Stream Channel Cross Sections for a Reach of the Boise River in Ada County, Idaho

U.S. Department of the Interior U.S. Geological Survey In cooperation with Federal Emergency Management Agency, City of Boise, City of Garden City, City of Eagle, and Ada County Stream Channel Cross Sections for a Reach of the Boise River in Ada County, Idaho Open-File Report 99 211

Stream Channel Cross Sections for a Reach of the Boise River in Ada County, Idaho By Jon E. Hortness and Douglas C. Werner Open-File Report 99 211 In cooperation with Federal Emergency Management Agency, City of Boise, City of Garden City, City of Eagle, and Ada County Boise, Idaho 1999

U.S. DEPARTMENT OF THE INTERIOR BRUCE BABBITT, Secretary U.S. GEOLOGICAL SURVEY Charles G. Groat, Director Any use of firm, trade, and brand names in this report is for identification purposes only and does not constitute endorsement by the U.S. Government. Additional information can be obtained from: Copies of this report can be purchased from: District Chief U.S. Geological Survey U.S. Geological Survey Information Services 230 Collins Road Box 25286 Boise, ID 83702-4520 Federal Center http://idaho.usgs.gov Denver, CO 80225 e-mail: infoservices@usgs.gov

CONTENTS Abstract... 1 Introduction... 1 Purpose and scope... 3 Description of study area... 3 Collection of cross-section data... 3 Horizontal referencing... 5 Vertical referencing... 5 References cited... 10 FIGURES 1 5. Maps showing: 1. Location of the Boise River drainage basin, Idaho... 2 2. Location of the study area in Ada County, Idaho... 4 3. River mile locations and index of enlarged figures showing cross-section locations on the Boise River in Ada County, Idaho... 6 4. Location of elevation reference marks used for the study of the Boise River flood plain in Ada County, Idaho... 7 5. Locations of cross sections on the Boise River from the Ada/Canyon County boundary to river mile 37, in Ada County, Idaho... 13 6. Graphs showing segments of channel cross sections on the Boise River from the Ada/Canyon County boundary to river mile 37, in Ada County, Idaho... 14 7. Map showing locations of cross sections on the Boise River from river mile 37 to 42, in Ada County, Idaho... 23 8. Graphs showing segments of channel cross sections on the Boise River from river mile 37 to 42, in Ada County, Idaho... 24 9. Graphs showing segments of channel cross sections on the south channel of the Boise River from river mile 0 to 3.5, in Ada County, Idaho... 35 10. Map showing locations of cross sections on the Boise River from river mile 42 to 47, in Ada County, Idaho... 44 11. Graphs showing segments of channel cross sections on the Boise River from river mile 42 to 47, in Ada County, Idaho... 45 12. Graphs showing segments of channel cross sections on the south channel of the Boise River from river mile 3.5 to 6.71, in Ada County, Idaho... 58 13. Map showing locations of cross sections on the Boise River from river mile 47 to 51, in Ada County, Idaho... 66 14. Graphs showing segments of channel cross sections on the Boise River from river mile 47 to 51, in Ada County, Idaho... 67 15. Map showing locations of cross sections on the Boise River from river mile 51 to 55, in Ada County, Idaho... 77 16. Graphs showing segments of channel cross sections on the Boise River from river mile 51 to 55, in Ada County, Idaho... 78 17. Map showing locations of cross sections on the Boise River from river mile 55 to 59, in Ada County, Idaho... 89 18. Graphs showing segments of channel cross sections on the Boise River from river mile 55 to 59, in Ada County, Idaho... 90-1 iii

TABLE 1. Site information for elevation reference marks established for horizontal and vertical control for the study of the Boise River flood plain in Ada County, Idaho... 8 CONVERSION FACTORS Multiply By To obtain acre-foot (acre-ft) 1,233 cubic meter cubic foot per second (ft 3 /s) 0.02832 cubic meter per second foot (ft) 0.3048 meter inch (in.) 2.54 centimeter mile (mi) 1.609 kilometer square mile (mi 2 ) 2.590 square kilometer iv 0

Stream Channel Cross Sections for a Reach of the Boise River in Ada County, Idaho By Jon E. Hortness and Douglas C. Werner Abstract The Federal Emergency Management Agency produces maps of areas that are likely to be inundated during major floods, usually the 100-year, or 1-percent probability, flood. The maps, called Flood Insurance Rate Maps, are used to determine flood insurance rates for homes, businesses, or other structures located in flood-prone areas. State and local governments also use these maps for help with, among other things, development planning and disaster mitigation. During the period October 1997 through December 1998, the initial phase of a hydraulic analysis project of the Boise River from Barber Dam to the Ada/Canyon County boundary, the U.S. Geological Survey collected stream channel cross-section data at 238 locations along the river and documented 108 elevation reference marks established for horizontal and vertical control. In the final phase of the project, the Survey will use these data to determine water-surface elevations for the 10-, 50-, 100-, and -year floods and to define floodway limits. The Federal Emergency Management Agency will use the results of this hydraulic analysis to update the 100- and -year flood boundaries and the floodway limits on their Flood Insurance Rate Maps. INTRODUCTION The Federal Emergency Management Agency (FEMA) produces maps of areas that are likely to be inundated during major floods, usually the 100-year, or 1-percent probability, flood. The chance of a given flow being exceeded once in any given year is expressed as an annual probability. Thus, a 1-percent probability flood has a 1-in-100 chance of occurring in any given year. Similarly, a 50-year flood has a 1-in-50 chance of occurring in any given year. The return period of a flow is defined as the average elapsed time between events that equal or exceed that flow. An annual probability of 1 percent results in a return period of 100 years, which is why the flood is sometimes referred to as the 100- year flood. FEMA uses these maps, called Flood Insurance Rate Maps (FIRMs), to determine flood insurance rates for homes, businesses, or other structures located in flood-prone areas. State and local governments also use these maps for help with, among other things, development planning and disaster mitigation. The current FIRMs were produced in 1979 and since have not been updated. About 30 percent of Idaho s population resides in the lower Boise River Basin (Idaho Department of Commerce, written commun., 1999) between Lucky Peak Lake and the Snake River, the fastest growing area in Idaho (fig.1). The population of Ada County, alone, increased nearly 30 percent between 1990 and 1997, to approximately 267,000. The increase in population, the resulting development along the Boise River, and the time elapsed since the FIRMs were produced were factors that led FEMA to a decision to update the FIRMs. In 1997, the U.S. Geological Survey (USGS), in cooperation with FEMA; the cities of Boise, Garden City, and Eagle; and Ada County, began the initial phase of a hydraulic analysis project on the Boise River between Barber Dam, about 5 mi downstream from Lucky Peak Lake, and the Ada/Canyon County boundary. During the initial phase of the project (October 1997 through December 1998), the USGS collected cross-section data at 238 locations along the river channel and documented 108 elevation reference marks established for horizontal and vertical control. The USGS will use these data in the final phase of the 1

116 00' 116 30' 117 00' Boise River drainage basin 2 115 00' Boise 115 00' Snake Caldwell River 115 30' Nampa Star 115 30' 44 00' 44 00' BOISE,,, yyy,,, yyy,,yy,, yy Meridian Boise CANYON Lucky 43 30' 43 Peak 00' Lake CAMAS River Eagle Study area ADA Garden City Arrowrock Reservoir South North Fork Fork Middle ELMORE Boise Fork Boise River Anderson Ranch Reservoir Boise River River 117 30' IDAHO 117 00' 117 30' Base from U.S. Geological Survey digital data, 1:100,000, 1980 Albers Equal-Area projection Standard parallels 43 30', 47 30', and -114 00', 41 45' No false easting or false northing Snake River C.J. Strike 43 00' Reservoir 43 00' 116 00' 116 30' Snake River 0 10 20 0 10 20 30 30 40 KILOMETERS 40 MILES Figure 1. Location of the Boise River drainage basin, Idaho.

