Section 1 Introduction ........................................................................................4 1.1 Propose...................................................................................................................... 4 1.2 Project Authority....................................................................................................... 4 1.3 Project Location ........................................................................................................ 5 1.3 Hydrologic and Hydraulic Methods.......................................................................... 5 1.4 Acknowledgment ...................................................................................................... 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 .................................................................... 10 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 Spatial Parameters............................................................................................ 12 4.2.5 Precipitation ..................................................................................................... 13 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 .......................................................... 15 4.4 Calibration............................................................................................................... 15 4.5 Final Results........................................................................................................ 15 4.5.1 Hydrologic Analysis Results........................................................................ 15 4.5.2 Verification results....................................................................................... 15 Section 5 Hydraulics.........................................................................................16 5.1 Method Description ................................................................................................ 16 5.2 Work Study Maps ................................................................................................... 17 5.3 Parameter Estimation .............................................................................................. 17 5.3.1 Roughness Coefficients ................................................................................... 17 5.3.2 Expansion and Contraction Coefficients ......................................................... 17 5.4 Cross-Section Description ...................................................................................... 17 5.5 Modeling Consideration.......................................................................................... 17 5.5.1 Hydraulic Jump and Drop Analysis................................................................. 17 5.5.2. Bridges and Culverts....................................................................................... 18 2 5.5.3 Levees and Dikes ............................................................................................. 18 5.5.4 Island and Flow Splits...................................................................................... 18 5.5.5 Ineffective Flow Areas..................................................................................... 18 5.6 Floodway Modeling ................................................................................................ 18 5.7 Problems Encountered ............................................................................................ 18 5.7.1 Special Problems and Solutions....................................................................... 18 5.7.2 Model Warnings and Errors............................................................................. 18 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 ...................................................19 Section 7 Draft FIS Report Data.......................................................................19 7.1 Summary of Discharges.......................................................................................... 19 7.2 Floodway Data ........................................................................................................ 20 7.3 Annotated Flood Insurance Rate Map .................................................................... 20 7.4 Flood Profiles.......................................................................................................... 20 List of Tables Table 1 Methods used for a HEC-HMS analysis.............................................................. 13 Table 2 Physical Parameters for the Sub-Basins .............................................................. 14 Table 3 Summary of the Hydrologic Analysis Results for Sub-Basins............................ 15 Table 4 Summary of the Hydrologic Analysis Results at the Concentration Points ........ 15 Table 5 Comparison of a peak discharge.......................................................................... 