Sodom and Shearer Dam Removal Hydraulic Modeling Report

Prepared For Prepared By Calapooia Watershed Council Design Group, Inc. PO Box 844 311 SW Jefferson Avenue Brownsville, Oregon 97327 Corvallis, Oregon 97333

DRAFT April 2011 DRAFT Sodom and Shearer Dam Removal Hydraulic Modeling Report Executive Summary

The Calapooia Watershed Council, in cooperation with private landowners and the Oregon Parks and Recreation Department, is leading the effort to remove Sodom and Shearer dams in the Calapooia River watershed. In order to facilitate this effort, hydraulic modeling of the existing condition and proposed condition after the dams are removed is necessary. This report details the different hydraulic models that were developed to evaluate typical flow conditions and the 100-year base . Four hydraulic models were developed as summarized below:

 Stage- Model: The first model is a simple at-a-section hydraulic cross-section model to help develop stage-discharge relationships and also used to help calibrate more complex models.

 Calapooia River – Sodom Ditch Bifurcation Model: The second model is a detailed 1- dimensional model of the Sodom Ditch – Calapooia River bifurcation area used primarily for flows below the 5-year peak flow. The model was run for both the existing and proposed channel conditions associated with the Sodom Dam removal and Sodom Ditch reconstruction.

 Shearer Dam Model: The third model is a detailed model at the Shearer Dam project site that again addresses flows less than the 5-year peak.

 Base Flood Model: The final hydraulic model evaluates dam removal impacts on the 100-year at both the Sodom and Shearer dams.

Hydraulic modeling results from the bifurcation downstream to Sodom Dam, demonstrated that the proposed dam removal and Sodom Ditch reconstruction will maintain split flow conditions similar to the existing condition. Hydraulic modeling for the Shearer Dam removal and channel reconstruction yielded similar results. The post-dam removal condition computed water surface elevations were reduced in the proposed project condition model immediately upstream of the dam, compared to the existing condition model results. The reduced water surface elevations are attributed to the removal of the backwater condition created by the dam.

The Base Flood model predicted that the proposed dam removals and channel reconstruction will have little or no influence on the 100-year water surface elevation through the project area. A small difference in water surface elevations was identified at Sodom Dam due to the localized hydraulic effects of the structure. These effects were slight and the proposed condition resulted in lowered base flood water surface elevations in the reach upstream of the dam due to channel restoration and vertical realignment. The removal of Sodom Dam and Shearer Dam has little discernible effect on the base flood water surface elevations due to the broad, low velocity inundation and flooding extents within the bottom. These conditions have a greater hydraulic influence than the two structures on the base flood elevation. Based on this analysis the proposed project has no effect on the overall Base Flood elevation within the

i April 2011 Sodom and Shearer Dam Removal Hydraulic Modeling Report project area. There are no insured structures that will be impacted by the project and National Flood Insurance Program (NFIP) flood risk status is not affected

(electronic signatures)

ii April 2011 Sodom and Shearer Dam Removal Hydraulic Modeling Report Table of Contents

1 Introduction ...... 1 2 Supporting Model Input Information ...... 2 2.1 Topographic Surface Model ...... 2 2.2 Hydrology ...... 4 2.2.1 100-year Flows ...... 5 2.2.2 Summer Flows ...... 5 2.2.3 Bifurcation Split Flows ...... 5 3 Hydraulic Models ...... 8 3.1 Stage-Discharge Models ...... 9 3.2 Bifurcation Model...... 10 3.2.1 Bifurcation Model Calibration...... 12 3.3 Shearer Dam Model ...... 13 3.3.1 Shearer Dam Model Calibration ...... 14 3.4 Base Flood Model ...... 14 3.4.1 Base Flood Model Calibration ...... 17 4 Results ...... 19 4.1 Calapooia River – Sodom Ditch Bifurcation Model (5-year and Lower Flows) ...... 19 4.2 Shearer Dam Model (5-year and Lower Flows) ...... 23 4.3 Base Flood Model ...... 24 5 Conclusions ...... 28 5.1 Sodom Dam Removal and Bifurcation ...... 29 5.2 Shearer Dam Removal ...... 29

Appendix A: Sodom and Shearer Dam Removal and Restoration Drawings Appendix B: Hydraulic Modeling Output Appendix C: FEMA 100-year Profiles

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1 Introduction River Design Group, Inc. (RDG) was retained by the Calapooia Watershed Council (CWC) to prepare dam removal and restoration designs for the Calapooia River and Sodom Ditch near Shedd, Oregon. The project included remote sensing, field data collection, geomorphic assessment, hydraulic modeling and dam removal plans with channel restoration designs. Hydrologic and hydraulic modeling was completed to evaluate flow conditions at the bifurcation, floodplain impacts, and restoration treatments for the Calapooia River and Sodom Ditch. This report describes the hydraulic models developed for analyzing project impacts, the results of the proposed dam removals, and the rationale supporting proposed restoration designs to mitigate altered conditions. The project vicinity map with Shearer Dam and Sodom Dam is shown in Figure 1-1.

Figure 1-1. Project vicinity map showing the dam locations, Calapooia River, and Sodom Ditch.

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2 Supporting Model Input Information

2.1 Topographic Surface Model In order to develop an accurate hydraulic model, it was necessary to procure a comprehensive bare-earth surface model of the floodplain and surrounding area. The floodplain and extended surface model data for the study reach were developed by Watershed Sciences Inc. using Light Detection and Ranging (LiDAR) methods in September 2008 as part of the larger Willamette Valley Phase I study conducted for the Oregon Department of Geology and Mineral Industries (DOGAMI). Data were delivered to DOGAMI in OGIC(HARN), Projection: Oregon Statewide Lambert Conformal Conic; horizontal and vertical datums: NAD83 (HARN)/NAVD88(Geoid03); Units: International Feet. Average pulse density of points delivered was 0.80 points per square foot. Average relative elevation accuracy of over fifteen billion points collected was 0.103 feet (3.1 cm).

LiDAR does not accurately penetrate through water so physical field surveys were conducted to supplement the LiDAR data. Field data collection to characterize existing conditions within the study reach was conducted by RDG at various locations between October 2008 and January 2009. Data collection included quality control topographic survey of channel features, floodplain areas, and water surface elevations for subsequent hydraulic model calibration. Quality control topography and bathymetry were measured with survey-grade real-time kinematic GPS methods with a nominal accuracy of ±3 cm, consistent with LiDAR accuracy. Data from surveyed locations were processed and integrated into the topographic surface model developed from the LiDAR data at each of the dam locations as shown in Figures 2-1 and 2-2. Survey control monuments were also installed through the study reach for reference during future surveying or construction.

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Figure 2-1. A map of the bifurcation area showing Sodom Ditch and Calapooia River, and Sodom Dam.

Topographic and bathymetric survey measurements were merged with the LiDAR measurements to prepare a seamless terrain model of the study reach suitable for hydraulic modeling. Approximate channel invert elevations at un-surveyed locations were interpolated based on a LiDAR-channel reduction estimate. The nominal accuracy for the merged LiDAR- channel reduction terrain model is estimated to be on the same order as the data acquisition accuracy and is sufficient for hydraulic modeling purposes.

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Figure 2-2. A map of the Shearer Dam project area including the Calapooia River, Walton Slough, Thompson’s Mills millrace, and Spillway Dam.

2.2 Hydrology Flows in the Calapooia River vary greatly throughout the year due to seasonal precipitation and to a lesser extent, summer water use. The average monthly January flow in Albany is 55 times the average August monthly flow. Nearly 90 percent of the runoff occurs during the six wettest months (November through April). Rain-on-snow flood events have been responsible for the largest of record. These events typically occur between December and February when warm storms rain on low elevation snowpack that rapidly melts and contributes to runoff.

As part of an initial planning process to provide fish passage at Sodom Dam, Tetra Tech (2008) developed a hydrologic analysis of flows at the bifurcation. The flow analysis was performed based on the Guidelines for Determining Flood Flow Frequency, Bulletin #17B (USGS 1982). Data were obtained from two historical gage stations. Gage station 1417200 is located upstream of the study area near the town of Holley, and has a period of record from 1935 to 1990. The second station, 14173500, is located downstream of the study area near Albany with a period of record from 1940 to 1981. Once the peak flows were determined for each gage station, in accordance with Bulletin 17B, corresponding flow rates were calculated for the bifurcation using proportional ratios of drainage areas as summarized in Table 2-1. These predicted flows at the bifurcation serve as the basis for hydraulic modeling flows.