project to perform a one-dimensional step-backwater analysis to determine water-surface elevations for the 10-, 50-, 100-, and -year floods and to define the floodway limits. FEMA will use the results of the 100- and -year analyses to update the current FIRMs. Purpose and Scope The purposes of this report are to (1) present stream channel cross-section data that were collected for use in defining the 100- and -year flood plain of the Boise River in Ada County, and (2) document elevation reference mark data established for horizontal and vertical control for the entire study area from Barber Dam to the Ada/Canyon County boundary. General locations and land-surface elevation profiles are presented for each cross section. The profile data are available in tabular ASCII format from the USGS, Idaho District, Website. Horizontal and vertical control data are presented for all elevation reference marks used in this project. These data are also available from the USGS, Idaho District, Website. Additional cross-section data were obtained at bridges and diversion structures located throughout the study area. Only structures that control flow in the Boise River were surveyed for this study. Those data are not published in this report but can be obtained by contacting the USGS office listed on the back of the inside cover page. Description of Study Area The Boise River originates in the Sawtooth Mountains in central Idaho as three separate forks North Fork, Middle Fork, and South Fork that flow in a southwesterly direction. All three forks eventually flow into Lucky Peak Lake in eastern Ada County, Idaho. From Lucky Peak Lake, the Boise River flows in a single channel in a northwesterly direction until it joins the Snake River near the Idaho/Oregon border (fig. 1). The study area is the 26-mi reach of the lower Boise River that extends from Barber Dam downstream through the cities of Boise, Garden City, and Eagle to the Ada/Canyon County boundary (fig. 2). This reach also includes an approximately 6.5-mi-long channel around the south side of Eagle Island, just west of Garden City. The total river length in the study area is about 32.5 mi. Several diversion structures in the study area are used to divert flow for irrigation purposes. A detailed description of these structures and their locations is available in the Task 1 Report for the Boise and Payette Rivers diversion upgrade project (Quadrant Consulting, Inc., and others, 1997). A USGS streamflow-gaging station, Boise River at Glenwood Bridge (13206000), is located at Glenwood Street in Garden City (fig. 2). Much of the 2,800 mi 2 of drainage area upstream from the gaging station is mountainous. Discharge at the gage is regulated by flows out of Lucky Peak Lake. Arrowrock and Anderson Ranch Reservoirs (fig. 1) regulate discharges farther upstream. The total combined storage available in Lucky Peak Lake and Arrowrock and Anderson Ranch Reservoirs is about 974,200 acre-ft. For the period of record October 1981 through September 1998 (water years 1982 through 1998), the annual mean discharge at the Glenwood gage was about 1,367 ft 3 /s; the maximum discharge was 9,840 ft 3 /s and the minimum was 42 ft 3 /s (Brennan and others, 1999). During this period, three separate flow events exceeded the 10-year flood flow of 7,200 ft 3 /s. COLLECTION OF CROSS-SECTION DATA Cross-section data were collected at 238 locations spaced approximately 700 ft apart along the entire study reach. Cross-section locations were placed closer together in areas near bridges or diversion structures. Each cross section was given a station number that corresponded to its location on the river, in river miles. A river mile is the actual river channel distance, measured along the thalweg (centerline), that covers one linear mile. River miles are calculated in an upstream direction beginning with zero at the river mouth. River miles are designated by the USGS National Mapping Division on 7.5-minute (1:24,000-scale) maps. With regard to river miles, the north channel around Eagle Island is designated as the main channel and, thus, was numbered in an upstream progression. The south channel around Eagle Island is designated as a side channel 3

116 29' 116 27' 116 25' 116 23' 116 21' 116 19' 43 43' 43 41' 43 39' CANYON COUNTY ADA COUNTY Star Road Star,,,,,,,,,,, 43 43' 116 17',,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 116 29' 116 27' 116 25' 116 23',,,,,,,,,,,,,,,,,, Base from U.S. Geological Survey digital data, 1:24,000; 116 Boise North, 1976; Boise South,1976; Eagle, 1979; 21',,,,,,,,, Middleton, 1971; Star, 1971; 4,,,,,,,,, State Plane Coordinate System, State Plane Zone 1103, (West Idaho), in feet North American Datum of 1983 Boise 44 20 26 EXPLANATION Linder Road U.S. Geological Survey streamflow-gaging station, Boise River at Glenwood Bridge (13206000) Eagle River Island Eagle Road 55,,,,,,,,,,,,,,,,,, 43 37' 43 35' Eagle Glenwood,,,,,,,, 84 55 Chinden 116 19' 43 33' 44 Blvd Garden City 184 116 15' 116 13' State Boise Boise Vista Ave Street 84 Broadway Ave 116 11' Warm Springs 43 41' 116 09' 43 39' 116 07' 43 37' 43 35' 43 33' 116 17' 116 15' 116 13' 116 11' 116 09' 116 07' Boise River Ave Ave Warm Springs Eckert Road Rd Barber Dam 0 1 2 3 4 5 MILES 0 1 2 3 4 5 KILOMETERS Figure 2. Location of the study area in Ada County, Idaho.

and, thus, was numbered beginning with zero at the downstream end. River mile locations are shown in figure 3. A minimum of two control points (hubs) were established at each cross-section location. These control points were placed to allow for the cross sections to be oriented perpendicular to the direction of flow at each location. At least one of the control points at each cross section was marked with both a wooden stake and metal rebar, and the rest were marked with either a stake or rebar. Cross-section data were collected using an electronic total station. The total station was set up over one of the control points, then horizontal and vertical coordinates were obtained at several points across the river channel. In some locations, the water level was too high to allow the survey crews to wade across safely. In these instances, points in the river channel were surveyed using a boat. The channel depth was obtained at several locations across the river and referenced to one of the control points by using the watersurface elevation. The number of depths obtained at each location depended on the width of the channel but was sufficient to obtain a good representation of the channel bottom. The cross sections also were referenced to horizontal and vertical datums, which will be discussed in subsequent sections. Figure 3 presents an index of enlarged figures (5, 7, 10, 13, 15, and 17) that show the locations of cross sections in greater detail. Included on each enlarged map is the station number for each cross section. The cross-section profiles (figs. 6, 8, 9, 11, 12, 14, 16, and 18) show distance across the channel, in feet, from the left-most surveyed point, and land-surface elevation, in feet, above the North American Vertical Datum of 1988 (NAVD 88). For consistency, a maximum of horizontal feet at each cross section is presented. If a particular cross section is longer than ft, only the ft near the river channel is presented. Complete information for each cross section also is available in tabular ASCII format from the USGS, Idaho District, Website located at http://idaho.usgs.gov/projects/boiseriver/boiseriver.htm Horizontal Referencing Horizontal control was based on the North American Datum of 1983 (NAD 83), State Plane Coordinates, Idaho West Zone, in feet. Horizontal referencing of the cross sections was accomplished using a differential Global Positioning System (GPS). A GPS receiver (base station) was located within several miles of the cross sections on a known, geographically referenced point. A second GPS receiver was used to obtain coordinates at a minimum of one control point (hub) at each cross section. The horizontal accuracy for this process was determined to be 3 ft. Each cross section was surveyed in a local coordinate system by using conventional surveying techniques. The cross-section data then were transformed to NAD 83 by using the GPS control data and a geographic information system (GIS). Vertical Referencing The vertical control was based on the North American Vertical Datum of 1988. The vertical control for this project was established as part of a subcontract for contour mapping of the area. Elevation reference marks (ERMs) were set by the contractor for use in the development of 2-ft contour maps. The general location and identification number of each ERM are shown in figure 4. Latitude, longitude, elevation, and a short description of each ERM are presented in table 1. In addition, this information, as well as detailed site descriptions, can be downloaded from the USGS, Idaho District, Website. Differential, dual frequency GPS units were used to determine the vertical and horizontal locations of each ERM. The minimum setup session at each point lasted about 15 minutes, but most sessions were 20 minutes or longer. Satellite data were logged by the receiver at 10-second intervals. The GPS network consisted of several loops with a maximum of 10 ERMs per loop. Each loop was closed separately by using GPS software. The final vertical adjustment was based on holding 10 local surveyed bench marks constant. 5

