sub-basins were delineated for the Trails End Wash basin. The 100-year peak
discharge was calculated for three concentration points (CP A, B, C) and used in the
HEC-RAS hydraulic analysis for the floodplain maps (Exhibit A).

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 Trails End Wash and therefore no Bulletin 17B
analysis was used for this TDN.

4.2.5 Precipitation
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 Trails End 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 (Latitude 32.2506°, Longitude -111.0607°). 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 1 and 2. As mentioned in 4.1, all the methods and parameters were
determined based on Tech-018. Table 1 summarizes the method used for the HEC-HMS
analysis.

13

Table 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. 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 velocity for
channel was calculated using Manning’s equation. The detail of the Tc calculation is
included in Appendix D.
Table 2 Physical Parameters for the Sub-Basins
Area
Impervious Vegetation
Sub-basin
CN
(sq mi)
Area (%)
Cover (%)
TRA A
0.125
86.0
8.0
20
TRA B
0.316
88.4
24.1
20
TRA C
0.079
86.0
18.6
20
TRA D
0.562
88.6
23.4
20
TRA E
0.364
90.3
25.2
20
TRA F
0.124
87.0
24.8
20
TRA G
0.372
90.8
9.2
20
TRA H
0.899
90.9
10.2
20

Lag Time
(min)
19.0
14.3
15.7
22.9
16.9
18.3
18.5
27.8

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:

14

Figure 4.2
Soil Classification Map
Trails End Wash

EL MORAGA

SWEETWATER

TRA A
LV
SI
L
BE
ER
L
Subbasin

TRA B

Soil Classification
Soil Group: A (100%), ARIZO-RIVERWASH COMPLEX, 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: C (47%) D (53%), PANTANO-GRANOLITE COMPLEX, 5 TO 25 PERCENT SLOPES

GORET

Soil Group: C (53%) D (47%), PALOS VERDES-JAYNES COMPLEX, 2 TO 8 PERCENT SLOPES
Soil Group: D (100%), ANKLAM-CELLAR-ROCK OUTCROP COMPLEX, 15 TO 55 PERCENT SLOPES

TRA E

TRA C

2008PAGclr01ft.ecw

TRA F
TRA D

IRONWOOD HILL

Pima County Index Map

CAMINO DE OESTE

TRA G

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.

TRA H
SPEEDWAY

TE
GA

AS
SP

S

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

ANK
LA

Scale 1:2000'

M
03/2010
\\gislib\rfcd\projects\imd\xavi\mxd\AKITSU\Trails_End_wash_Watershed_Fig4_2.mxd

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 the HEC-HMS;
•

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 Trails End Wash were
determined using HEC-HMS. The results are summarized in Tables 3 and 4. CP B 2

16

refers to the junction in the HEC-HMS model that receives flow from only the reach
included in the hydraulic analysis and the TRA B sub-basin. The junction labeled CP B
is the same location as CP B 2 but includes all incoming reaches at concentration point B
and the TRA B sub-basin. The discharge at CP B 2 was used for the hydraulic analysis
of the study reach above concentration point B.
Table 3. Summary of the Hydrologic Analysis Results for Sub-Basins.
Peak
Area
Rainfall
Runoff
Sub-basin
Discharge
(Sq mi) Depth (in) Volume (in)
(cfs)
TRA A
0.125
3.16
1.80
201.3
TRA B
0.316
3.16
2.00
671.3
TRA C
0.079
3.16
1.80
143.1
TRA D
0.562
3.16
2.01
891.8
TRA E
0.364
3.16
2.16
756.8
TRA F
0.124
3.16
1.88
214.0
TRA G
0.372
3.16
2.20
746.2
TRA H
0.899
3.16
2.21
1377.2

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

Location

Area
(Sq mi)

Rainfall
Depth (in)

CP A

At Silverbell Rd.