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Table 2-1. Results of the log-Pearson Type III probability distribution for Gage 14173500, Gage 1417200, and regionalized flow at bifurcation point (Tetra Tech 2008). Drainage Recurrence Interval (yrs) and Instantaneous Peak Flow (cfs) Area Location (sq. mi.) 1.01 2 5 10 25 50 100 500 Gage 14173500 372 2,921 12,104 19,727 25,300 32,954 38,967 45,219 51,798 (Albany)

Gage 14172000 101 1,904 5,488 7,915 9,552 11,644 13,214 14,787 16,387 (Holley) Calculated Bifurcation 164 2,140 7,021 10,652 13,207 16,582 19,181 21,837 24,591 Flow

2.2.1 100-year Flows Hydraulic modeling of peak flows are of interest to understand potential changes to water surface elevations and conditions upstream and downstream of the dam removal projects. The 100-year discharge in Table 2-1 is in agreement with the 22,000 cfs defined in the Flood Insurance Study for Linn County, Oregon and Incorporated Areas as defined at the Brownsville Bridge on the Calapooia River (FEMA 2010). Modeling of the 100-year flow provides the necessary analysis for evaluating the impacts to the base flood elevation as established by FEMA for a no-rise certification.

2.2.2 Summer Flows Low summer flows are also of primary interest to ensure flow continues to be routed to the Calapooia River downstream of the bifurcation and that conditions are suitable for fish passage on both the Calapooia River and Sodom Ditch. Flows at or less than 100 cfs are modeled to determine the estimated split flow conditions based on the restoration design at the bifurcation.

2.2.3 Bifurcation Split Flows The bifurcation area, where flow splits from the Calapooia River into the Sodom Ditch, has historically been a highly dynamic area as shown in Figure 2-3. The bifurcation is a natural collection site for large wood and sediment that deposits as a result of split flow conditions and lack of flow competence. As a result, the split flow conditions are highly variable and often change after high flow events. Understanding the flow split is an important part of the hydraulic modeling effort and necessary to appropriately design the bifurcation area to improve stability.

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Figure 2-3. View of bifurcation showing variable conditions resulting from large wood and sediment accumulation and historical maintenance (right photo).

Measured discharge from 2002 to 2004 by the Oregon Water Resources Department (OWRD) watermaster concluded that approximately 67% of the flow was being conveyed down the Sodom Ditch and 33% down the Calapooia River. Subsequent hydraulic modeling in 2008 by Tetra Tech concluded that the flow split to Sodom Ditch was higher than previously estimated, ranging from 69% to 78% based on an uncalibrated HEC-RAS hydraulic modeling effort (Tetra Tech 2008). To further investigate the flow split, RDG performed actual flow measurements at the bifurcation from 2008 through 2011 (assistance provided by Oregon State University in 2010 and 2011). This field data collection effort revealed the flow division at the bifurcation is currently closer to 85% or more in favor of Sodom Ditch. Table 2-2 summarizes measured discharge upstream and downstream of the bifurcation. The data are a combination of measurements from Oregon State University (OSU) and RDG.

Table 2-2. Summary of measured discharge data near bifurcation. Calapooia River at Linn West Sodom Ditch at Linn West Rd Rd Upstream of Field Data Discharge Percent of Total Discharge Percent of Bifurcation Collection Date (cfs) Flow (cfs) Total Flow (cfs)* Nov. 5, 2009 91 17 18% 79 82%

June 16, 2010 448 96 9% 407 91%

Jan. 13, 2011 752 89 12% 663 88%

Jan. 18, 2011 2,532 309 14% 1,894 86%

Feb. 8, 2011 400 37 11% 302 89%

*Calapooia River discharge measured or estimated from rating table for the Calapooia River at Brownsville bridge and does not represent the sum of Sodom Ditch and Calapooia River downstream of bifurcation.

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In summary, the following conclusions regarding the split flow conditions were determined from the historical documentation, hydraulic analysis performed by Tetra Tech and the additional field data collected by OSU and RDG.  The division of flow to Sodom Ditch from the bifurcation is highly variable depending on stage and discharge, but is generally in the range of 85% or more of the split flow being conveyed down Sodom Ditch.  Reduced bifurcation area maintenance (e.g., sediment and debris removal), continued sediment and large wood accumulation, and natural river processes have put the river on a trajectory to reduce flows down the Calapooia River over time. Debris and sediment accumulations during peak flow events have in the past, required maintaining the opening to the Calapooia River. Routine maintenance has included excavating sediment and removing large wood to ensure low flow conveyance to the Calapooia River.

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3 Hydraulic Models Hydraulic modeling was performed using HEC-RAS v4.1 (Army Corps of Engineers 2010), a 1- dimensional, steady-state, hydraulic model. This program was selected for several reasons. First, the software is publicly available and has excellent support from the Hydrologic Engineering Center (HEC) for continual updates. Second, the software is an industry standard for modeling river environments and restoration projects. Third, the information and modeling is easily transferable to other platforms for additional rendering. Fourth, the watershed council or review agencies (i.e. Linn County) can use the files and information we generate to do further analysis if desired. The models are calibrated and adjusted based on field discharge measurements, field survey data, and channel bed material information. Correcting the hydraulic model is a critical step to enhance the accuracy of the model and calibrate roughness coefficients for model validity.

The HEC-RAS model solves the energy equation using an iterative technique for a given hydraulic condition. This technique results in a solution to all variables in the energy equation (i.e., velocity, hydraulic head, fiction losses, etc.) at any given or interpolated cross-section. Inherent assumptions of the model are that the situation is steady-state, gradually varied, channel slopes are less than 1 on 10, and flow is 1-dimensional and uniform within a streamline. The model has the ability to simulate subcritical flow, supercritical flow, and a combination of the two for open channels. The model will produce average channel velocities at each cross-section and has the ability to produce pseudo two-dimensional velocities at a cross-section. The pseudo two-dimensional velocity analysis is performed by a combination of applying variable Manning’s n-value coefficients across the cross-section and subdividing each cross-section into vertical slices, computing the slice conveyance and calculating resulting velocities in each slice for a given discharge.

Multiple hydraulic models were developed in order to generate the hydraulic analysis needed for evaluating the proposed dam removals and potential impacts on the adjancent project areas. An overview and the purpose for each model is provided below:

 Stage-Discharge Model: The most basic model is an at-a-section hydraulic cross-section model. This is the only non HEC-RAS model developed and is only used to create stage- discharge relationships useful for calibrating the more complex HEC-RAS models.

 Bifurcation Model: The second model is a detailed 1-dimensional model of the Sodom Ditch – Calapooia River bifurcation area used primarily for flows below the 5-year peak flow. The model was run for both the existing and proposed channel conditions associated with the Sodom Dam removal and Sodom Ditch reconstruction.

 Shearer Dam Model: The third model is a detailed model at the Shearer Dam project site that again addresses flows less than the 5-year peak.

 Base Flood Model: The final hydraulic model evaluates dam removal impacts on the 100-year floodplain at both the Sodom and Shearer dams.

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A thorough understanding of 1-dimensional hydraulic modeling capabilities is necessary to accurately model the dam removals due to the low gradient of the project area, numerous floodplain obstructions (i.e. Linn West Road bridges, other bridges, Interstate 5 road prism, etc.), and inflows from the west side of Interstate 5. The following sections describe the four hydraulic models developed for the dam removal projects.

3.1 Stage-Discharge Models Multiple hydraulic cross-sections were established on the Calapooia River and Sodom Ditch as shown in Figure 3-1. These cross-sections were located to 1) develop stage-discharge relationships at particular locations in the project area, 2) to determine flow partitioning between the Sodom Ditch and Calapooia River by recording discharge in the two segments, and 3) to develop Manning’s n-values useful for the more complex HEC-RAS hydraulic models. Staff plates were established at several locations to facilitate repeated stage observations.

Figure 3-1. The project area map showing detailed hydraulic cross-section locations.

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An example of a hydraulic channel cross-section established for the project is shown in Figure 3- 2. The cross-section is located upstream of the bifurcation on the Calapooia River. The survey included a cross-section, channel profile, discharge measurement, and river bed material characterization with a pebble count. The cross-section, like the other hydraulic cross-sections, provides observed water surface elevations for calculating reach roughness coefficients (e.g. Manning's n-values).