16 List of Figures Figure 1.1 Watershed Map.................................................................................................. 7 Figure 1.2 Study limits........................................................................................................ 8 Figure 1.3 Soil Classification.............................................................................................. 9 Appendix A: References Appendix B: FEMA MT-2 Forms, General Documentation and Correspondence Appendix C: Survey Field Notes Appendix D: Hydrologic Analysis, Supporting Documents Appendix E: Hydraulic Analysis, Supporting Documents Appendix F: Erosion Analysis, Supporting Documents Exhibit Exhibit 1 100-yr floodplain limit for the Sweetwater Wash Exhibit 2 Annotated Flood Insurance Rate Map for the Sweetwater Wash 3 Section 1 Introduction 1.1 Propose This Technical Data notebook (TDN) has been prepared for a Letter of Map Revision (LOMR) application for a portion of the Sweetwater Wash (SWT) located in Pima County, Arizona. The objective of the TDN and LOMR submission is provide regulatory discharge rates and floodplain limits along the Sweetwater 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: Akitsu Kimoto, Ph.D., C.F.M., Principal Hydrologist. Pima County Regional Flood Control District 97 East Congress, Tucson, AZ 85701 1.3 Project Location The study reach of the Sweetwater Wash (SWT) is located within a Federal Emergency Management Agency (FEMA)-designated “Zone A” flood-hazard area, as depicted on FIRM Map Panel Numbers 04019C1616K and 1618K (February 8, 1999). No documented hydraulic analyses were found to determine the “Zone A”, and the existing “Zone A” depiction is not consistent with current topography. The objective of the TDN and LOMR submission is provide regulatory discharge rates and floodplain limits along the Sweetwater Wash using better topographic, hydrologic, and hydraulic data. The study reach of the Sweetwater Wash is located primarily west of Silverbell Rd. Section 19 and 20, Township 13 South, Range 13 East, Pima County, Arizona (Fig. 1.1). The Sweetwater Wash enters study limit from the west and flows east until it converges with the Santa Cruz River. The study limit for the Sweetwater Wash is from Sweetwater Dr. to the confluence with the Santa Cruz River in Section 19 of Township 13 South, Range 13 East. 1.3 Hydrologic and Hydraulic Methods Hydrologic analysis was preformed to determine proposed regulatory discharge rate at Silverbell Rd using U.S. Army Corps of Engineers Computer Hydrologic Modeling System, HEC-HMS. Parameterization followed guidelines developed by Pima County Regional Flood Control District and described in Technical Policy 018 (Tech 018, Appendix A). The proposed regulatory discharge is a flow rate that has a 1-percent chance of being equaled or exceeded each year (“100-year” discharge rates). Hydraulic analysis was performed to delineate floodplain limit along the study reach of the Sweetwater Wash using U.S. Army Corps of Engineers Computer Backwater Model, HEC-RAS and FLO-2D. A flow split occurs approximately 1500 feet upstream of the 5 Silverbell Rd. The flow becomes distributary after crossing Silverbell Rd. FLO-2D was used to delineate a floodplain limit in the distributary area (approximately 1700 feet from Silverbell Rd. to a confluence with the Santa Cruz River). HEC-RAS was used to map a floodplain at the upstream of the distributary area. 1.4 Acknowledgment This study relied on assistance of RFCD GIS staff, who were integral to the development of the models and maps. 1.5 Study Results The regulatory peak discharge rate was calculated at Silverbell Rd (CP A; Fig. 1.3). The estimated regulatory discharge rate is 5622 cubic feet per second (cfs) with a drainage area of 4.8 square mile at CP A (at Silverbell Rd.). The discharge at CP A was used for the steady flow analysis with HEC-RAS. The hydrograph at CP A input to the FLO-2D model. The HEC-RAS and FLO-2D results showed that the existing FEMA floodplain (Zone A) is narrower than a floodplain limit proposed in this study. 6 2920 2200 224 0 2200 3040 EL MORAGA 336 0 3400 3080 3360 3,000 1,500 39 60 40 24 2640 26 00 S PA AT 3,000 Feet G 0 0 288 27 60 S ES 276 0 0 80 272 26 3000 60 25 260 0 SPEEDWAY 3040 376 0 26 00 Index Map Scale 1:5,250,000 40 24 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 1:3000 2480 ANK 2840 2800 26 80 2560 2720 3080 30 00 0 344 2760 3720 20 31 0 272 34 00 3200 39 20 364 38 80 3960 0 3400 3480 3000 3040 3360 4000 3 40 720 00 2240 2320 24 00 28 00 00 26 2680 0 392 80 36 3240 2800 24 00 272 0 40 34 40 28 27 60 28 40 3120 384 0 276 0 IRONWOOD HILL 2880 32 40 36 00 28 80 28 40 2760 Pima County Index Map 24 80 320 0 316 0 3600 35 20 3440 3400 60 37 32 00 39 20 29 60 2720 3760 2960 28 40 33 60 3600 31 60 3840 60 29 28 00 4120 416 40 00 0 0 272 40 28 0 428 26 40 2920 20 29 38 80 2560 2640 40 28 0 404 3960 38 00 60 41 3560 0 280 276 0 284 0 3400 3040 3000 00 34 20 33 3280 20 39 3440 00 38 3760 0 388 0 348 40 40 26 00 2800 26 40 3320 20 35 2600 2720 24 40 2640 2760 Aerial Photo: 2008 Pima Association of Government GORET 2560 2600 2920 SWT G SWT H 27 20 2920 36 40 4160 ( ! 