116 29' 116 27' 116 25' 116 23' 116 21' 116 19' 6 43 43' 43 41' 43 39' 36 33 Figure 7 Star Road 34 Star 35 Boise 36 37 116 29' 116 27' 38 0 Linder Road 39 1 40,,,, River Figure 5 Figure 7 EXPLANATION River mile marker and mileage from mouth of river Area of map enlarged to show locations of cross sections 44 20 26 Eagle 2 41 116 25' 116 23' Eagle Road 42 Island 3 4,,,,,,, 55 43,,,,,,,,,,,,,,,,,, 5 116 21' 43 37' 43 35' Eagle 44 Chinden 6 45 43 43' 116 17' 44,,,,,, 46 47,,,,,, 48 49,,,,,, 50,,,,,, 51,,,,,, Figure 13,,,,,, 52,,,,,,,, 84 55 Figure 10 116 19' Blvd Glenwood Garden City 184 116 15' 116 13' State Boise Boise Figure 15 Vista Ave Street 53 84 Broadway Ave 116 11' Warm Springs 54 55 Boise River Ave 56 43 41' Ave 116 09' Warm 43 39' Figure 17 57 Springs 58 116 07' 43 37' Rd 43 35' 43 33' 43 33' 116 17' 116 15' 116 13' 116 11' 116 09' 116 07' Barber Dam 59 0 1 2 3 4 5 MILES 0 1 2 3 4 5 KILOMETERS Figure 3. River mile locations and index of enlarged figures showing cross-section locations on the Boise River in Ada County, Idaho.

116 29' 116 27' 116 25' 116 23' 116 21' 116 19' 7 43 43' 43 41' 43 39' 337 338 Star Road 153 339 154 340 341 146 155 152 Star 156 332 143 142 ADA17 ADA16 148 144 328 138 334 149 145 329 139 44 Boise 335 150 336 151 116 29' 116 27' EXPLANATION 146 147 20 26 Elevation reference mark and number See table 1 330 140 River 331 Eagle 324 325 137 326 327 136 116 25' 116 23' Eagle Road Island 116 21' 43 37' 43 35' Eagle 133 129 321 ADA15 134 135 131 55 132 NEB2 128 323 322 127 125 126 Y415ECC 84 55 116 19' 44 0057 320 1320 43 43' 116 17' D3417ECC 0054 0058 123 122 0061 0062 0065 119 Garden City 315 116 184 116 15' 116 13' 0096 1001 0067 0066 114 0069 IDTD 310 1000 311 0074 0071 0073 Boise 309 116 11' 111 0078 0077 0081 0079 0080 0083 0082 0085 105 305 43 41' 116 09' 0087 88 0089 43 39' 1003 0095 102 101 116 07' 43 37' 43 35' 84 43 33' 303 0093 157 43 33' IDA8060 116 17' 116 15' 116 13' 116 11' 116 09' 116 07' 0 1 2 3 4 5 MILES 0 1 2 3 4 5 KILOMETERS Figure 4. Location of elevation reference marks used for the study of the Boise River flood plain in Ada County, Idaho.

Table 1. Site information for elevation reference marks established for horizontal and vertical control for the study of the Boise River flood plain in Ada County, Idaho [Locations of reference marks are shown in figure 4; latitude and longitude are based on the North American Datum of 1983 and shown in degrees, minutes, and seconds; reference mark elevations are based on the North American Vertical Datum of 1988; in., inch] Reference mark Location Elevation, number Latitude Longitude in feet Descriptions 88 43 34' 21.577193" 116 09' 17.512178" 2758.08 Towill, Inc., rebar and cap 101 43 34' 20.147949" 116 07' 42.355435" 2770.04 Towill, Inc., rebar and cap 102 43 34' 17.177148" 116 08' 33.231115" 2747.38 Towill, Inc., rebar and cap 105 43 36' 05.270297" 116 10' 03.785220" 2734.91 Towill, Inc., rebar and cap 111 43 37' 42.299474" 116 12' 45.893360" 2693.55 Towill, Inc., rebar and cap 114 43 38' 57.523940" 116 14' 13.852333" 2666.83 Towill, Inc., rebar and cap 116 43 37' 57.875275" 116 15' 24.668973" 2699.45 Towill, Inc., rebar and cap 119 43 39' 25.220324" 116 16' 00.849641" 2624.69 Towill, Inc., rebar and cap 122 43 39' 38.638294" 116 17' 07.386349" 2612.26 Towill, Inc., rebar and cap 123 43 38' 52.414167" 116 17' 23.868224" 2670.21 Towill, Inc., rebar and cap 125 43 40' 50.787069" 116 18' 49.768673" 2584.01 Towill, Inc., rebar and cap 126 43 40' 05.558918" 116 19' 10.769139" 2587.51 Towill, Inc., rebar and cap 127 43 39' 27.127530" 116 19' 47.642266" 2640.42 Towill, Inc., 1-1/8 in. brass disk 128 43 41' 06.643208" 116 19' 44.929204" 2574.67 Towill, Inc., 1-1/8 in. brass disk 129 43 42' 04.736837" 116 20' 59.719397" 2615.79 Towill, Inc., rebar and cap 131 43 40' 29.874323" 116 21' 14.648493" 2565.79 Towill, Inc., 1-1/8 in. brass disk 132 43 39' 50.871972" 116 21' 15.344728" 2618.98 Towill, Inc., 1-1/8 in. brass disk 133 43 42' 06.853523" 116 21' 58.400610" 2590.37 Towill, Inc., rebar and cap 134 43 41' 31.444666" 116 22' 06.651284" 2554.78 Towill, Inc., rebar and cap 135 43 40' 54.150137" 116 22' 24.359001" 2544.75 Towill, Inc., rebar and cap 136 43 40' 05.686137" 116 22' 27.999731" 2601.60 Towill, Inc., rebar and cap 137 43 41' 03.681838" 116 23' 17.283672" 2533.83 Towill, Inc., rebar and cap 138 43 42' 22.442082" 116 23' 59.052413" 2553.63 Towill, Inc., rebar and cap 139 43 41' 40.392844" 116 24' 14.423115" 2528.99 Towill, Inc., 1-1/8 in. brass disk 140 43 40' 52.711432" 116 24' 12.573232" 2525.09 Towill, Inc., rebar and cap 142 43 42' 31.539992" 116 25' 24.737501" 2527.91 Towill, Inc., rebar and cap 143 43 42' 39.677461" 116 26' 36.007580" 2525.33 Towill, Inc., rebar and cap 144 43 42' 24.321955" 116 26' 36.620748" 2502.97 Towill, Inc., rebar and cap 145 43 41' 29.751665" 116 26' 21.199269" 2506.25 Towill, Inc., rebar and cap 146 43 40' 48.311002" 116 26' 18.139612" 2499.90 Towill, Inc., rebar and cap 147 43 40' 14.566707" 116 26' 19.802089" 2517.41 Towill, Inc., rebar and cap 148 43 42' 23.740882" 116 27' 29.886349" 2502.84 Towill, Inc., rebar and cap 149 43 41' 33.913900" 116 27' 30.353108" 2493.01 Towill, Inc., rebar and cap 150 43 40' 48.857680" 116 27' 35.189944" 2488.61 Towill, Inc., rebar and cap 151 43 39' 57.835181" 116 27' 20.680106" 2544.07 Towill, Inc., rebar and cap 152 43 42' 55.233573" 116 29' 17.439938" 2520.66 Towill, Inc., rebar and cap 153 43 42' 23.334493" 116 29' 35.561515" 2468.18 Towill, Inc., rebar and cap 154 43 41' 37.761844" 116 29' 39.825473" 2470.02 Towill, Inc., rebar and cap 155 43 40' 46.111224" 116 29' 35.014166" 2481.84 Towill, Inc., rebar and cap 156 43 40' 03.079664" 116 29' 35.831860" 2504.77 Towill, Inc., rebar and cap 157 43 33' 31.308285" 116 07' 26.884005" 2802.14 Towill, Inc., rebar and cap 303 43 33' 37.459483" 116 08' 39.779794" 2841.68 Towill, Inc., rebar and cap 305 43 35' 14.817366" 116 09' 59.076299" 2727.57 Towill, Inc., rebar and cap 309 43 36' 15.087363" 116 13' 01.239630" 2747.31 Towill, Inc., 1-1/8 in. brass disk 310 43 38' 20.775957" 116 13' 32.716111" 2673.48 3 in. brass disk 311 43 37' 52.120804" 116 13' 56.015897" 2662.68 Towill, Inc., rebar and cap 315 43 38' 33.161712" 116 16' 00.578514" 2638.87 Towill, Inc., rebar and cap 320 43 39' 13.431315" 116 18' 28.535558" 2660.74 Towill, Inc., rebar and cap 321 43 41' 47.645719" 116 19' 55.717961" 2587.34 Towill, Inc., 1-1/8 in. brass disk 322 43 40' 18.752895" 116 20' 03.553330" 2578.03 Towill, Inc., rebar and cap 323 43 39' 42.251733" 116 20' 30.401965" 2626.82 Towill, Inc., rebar and cap 324 43 42' 19.774362" 116 23' 04.549530" 2570.86 Towill, Inc., rebar and cap 325 43 41' 43.680128" 116 23' 13.367703" 2548.87 Towill, Inc., rebar and cap 326 43 40' 53.591881" 116 23' 34.435735" 2529.28 Towill, Inc., rebar and cap 327 43 40' 18.774000" 116 23' 36.623777" 2587.64 Towill, Inc., rebar and cap 8