2.84

2.91

1.87

2546.0

2:21

CP B

2.72

2.92

1.89

2543.5

2:16

CP B 2
CP C

1.98
1.46

2.92
3.03

1.86
2.02

1749.5
1645.7

2:17
2:09

Runoff
100-yr Peak
Volume (in) Discharge (cfs)

Time to
Peak

4.5.2 Verification results
The modeled discharges were found to be relatively close to the Regional Regression
Equation 13 (RRE) (Thomas et al., 1997) peak discharges (Table 5).

Table 5. Comparison of modeled 100-yr peak discharges to Regional Regression
Equation 13 peak discharges.
Area
Qp100 HMS
Qp100 RRE
CP
Location
2
(cfs)
(cfs)
(mi )
CP A
At Silverbell Rd. 2.84
2546.0
2426.5
CP B
2.72
2543.5
2362.6
CP B 2
1.98
1749.5
1951.6
CP C
1.46
1645.7
1612.7

17

Section 5 Hydraulics
5.1 Method Description
The hydraulic modeling for the Trails End Wash 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 in the Silverbell Road, Grant Road to Ina Road Design Concept Report (2009)
(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 downstream boundary
condition for the reach was assumed to be normal depth with a slope estimated as the bed
slope between the two farthest downstream cross sections.
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.

5.2 Work Study Maps
The work study map for the Trails End Wash is included in Exhibit B.

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). A Manning’s n value of 0.045 was assigned for the channel based on the
sand and cobble bed material with dense vegetation in some areas, and a value of 0.060
was assigned for the overbanks based on the desert brush (Figures 5.1 and 5.2).

18

Figure 5.1. Trails End Wash Photo 1. A location of the Trails End Wash containing
cobbles and dense vegetation at Lloyd Bush Rd., farther upstream in the watershed than
Silverbell Rd.

Figure 5.2. Trails End Wash Photo 2. A location of the Trails End Wash with a
primarily sand channel and scattered vegetation immediately downstream of Silverbell
Rd.

19

5.3.2 Expansion and Contraction Coefficients
The Trails End 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. 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 Trails End 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
Ineffective flow option was modeled in situations where:
• The floodplain areas are not hydraulically connected
• There is a contraction or expansion of the effective flow area.

20

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

5.7 Problems Encountered
5.7.1 Special Problems and Solutions

At three locations along the Trails End Wash near Silverbell Rd., the 100-yr discharge
was not contained in the channel and a discharge could leave the channel without
returning to the main flow path. As a result, River Stations 2093, 1030, and 684 have
“hanging” cross sections. These locations were modeled in HEC-RAS using lateral
structures along the overbank of the channel. The discharge leaving the channel was
determined using the optimization feature in HEC-RAS for the lateral structures. The
“break out” flow paths were modeled as separate reaches of the Trails End Wash using
the discharge determined from the optimization feature. Two of these “break out” flow
paths (River Station 2200 “Breakout 1,” and River Station 830 “Breakout 2”) are
proposed as a Shallow 100 yr Flooding Zone where flow depth is less than one foot.
The third location of a break out leads to a depression in the floodplain of the Santa Cruz
(River Station 1430, “Overbank Ponding”). The stage-storage relationship for this
depression was determined in a GIS using the 2-ft contour lines and the area
measurement tool. The volume of the depression was calculated by assuming a conical
volume change for increases in elevation and area (Table 6). The volume of flow leaving
the channel was found by calculating the area of the top of the hydrograph that was
determined to leave the channel by the lateral structure optimization feature. The peak
discharge in the channel at Silverbell Rd. was determined as 2546.04 cfs, and the peak
discharge leaving the channel into the depression was found as 20.28 cfs. The volume
leaving the channel was calculated as 0.079 ac-ft by finding the area of the hydrograph
with discharge exceeding 2525.76 cfs, or 20.28 cfs lower than the maximum discharge.
The depth of the flow stored in the depression was determined as 1.24 ft from the
calculated volume and the stage-storage relationship. The depression was found to
contain the volume of flow leaving the channel and the depression was added to the
floodplain map as a proposed Zone A.
Table 6. Stage-storage relationship for overbank ponding located at River Station 1430.
Elevation Depth (ft) Area (ac)
2254
2256
2258
2260