100 Bed Surface Bankfull Series 95 Water Surface

90 Elevation (ft) 85

80 0 20 40 60 80 100 120 140 160 180 200 Distance (ft)

Bankfull Area Mean Depth Maximum Depth Feature Width (ft) (ft2) (ft) (ft) /Run 111.0 613.5 5.5 7.1

Figure 3-2. A Calapooia River hydraulic cross-section established upstream of the bifurcation. The left photo shows a view looking upstream at the cross-section during low flow conditions and the right photo shows higher flow conditions, approximately 1,800 cfs. The surveyed hydraulic cross-section and sectional properties are shown in the table.

3.2 Bifurcation Model A detailed HEC-RAS model was developed from LiDAR and bathymetric survey data for the bifurcation area as shown in Figure 3-3. The model was developed to analyze low flows and flow conditions less than the 5-year peak flow. The primary purposes of this model were to 1) aid with design of the bifurcation configuration, 2) develop representative split flow conditions consistent with measured field data, and 3) evaluate proposed characteristics for

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Sodom Ditch following dam removal with restoration. High flow and flood conditions that activate the adjacent floodplain for conveyance required a separate hydraulic model that is presented in Section 3.4.

Figure 3-3. Detailed HEC-RAS hydraulic model cross-section locations through the Calapooia River – Sodom Ditch bifurcation area that were used for modeling flows less than the 5-year peak flow.

The Bifurcation Model consists of 100 cross-sections with a split flow junction at the channel bifurcation between the Calapooia River and Sodom Ditch. The main channel consists of two reaches including the Upper Calapooia River and the Sodom Ditch and includes a combined 71 cross-sections. The Calapooia reach downstream from the bifurcation was modeled with 29 cross-sections.

The existing Sodom Dam configuration was modeled using the HEC-RAS inline weir option with structure geometry taken from topographic survey data collected on-site. The proposed condition model used the same section lines, ineffective flow locations, reach lengths and generally the same bank stations as the existing condition model. Modifications for the proposed condition model included the removal of Sodom Dam and updated cross-section geometries from the topographic surface model prepared from the restoration project design grading plan. The proposed restoration design grading for Sodom Ditch includes three engineered rock , multiple pools, and vertical channel realignment from the bifurcation through the Sodom Dam location.

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3.2.1 Bifurcation Model Calibration The Calapooia River – Sodom Ditch reach scale hydraulic model was evaluated by determining local roughness coefficients from measured water surface elevations, velocities and discharges summarized in Section 2.1. Low flow measurements allowed for the calibration of the section Manning’s roughness coefficient that was extended to the overall project reach. Three flow events were analyzed to determine the Manning’s n-value coefficient at the hydraulic section near the bifurcation. Table 3-1 presents the flows and calculated coefficients for this site that were used for the reach scale hydraulic model. Selection of the proper roughness coefficient is critical because it has a significant influence on the calculated water surface elevations for the hydraulic model. A range of Manning's roughness values between 0.04 and 0.07 where used for the modeling efforts.

Table 3-1. Summary of flows and calculated Manning’s n-values for the Calapooia River-Sodom Ditch bifurcation area. Channel Parameters Calculated Calculated Manning’s Date Discharge (cfs) Area (ft2) Slope (ft/ft) n-value 10/28/2009 136.3 3,775 0.022 0.062 6/16/2010 157.5 5,425 0.022 0.040

Figure 3-4 shows the hydraulic model water surface profile at a flow of 136 cfs in the Upper Calapooia and Sodom Ditch reach. This was a low flow condition with observed water surface elevations and the modeled water surface included in the hydraulic model for calibration purposes.

Figure 3-4. Calibration of existing conditions model at the bifurcation and Sodom Ditch segment with observed water surface (OWS) markers and modeled water surface elevations at measured discharge.

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3.3 Shearer Dam Model Similar to the Sodom Dam and bifurcation area, a detailed HEC-RAS model was developed from LiDAR and bathymetric survey data for Shearer Dam as shown in Figure 3-5. The model was developed to analyze flow conditions less than the 5-year peak flood. The primary purpose of this model is to 1) evaluate existing conditions, 2) develop proposed conditions and impacts on surrounding water levels, and 3) evaluate stream characteristics of the proposed design for the Calapooia River after the Shearer Dam removal. For higher flow conditions that activate the adjacent floodplain for conveyance, a separate model was developed and is presented in Section 3.4.

Figure 3-5. Image of detailed HEC-RAS hydraulic model cross-section locations for Shearer Dam. The model was developed for flows less than the 5-year peak flood.

Similar to the Calapooia River-Sodom Ditch Bifurcation Model, the Shearer Dam reach scale hydraulic model was developed to evaluate the existing river conditions and the hydraulic effects of the proposed project. The Shearer Dam reach model consists of 18 cross-sections with Shearer Dam modeled using the inline weir option within HEC-RAS. The structure geometry was taken from topographic survey data collected on-site. The proposed condition model used the same section lines, locations, ineffective flow locations, reach lengths and generally the same bank stations for the proposed condition model. In the proposed condition model, Shearer Dam was removed and the cross-section geometries were updated from the topographic surface model prepared from the project design grading plan.

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3.3.1 Shearer Dam Model Calibration The Shearer Dam hydraulic model was calibrated based on survey measurements taken at the project site on 07/22/10. Velocity measurements and channel geometry were used to perform a discharge calculation for the date of the survey. The calculated flow at Shearer Dam was 29 cfs on this date. The hydraulic grade line was also surveyed to provided calibration data points for the hydraulic model. Manning’s roughness coefficients were incrementally adjusted within the model until the computed water surface profile closely matched the measured values. The calibrated Manning’s n-value for the Shearer Dam reach resulted in reasonable values considering the channel morphology, vegetation, and characteristics. A value of 0.04 was determined by adjusting the model to match the observed water surface elevations. Figure 3-6 includes the water surface profile for Shearer Dam at 29 cfs showing observed water surfaces from field data collection.

River #1 Reach #1 264 Legend

WS 072210 Field Wor

Ground 262 OWS 072210 Field Wor

260

258 Elevation(ft)

256

254

30 40 50 60 70 80 90 100 110 115 Shearer Dam 130 140 150 160 170 180 252 20 0 200 400 600 800 1000 Main Channel Distance (ft) Figure 3-6. The HEC-RAS model channel profile for Shearer Dam showing observed water surfaces at the calibration flow.

3.4 Base Flood Model The study reach from the bifurcation to Shearer Dam is characterized by a broad floodplain with a nominal valley slope of ~0.1%. for both the Calapooia River and Sodom Ditch are effectively divided by Interstate 5 into east and west areas, and by Linn West Road into north and south areas. Flow in the reach can be broadly divided into a dual conveyance regime whereby under low to moderate discharge conditions, the incoming flow from the Calapooia River splits and is routed separately through the Calapooia River and Sodom Ditch. As the flow increases beyond the point of incipient flooding, the Calapooia River and Sodom Ditch share a common floodplain and overbank flows are no longer distinct between the two channels. In general, this transition to overbank flooding begins around 7,000 cfs with a nominal recurrence

14 April 2011 Sodom and Shearer Dam Removal Hydraulic Modeling Report interval of 2 years. At this discharge, the Calapooia River downstream of the bifurcation appears to convey less than 20% of the total flow (as measured upstream of the bifurcation) with overbank flow inundating the low floodplain areas to the west. The Sodom Ditch conveys the remaining 80% of the flow. The resultant, approximately 5,600 cfs, remains in-channel on Sodom Ditch.

In order to predict the hydraulic response of dam removal at high flow regimes and the potential impacts to the 100-year floodplain, the Base Flood model was developed to include the bifurcation, Sodom Dam, and Shearer Dam areas. Figure 3-7 shows the Base Flood model’s cross-section locations that were used for evaluating peak flows between the 5-year event (10,000 cfs) and the 100-year event (22,000 cfs). The model required that modified cross- section geometry be prepared to account for the fully effective floodplain. Base flood elevations (BFE) from FIRM Panels 410136-(355B, 365B and 370B) were incorporated into the model to provide comparison points and for calibration.