Table 1. Site information for elevation reference marks established for horizontal and vertical control for the study of the Boise River flood plain in Ada County, Idaho Continued Reference mark Location Elevation, number Latitude Longitude in feet Descriptions 328 43 42' 22.509411" 116 25' 07.160758" 2528.47 Towill, Inc., rebar and cap 329 43 41' 36.183628" 116 25' 05.349470" 2520.82 Towill, Inc., rebar and cap 330 43 40' 50.331838" 116 25' 11.480220" 2511.64 Towill, Inc., rebar and cap 331 43 40' 15.159427" 116 24' 48.909956" 2568.83 Towill, Inc., rebar and cap 332 43 42' 47.083332" 116 28' 05.777778" 2521.16 Towill, Inc., rebar and cap 334 43 41' 39.006632" 116 28' 23.895954" 2483.18 Towill, Inc., rebar and cap 335 43 40' 51.338679" 116 28' 51.650279" 2475.68 Towill, Inc., rebar and cap 336 43 40' 09.432830" 116 28' 19.476125" 2515.92 Towill, Inc., rebar and cap 337 43 43' 03.759108" 116 30' 45.388276" 2493.59 Towill, Inc., rebar and cap 338 43 42' 18.600536" 116 30' 45.354820" 2459.58 Towill, Inc., rebar and cap 339 43 41' 39.004453" 116 30' 45.570426" 2459.57 Towill, Inc., rebar and cap 340 43 40' 57.092778" 116 30' 45.796627" 2459.06 Towill, Inc., rebar and cap 341 43 40' 10.005013" 116 30' 46.032136" 2497.75 Towill, Inc., rebar and cap 1000 43 38' 01.878959" 116 13' 43.892313" 2667.88 Survey spike 1001 43 39' 47.602157" 116 14' 43.588286" 2677.62 Towill, Inc., rebar and cap 1003 43 34' 49.289124" 116 08' 05.064577" 2794.36 Towill, Inc., rebar and cap 1320 43 39' 49.579858" 116 17' 57.394603" 2601.81 Towill, Inc., rebar and cap 0054 43 41' 29.743950" 116 18' 29.746747" 2593.59 City of Boise 3-1/2 in. brass disk 0057 43 40' 35.534012" 116 17' 59.096446" 2594.49 City of Boise 3-1/2 in. brass disk 0058 43 41' 17.968065" 116 17' 35.181041" 2627.99 City of Boise 3-1/2 in. brass disk 0061 43 40' 21.092060" 116 16' 45.139090" 2613.50 City of Boise 3-1/2 in. brass disk 0062 43 40' 59.141179" 116 16' 35.368934" 2647.24 City of Boise 3-1/2 in. brass disk 0065 43 40' 07.764874" 116 15' 48.158583" 2623.52 City of Boise 3-1/2 in. brass disk 0066 43 38' 51.089084" 116 15' 23.800597" 2636.64 City of Boise 3-1/2 in. brass disk 0067 43 39' 28.391900" 116 14' 54.313479" 2653.02 City of Boise 3-1/2 in. brass disk 0069 43 38' 29.219768" 116 14' 51.240587" 2646.39 City of Boise 3-1/2 in. brass disk 0071 43 37' 24.651125" 116 14' 40.826475" 2660.28 City of Boise 3-1/2 in. brass disk 0073 43 36' 49.706135" 116 13' 48.065" 2730.60 City of Boise 3-1/2 in. brass disk 0074 43 37' 21.848898" 116 13' 08.872" 2679.30 City of Boise 3-1/2 in. brass disk 0077 43 36' 49.214741" 116 12' 19.309962" 2697.61 City of Boise 3-1/2 in. brass disk 0078 43 37' 08.344759" 116 11' 52.592248" 2713.75 City of Boise 3-1/2 in. brass disk 0079 43 35' 43.446757" 116 12' 08.597256" 2714.17 City of Boise 3-1/2 in. brass disk 0080 43 36' 15.195497" 116 11' 27.532879" 2703.36 City of Boise 3-1/2 in. brass disk 0081 43 36' 41.762798" 116 10' 56.335451" 2720.12 City of Boise 3-1/2 in. brass disk 0082 43 35' 14.322297" 116 11' 16.466805" 2725.62 City of Boise 3-1/2 in. brass disk 0083 43 35' 35.925948" 116 10' 35.729307" 2717.91 City of Boise 3-1/2 in. brass disk 0085 43 34' 36.996713" 116 10' 24.121308" 2747.67 City of Boise 3-1/2 in. brass disk 0087 43 35' 48.203490" 116 09' 48.783348" 2746.45 City of Boise 3-1/2 in. brass disk 0089 43 34' 53.750875" 116 08' 57.156839" 3010.49 City of Boise 3-1/2 in. brass disk 0093 43 33' 50.909839" 116 08' 01.099429" 2788.72 City of Boise 3-1/2 in. brass disk 0095 43 33' 58.056905" 116 06' 56.494525" 2796.71 City of Boise 3-1/2 in. brass disk 0096 43 40' 27.284289" 116 15' 37.489770" 2688.30 City of Boise 3-1/2 in. brass disk ADA15 43 41' 31.342325" 116 20' 02.467871" 2570.11 3 in. brass disk ADA16 43 42' 22.988882" 116 28' 23.876911" 2487.48 3 in. brass disk ADA17 43 42' 22.651553" 116 24' 48.872507" 2538.78 3 in. brass disk D3417ECC 43 41' 43.316446" 116 18' 49.570241" 2645.79 PK nail 1 F141 43 36' 34.989986" 116 28' 25.475245" 2527.38 Brass disk IDA8060 43 32' 31.195960" 116 09' 44.588449" 3012.20 Brass disk IDTD 43 38' 01.848780" 116 13' 49.074870" 2666.17 Brass disk 1 K 143 43 42' 57.847043" 116 37' 20.062419" 2419.77 Brass disk NEB 2 43 41' 26.637781" 116 21' 15.207965" 2559.06 Aluminum disk 1 P84RES 43 25' 33.433520" 116 02' 55.651840" 3401.29 Brass disk Y415ECC 43 36' 17.272400" 116 20' 11.002853" 2648.51 Survey spike 1 Elevation reference marks not shown in figure 4 (outside of map limits). 9