2720 0 328 2600 40 26 CP G ! ( CP D SWT F 25 20 28 00 3680 CP C 2560 CAMINO DE OESTE 2760 40 26 26 80 2920 CP F ( CP E ! 0 400 4040 280 0 SWT E 26 40 0 332 3960 38 00 284 0 20 31 SWT D 2800 27 60 2720 31 60 42 40 00 28 2960 SWEETWATER 25 60 3360 40 40 60 41 0 432 60 35 3720 24 80 25 60 2680 SWT B 256 0 372 0 340 0 SWT A SWT C CP B 00 24 ! ( 00 26 272 0 3600 2800 3840 3880 22 80 23 60 27 60 26 40 28 40 0 260 272 0 39 20 40 24 SWT Subbasins LL 20 31 2240 0 236 2400 20 25 27 20 27 60 27 60 268 0 0 240 SWT CP contour 40 feet CP A ( ! BE 00 32 0 380 3520 236 0 2440 25 60 28 80 2360 2800 292 0 26 80 280 0 80 26 0 6 2 4 80 22 2400 40 22 3200 26 00 2400 ( ! River 2240 2240 R VE SIL 3520 372 0 40 26 80 22 EL CAMINO DEL CERRO 2360 40 26 3440 0 436 4120 4200 60 23 20 25 3240 40 26 3200 80 40 00 44 2680 20 27 00 30 29 20 0 268 E AG NT 2720 20 23 O 0 272 FR 80 30 28 80 2920 27 60 28 80 26 40 300 0 2840 60 29 60 23 80 26 0 I1 284 0 20 23 Figure 1.1 Watershed Map Sweetwater Wash 40 22 28 00 SUNSET RIV ER I1 0 40 22 2640 2800 34 00 0 240 2480 00 28 0 324 00 24 25 20 00 22 2840 80 28 2520 20 27 28 80 2640 0 232 40 22 2680 2480 2760 I1 0 60 25 26 00 40 22 20 27 40 24 2640 LAM 2600 26 80 2640 04/2010 2520 \\gislib\rfcd\projects\imd\xavi\mxd\AKITSU\Swetwater_wash_Watershed_Fig1_1.mxd I10 SUNSET I10 Figure 1.2 Study Limit Map Sweetwater Wash RO CAMINO DE OESTE F I10 E AG NT VE SIL RB EL CAMINO DEL CERRO EL L Study Limit CP A ( ! Study Limit SWT A CP B ( ! SWT B CP E CP F ! ( EL MORAGA SWT E SWT C SWEETWATER CP D CP C ! ( SWT CP River SWT Subbasins2 Existing Floodplain ZONE A ZONE AE ZONE X - SHADED ( ! 2008PAGclr01ft.ecw SWT D CP G ( ! SWT H GORET SWT F SWT G Pima County Index Map CAMINO DE OESTE IRONWOOD HILL Index Map Scale 1:5,250,000 SPEEDWAY 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 3,000 1,500 0 3,000 Feet Scale 1:3000' S AS SP TE GA NN KI ANK LAM EY 03/2010 \\gislib\rfcd\projects\imd\xavi\mxd\AKITSU\Sweetwater_wash_Watershed_Fig1_2.mxd Figure 1.3 Soil Classification Sweetwater Wash EL CAMINO DEL CERRO CP A ( ! R VE SIL ( SWT CP ! River SWT Subbasins2 Soil Classification LL BE SWT A Soil Group: B (100%), ANTHONY FINE SANDY LOAM, 0 TO 3 PERCENT SLOPES CP B Soil Group: B (100%), ANTHONY GRAVELLY SANDY LOAM,1 TO 3 PERCENT SLOPES ( ! SWEETWATER 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 ! ( EL MORAGA SWT B CP E CP F SWT E CP D CP C SWT C CP G Soil Group: B (82%) C (18%), ! ( PINALENO-STAGECOACH-PALOS VERDES COMPLEX, 10 TO 35 PERCENT SLOPES Soil Group: C (47%) D (53%), PANTANO-GRANOLITE COMPLEX, 5 TO 25 PERCENT SLOPES Soil Group: D (100%), ANKLAM-CELLAR-ROCK OUTCROP COMPLEX, 15 TO 55 PERCENT SLOPES 2008PAGclr01ft.ecw SWT D ( ! SWT H GORET SWT F SWT G Pima County Index Map CAMINO DE OESTE IRONWOOD HILL 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 T GA S PA ES This product is subject to the Department of Transportation Technical Services Division's Use Restriction Agreement. Pima County Regional Flood Control District Scale 1:3000' NN KI EY 3,000 1,500 0 3,000 Feet ANKLAM 03/2010 \\gislib\rfcd\projects\imd\xavi\mxd\AKITSU\Sweetwater_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 Akitsu Kimoto, Ph.D, C.F.M., Principal Hydrologist. 2.1.3 Local Technical Reviewer: Terry Hendricks, C.F.M, Chief Hydrologist Planning and Development Division, Pima County Regional Flood Control District 97 East Congress, Tucson, AZ 85701 (520) 243-1800 2.1.4 Reach Description The study reach of the Sweetwater Wash is located within a Federal Emergency Management Agency (FEMA)-designated “Zone A”, as depicted on FIRM Map Panel Numbers 04019C1616 K and 1618K (February 8, 1999). The study reach of the Sweetwater Wash is located primarily west of Silverbell Rd., Pima County, Arizona (Fig. 1.1). The study reach of the Sweetwater Wash is primarily composed of a channel with cobble, and the bottom of the reach is relatively clean with vegetation cover. The overbank of the reach is covered with desert brush. 2.1.5 USGS Quad Sheets Not available for this study 2.1.6 Unique Conditions and Problems 10 Hydrograph at Silverbell Rd. was generated with HEC-HMS. Flow in the distributary flow area at the downstream of Silverbell Rd. was modeled with FLO-2D. Flow at the upstream of the distributary area was modeled with HEC-RAS. 2.1.7 Coordination of Peak Discharges The 100-year regulatory discharge rate at the Silverbell Rd. was computed using HECHMS, assuming no base flow in the watersheds and no transmission loss within the reaches. The hydraulic data used to derive parameters for HEC-HMS was obtained using HEC-RAS. The discharge rate was acceptable per Suzanne Shield, Director of the Pima County Regional Flood Control District. 