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Figure 3-7. The HEC-RAS Base Flood hydraulic model schematic layout including the Upper Calapooia, Old Calapooia, and Sodom Ditch.

The floodplain model was developed on a terrain surface generated from combined bathymetry and LiDAR. In some areas, only LiDAR surface information was available for the model. The model consists of 64 cross-sections, and includes 6 bridge cross-sections and 2 inline structures for Sodom and Shearer dams. Similar to the reach scale models discussed previously, both existing condition and proposed condition models were prepared. The proposed condition

16 April 2011 Sodom and Shearer Dam Removal Hydraulic Modeling Report model was modified by removing Sodom and Shearer dams with updated cross-section geometry representing the proposed channel improvements.

3.4.1 Base Flood Model Calibration The Base Flood model was compared against water surface profile elevations presented in the Flood Insurance Study (FIS), Linn County, Oregon and Incorporated Areas (FEMA 2010). In the FIS, base flood water surface elevations were published and were entered into the project hydraulic model as observed water surfaces (OWS). The FIS contained three model cross- sections (W, X, and Y as shown in Appendix C) within the reach represented by the Base Flood model. The FIS Report identified:

“Hydraulic roughness values (Manning’s “n”) for the channel and overbanks were first estimated from field observation. The “n” values were then adjusted to match high- water marks where available. The “n” values are shown in Table 7 for all studied in detailed using the HEC-2 computer model.”

For the Calapooia River on the FIS Calapooia River Split Flow Model Reach, roughness coefficients were reported as 0.070 for the channel and 0.200 for the floodplain areas. These coefficients were used by RDG in the Base Flood model analysis to maintain consistency with the FIS report. As shown in Figure 3-8, the computed 100-year water surface elevations track well with the published values in the upper and lower reaches of the model. The differences in the middle of the model are attributed to bridge effects and the increased number of cross-sections used by RDG in the Base Flood model as well as the influence of Interstate 5.

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Sodom and Shearer Dam Removal FP Calapooia River Sodom - Shearer 320 Legend

WS 100 YR Flow (22 Ground OWS 100 YR Flow (22 300

280 Elevation(ft)

260

240

1.730 2.085 2.249 2.806 3.396 3.913 4.129 4.344 4.704 4.889 5.141 5.249 5.338 5.442 5.547 5.680 5.826 5.922 6.013 6.297 6.643 6.947 7.082 7.188 7.491 7.596 7.65 7.961 8.078 8.290 8.423 8.523 8.766 9.027 9.292 9.575 9.735 9.954 10.183 10.367 10.551 10.720 10.820 220 1.328 0 10000 20000 30000 40000 50000 60000 Main Channel Distance (ft) Figure 3-8. The hydraulic model longitudinal profile for the 100-year base flood extending from the Calapooia River upstream of the bifurcation to downstream of Shearer Dam. The published 100-year water surface elevations are included as observed water surfaces (OWS). RDG’s Base Flood model water surface profile matches the OWS in the upper and lower portion of the profile. Predicted water surface and OWS diverge in the middle of the model largely due to bridge effects and the increased number of cross-sections (i.e. model detail) in the RDG model relative to the FIS model.

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4 Results The following sections provide modeling results for the proposed dam removal projects. Results are separated by the reach scale models for Sodom and Shearer dams (i.e. 5-year flows or lower) and 100-year floodplain evaluation.

4.1 Calapooia River – Sodom Ditch Bifurcation Model (5-year and Lower Flows) The current split flow condition at the bifurcation is extremely dynamic and potentially changes after each storm event due to deposition of sediment and accumulation of flood borne debris. Under the current configuration, the portion of flow coming into the bifurcation and routed down Sodom Ditch ranges from 80% to 89% based on actual discharge measurements in 2010 and 2011. Historical anecdotal accounts and records (e.g., Tetra Tech modeling) indicate that the Sodom Ditch only took 60% to 75% of the split flow. The increase flow capture in Sodom Ditch appears to be the result of decreased maintenance at the bifurcation and potentially higher sediment loadings into the bifurcation area as a result of reduced mineral resource extraction upstream.

The proposed condition at the bifurcation will provide a split flow that conveys approximately 75% to 80% of flow down the Sodom Ditch with the remainder routed to the Calapooia River. The intent of the design is to maintain current high flow partitioning at the bifurcation while maintaining an approximate 50% split flow condition during summer low flows. The 5-year water surface profiles with and without Sodom Dam in place are shown in Figure 4-1. Hydraulic modeling results are summarized in Table 4-1.

Sodom Ditch Sodom Ditch Calapooia Upper Calapooia 305 Legend

WS 10.6 kcfs - FG3 BO

WS 10.6 kcfs - EG BO 300 Ground

295

290

Elevation(ft) 285

280

275

3 4 5 6 7 8 9... 10 11 12 13 14 16 21 24 26 28 30 32 34 36 38 40 42 44 46 48 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 71 270 2 0 1000 2000 3000 4000 5000 6000 Main Channel Distance (ft) Figure 4-1. The 5-year (10,600 cfs) flow profile comparison for Sodom Ditch from the bifurcation area, downstream through Sodom Dam to Linn West Road. The red line shows the water surface elevation with Sodom Dam in place. The filled water surface profile shows proposed conditions under the 5-year event.

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Table 4-1. Summary of modeled discharge data at bifurcation with the removal of Sodom Dam. Upstream Proposed of Sodom Ditch Calapooia River Design Bifurcation Discharge Percent of Discharge Percent of Conditions (cfs) (cfs) Total Flow (cfs) Total Flow Moderate Flow 5,000 3,775 76% 1,225 24% Moderate Flow 6,500 5,000 77% 1,500 23% 2-Year Flow 7,000 5,425 78% 1,575 22% 5-Year Flow 10,600 8,250 78% 2,350 22%

The net effect of removing Sodom Dam and stabilizing Sodom Ditch is to lower the water surface elevation from the bifurcation area to just downstream of the Sodom Dam. The actual flow split is intended to remain similar to existing conditions. After the dam is removed, velocities downstream of the structure will remain similar to existing conditions and velocities upstream of the dam and within the dam’s influence will increase from 4-5 feet per second (fps) to 8-10 fps, as shown in Figure 4-2, due to the dam’s removal. A flow of 2,140 cfs was used for this illustration that represents the yearly flow and provides a typical flow that will be realized every year. Upstream of the bifurcation, outside of the dam’s influence, water velocities will experience little or no change after Sodom Dam removal. Likewise, the flow conditions down the Calapooia River branch will experience similar conditions that exist prior to dam removal.

Increased velocities and shear stresses from the bifurcation downstream to the former Sodom Dam site will be mitigated with the proposed restoration design scheduled for Sodom Ditch. The restoration design consists of installing engineered riffles with large rock and boulders that can withstand the high velocities and remain stable. It is important that the rocks and riffle gradation be stable since the reach between the bifurcation and the Sodom Dam will be a transport reach due to the high velocities and shear stresses. Large scale roughness, in the form of boulders and large wood, is also an integral part of the design for dissipating energy through turbulence and roughness. Likewise, vegetation is an integral component for the long-term stability and restoration of this reach after dam removal. Drawings for this restoration effort are included in Appendix A.

20 April 2011 Sodom and Shearer Dam Removal Hydraulic Modeling Report

Figure 4-2. Comparative plots of average velocity before (left) and after dam removal (right) for the 1- year flow (2,140 cfs). The model shows how the velocity signature is similar downstream of the dam after removal, but higher velocities in the former reservoir area result from the removal of the dam- induced backwater condition.

Figure 4-3 shows predicted shear stress values for the 5-year peak flow before and after dam removal. The modeled shear stresses are used to compare the before and after removal conditions and to identify critical areas that may require stabilization due to possible . Further analysis of the 5-year peak flow also shows the limitations of a split flow model at the bifurcation as significant portions of the floodplain begin to activate; hence, a separate model is used to analyze higher flow conditions as described in Section 4.3.

An important feature of the hydraulic model is to identify trends and critical areas that depart from the existing conditions. This type of a comparison provides predictive results that are used in the restoration design to ensure vital areas are stabilized or effectively mitigated with restoration design concepts. As previously mentioned, the increased velocity in Sodom Ditch has been an area of special focus to mitigate potential problems before they occur by reconstructing the channel in this area. Another feature of this model is to evaluate changes in depth and velocity for low flow conditions during the summer and for fish passage. Figure 4-4 shows the fish passage high and low flow conditions for the restored Sodom Ditch reach. It can be seen that modeling results show adequate depth through the proposed restored reach with depths in the range of 6 inches or more.