Geoid96 was used as the geoid model for the adjustment. The accuracy for these points was determined to be about 2 cm (0.787 in.) vertical and 1 cm (0.394in.) horizontal. Prior to placement of the ERMs, all cross sections were connected vertically by running level lines between the hubs located at each cross section. Each level loop was closed separately and then connected by a level line to at least one ERM before the elevation was transformed to NAVD 88. Finally, all loops were connected and closed according to FEMA guidelines (1995). REFERENCES CITED Brennan, T.S., Lehmann, A.K., O Dell, I., and Tungate, A.M., 1999, Water resources data, Idaho, water year 1998: U.S. Geological Survey Water-Data Report ID 98 2, 366 p. Federal Emergency Management Agency, 1995, Guidelines and specifications for study contractors: U.S. Government Printing Office, 174 p. Quadrant Consulting, Inc., Mc Laughlin Water Engineers, LTD., and Resource Systems, Inc., 1997, An inventory of irrigation diversion structures on the lower Boise and Payette Rivers, Task 1 Report: Boise, Idaho, Quadrant Consulting, Inc., Project Report, 128 p. 10

Star 116 29' 116 27' 44 36 35.29 EXPLANATION River mile marker and mileage from mouth of river Cross section and identification number in river mileage 43 41' 32.89 33.29 33 Boise 33.90 33.60 33.43 33.10 33.76 34.00 34.31 34 34.15 River 34.61 34.47 34.98 35 35.29 35.64 35.94 36.20 36 Boise 36.71 River 34.84 35.14 37 35.49 36.05 36.47 35.79 36.34 36.96 43 41' 13 Ada County Star Road 20 26 43 39' 43 39' 116 29' 116 27' 0 0.5 1.0 1.5 MILES 0 0.5 1.0 1.5 KILOMETERS Figure 5. Locations of cross sections on the Boise River from the Ada/Canyon County boundary to river mile 37, in Ada County, Idaho.

2,466 2,464 2,462 CROSS SECTION 32.89 2,460 2,458 Land Surface 2,456 2,454 2,452 2,450 2,448 2,446 1,600 1,650 1,700 1,750 1,800 1,850 1,900 1,950 2,000 2,050 2,100 2,468 2,466 2,464 2,462 2,460 2,458 2,456 2,454 2,452 2,450 2,448 1,050 1,100 1,150 1,200 1,250 1,300 1,350 1,400 1,450 1, 1,550 2,468 2,466 2,464 2,462 2,460 CROSS SECTION 33.10 CROSS SECTION 33.29 2,458 2,456 2,454 2,452 2,450 2,448 800 850 900 950 1,000 1,050 1,100 1,150 1,200 1,250 1,300 Figure 6. Segments of channel cross sections on the Boise River from the Ada/Canyon County boundary to river mile 37, in Ada County, Idaho. 14

2,474 2,472 2,470 CROSS SECTION 33.43 2,468 2,466 2,464 2,462 2,460 2,458 2,456 2,454 550 600 650 700 750 800 850 900 950 1,000 2,474 2,472 2,470 2,468 2,466 2,464 2,462 2,460 2,458 2,456 2,454 2,476 2,474 2,472 2,470 2,468 CROSS SECTION 33.60 CROSS SECTION 33.76 2,466 2,464 2,462 2,460 2,458 2,456 Figure 6. Segments of channel cross sections on the Boise River from the Ada/Canyon County boundary to river mile 37, in Ada County, Idaho--Continued. 15

2,474 2,472 2,470 CROSS SECTION 33.90 2,468 2,466 2,464 2,462 2,460 2,458 2,456 2,480 2,478 2,476 2,474 2,472 2,470 2,468 2,466 2,464 2,462 2,460 2,480 2,478 2,476 2,474 2,472 CROSS SECTION 34.00 CROSS SECTION 34.15 2,470 2,468 2,466 2,464 2,462 2,460 Figure 6. Segments of channel cross sections on the Boise River from the Ada/Canyon County boundary to river mile 37, in Ada County, Idaho--Continued. 16

2,482 2,480 2,478 CROSS SECTION 34.31 2,476 2,474 2,472 2,470 2,468 2,466 2,464 2,462 2,484 2,482 2,480 2,478 2,476 2,474 2,472 2,470 2,468 2,466 2,464 300 350 400 450 550 600 650 700 750 800 2,486 2,484 2,482 2,480 2,478 CROSS SECTION 34.47 CROSS SECTION 34.61 2,476 2,474 2,472 2,470 2,468 2,466 300 350 400 450 550 600 650 700 750 800 Figure 6. Segments of channel cross sections on the Boise River from the Ada/Canyon County boundary to river mile 37, in Ada County, Idaho--Continued. 17

2,486 2,484 2,482 CROSS SECTION 34.84 2,480 2,478 2,476 2,474 2,472 2,470 2,468 2,466 1,300 1,350 1,400 1,450 1, 1,550 1,600 1,650 1,700 1,750 1,800 2,488 2,486 2,484 2,482 2,480 2,478 2,476 2,474 2,472 2,470 2,468 2,100 2,150 2,200 2,250 2,300 2,350 2,400 2,450 2, 2,550 2,600 2,490 2,488 2,486 2,484 2,482 CROSS SECTION 34.98 CROSS SECTION 35.14 2,480 2,478 2,476 2,474 2,472 2,470 1,600 1,650 1,700 1,750 1,800 1,850 1,900 1,950 2,000 2,050 2,100 Figure 6. Segments of channel cross sections on the Boise River from the Ada/Canyon County boundary to river mile 37, in Ada County, Idaho--Continued. 18

2,492 2,490 2,488 CROSS SECTION 35.29 2,486 2,484 2,482 2,480 2,478 2,476 2,474 2,472 450 550 600 650 700 750 800 850 900 950 2,488 2,486 2,484 2,482 2,480 2,478 2,476 2,474 2,472 2,470 2,468 550 600 650 700 750 800 850 900 950 1,000 2,494 2,492 2,490 2,488 2,486 CROSS SECTION 35.49 CROSS SECTION 35.64 2,484 2,482 2,480 2,478 2,476 2,474 650 700 750 800 850 900 950 1,000 1,050 1,100 1,150 Figure 6. Segments of channel cross sections on the Boise River from the Ada/Canyon County boundary to river mile 37, in Ada County, Idaho--Continued. 19

2,496 2,494 2,492 CROSS SECTION 35.79 2,490 2,488 2,486 2,484 2,482 2,480 2,478 2,476 1,300 1,350 1,400 1,450 1, 1,550 1,600 1,650 1,700 1,750 1,800 2,496 2,494 2,492 2,490 2,488 2,486 2,484 2,482 2,480 2,478 2,476 2,050 2,100 2,150 2,200 2,250 2,300 2,350 2,400 2,450 2, 2,550 2, 2,498 2,496 2,494 2,492 CROSS SECTION 35.94 CROSS SECTION 36.05 2,490 2,488 2,486 2,484 2,482 2,480 2,050 2,100 2,150 2,200 2,250 2,300 2,350 2,400 2,450 2, 2,550 Figure 6. Segments of channel cross sections on the Boise River from the Ada/Canyon County boundary to river mile 37, in Ada County, Idaho--Continued. 20