2.2 FEMA Forms The FEMA MT-2 forms are included in Appendix B. Section 3 Survey and Mapping Information 3.1 Field Survey Information None. 3.2 Mapping The topographic data was obtained using HEC-GeoRAS and ArcGIS. Digital Elevation Model (DEM) derived from 2008 Light Detection and Ranging (LiDAR) data was used for the HEC-RAS analysis (approximately 1700 feet upstream of Silverbell Rd. to the upstream end of the existing FEMA Zone A), while Digital Terrain Model (DTM) derived from 2005 LiDAR was used for the FLO-2D analysis (from a confluence with the Santa Cruz River to approximately 1700 feet upstream of the Silverbell Rd.). The DTM with the 2005 LiDAR was developed by HDR in the Silverbell Road, Grant Road to Ina Road Design Concept Report (2009). It includes break lines, which is considered to be more accurate topographic data set. The sealed document for the field survey of the break lines is included in Appendix C. The DTM is available only in the downstream area of the Sweetwater Wash. The documentation showing that 2008 Lidar data set is FEMAcompliant is included in Appendix C. The following data was used in this TDN; The aerial photo: 2008 PAG aerial photo Projection: UTM, Zone 12 Units: International feet 11 The contour interval of the topographic map is 2 feet. Section 4 Hydrology 4.1 Method Description The 100-year peak discharges for the eight subbasins of the Sweetwater Wash (SWT A, B, C, D, E, F, G, and H; Fig. 1.3) were calculated using U.S. Army Corps of Engineers Computer Hydrologic Modeling System, (HEC-HMS) version 3.4. The HEC-HMS model requires the parameters regarding rainfall, topography, soil, vegetation, and channel characteristics to determine runoff volume and peak discharge. Those parameters were determined by following 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 Subbasin boundaries were delineated using the hydrology function of ArcGIS with 2008 LiDAR Data. A 5-ft contour map derived from 2008 LiDAR was used to make sure if the subbasin delineation was reasonable. 4.2.2 Watershed Work Map A watershed work map is included in Exhibit 1. Eight subbasins were delineated for the HEC-HMS hydrologic analysis. A 100-yr peak discharge at CP A (at Silverbell Rd.) was estimated in this study. The peak discharge was used as input for the HEC-RAS and FLO-2D analysis. 4.2.3 Gage Data No gage data were used in this TDN. 4.2.4 Spatial Parameters No spatial parameters were used in this TDN. 12 4.2.5 Precipitation According to the Tech-018, the 3-hour storm shall be used as rainfall data in the HECHMS model in case that a time of concentration (Tc) is equal or less than three hours. A 3-hour storm was selected for a peak discharge calculation for the Sweetwater Wash, since Tc was less than 3 hours in all the subbasins. A point 3-hour rainfall depth at the coordinates of the centroid of the watershed was obtained from NOAA Atlas 14, upper 90% confidence interval precipitation frequency estimate (NOAA 14 rainfall). Areal reduction factor was applied to watersheds larger than 1 square mile, as described in Tech-018. The 3-hour rainfall depth for the Sweetwater Wash watershed is 2.69 inches. The areal reduction factor of 0.87 was applied to CP A. 4.2.6 Physical Parameters The physical parameters for the subbasins and reaches of the HEC-HMS model were summarized in Tables 1 and 2. As mentioned in 4.1, all the methods and parameters were determined following Tech-018. Table 1 summarizes the method used for a HEC-HMS analysis. Table 1 Methods used for a HEC-HMS analysis Rainfall Depth Rainfall Distribution Rainfall Loss Time of Concentration Transform Routing Selected Method NOAA 14, upper 90% Confidence Interval 3-hr SCS Type II Storm SCS Curve number SCS Segmental Method SCS Unit Hydrograph Modified-Puls The SCS Curve Number (CN) method was utilized as a rainfall loss method in the HECHMS model. The CN was determined using the Curve Number table associated with the PC Hydro User Guide (Arroyo Engineering, 2007) and a Hydrologic Soils Group map. The CN was not adjusted for rainfall intensity or antecedent moisture conditions in the HEC-HMS model. The SCS Unit Hydrograph method was used as a transform method. Impervious cover was determined using the 2008 PAG aerial photograph and Table 3 in the PC Hydro User Guide (Arroyo Engineering, 2007). The combination of the kinematic wave method and the U.S. Natural Resources Conservation Service (NRCS) segmented Time of Concentration (Tc) calculation method (USDA-NRCS, 1986) was used to determine Tc, following the recommendation on Tech-018. The Tc was calculated by summing the travel time for sheet flow, shallow concentrated flow and channel flow. The Tc for sheet flow was estimated using the kinematic wave equation. Manning’s roughness coefficient for sheet flow was obtained using Table 3-1 in Technical Release 13 55, Urban Hydrology for Small Watersheds (USDA-NRCS, 1986). HEC-GeoRAS and HEC-RAS were used to estimate average velocity of channels. The detail of the Tc calculation is included