21 April 2011 Sodom and Shearer Dam Removal Hydraulic Modeling Report

Figure 4-3. Comparative shear stress plots before (left) and after (right) dam removal for a typical 5- year flow (10,652 cfs). The model helps identify high shear stress areas for consideration in the restoration design.

SODOM 11-5-2010 Plan: Fish Passage Design 12/15/2010 Sodom Ditch Sodom Ditch 295 Legend

WS 5% Exceedance

290 WS 95% Exceedance

Ground

285 Elevation (ft)Elevation 280

275

270 0 500 1000 1500 2000 2500 3000 Main Channel Distance (ft) Figure 4-4. Longitudinal profile showing water surface elevations on the restored portion of the Sodom Ditch for the 5% (1,733 cfs) and 95% (10 cfs) exceedance flows.

22 April 2011 Sodom and Shearer Dam Removal Hydraulic Modeling Report

4.2 Shearer Dam Model (5-year and Lower Flows) Flows for the Shearer Dam model were obtained from the estimated split flow conditions at the bifurcation. Flows conveyed by the Calapooia River were increased by 10% to account for inflows from surrounding and overland flow from surrounding agricultural fields. The revised flow estimate was used to develop the discharge for the low flow (i.e. less than 5-year peak flow) Shearer Dam model. The dam is located in an area with a flat valley slope and the hydraulic effects of the existing dam are muted at relatively low flows caused by downstream backwater conditions. Figure 4-5 shows the dam transitioning into a backwatered condition during a typical winter storm condition.

Figure 4-5. Left photo shows Shearer Dam during a typical winter flow condition which happens multiple times each year. Right photo shows the height of Shearer Dam under moderate flow conditions when downstream backwater conditions have limited effect on flow over the dam.

A HEC-RAS longitudinal water surface profile, provided in Figure 4-6, shows the existing water surface (red line) compared to the post-dam water surface elevation (filled water surface profile). The existing condition water surface upstream of the dam is slightly lower, by approximately 6 inches, during a 5-year peak flow event relative to the post-Shearer Dam removal condition. The downstream water surface elevations remain the same post-dam due to the flat slope and subcritical flow regime through the reach. The in-channel Froude numbers for the proposed conditions are all less than 0.5 and reinforce how the flow regime is subcritical and controlled by backwater hydraulics created by downstream channel and vegetation conditions rather than the dam.

23 April 2011 Sodom and Shearer Dam Removal Hydraulic Modeling Report

Shearer Dam Removal River #1 Reach #1 270 Legend

WS 5 yr (2662 cfs) - EG WS 5 yr (2662 cfs) - FG Ground Ground

265

Elevation(ft) 260

255

20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 0 200 400 600 800 1000 Main Channel Distance (ft) Figure 4-6. The 5-year flow (2,900 cfs) at Shearer Dam showing the change in water surface post-dam removal. The existing condition water surface profile is red and the proposed condition is blue. The drop in upstream water surface is on the order of 6 inches or less. Stream bed profiles show Shearer Dam and the proposed channel bed post-removal.

The net result of removing Shearer Dam will be to lower the water surface upstream of the dam during low flow conditions. The effect during high flows will be minimal due to the flat slope of the river in this location and the subcritical flow regime that inundates the dam during annual storm flows. Dam removal and restoration design drawings are contained in Appendix A.

Due to the relatively minor amount of stored sediment behind the dam, approximately 1,000 cubic yards, a model was not developed. The existing stored sediment consists primarily of silts and sands with small amounts of fine gravel. A portion of this material around the dam will be removed during dam removal and the rest will be eroded during the first high water conditions. Upstream of the dam site, a layer of fine silt and sediment along the bottom of the channel will likely mobilize and scour away during typical storm events less than the 1-year peak flow. This layer ranges in thickness from 1 ft to more than 2 ft with scour being caused by low flows not being obstructed by the dam, however, high flows will have similar velocities as current conditions and will likely not cause additional scour.

4.3 Base Flood Model At high flow conditions such as the 100-year peak flow, the entire floodplain and much of the valley bottom is inundated. Due to the flat slope of the valley and numerous road fills, the area functions as a lake with low velocities on the floodplain. The FEMA FIRM shows water surface elevations for the 100-year base flood elevation that inundate all of the valley floor with the

24 April 2011 Sodom and Shearer Dam Removal Hydraulic Modeling Report exception of the I-5 road prism (Figure 4-7). The I-5 road prism is a significant blockage on the floodplain with numerous small openings in the form of bridges.

The FEMA floodplain study only had three cross-sections located in the project area; whereas, the Base Flood model we prepared has 64 cross-sections. The RDG model also has 6 bridges and the dams included in the model which is more detailed and accurate than the FEMA model.

25 April 2011 Sodom and Shearer Dam Removal Hydraulic Modeling Report

Shearer Dam

Sodom Dam

Figure 4-7. The FIRM floodplain for the Calapooia River downstream of Brownsville and through the project area showing broad extents of floodplain.

As a result of the flat valley slopes and backwater effects from I-5, the Sodom and Shearer dams have essentially no effect on the water surface elevation for the 100-year peak flow. Therefore, removal of the dams and associated restoration activities have little to no impacts on the 100-

26 April 2011 Sodom and Shearer Dam Removal Hydraulic Modeling Report

year floodplain. Figure 4-8 provides a comparison of the existing and post-project conditions with the dams removed. At the Sodom Dam location, the change in water surface post-project is a rise of less than 3 inches, localized to the existing dam location and barely detectable by the hydraulic modeling. This small rise results from the apparent submerged hydraulic jump at the dam location caused by a change in slope from the restored channel to the natural channel at the 100-year event.

Upstream, the post-project water surface elevations have been lowered in the proposed condition as a response to the removal of the dam induced backwater. Hydraulic effects are localized in the project reach and the computed water surface profiles become coincident immediately upstream and downstream of the Sodom Dam, bifurcation area. There are no discernible changes in the water surface profiles at the Shearer Dam site. This response is indicative of the subcritical (Froude number of 0.12), low velocity condition on the Calapooia River floodplain for the 100-year event. Water velocities on the floodplain are less than 0.4 fps. Calapooia River Sodom - Shearer 320 Legend

Calapooia River Sodom - Shearer WS 100 YR Flow (22 - _EG_ 320 Legend WS 100 YR Flow (22 - _FG_ WS 100 YR Flow (22 - _EG_ Ground WS 100 YR Flow (22 - _FG_ 300 Ground Ground

300 Ground

280

280 Elevation(ft)

260 Elevation(ft) 260

240

240

Sod_Cal_Millrace Boston@ Mil... Sodom I-5 @ Shearer Dam Calapooia Roberts@ Stream I-5 @ F Stream I-5 @ E Calapooia Linn@ West Calapooia I-5 @ I-5 creek bridges Sodom Dam 220 Calapooiat Wirth @

0 10000 20000 30000 40000 50000 60000

Calapooiat Wirth @ Sod_Cal_Millrace Boston@ Mil... Sodom I-5 @ Shearer Dam Calapooia Roberts@ Stream I-5 @ F Stream I-5 @ E Calapooia Linn@ West Calapooia I-5 @ I-5 creek bridges Sodom Dam 220 Main Channel Distance (ft) 0 10000 20000 30000 40000 50000 60000

Main Channel Distance (ft) Figure 4-8. The computed water surface profiles for the 100-year flood for the Sodom Dam and Shearer Dam project reach. The existing condition water surface profile is in blue and the proposed condition water surface profile in red. The water surface profiles are coincident for the entire 9.8 mile reach except for a slight departure at the Sodom Dam.

27 April 2011 Sodom and Shearer Dam Removal Hydraulic Modeling Report

Figure 4-9 provides a water surface departure analysis for the entire project area. The analysis shows the change in water surface elevation for the 2-year through 100-year peak flows and represents the change in water surface elevation from existing conditions. For the Shearer Dam there is barely a detectable change in water surface for all flows. For the Sodom Dam a drop in water surface elevation of over 1 ft is developed during the 2-year and 5-year events with the water surface drop decreasing as peak flows increase. Finally, a small increase in water surface elevation, less than 3 inches, is detected just downstream and upstream of the dam as a result of the proposed restoration design for the low and intermediate flows after dam removal.