2,502 2, 2,498 CROSS SECTION 36.20 2,496 2,494 2,492 2,490 2,488 2,486 2,484 2,482 2,000 2,050 2,100 2,150 2,200 2,250 2,300 2,350 2,400 2,450 2, 2, 2,498 2,496 2,494 2,492 2,490 2,488 2,486 2,484 2,482 2,480 1,550 1,600 1,650 1,700 1,750 1,800 1,850 1,900 1,950 2,000 2,050 2,506 2,504 2,502 2, 2,498 CROSS SECTION 36.34 CROSS SECTION 36.47 2,496 2,494 2,492 2,490 2,488 2,486 2,300 2,350 2,400 2,450 2, 2,550 2,600 2,650 2,700 2,750 2,800 Figure 6. Segments of channel cross sections on the Boise River from the Ada/Canyon County boundary to river mile 37, in Ada County, Idaho--Continued. 21

2,506 2,504 2,502 CROSS SECTION 36.71 2, 2,498 2,496 2,494 2,492 2,490 2,488 2,486 1,600 1,650 1,700 1,750 1,800 1,850 1,900 1,950 2,000 2,050 2,100 2,510 2,508 2,506 CROSS SECTION 36.96 2,504 2,502 2, 2,498 2,496 2,494 2,492 2,490 1,900 1,950 2,000 2,050 2,100 2,150 2,200 2,250 2,300 2,350 2,400 Figure 6. Segments of channel cross sections on the Boise River from the Ada/Canyon County boundary to river mile 37, in Ada County, Idaho--Continued. 22

116 25' 116 23' 23 43 41' 37.06 37 Boise 37.22 37.39 38.43 38.57 37.69 37.83 38 37.96 0.32 38.71 0 0.51 Boise 39 38.95 20 26 Linder Road 1 44 38.27 39.12 39.30 39.20 38.10 38.00 0.00 0.20 River 0.69 39.06 39.48 River 1.06 0.86 0.94 39.66 1.24 39.79 40 40.26 40.10 Eagle Island 1.31 1.43 1.75 1.61 Chinden Boise 40.37 41 Eagle,,,,,,,,,,,, 2 1.90 40.64 40.88 40.99 41.31 41.02 2.02 2.26 2.41 Boise 2.55 2.75 2.89 2.67 41.65 41.74 41.43 2.98 3 3.11 41.89 3.31 3.47 43 41',,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, Blvd River River,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 42,,,,,,,,,,,,,,,,,,,,,, 40 40.37 EXPLANATION River mile marker and mileage from mouth of river Cross section and identification number in river mileage 43 39' 43 39' 116 25' 116 23' 0 0.5 1.0 1.5 MILES 0 0.5 1.0 1.5 KILOMETERS Figure 7. Locations of cross sections on the Boise River from river mile 37 to 42, in Ada County, Idaho.

2,510 2,508 2,506 CROSS SECTION 37.06 2,504 2,502 Land Surface 2, 2,498 2,496 2,494 2,492 2,490 750 800 850 900 950 1,000 1,050 1,100 1,150 1,200 1,250 2,510 2,508 2,506 2,504 2,502 2, 2,498 2,496 2,494 2,492 2,490 1,050 1,100 1,150 1,200 1,250 1,300 1,350 1,400 1,450 1, 1,550 2,514 2,512 2,510 2,508 2,506 CROSS SECTION 37.22 CROSS SECTION 37.39 2,504 2,502 2, 2,498 2,496 2,494 200 250 300 350 400 450 550 600 650 700 Figure 8. Segments of channel cross sections on the Boise River from river mile 37 to 42, in Ada County, Idaho. 24

2,516 2,514 2,512 CROSS SECTION 37.69 2,510 2,508 2,506 2,504 2,502 2, 2,498 2,496 1,200 1,250 1,300 1,350 1,400 1,450 1, 1,550 1,600 1,650 1,700 2,518 2,516 2,514 2,512 2,510 2,508 2,506 2,504 2,502 2, 2,498 1,100 1,150 1,200 1,250 1,300 1,350 1,400 1,450 1, 1,550 1,600 2,516 2,514 2,512 2,510 2,508 CROSS SECTION 37.83 CROSS SECTION 37.96 2,506 2,504 2,502 2, 2,498 2,496 1,450 1, 1,550 1,600 1,650 1,700 1,750 1,800 1,850 1,900 1,950 Figure 8. Segments of channel cross sections on the Boise River from river mile 37 to 42 in Ada County, Idaho--Continued. 25

2,512 2,510 2,508 CROSS SECTION 38.00 2,506 2,504 2,502 2, 2,498 2,496 2,494 2,492 2,520 2,518 2,516 2,514 2,512 2,510 2,508 2,506 2,504 2,502 2, 2,520 2,518 2,516 2,514 2,512 CROSS SECTION 38.10 CROSS SECTION 38.27 2,510 2,508 2,506 2,504 2,502 2, Figure 8. Segments of channel cross sections on the Boise River from river mile 37 to 42 in Ada County, Idaho--Continued. 26

2,522 2,520 2,518 CROSS SECTION 38.43 2,516 2,514 2,512 2,510 2,508 2,506 2,504 2,502 2,522 2,520 2,518 2,516 2,514 2,512 2,510 2,508 2,506 2,504 2,502 2,524 2,522 2,520 2,518 2,516 CROSS SECTION 38.57 CROSS SECTION 38.71 2,514 2,512 2,510 2,508 2,506 2,504 100 150 200 250 300 350 400 450 550 600 Figure 8. Segments of channel cross sections on the Boise River from river mile 37 to 42 in Ada County, Idaho--Continued. 27

2,526 2,524 2,522 CROSS SECTION 38.95 2,520 2,518 2,516 2,514 2,512 2,510 2,508 2,506 2,528 2,526 2,524 2,522 2,520 2,518 2,516 2,514 2,512 2,510 2,508 50 100 150 200 250 300 350 400 450 550 2,530 2,528 2,526 2,524 2,522 CROSS SECTION 39.06 CROSS SECTION 39.12 2,520 2,518 2,516 2,514 2,512 2,510 350 400 450 550 600 650 700 750 800 850 Figure 8. Segments of channel cross sections on the Boise River from river mile 37 to 42 in Ada County, Idaho--Continued. 28

2,530 2,528 2,526 CROSS SECTION 39.20 2,524 2,522 2,520 2,518 2,516 2,514 2,512 2,510 2,530 2,528 2,526 2,524 2,522 2,520 2,518 2,516 2,514 2,512 2,510 50 100 150 200 250 300 350 400 450 550 2,532 2,530 2,528 2,526 2,524 CROSS SECTION 39.30 CROSS SECTION 39.48 2,522 2,520 2,518 2,516 2,514 2,512 Figure 8. Segments of channel cross sections on the Boise River from river mile 37 to 42 in Ada County, Idaho--Continued. 29

2,532 2,530 2,528 CROSS SECTION 39.66 2,526 2,524 2,522 2,520 2,518 2,516 2,514 2,512 100 150 200 250 300 350 400 450 550 600 2,534 2,532 2,530 2,528 2,526 2,524 2,522 2,520 2,518 2,516 2,514 100 150 200 250 300 350 400 450 550 600 2,534 2,532 2,530 2,528 2,526 CROSS SECTION 39.79 CROSS SECTION 40.10 2,524 2,522 2,520 2,518 2,516 2,514 550 600 650 700 750 800 850 900 950 1,000 1,050 Figure 8. Segments of channel cross sections on the Boise River from river mile 37 to 42 in Ada County, Idaho--Continued. 30