in Appendix D. Table 2 Physical Parameters for the Sub-Basins Sub-Basin SWT A SWT B SWT C SWT D SWT E SWT F SWT G SWT H Area (sq mi) 0.45 0.55 0.22 0.18 0.62 1.49 1.05 0.24 CN 82.9 86.3 88.9 89.2 89.8 89.2 89.0 89.3 Vegetation Cover (%) 30 30 30 30 30 35 35 30 Lag Time (min) 16.1 18.7 13.6 12.7 12.8 16.8 15.5 17.7 Runoff from subbasins was routed using the Modified-Puls method. Storage discharge tables for the channel routing were developed using HEC-GeoRAS and HEC-RAS. Six different discharges were used for storage-discharge relations. The number of subreaches was calculated using the following method: Vw = 1.5 * Vave .........eq.1 K= L ...................eq.2 Vw Therefore, K N = ..................eq.3 Δt where Vave is average flow velocity, L is reach length, Vw is velocity of flood wave (a conversion factor of 1.5 is used for natural channels), K is hydrograph travel time, Δt is the time interval for computations in the model, and N is the number of steps in the reach routing. Eq.4 was obtained from eq.1, 2, and 3. The detail of the calculation of the number of subreach is included in Appendix D. 4.3 Problems Encountered During the Study 4.3.1 Special Problems and Solutions There were no problems with the hydrologic modeling. 14 4.3.2 Modeling Warning and Error Messages The time interval of the rainfall data used in this study is 5 minutes, while the simulation time interval is 1 minute. The HEC-HMS model interpolated the 5-minute time interval of the rainfall data to 1-minute time interval. 4.4 Calibration No calibration was conducted in this study. 4.5 Final Results 4.5.1 Hydrologic Analysis Results The 100-year peak discharges for the Sweetwater Wash subbasins and at CP A were determined using the HEC-HMS. The results are summarized Tables 3 and 4. Table 3 Summary of the Hydrologic Analysis Results for Sub-Basins Sub-Basin SWT A SWT B SWT C SWT D SWT E SWT F SWT G SWT H Area (sq mi) 0.45 0.55 0.22 0.18 0.62 1.49 1.05 0.24 Rainfall Depth (in) 3.11 3.11 3.11 3.11 3.11 3.11 3.11 3.11 Runoff Volume (in) 1.53 1.78 1.99 2.01 2.07 2.01 2.00 2.03 Peak Discharge (cfs) 680.3 882.8 478.5 410.3 1443.9 2904.8 2128.7 456.2 Table 4 Summary of the Hydrologic Analysis Results at the Concentration Points Concentration Point Location CP A at Silverbell Rd. Area (sq Rainfall Runoff Q100 Time to mile) Depth (in) Volume HMS (cfs) Peak (in) 4.8 2.69 1.57 5622 2:07 4.5.2 Verification results Peak discharge estimated using a HEC-HMS model was compared with an existing 100year regulatory discharge at CP A (Table 5). The comparison shows that the 100-year peak discharge estimated with a HMS model is in relatively good agreement with the accepted regulatory discharge of 6011 cfs. The HMS-derived peak discharge was also compared with the peak discharge obtained from USGS Regression Equation 13 (RRE; 15 Thomas et al., 1997) (Table 5). The comparison showed that the HMS-derived peak discharge was higher than the one derived from the Regression Equation. The higher HMS-derived peak discharge compared to the RRE-derived peak discharge would be expected, because these steep watersheds could be expected to produce higher than average at the sub-basin scale. Table 5 Comparison of a peak discharge Concentration Point Location CP A at Silverbell Rd. Area (sq Q100 Q100 mile) HMS (cfs) RRE (cfs) 4.8 5622 3275 Existing Regulatory Discharge (cfs) 6011 RRE: USGS Regression Equation 13 Section 5 Hydraulics 5.1 Method Description The hydraulic modeling for the Sweetwater was performed using HEC-RAS, Version 4.0 (HEC-RAS), HEC-GeoRAS, Version 4.1.1 (HEC-GeoRAS), ArcGIS, Version 9.3, and FLO-2D (Version 2007-6). Hydraulic analysis was performed in the area currently mapped as FEMA Zone A. Corrected model is proposed in this study. The model name is SWT, and the plan name is Plan 01. Steady flow analysis was performed using HEC-RAS in order to determine a floodplain limit for the upstream of the Sweetwater Wash (from the upstream end of the existing FEMA Zone A to approximately 1700 feet upstream of the Silverbell Rd). The locations of the stream centerline, flowpath, and cross sections of the Sweetwater Wash were determined using a 2-ft contour map and 2008 PAG aerial photos. The physical attributes of the wash were digitized in ArcGIS using the HEC-GeoRAS extension and exported to HEC-RAS to create geospatially referenced geometric data (cross section, reach profile). Other parameters for the steady-state analysis, such as Manning’s n-values, expansion and contraction coefficients, boundary condition, and ineffective flow areas were manually input into HEC-RAS. Normal-depth with a slope of 0.013 was assumed for the downstream boundary condition. The hydraulic data obtained from HEC-RAS were imported into HEC-GeoRAS to delineate a floodplain boundary for the Sweetwater Wash. FLO-2D was used for the downstream distributary area (from approximately 1700 feet upstream of the Silverbell Rd to a confluence with the Santa Cruz River). Geometric data for the FLO-2D model were derived from the 2005 Lidar data. Grid cell size of 20 feet was used to map a floodplain in the distributary area. The time interval used for the computation was 5 minutes. The FLO-2D model includes floodplain cross sections at immediately upstream of Silverbell Rd to estimate discharge crossing the road. The model does not include infiltration or rainfall. A hydrograph from the HMS at CP A (at Silverbell Rd.) was used as inflow data at a cell located at the upstream of the flow split. 