Water Surface Post-project Departures from Existing Conditions

1 0.8 0.6 0.4 2-YR

0.2 Higher Water Surface Dam Sodom Shearer Dam Shearer 5-YR 0 10-YR -0.2 -0.4 Lower Water Surface 25-YR

-0.6 50-YR Post ProjectPost Changein WSEL (ft) -0.8 100-YR -1 0 10000 20000 30000 40000 50000 60000

Channel Length (ft) Figure 4-9. A departure analysis showing changes in water surface elevations before and after dam removals.

5 Conclusions Hydraulic modeling of both reach and floodplain scales was performed to ascertain the effects of the proposed dam removal projects. Three detailed models were required to more accurately characterize the project hydraulics. The reach scale models were used to complete detailed evaluations of existing condition versus proposed condition hydraulic effects to incipient flood events. The models were prepared for both Sodom and Shearer dams and allowed for determination of in-channel hydraulics to assist in the assessment of the existing condition and predict the potential post-restoration hydraulic effects.

To evaluate floodplain effects, a separate model was required due to the significant size and conveyance capacity of the floodplain. The Base Flood model was prepared over an approximate 10 mile reach with valley-wide cross-sections to evaluate existing and post-project

28 April 2011 Sodom and Shearer Dam Removal Hydraulic Modeling Report floodplain effects at the 100-year flood flow of 22,000 cfs. The following section summarizes the hydraulic effects of the proposed dam removal projects.

5.1 Sodom Dam Removal and Bifurcation The hydraulic modeling of the bifurcation and Sodom Dam area demonstrated that the proposed condition Base Flood model will result in lower water surface elevations from the bifurcation downstream to Sodom Dam. The reduction in water surface profiles is most pronounced under higher discharges where the proposed condition alleviates the dam-induced backwater effect. Under low flow conditions, the channel restoration design correlates with the existing condition in maintaining the flow partitioning between the Calapooia River and Sodom Ditch in order to maintain fish passage and satisfy water rights on the Calapooia River.

The Base Flood model predicts that the proposed dam removals and channel restoration actions will have very limited effects on the 100-year water surface elevation through the project area. A small difference in water surface elevation was identified at Sodom Dam due to the localized hydraulic effects of the structure. These effects were slight and the proposed condition resulted in lowered elevations in the reach upstream of the dam due to the removal of the backwater condition. Based on this analysis the proposed project has no effect on the overall Base Flood elevation within the project area. There are no insured structures that will be impacted by the project and NFIP flood risk status is not affected.

5.2 Shearer Dam Removal A reach scale model analysis of the Shearer Dam was developed similar to the analysis described for the Sodom Dam removal. The Shearer Dam site is less complex than the Sodom Dam – bifurcation site in that a split flow condition was not required. Modeling results were similar for the existing condition and post-dam removal condition in that the computed water surface elevations were reduced in the proposed project condition model. The reduced water surface elevations are attributed to the removal of the backwater condition created by the dam.

The floodplain area around the Shearer Dam is completely inundated under the 100–year flood. As such, the removal of the small dam has little discernible effect on the water surface elevations considering the broad, low velocity inundation and flooding extents within the valley. Based on this analysis the proposed project has no effect on the overall Base Flood elevations within the project area. There are no insured structures that will be impacted by the project and NFIP flood risk status is not affected.

29 April 2011

Appendix A

Sodom and Shearer Dam Removal and Restoration Drawings

Appendix B

Hydraulic Model Output

HEC-RAS River: Calapooia River Reach: Sodom - Shearer Profile: 100 YR Flow (22 Reach River Sta Profile Plan Q Total W.S. Elev Vel Chnl Shear Chan Flow Area Top Width Froude # Chl (cfs) (ft) (ft/s) (lb/sq ft) (sq ft) (ft) Sodom - Shearer 10.820 100 YR Flow (22 EG FIS 22000.00 314.42 3.72 0.93 21495.22 5063.15 0.22 Sodom - Shearer 10.820 100 YR Flow (22 FG FIS 22000.00 314.42 3.72 0.93 21495.22 5063.15 0.22

Sodom - Shearer 10.720 100 YR Flow (22 EG FIS 22000.00 313.47 4.10 1.09 17858.52 5125.94 0.23 Sodom - Shearer 10.720 100 YR Flow (22 FG FIS 22000.00 313.47 4.10 1.09 17858.52 5125.94 0.23

Sodom - Shearer 10.551 100 YR Flow (22 EG FIS 22000.00 311.99 4.56 1.35 20086.83 6435.91 0.26 Sodom - Shearer 10.551 100 YR Flow (22 FG FIS 22000.00 311.99 4.56 1.35 20086.83 6435.91 0.26

Sodom - Shearer 10.367 100 YR Flow (22 EG FIS 22000.00 310.44 4.29 1.25 20826.40 6592.46 0.26 Sodom - Shearer 10.367 100 YR Flow (22 FG FIS 22000.00 310.44 4.29 1.25 20826.40 6592.46 0.26

Sodom - Shearer 10.183 100 YR Flow (22 EG FIS 22000.00 308.70 4.97 1.61 20590.54 7485.05 0.28 Sodom - Shearer 10.183 100 YR Flow (22 FG FIS 22000.00 308.70 4.97 1.61 20590.54 7485.05 0.28

Sodom - Shearer 9.954 100 YR Flow (22 EG FIS 22000.00 307.07 3.96 1.02 22757.06 8163.86 0.22 Sodom - Shearer 9.954 100 YR Flow (22 FG FIS 22000.00 307.07 3.96 1.02 22757.06 8163.86 0.22

Sodom - Shearer 9.735 100 YR Flow (22 EG FIS 22000.00 305.48 4.50 1.29 20934.79 7899.35 0.24 Sodom - Shearer 9.735 100 YR Flow (22 FG FIS 22000.00 305.48 4.50 1.29 20934.79 7899.35 0.24

Sodom - Shearer 9.575 100 YR Flow (22 EG FIS 22000.00 303.87 3.43 0.87 20248.70 6811.59 0.23 Sodom - Shearer 9.575 100 YR Flow (22 FG FIS 22000.00 303.87 3.43 0.87 20249.12 6811.62 0.23

Sodom - Shearer 9.292 100 YR Flow (22 EG FIS 22000.00 301.51 4.05 1.08 23345.70 8210.29 0.23 Sodom - Shearer 9.292 100 YR Flow (22 FG FIS 22000.00 301.51 4.05 1.08 23342.44 8210.26 0.23

Sodom - Shearer 9.027 100 YR Flow (22 EG FIS 22000.00 299.93 3.04 0.63 26219.15 7295.17 0.19 Sodom - Shearer 9.027 100 YR Flow (22 FG FIS 22000.00 299.93 3.04 0.64 26205.57 7295.05 0.19

Sodom - Shearer 8.766 100 YR Flow (22 EG FIS 22000.00 297.74 3.80 1.01 22025.63 7014.36 0.24 Sodom - Shearer 8.766 100 YR Flow (22 FG FIS 22000.00 297.71 3.84 1.03 21824.94 7007.80 0.24

Sodom - Shearer 8.523 100 YR Flow (22 EG FIS 22000.00 294.06 5.35 1.95 18674.11 7229.50 0.32 Sodom - Shearer 8.523 100 YR Flow (22 FG FIS 22000.00 293.87 5.89 2.27 17444.88 6962.76 0.33

Sodom - Shearer 8.441 100 YR Flow (22 EG FIS 22000.00 292.55 5.30 1.92 19168.92 6851.52 0.31 Sodom - Shearer 8.441 100 YR Flow (22 FG FIS 22000.00 292.81 4.87 1.43 21628.72 7190.57 0.24

Sodom - Shearer 8.4374 Inl Struct

Sodom - Shearer 8.423 100 YR Flow (22 EG FIS 22000.00 292.48 4.84 1.35 21720.29 7191.18 0.22 Sodom - Shearer 8.423 100 YR Flow (22 FG FIS 22000.00 292.58 4.75 1.35 22123.39 7413.69 0.23