2,540 2,538 2,536 CROSS SECTION 40.26 2,534 2,532 2,530 2,528 2,526 2,524 2,522 2,520 650 700 750 800 850 900 950 1,000 1,050 1,100 1,150 2,540 2,538 2,536 2,534 2,532 2,530 2,528 2,526 2,524 2,522 2,520 1,000 1,050 1,100 1,150 1,200 1,250 1,300 1,350 1,400 1,450 1, 2,542 2,540 2,538 2,536 2,534 CROSS SECTION 40.37 CROSS SECTION 40.64 2,532 2,530 2,528 2,526 2,524 2,522 1,700 1,800 1,900 2,000 2,100 2,200 2,300 Figure 8. Segments of channel cross sections on the Boise River from river mile 37 to 42 in Ada County, Idaho--Continued. 31

2,544 2,542 2,540 CROSS SECTION 40.88 2,538 2,536 2,534 2,532 2,530 2,528 2,526 2,524 2,800 2,900 3,000 3,100 3,200 3,300 2,546 2,544 2,542 2,540 2,538 2,536 2,534 2,532 2,530 2,528 2,526 2,300 2,350 2,400 2,450 2, 2,550 2,600 2,650 2,700 2,750 2,800 2,546 2,544 2,542 2,540 2,538 CROSS SECTION 40.99 CROSS SECTION 41.02 2,536 2,534 2,532 2,530 2,528 2,526 1,600 1,650 1,700 1,750 1,800 1,850 1,900 1,950 2,000 2,050 2,100 Figure 8. Segments of channel cross sections on the Boise River from river mile 37 to 42 in Ada County, Idaho--Continued. 32

2,550 2,548 2,546 CROSS SECTION 41.31 2,544 2,542 2,540 2,538 2,536 2,534 2,532 2,530 2,100 2,150 2,200 2,250 2,300 2,350 2,400 2,450 2, 2,550 2,600 2,552 2,550 2,548 2,546 2,544 2,542 2,540 2,538 2,536 2,534 2,532 450 550 600 650 700 750 800 850 900 950 2,554 2,552 2,550 2,548 2,546 CROSS SECTION 41.43 CROSS SECTION 41.65 2,544 2,542 2,540 2,538 2,536 2,534 2, 2,550 2,600 2,650 2,700 2,750 2,800 2,850 2,900 2,950 3,000 Figure 8. Segments of channel cross sections on the Boise River from river mile 37 to 42 in Ada County, Idaho--Continued. 33

2,556 2,554 2,552 CROSS SECTION 41.74 2,550 2,548 2,546 2,544 2,542 2,540 2,538 2,536 2,300 2,350 2,400 2,450 2, 2,550 2,600 2,650 2,700 2,750 2,800 2,556 2,554 2,552 CROSS SECTION 41.89 2,550 2,548 2,546 2,544 2,542 2,540 2,538 2,536 1,900 1,950 2,000 2,050 2,100 2,150 2,200 2,250 2,300 2,350 2,400 Figure 8. Segments of channel cross sections on the Boise River from river mile 37 to 42 in Ada County, Idaho--Continued. 34

2,518 2,516 2,514 CROSS SECTION 0.00 2,512 2,510 2,508 Land Surface 2,506 2,504 2,502 2, 2,498 2,522 2,520 2,518 2,516 2,514 2,512 2,510 2,508 2,506 2,504 2,502 2,524 2,522 2,520 2,518 2,516 CROSS SECTION 0.20 CROSS SECTION 0.32 2,514 2,512 2,510 2,508 2,506 2,504 Figure 9. Segments of channel cross sections on the south channel of the Boise River from river mile 0 to 3.5, in Ada County, Idaho. 35

2,524 2,522 2,520 CROSS SECTION 0.51 2,518 2,516 2,514 2,512 2,510 2,508 2,506 2,504 2,526 2,524 2,522 2,520 2,518 2,516 2,514 2,512 2,510 2,508 2,506 2,528 2,526 2,524 2,522 2,520 CROSS SECTION 0.69 CROSS SECTION 0.86 2,518 2,516 2,514 2,512 2,510 2,508 Figure 9. Segments of channel cross sections on the south channel of the Boise River from river mile 0 to 3.5, in Ada County, Idaho--Continued. 36

2,530 2,528 2,526 CROSS SECTION 0.94 2,524 2,522 2,520 2,518 2,516 2,514 2,512 2,510 2,530 2,528 2,526 2,524 2,522 2,520 2,518 2,516 2,514 2,512 2,510 2,534 2,532 2,530 2,528 2,526 CROSS SECTION 1.06 CROSS SECTION 1.24 2,524 2,522 2,520 2,518 2,516 2,514 Figure 9. Segments of channel cross sections on the south channel of the Boise River from river mile 0 to 3.5, in Ada County, Idaho--Continued. 37

2,534 2,532 2,530 CROSS SECTION 1.31 2,528 2,526 2,524 2,522 2,520 2,518 2,516 2,514 2,534 2,532 2,530 2,528 2,526 2,524 2,522 2,520 2,518 2,516 2,514 2,538 2,536 2,534 2,532 2,530 CROSS SECTION 1.43 CROSS SECTION 1.61 2,528 2,526 2,524 2,522 2,520 2,518 100 150 200 250 300 350 400 450 550 600 Figure 9. Segments of channel cross sections on the south channel of the Boise River from river mile 0 to 3.5, in Ada County, Idaho--Continued. 38

2,538 2,536 2,534 CROSS SECTION 1.75 2,532 2,530 2,528 2,526 2,524 2,522 2,520 2,518 2,540 2,538 2,536 2,534 2,532 2,530 2,528 2,526 2,524 2,522 2,520 550 600 650 700 750 800 850 900 950 1,000 2,542 2,540 2,538 2,536 2,534 CROSS SECTION 1.90 CROSS SECTION 2.02 2,532 2,530 2,528 2,526 2,524 2,522 Figure 9. Segments of channel cross sections on the south channel of the Boise River from river mile 0 to 3.5, in Ada County, Idaho--Continued. 39

2,544 2,542 2,540 CROSS SECTION 2.26 2,538 2,536 2,534 2,532 2,530 2,528 2,526 2,524 2,546 2,544 2,542 2,540 2,538 2,536 2,534 2,532 2,530 2,528 2,526 2,548 2,546 2,544 2,542 2,540 CROSS SECTION 2.41 CROSS SECTION 2.55 2,538 2,536 2,534 2,532 2,530 2,528 Figure 9. Segments of channel cross sections on the south channel of the Boise River from river mile 0 to 3.5, in Ada County, Idaho--Continued. 40

2,550 2,548 2,546 CROSS SECTION 2.67 2,544 2,542 2,540 2,538 2,536 2,534 2,532 2,530 2,548 2,546 2,544 2,542 2,540 2,538 2,536 2,534 2,532 2,530 2,528 2,550 2,548 2,546 2,544 2,542 CROSS SECTION 2.75 CROSS SECTION 2.89 2,540 2,538 2,536 2,534 2,532 2,530 Figure 9. Segments of channel cross sections on the south channel of the Boise River from river mile 0 to 3.5, in Ada County, Idaho--Continued. 41

2,552 2,550 2,548 CROSS SECTION 2.98 2,546 2,544 2,542 2,540 2,538 2,536 2,534 2,532 2,556 2,554 2,552 2,550 2,548 2,546 2,544 2,542 2,540 2,538 2,536 2,556 2,554 2,552 2,550 2,548 CROSS SECTION 3.11 CROSS SECTION 3.31 2,546 2,544 2,542 2,540 2,538 2,536 Figure 9. Segments of channel cross sections on the south channel of the Boise River from river mile 0 to 3.5, in Ada County, Idaho--Continued. 42