16 5.2 Work Study Maps The work study map for the Sweetwater Wash is included in Exhibit 2. 5.3 Parameter Estimation 5.3.1 Roughness Coefficients Manning’s n values were determined by a combination of a site visit and 2008 PAG aerial photo. In the HEC-RAS model, Manning’s n value of 0.06 was assigned for the overbank with desert brush, and the value of 0.045-0.05 was assigned to a channel. In the FLO-2D model, selected Manning’s n values are 0.045-0.05 for a channel, 0.035 for roads (Camino del Cerro and Silverbell Rd.), and 0.05-0.065 for the other area. 5.3.2 Expansion and Contraction Coefficients In the HEC-RAS model, the channel of the Sweetwater Wash is assumed to have generally gradual transitions with minimum curvature. The expansion coefficient of 0.30 and contraction coefficient of 0.10 were used for the entire reach. 5.4 Cross-Section Description For the HEC-RAS model, a 5-foot interval contour map was used to select the location of cross sections. Cross-section locations were determined primarily based on the channel topography. The cross-section lines were drawn to be perpendicular to flow paths in HEC-GeoRAS. In the FLO-2D model, two cross sections were placed at immediately upstream of Silverbell Rd to obtain peak discharge crossing the road. 5.5 Modeling Consideration 5.5.1 Hydraulic Jump and Drop Analysis No hydraulic, drop analyses or adjustment of the floodplain was conducted in this study. 17 5.5.2. Bridges and Culverts None. 5.5.3 Levees and Dikes There are no levees or dikes located within the study limit. 5.5.4 Island and Flow Splits At approximately 1500 feet upstream of Silverbell Rd., the flow splits into two major flow paths. The flow becomes distributary at the downstream of Silverbell Rd. 5.5.5 Ineffective Flow Areas In the HEC-RAS model, ineffective flow option was modeled in the following situations. In general these ineffective flow areas were disconnected overbank areas that would not convey flow to the next downstream cross-section. 5.6 Floodway Modeling No floodway modeling was performed in this study. 5.7 Problems Encountered 5.7.1 Special Problems and Solutions Flow in the distributary flow area at the downstream of Silverbell Rd. was modeled with FLO-2D. For a floodplain mapping with FLO-2D, shallow flow depth less than 0.2 feet is considered to be negligible and cells with flood depth less than 0.2 feet were removed from a 100-year flood hazard area. In other words, cells with flow depth deeper than 0.2 feet were considered as a floodplain in this study. Flow at the upstream of the distributary area was modeled with HEC-RAS. 5.7.2 Model Warnings and Errors No errors occurred. The following warning messages occurred in the HEC-RAS model: 18 Divided flow Energy loss greater than 1.0 Energy equation could not be balanced and defaulted to critical. Cross-section extended vertically. Multiple critical depths calculated. Conveyance ratio is less than 0.7 or greater than 1.4. Inspection indicated that the modeling is accurate given the steep channel conditions. Most of these errors force a critical solution which is reasonable for these steep watercourses. A summary of the HEC-RAS 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 and FLO-2D modeling results are shown in Exhibit 2. 5.9.2 Verification of Results The floodplain limit produced in this Sweetwater Wash LOMR study was compared to the existing FEMA floodplain limit. The proposed floodplain limit tends to follow the existing floodplain limit in the upstream area, while the proposed floodplain limit is wider in south and narrower in north. The results suggest that the proposed floodplain limit is reasonable based on the topography. 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 19 Peak discharges at CP A (Silverbell Rd.) was used for the hydraulic analysis in this study. The estimated regulatory discharge rates are 5622 cubic feet per second (cfs) with a drainage area of 4.8 square mile. 7.2 Floodway Data Not applicable. 7.3 Annotated Flood Insurance Rate Map An annotated Flood Insurance Rate Map (FIRM) is included in Exhibits 2. 