0
2
4
6

0.003
0.192
0.749
1.229

Increase in
Volume (ac-ft)
0.000
0.128
0.870
1.461

Total Volume
(ac-ft)
0.000
0.128
0.998
2.459

21

River Station 495 is a “hanging” cross section with an ineffective area that extends over a
wastewater treatment pond near the Santa Cruz river and no right bank extending above
the water surface elevation ; however, the cross section is within the current FEMA Zone
A for the Santa Cruz River and should not affect the proposed Zone A for the Trails End
Wash.

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
• Cross sections end points were extended vertically for the computed cross
section
A summary of errors is available in Appendix E.

5.8 Calibration
The model was not calibrated in this study.

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

5.9.2 Verification of Results
The floodplain limit produced in this LOMR study was compared to the existing FEMA
floodplain limit. The proposed limits are similar to the existing FEMA floodplain limit,
but provide additional detail. This similarity to the existing FEMA floodplain limit
suggests that the results are reasonable.

22

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 Silverbell Rd. (CP A) was determined as 2546 cfs for the drainage
area of 2.84 square miles. The discharges along the flow path upstream of Silverbell Rd.,
CP B 2 and CP C, were found to be 1749.5 and 1645.7 respectively with drainage areas
of 1.98 and 1.46 square miles.

7.2 Floodway Data
Not applicable.

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

7.4 Flood Profiles
Flood profiles are included in Appendix E.

23

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

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Transportation Technical Services Division makes no
claims regarding the accuracy of the information depicted
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Topo: 2008 Pima Association of Government
Vertical Datum: NAVD 1988

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SWEETWATER

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\Trails_End_watershed_100yrFINALexh1.mxd

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ZONE A

Exhibit 2
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04019C1618 K
Trails End Wash

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the collective accuracy of these databases on the date
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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
97 East Congress Street - 3rd Floor
Tucson. Arizona 85701-1207
(520)243-1800 - FAX (520)243-1821
http://www.rfcd.pima.gov

Streets
FIRM X-Sections

125

250

500
Feet

ç ç ç ç ç Base Flood Elevations
Proposed Floodplain
LOMRs
FIRM - Flood Insurance Rate Map
Sections
Jurisdictions
Existing Floodplain Zone
A
AE
AO
X
X (SHADED)

Pima County Index Map

gislib\rfcd\projects\imd\xavi\mdx\AKITSU\Trails_End\Trails_End_watershed_Anno_FIRM8X11.mxd

A.1 Data Collection Summary
Aldridge, B. and J. Garrett. 1973. Roughness Coefficients for Stream Channels in
Arizona. US Department of the Interior Geological Survey. Tucson, AZ.
Arizona Department of Water Resources, Flood Mitigation Section
“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

040078

City of Tucson

AZ

04019C

2.

Panel No.
0005D
0220G
1618K
1619K
1619K

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

a. Flooding Source: Trails End 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: Trails End 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

040078

City of Tucson

AZ

04019C

2.

Panel No.
0005D
0220G
1618K
1619K
1619K

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

a. Flooding Source: Trails End 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: Trails End 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: Trails End 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.)
2.84

Effective/FIS (cfs)
N/A

Revised (cfs)
2546.0

Near N. Grannen Rd.

2.72

N/A

2543.5

Near Wilma Dell Rd.

1.46

N/A

1645.7

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

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

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

B. HYDRAULICS
1. Reach to be Revised
Description

Cross Section

Water-Surface Elevations (ft.)
Effective

Downstream Limit

Confluence with the Santa Cruz
River

St#62.17

Upstream Limit

Goret Rd.

St# 7662.95

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:

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

Floodway Run

Datum

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

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