2,560 2,558 CROSS SECTION 3.47 2,556 2,554 2,552 2,550 2,548 2,546 2,544 2,542 2,540 Figure 9. Segments of channel cross sections on the south channel of the Boise River from river mile 0 to 3.5, in Ada County, Idaho--Continued. 43

116 21' 116 19' EXPLANATION 44 42.01 42.31 42 Eagle Road Eagle 42.17 42.46 42.85 43.21 43.45 43.61 44 44.02 42.75 43 44 43 41' 43.35 43.01 44.31 43 41' 3.94 Eagle Island 43.85 44.57 44.80 3.75 4.37 4.60 4 4.98 44.20 45.00 45.20 5 44.43 44.66 5.26 4.52 4.80 5.51 45.41 3.65 4.06 45 45.94 45.57 45.73 4.24 5.09 55 5.63 5.39 5.69 6 6.20 5.88 6.02 6.35 6.52 6.62 6.71 45.75,,,,,,,,,, 20 26 Boise Eagle Road 42.64 43.40 River Boise Chinden,,,,,,,,,,,,,,,,,,,,,,,,, Boise,,,,,, 45.94,,,,,,,,,,,, 46.19 46.32 46 46.07 46.64,,,,,, 46.91 46.29 46.52,,,,,, 46.76 47,,,,,, Garden City,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 43 39' 43 39' 116 21' 116 19' 55 River Boise State Street Blvd 0 River 0.5 44 44.43 River mile marker and mileage from mouth of river Cross section and identification number in river mileage 1.0 1.5 MILES Figure 10. Locations of cross sections on the Boise River from river mile 42 to 47, in Ada County, Idaho. 0 0.5 1.0 1.5 KILOMETERS

2,556 2,554 2,552 2,550 Land Surface CROSS SECTION 42.01 2,548 2,546 2,544 2,542 2,540 2,538 2,536 2,000 2,050 2,100 2,150 2,200 2,250 2,300 2,350 2,400 2,450 2, 2,560 2,558 2,556 2,554 2,552 2,550 2,548 2,546 2,544 2,542 2,540 2,000 2,050 2,100 2,150 2,200 2,250 2,300 2,350 2,400 2,450 2, 2,560 2,558 2,556 2,554 2,552 CROSS SECTION 42.17 CROSS SECTION 42.31 2,550 2,548 2,546 2,544 2,542 2,540 2,000 2,050 2,100 2,150 2,200 2,250 2,300 2,350 2,400 2,450 2, Figure 11. Segments of channel cross sections on the Boise River from river mile 42 to 47, in Ada County, Idaho. 45

2,562 2,560 2,558 CROSS SECTION 42.46 2,556 2,554 2,552 2,550 2,548 2,546 2,544 2,542 1,900 1,950 2,000 2,050 2,100 2,150 2,200 2,250 2,300 2,350 2,400 2,562 2,560 2,558 2,556 2,554 2,552 2,550 2,548 2,546 2,544 2,542 2,300 2,350 2,400 2,450 2, 2,550 2,600 2,650 2,700 2,750 2,800 2,566 2,564 2,562 2,560 2,558 CROSS SECTION 42.64 CROSS SECTION 42.75 2,556 2,554 2,552 2,550 2,548 2,546 1,600 1,650 1,700 1,750 1,800 1,850 1,900 1,950 2,000 2,050 2,100 Figure 11. Segments of channel cross sections on the Boise River from river mile 42 to 47, in Ada County, Idaho--Continued. 46

2,566 2,564 2,562 CROSS SECTION 42.85 2,560 2,558 2,556 2,554 2,552 2,550 2,548 2,546 50 100 150 200 250 300 350 400 450 550 2,570 2,568 2,566 2,564 2,562 2,560 2,558 2,556 2,554 2,552 2,550 2,570 2,568 2,566 2,564 2,562 CROSS SECTION 43.01 CROSS SECTION 43.21 2,560 2,558 2,556 2,554 2,552 2,550 Figure 11. Segments of channel cross sections on the Boise River from river mile 42 to 47, in Ada County, Idaho--Continued. 47

2,570 2,568 2,566 CROSS SECTION 43.35 2,564 2,562 2,560 2,558 2,556 2,554 2,552 2,550 2,574 2,572 2,570 2,568 2,566 2,564 2,562 2,560 2,558 2,556 2,554 2,576 2,574 2,572 2,570 2,568 CROSS SECTION 43.40 CROSS SECTION 43.45 2,566 2,564 2,562 2,560 2,558 2,556 Figure 11. Segments of channel cross sections on the Boise River from river mile 42 to 47, in Ada County, Idaho--Continued. 48

2,576 2,574 2,572 CROSS SECTION 43.61 2,570 2,568 2,566 2,564 2,562 2,560 2,558 2,556 2,578 2,576 2,574 2,572 2,570 2,568 2,566 2,564 2,562 2,560 2,558 2,580 2,578 2,576 2,574 2,572 CROSS SECTION 43.85 CROSS SECTION 44.02 2,570 2,568 2,566 2,564 2,562 2,560 Figure 11. Segments of channel cross sections on the Boise River from river mile 42 to 47, in Ada County, Idaho--Continued. 49

2,582 2,580 2,578 CROSS SECTION 44.20 2,576 2,574 2,572 2,570 2,568 2,566 2,564 2,562 2,584 2,582 2,580 2,578 2,576 2,574 2,572 2,570 2,568 2,566 2,564 2,586 2,584 2,582 2,580 2,578 CROSS SECTION 44.31 CROSS SECTION 44.43 2,576 2,574 2,572 2,570 2,568 2,566 Figure 11. Segments of channel cross sections on the Boise River from river mile 42 to 47, in Ada County, Idaho--Continued. 50

2,586 2,584 2,582 CROSS SECTION 44.57 2,580 2,578 2,576 2,574 2,572 2,570 2,568 2,566 2,588 2,586 2,584 2,582 2,580 2,578 2,576 2,574 2,572 2,570 2,568 2,590 2,588 2,586 2,584 2,582 CROSS SECTION 44.66 CROSS SECTION 44.80 2,580 2,578 2,576 2,574 2,572 2,570 Figure 11. Segments of channel cross sections on the Boise River from river mile 42 to 47, in Ada County, Idaho--Continued. 51

2,594 2,592 2,590 CROSS SECTION 44.94 2,588 2,586 2,584 2,582 2,580 2,578 2,576 2,574 2,594 2,592 2,590 2,588 2,586 2,584 2,582 2,580 2,578 2,576 2,574 2,596 2,594 2,592 2,590 2,588 CROSS SECTION 45.00 CROSS SECTION 45.20 2,586 2,584 2,582 2,580 2,578 2,576 1,100 1,150 1,200 1,250 1,300 1,350 1,400 1,450 1, 1,550 1,600 Figure 11. Segments of channel cross sections on the Boise River from river mile 42 to 47, in Ada County, Idaho--Continued. 52

2,600 2,598 2,596 CROSS SECTION 45.41 2,594 2,592 2,590 2,588 2,586 2,584 2,582 2,580 550 600 650 700 750 800 850 900 950 1,000 2,602 2,600 2,598 2,596 2,594 2,592 2,590 2,588 2,586 2,584 2,582 800 850 900 950 1,000 1,050 1,100 1,150 1,200 1,250 1,300 2,604 2,602 2,600 2,598 2,596 CROSS SECTION 45.57 CROSS SECTION 45.73 2,594 2,592 2,590 2,588 2,586 2,584 Figure 11. Segments of channel cross sections on the Boise River from river mile 42 to 47, in Ada County, Idaho--Continued. 53