7.4 Flood Profiles Flood profile for the upstream area is included in the HEC-RAS model in Appendix E. 20 22 30 22 60 20 22 20 22 2290 0 223 Exhibit 1 100-year Floodplain with Cross Sections & Flow Depth Sweetwater Wash 20 22 30 23 30 22 2300 2230 225 0 2300 2270 90 22 226 0 2260 2220 EL CAMINO DEL CERRO 2230 2240 2280 2240 L 23 10 2300 70 22 2290 30 22 22 70 23 20 EL 22 60 2240 RB 0 236 0 223 VE SIL 2260 0 224 0 223 50 22 2350 CP A 225 0 933 ! ( 30 22 2280 V U 23 00 236 0 2270 V U 1068 2370 22 91 .9 .559 22 89 .4 04 08 2296.608 2300 23 10 2663 2754 2850 V U V U U V V U 12 31 23 01 .3 226 0 49 V U 29 2250 2310 229 3 3 Aerial: 2008 Pima Arizona Government Topo: 2008 Pima Arizona Government vertical Datum: NAVD 1988 38 67 22 99 .0 2260 0 228 22 95 .7 22 90 .6 39 2283.7 00 96 .238 2285 2 2270 4 .3 87 22 162 V U 20 99 V U 59 2290 V U 19 53 V U 17 V U 12 36 V U 14 V U 15 Discharge Points Xsections Contour 2ft Contour 10ft River Proposed Floodplain Downstream Upstream Existing Zone AE ZONE ZONE A ZONE AE Flow Depth at Cell Feet => 0.200 => 0.500 => 1.000 => 2.000 ! ( 2280 22 80 70 2 2 2250 2340 0 224 22 20 0 223 2280 20 22 20 22 00 23 59 90 22 44 V U 33 6 .42 8 .16 .01 2305 .343 68 9 230 85 14 .1 13 23 30 23 23 15 .9 02 .3 2307 .8 10 23 10 2 230 35 4 230 V U V U 3674 44 232 5 .10 8 6 69 232 7 V U V U 47 38 23 30 .5 77 23 31 .9 V U 49 V U 82 70 23 43 .5 62 V U 2310 2360 2390 23 90 70 23 237 0 00 23 200 100 0 200 Feet 2300 2310 0 659 V U .047 236 0 2361.2 69 2370 0 230 2300 SWEETWATER 2290 231 0 6687 V U 6895 6805 2362.326 0 230 7 .59 25 .5 53 23 5 235 8 2357.20 2363.076 6430 2364.647 This product is subject to the Department of Transportation Technical Services Division's Disclaimer and Use Restrictions. Pima County Regional Flood Control District 23 47 .8 72 23 51 .7 94 3 236 0 23 50 .2 24 43 UU V V 7027 60 23 46 .0 05 11 630 U V V U V U 59 23 40 .7 62 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. 230 0 23 38 .2 03 2350 0 239 U V V U 2380 ! ( 39 Index Map Scale 1:1,500,000 EL MORAGA 57 92 23 40 38 V U 55 30 23 67 23 36 .8 68 42 V U 54 23 34 .7 1 V U 50 52 45 .47 2 23 50 46 2270 1 233 0 23 50 2321.104 3824 U V V U 425 Pima County Index Map 23 00 V VU U 406 80 22 23 20 2319 .093 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 04/2010 gislib\rfcd\projects\imd\xavi\mdx\AKITSU\Sweetwater\Sweetwater_watershed_FINALexh3.mxd ç ççççççç ççç ççççç çççç CAMINO DE LA TIERRA ç çç ç 22 ççççç 26 ç çç ççç " ) G 22 24 F RA LOMR Case Studies SAHARA I10 MP FIRM - Flood Insurance Rate Map AY W GH HI I10 ççç ççççç ç ç ç ç ç ç 2 ç ç çç ç 22ç2ç çç ç ç ç ç çççç ççççç ç ç ç ç ç çç EMERALD ççç ççç çç ç221 ççç 3 ççç ççç ççç ççç ççç ç RO G UA SA RT " ) PIMA COUNTY P AM N çççç Floodways PALMYRA Sections SA CA D AN GR Jurisdictions I10 E Existing Floodplain Zone I10 ç ç ç çç ç ç ç ç ç çç çççç çççç ç çççç ççççç çç ççç2ç231 ç ççç çç ç çççççç çç " ) X - (SHADED) ç 1 ççç 22ç3ç ç çç ç çç çççççç ZONE X - SHADED ) " EK çççç çççç ççç çççç ççç 223 2 " ) EL EL CAMINO DEL CERRO 3 5 çç ç 22ç ççç ç ç ç ççç ç çç ççç " ) EM çç 3 6 ççç 22ççç çç çç Pima County Index Map çççç OF GO LD 3 9ç ç ç 22çççç ç çç224 ççç 1 ççç 24 AD EL ADO VEN çç ççç çççç ççç ççç çç çç2ç2ç 47 çççç ççç çç ççç ç ççç ç çççç ç ç çç çççç çççç çççç ççç ç çççç ç A NZ " ) 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 RE CA CAM VE CA L LE CAM INO PINT ORE S CO ççç2ç 245 çççç ç ççç 20 çççç ZONE X-(SHADED) 19 ç çç çç RK YO ç ççççç W NE ççç ççç ç SA INU O VI A S ççç NEWLAND CERRITOS HIL LS ZONE A çç RAI N ZONE A )" LOST HORIZON BOW SUNSET LL ZONE A çç EN BE O RIC ITA SUNSET HILLS NT E MO ER PASEO DE LOS CERRITOS ççç ç ççç2234 ççç ççç ççç ççç V SI L PL A DE L CITA C PL A BARG HOUT WILD LIFE EL CAMINO DEL CERRO Proposed 100 year Floodplain VE X DIAMOND çççç çççç ççç çççççç çççç çççç ç çççç çççç ççç2ç2ç2çç9çç çççç ççççç çççç ççç2ç230 çççç çççç ççççç çççç ç ççççççç çççççççç ççç2ç2çç2ç7çç çççççççç ç EI VISTA DEL CERRO RANCH AO P M RA N P O M2 RA5 MP N 2 O MP A 2 T RA R 25 I FF F F IT X EX0 E 52 O O 2 I1 EXIT252 I10 IT " ) EJ TUCSON ZONE X PIMA COUNTY D RA AE 0 I1 CAMINO DE OESTE JAD E EX " ) EH çç çççççççç ç ççç ç I10 çç çççç ZONE AEç çççç ç çç 26çççç 2 ç 2 ç ç çç ç ç ç ç ççç çççç ç ç çççç çç ç ç çç ç çç ç DE CAMINO DE OESTE PETRANEK ç çççç A AN çççç ç GR ç çç çç ççç çççç ççç çççç 23 ççç 22çççç SA " ) EG CURTIS CURTIS 17 CA 18 çç çççç çççç çççç Base Flood Elevations Proposed Floodplain FR OF P AM çç ççççç ç ç ç ç çç FIRM X-Sections ççç ççç ççç ççç ççç ç ZONE X EF Streets 1 25 R O 1 25 ON DE SE E SUN IST A EV RD VE JUSNIC IT EX I10 IT " ) çç 51 T2 ç ççççç çç ççç ççç ç ççç ç ç ç ç 8 çç çç 22ç1ç çç çç ç ç çç EX ççç çççççç ç ç ç ç 8 ççç 22ç ç1ç ç çç ç ç ç ç ççç ZONE X-(SHADED) ççç ZONE X-(SHADED) I EX I10 ççç çççççç ç ç ç ç çç ç çç çççç çççççç ç ç çç çççç E AG NT çççç çççç çççç ççç çççç SUNSET RIVER 222 9 222 7 22 23 ççççç 2 ççççç 225 ççççç ççççç ZONE X - SHADED I10 ççç ç çççç ççç çççç çççç 16ççççç 2 2 çç çççç ççç çççç " ) 22 07 EB " ) ER ççççç çççç ççç IGH TS RIV ççççç ç ç ç ç ççççç ç HE ççç SET ç çççç ççç çççç ç SUNSET TRES NOGALES O FR I10 PA LO çç ç " ) EE E AG NT " ) T WO O D ç ççç ççç ç E ççç çç ççç ç ç ç ç ççç çç O FR I10 ççç ççç çç ç ç ç ç ççç ççççç ED DESER çççç ççç ç ççç çç ççç çç ççç çç ççç çç ççç çç P 08 Exhibit 2 Annotated Flood Insurance Rate Map 04019C1616 K Sweetwater Wash