Sodom - Shearer 8.290 100 YR Flow (22 EG FIS 22000.00 291.43 3.55 0.84 22200.52 7539.01 0.21 Sodom - Shearer 8.290 100 YR Flow (22 FG FIS 22000.00 291.43 3.55 0.84 22200.52 7539.01 0.21

Sodom - Shearer 8.078 100 YR Flow (22 EG FIS 22000.00 288.82 3.97 1.01 25375.24 8980.56 0.21 Sodom - Shearer 8.078 100 YR Flow (22 FG FIS 22000.00 288.82 3.97 1.01 25375.24 8980.56 0.21

Sodom - Shearer 7.961 100 YR Flow (22 EG FIS 22000.00 287.35 3.69 0.95 25046.89 10462.33 0.23 Sodom - Shearer 7.961 100 YR Flow (22 FG FIS 22000.00 287.35 3.69 0.95 25046.89 10462.33 0.23

Sodom - Shearer 7.738 100 YR Flow (22 EG FIS 22000.00 286.12 2.41 0.36 44921.42 12893.32 0.13 Sodom - Shearer 7.738 100 YR Flow (22 FG FIS 22000.00 286.12 2.41 0.36 44921.42 12893.32 0.13

Sodom - Shearer 7.695 100 YR Flow (22 EG FIS 22000.00 285.62 5.66 2.03 15820.52 5933.17 0.30 Sodom - Shearer 7.695 100 YR Flow (22 FG FIS 22000.00 285.62 5.66 2.03 15820.52 5933.17 0.30

Sodom - Shearer 7.65 Bridge

Sodom - Shearer 7.604 100 YR Flow (22 EG FIS 22000.00 281.93 11.87 9.84 3533.21 1945.38 0.74 Sodom - Shearer 7.604 100 YR Flow (22 FG FIS 22000.00 281.93 11.87 9.84 3533.21 1945.38 0.74

Sodom - Shearer 7.596 100 YR Flow (22 EG FIS 22000.00 282.58 6.89 3.13 13284.50 7889.79 0.39 Sodom - Shearer 7.596 100 YR Flow (22 FG FIS 22000.00 282.58 6.89 3.13 13284.50 7889.79 0.39

Sodom - Shearer 7.491 100 YR Flow (22 EG FIS 22000.00 282.28 2.16 0.31 37883.03 11971.35 0.13 Sodom - Shearer 7.491 100 YR Flow (22 FG FIS 22000.00 282.28 2.16 0.31 37883.41 11971.41 0.13

Sodom - Shearer 7.242 100 YR Flow (22 EG FIS 22000.00 281.60 2.34 0.42 33325.28 13108.30 0.17 Sodom - Shearer 7.242 100 YR Flow (22 FG FIS 22000.00 281.60 2.34 0.42 33325.68 13108.35 0.17

Sodom - Shearer 7.23 Mult Open HEC-RAS River: Calapooia River Reach: Sodom - Shearer Profile: 100 YR Flow (22 (Continued) Reach River Sta Profile Plan Q Total W.S. Elev Vel Chnl Shear Chan Flow Area Top Width Froude # Chl (cfs) (ft) (ft/s) (lb/sq ft) (sq ft) (ft) Sodom - Shearer 7.218 100 YR Flow (22 EG FIS 22000.00 281.44 2.55 0.48 29143.71 12852.78 0.17 Sodom - Shearer 7.218 100 YR Flow (22 FG FIS 22000.00 281.44 2.55 0.48 29143.71 12852.78 0.17

Sodom - Shearer 7.188 100 YR Flow (22 EG FIS 22000.00 281.12 3.13 0.77 29352.01 14279.12 0.23 Sodom - Shearer 7.188 100 YR Flow (22 FG FIS 22000.00 281.12 3.13 0.77 29352.01 14279.12 0.23

Sodom - Shearer 7.139 100 YR Flow (22 EG FIS 22000.00 280.55 3.20 0.74 32856.87 14164.21 0.21 Sodom - Shearer 7.139 100 YR Flow (22 FG FIS 22000.00 280.55 3.20 0.74 32856.87 14164.21 0.21

Sodom - Shearer 7.125 100 YR Flow (22 EG FIS 22000.00 280.37 4.34 1.27 24263.00 13133.03 0.26 Sodom - Shearer 7.125 100 YR Flow (22 FG FIS 22000.00 280.37 4.34 1.27 24263.00 13133.03 0.26

Sodom - Shearer 7.11 Bridge

Sodom - Shearer 7.107 100 YR Flow (22 EG FIS 22000.00 280.16 3.80 1.04 26575.94 12078.95 0.25 Sodom - Shearer 7.107 100 YR Flow (22 FG FIS 22000.00 280.16 3.80 1.04 26575.94 12078.95 0.25

Sodom - Shearer 7.082 100 YR Flow (22 EG FIS 22000.00 279.83 5.02 1.75 19053.03 12115.25 0.31 Sodom - Shearer 7.082 100 YR Flow (22 FG FIS 22000.00 279.83 5.02 1.75 19053.03 12115.25 0.31

Sodom - Shearer 6.947 100 YR Flow (22 EG FIS 22000.00 279.05 2.98 0.60 31129.28 13996.30 0.17 Sodom - Shearer 6.947 100 YR Flow (22 FG FIS 22000.00 279.05 2.98 0.60 31129.28 13996.30 0.17

Sodom - Shearer 6.663 100 YR Flow (22 EG FIS 22000.00 277.66 2.90 0.61 39235.83 16834.98 0.19 Sodom - Shearer 6.663 100 YR Flow (22 FG FIS 22000.00 277.66 2.90 0.61 39235.83 16834.98 0.19

Sodom - Shearer 6.65 Bridge

Sodom - Shearer 6.643 100 YR Flow (22 EG FIS 22000.00 277.51 2.57 0.52 39686.74 17128.58 0.19 Sodom - Shearer 6.643 100 YR Flow (22 FG FIS 22000.00 277.51 2.57 0.52 39686.74 17128.58 0.19

Sodom - Shearer 6.297 100 YR Flow (22 EG FIS 22000.00 275.56 2.34 0.38 44149.02 13346.04 0.14 Sodom - Shearer 6.297 100 YR Flow (22 FG FIS 22000.00 275.56 2.34 0.38 44159.59 13346.61 0.14

Sodom - Shearer 6.013 100 YR Flow (22 EG FIS 22000.00 274.43 2.11 0.33 46049.89 15534.00 0.14 Sodom - Shearer 6.013 100 YR Flow (22 FG FIS 22000.00 274.43 2.11 0.32 46092.08 15538.40 0.14

Sodom - Shearer 5.922 100 YR Flow (22 EG FIS 22000.00 274.17 2.13 0.33 49033.96 17561.63 0.14 Sodom - Shearer 5.922 100 YR Flow (22 FG FIS 22000.00 274.17 2.12 0.33 49096.13 17564.21 0.14

Sodom - Shearer 5.85 Bridge

Sodom - Shearer 5.826 100 YR Flow (22 EG FIS 22000.00 273.79 2.02 0.31 48310.57 17887.06 0.14 Sodom - Shearer 5.826 100 YR Flow (22 FG FIS 22000.00 273.79 2.02 0.31 48404.49 17896.22 0.14

Sodom - Shearer 5.680 100 YR Flow (22 EG FIS 22000.00 272.93 2.25 0.35 47108.95 15861.56 0.14 Sodom - Shearer 5.680 100 YR Flow (22 FG FIS 22000.00 272.95 2.24 0.35 47322.14 15891.90 0.14

Sodom - Shearer 5.590 100 YR Flow (22 EG FIS 22000.00 272.69 1.77 0.25 49410.34 16462.76 0.13 Sodom - Shearer 5.590 100 YR Flow (22 FG FIS 22000.00 272.71 1.76 0.24 49691.77 16471.71 0.13

Sodom - Shearer 5.57 Bridge

Sodom - Shearer 5.547 100 YR Flow (22 EG FIS 22000.00 272.51 2.08 0.31 49453.75 16186.98 0.13 Sodom - Shearer 5.547 100 YR Flow (22 FG FIS 22000.00 272.53 2.13 0.32 49786.53 16647.13 0.14

Sodom - Shearer 5.442 100 YR Flow (22 EG FIS 22000.00 271.88 1.87 0.25 53716.49 17067.56 0.12 Sodom - Shearer 5.442 100 YR Flow (22 FG FIS 22000.00 271.89 1.86 0.25 53927.97 17070.89 0.12