ER LOMR Case 04-09-0465X Effective Date4/22/2004 SUNSET HIDDENWOOD AMG TRA ççççç SUNSET RIV N 0 221ççççç çççççç ççççççç O ON 07 MARANA çççççç ççççççç 1 25 " ) EC çççç TR XI EF I1I100 ZA ç çççç ççç ç çççç çççç çççç B PL A ç " ) SE T ç ç ç ççç ç ç ç çç SU N ç çççç ççç çç ççç ççç ççççç ç ç ç ç ç ç çççç çç ççç ççç ççç ç ççç ççç SUNSET DUNES ççç ççççççç ç ç ç ç ç ç ççççççç ççççççç ççççççç ççç çç ççççççç ççççççç çç ççç çç çç ççç çç çç çç ççç ç ççç çç ççç çç ççç çç 08 çç 22ççççç ç çççç ç ççç çç ç ç ç ç çç çç ç ç çç çç ççç " ) EO ZONE A EP B OX OW 490 M CA O IN E NU " ) EQ RO ST DR IS L CO 245 0 225 0ççç çççççç çç ççç çç çç çççççç ççç ççç 225ç1çç ççççççç çç ççççç çççç çç çççççç ç ç ç ç çç ç ç ç ççççççç ççç ç ççççç ççççç ç ççççç 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\Sweetwater\Sweetwater_watershed_Anno_FIRM28x40.mxd 490 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 “Instruction for Organization and Submitting Technical Document for Flood Studies” SSA1-97, November 1997 Arizona Department of Water Resources, Flood Mitigation Section “Requirements for Flood Study Technical Documentation” SS1-97, November 1997 Arroyo Engineering. 2007. PC-Hydro User Guide. Pima County Regional Flood Control District City of Tucson (COT), Department of Transportation, 1989. Standards Manual for Drainage Design and Floodplain Management in Tucson, Arizona. Revised in 1998. National Weather Service. 1984. Depth-Area Ratios in the Semi-Arid Southwest United States, NOAA Technical Memorandum NWS Hydro-40 Phillips, J., and S. Tadayon. 2006. Selection of Manning’s roughness coefficient for natural and constructed vegetated and non-vegetated channels, and vegetation maintenance plan guidelines for vegetated channels in central Arizona: U.S. Geological Survey Scientific Investigations Report 2006–5108, 41 p. Phillips, J., and T. Ingersoll. 1998. Verification of Roughness Coefficients for Selected Natural and Constructed Stream Channels in Arizona. U.S. Geological Survey Professional Paper 1584. Pima County Regional Flood Control District “Pima County Mapguide Map”, 2008 U.S. Army Corps of Engineers (COE). 1998. HEC-1 Flood Hydrograph Package, Users Manual, CPD-1A, Hydraulic Engineering Center, Davis, CA. U.S. Army Corps of Engineers (COE). 2001. HEC-RAS, River Analysis System, Hydraulic Reference Manual, CPD-69, Hydraulic Engineering Center, Davis, CA. U.S. Army Corps of Engineers (COE). 2003. Geospatial Hydrologic Modeling Extension HEC-GeoHMS, (v 1.1) CPD-77, Hydraulic Engineering Center, Davis, CA. U.S. Army Corps of Engineers (COE). 2006. HEC-HMS, Hydrologic Modeling System User’s Manual, (v. 3.1.0) CPD-74A, Hydraulic Engineering Center, Davis, CA. U.S. Department of Agriculture Natural Resources Conservation Service (NRCS), 1986. Urban Hydrology for Small Watersheds, Technical Release 55. Washington, DC. A 2. Referenced Documents Arroyo Engineering. 2007. PC-Hydro User Guide. Pima County Regional Flood Control District Eychaner, J.H., 1984. Estimation of magnitude and frequency of floods in Pima County, Arizona, with comparisons of alternative methods: U.S. Geological Survey WaterResources Investigations Report 84-4142, 69 p. Haan, C.T., Barfield, B.J., Hayes, J.C. 1994. Design Hydrology and Sedimentology for Small Catchments, Academic Press. Thomas, B.E., H.W. Hjalmarson, and S.D. Waltemeyer. 1997. Methods for Estimating Magnitude and Frequency of Floods in the Southwestern United States. USGS Water Supply Paper 2433. 195 p. U.S. Department of Agriculture Natural Resources Conservation Service (NRCS), 1986. Urban Hydrology for Small Watersheds, Technical Release 55. Washington, DC. Appendix C: Survey Field Notes FW PAG 2008 OrthosLidar.txt From: Kenneth Maits Sent: Monday, May 03, 2010 12:20 PM To: Evan Canfield Subject: FW: PAG 2008 Orthos/Lidar Evan, I think this is the right email.... -------------------------------------------------------------------------------From: Terry Hendricks Sent: Thursday, November 12, 2009 8:30 AM To: Bill Zimmerman; Kenneth Maits; Evan Canfield; Chris Cawein Subject: FW: PAG 2008 Orthos/Lidar Read Ed Curtis's email below. It appears that FEMA accepts the 2008 LiDAR HOWEVER it looks in some places we may need to provide "additional ground survey data where necessary" -------------------------------------------------------------------------------From: Manny M. Rosas [mailto:MRosas@pagnet.org] Sent: Tuesday, November 10, 2009 4:26 PM To: 'Curtis, Edward' Cc: Terry Hendricks; 'Don Freeman'; 'Lucero, Andrew' Subject: RE: PAG 2008 Orthos/Lidar Thanks Ed, Good news!! Manny 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 Page 1 FW PAG 2008 OrthosLidar.txt 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 Manny M. Rosas Jr. GIS Administrator Page 2 FW PAG 2008 OrthosLidar.txt 177 N Church Ave. Suite 405 Tucson, Arizona 85701 520-792-1093 (tel) 520-620-6981 (fax) Page 3 Page 1 of 1 Terry Hendricks 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 2/25/2010