Sodom - Shearer 5.371 100 YR Flow (22 EG FIS 22000.00 271.42 2.00 0.28 53562.56 16623.83 0.12 Sodom - Shearer 5.371 100 YR Flow (22 FG FIS 22000.00 271.44 1.98 0.27 53891.33 16626.90 0.12

Sodom - Shearer 5.34 Bridge

Sodom - Shearer 5.338 100 YR Flow (22 EG FIS 22000.00 271.33 1.77 0.22 55859.34 16827.32 0.11 Sodom - Shearer 5.338 100 YR Flow (22 FG FIS 22000.00 271.36 1.76 0.22 56218.60 16852.52 0.11

Sodom - Shearer 5.249 100 YR Flow (22 EG FIS 22000.00 271.02 1.94 0.27 52877.88 16479.46 0.12 Sodom - Shearer 5.249 100 YR Flow (22 FG FIS 22000.00 271.05 1.91 0.26 53346.62 16480.99 0.12

Sodom - Shearer 5.191 100 YR Flow (22 EG FIS 22000.00 270.66 1.85 0.25 46792.90 12133.70 0.12 Sodom - Shearer 5.191 100 YR Flow (22 FG FIS 22000.00 270.71 1.81 0.24 47525.41 12133.22 0.12

Sodom - Shearer 5.18 Inl Struct HEC-RAS River: Calapooia River Reach: Sodom - Shearer Profile: 100 YR Flow (22 (Continued) Reach River Sta Profile Plan Q Total W.S. Elev Vel Chnl Shear Chan Flow Area Top Width Froude # Chl (cfs) (ft) (ft/s) (lb/sq ft) (sq ft) (ft) Sodom - Shearer 5.165 100 YR Flow (22 EG FIS 22000.00 270.65 1.99 0.27 47308.74 11910.91 0.12 Sodom - Shearer 5.165 100 YR Flow (22 FG FIS 22000.00 270.65 1.99 0.27 47316.69 11909.46 0.12

Sodom - Shearer 5.141 100 YR Flow (22 EG FIS 22000.00 270.33 2.31 0.37 42352.66 11132.80 0.14 Sodom - Shearer 5.141 100 YR Flow (22 FG FIS 22000.00 270.33 2.31 0.37 42349.94 11132.75 0.14

Sodom - Shearer 4.959 100 YR Flow (22 EG FIS 22000.00 270.03 2.24 0.33 42816.45 10684.64 0.13 Sodom - Shearer 4.959 100 YR Flow (22 FG FIS 22000.00 270.02 2.24 0.33 42812.89 10684.63 0.13

Sodom - Shearer 4.90 Mult Open

Sodom - Shearer 4.889 100 YR Flow (22 EG FIS 22000.00 269.78 2.19 0.34 40719.82 10558.79 0.14 Sodom - Shearer 4.889 100 YR Flow (22 FG FIS 22000.00 269.78 2.19 0.34 40716.59 10558.74 0.14

Sodom - Shearer 4.704 100 YR Flow (22 EG FIS 22000.00 269.44 2.69 0.47 38229.68 10163.00 0.15 Sodom - Shearer 4.704 100 YR Flow (22 FG FIS 22000.00 269.44 2.69 0.47 38225.96 10162.93 0.15

Sodom - Shearer 4.419 100 YR Flow (22 EG FIS 22000.00 268.39 2.71 0.48 39331.78 10760.99 0.15 Sodom - Shearer 4.419 100 YR Flow (22 FG FIS 22000.00 268.39 2.71 0.48 39322.90 10760.93 0.15

Sodom - Shearer 4.362 100 YR Flow (22 EG FIS 22000.00 267.97 2.30 0.37 38988.23 9459.80 0.14 Sodom - Shearer 4.362 100 YR Flow (22 FG FIS 22000.00 267.97 2.30 0.37 38977.27 9459.36 0.14

Sodom - Shearer 4.35 Mult Open

Sodom - Shearer 4.344 100 YR Flow (22 EG FIS 22000.00 267.47 2.98 0.59 34643.67 9824.79 0.17 Sodom - Shearer 4.344 100 YR Flow (22 FG FIS 22000.00 267.47 2.98 0.59 34643.67 9824.79 0.17

Sodom - Shearer 4.180 100 YR Flow (22 EG FIS 22000.00 266.89 2.49 0.44 35189.93 10004.87 0.16 Sodom - Shearer 4.180 100 YR Flow (22 FG FIS 22000.00 266.89 2.49 0.44 35189.93 10004.87 0.16

Sodom - Shearer 4.134 100 YR Flow (22 EG FIS 22000.00 266.62 2.75 0.54 32917.08 9787.09 0.17 Sodom - Shearer 4.134 100 YR Flow (22 FG FIS 22000.00 266.62 2.75 0.54 32917.08 9787.09 0.17

Sodom - Shearer 4.129 100 YR Flow (22 EG FIS 22000.00 266.58 3.00 0.59 33090.38 9730.18 0.17 Sodom - Shearer 4.129 100 YR Flow (22 FG FIS 22000.00 266.58 3.00 0.59 33090.38 9730.18 0.17

Sodom - Shearer 3.913 100 YR Flow (22 EG FIS 22000.00 265.17 2.88 0.62 30337.96 9353.82 0.20 Sodom - Shearer 3.913 100 YR Flow (22 FG FIS 22000.00 265.17 2.88 0.62 30337.96 9353.82 0.20

Sodom - Shearer 3.396 100 YR Flow (22 EG FIS 22000.00 263.56 1.72 0.19 48440.44 8486.63 0.09 Sodom - Shearer 3.396 100 YR Flow (22 FG FIS 22000.00 263.56 1.72 0.19 48440.44 8486.63 0.09

Sodom - Shearer 2.806 100 YR Flow (22 EG FIS 22000.00 262.55 2.94 0.53 34117.48 8976.17 0.15 Sodom - Shearer 2.806 100 YR Flow (22 FG FIS 22000.00 262.55 2.94 0.53 34117.48 8976.17 0.15

Sodom - Shearer 2.249 100 YR Flow (22 EG FIS 22000.00 260.50 3.60 0.77 30763.86 10090.37 0.17 Sodom - Shearer 2.249 100 YR Flow (22 FG FIS 22000.00 260.50 3.60 0.77 30764.15 10090.41 0.17

Sodom - Shearer 2.111 100 YR Flow (22 EG FIS 22000.00 259.88 3.59 0.78 30191.40 10035.62 0.18 Sodom - Shearer 2.111 100 YR Flow (22 FG FIS 22000.00 259.88 3.59 0.78 30192.01 10035.66 0.18

Sodom - Shearer 2.1 Mult Open

Sodom - Shearer 2.085 100 YR Flow (22 EG FIS 22000.00 259.75 3.30 0.66 32750.93 10373.58 0.17 Sodom - Shearer 2.085 100 YR Flow (22 FG FIS 22000.00 259.75 3.30 0.66 32750.93 10373.58 0.17

Sodom - Shearer 1.730 100 YR Flow (22 EG FIS 22000.00 258.83 2.10 0.28 42248.89 10214.41 0.11 Sodom - Shearer 1.730 100 YR Flow (22 FG FIS 22000.00 258.83 2.10 0.28 42248.89 10214.41 0.11

Sodom - Shearer 1.328 100 YR Flow (22 EG FIS 22000.00 258.29 1.99 0.23 42980.39 8151.18 0.09 Sodom - Shearer 1.328 100 YR Flow (22 FG FIS 22000.00 258.29 1.99 0.23 42980.39 8151.18 0.09

Sodom - Shearer 1 100 YR Flow (22 EG FIS 22000.00 258.00 1.54 0.15 50649.56 7985.55 0.08 Sodom - Shearer 1 100 YR Flow (22 FG FIS 22000.00 258.00 1.54 0.15 50649.56 7985.55 0.08

.2 . .2 300 0 7 Legend

295 WS 100 YR Flow (22 0.0 ft/s 290 0.5 ft/s 1.0 ft/s 285 1.5 ft/s

280 2.0 ft/s 2.5 ft/s 275 Ground Bank Sta Elevation (ft) 270

265

260

255

250 0 5000 10000 15000 20000

Station (ft)

Appendix C

FEMA 100-year Profiles