This data layer is part of a collection of GIS data created for the Okanagan Mainstem Floodplain Mapping Project. Notes below apply to the entire project data set.***Download Size is 12.5 GBGeneral Notes1. Please refer to the Disclaimer further below.2. Please review the associated project reports before using the floodplain maps: Northwest Hydraulic Consultants Ltd. (NHC). 2020. ‘Okanagan Mainstem Floodplain Mapping Project’. Report prepared for the Okanagan Basin Water Board (OBWB). 31 March 2020. NHC project number 3004430. Northwest Hydraulic Consultants Ltd. (NHC). 2021. ‘Okanagan Mainstem Floodplain Mapping Project – Development of CGVD1928 Floodplain Mapping’. Letter report prepared for the Okanagan Basin Water Board (OBWB). 30 March 2021. NHC project number 3006034.Northwest Hydraulic Consultants Ltd. (NHC). 2022. ‘Supplemental to the Okanagan Mainstem Floodplain Mapping Project – Current Operations Flood Construction Levels for Okanagan and Wood-Kalamalka Lakes’. Report prepared for the Okanagan Basin Water Board (OBWB). Final. 16 August 2022. NHC project number 3006613.3. These floodplain mapping layers delineate flood inundation extents under the specific flood events. Tributaries are not included in mapping.4. The mapped inundation is based on the calculated water level. Freeboard, wind effects, and wave effects have been added to the calculated water level where noted.5. Where noted, a freeboard allowance of 0.6 m has been added to the calculated flood water level. It has been added to account for local variations in water level and uncertainty in the underlying data and modelling.6. Where noted, the FCL (or COFCL) included in lake mapping layers includes an allowance for wind setup and wave runup based on co-occurrence of the seasonal 200-year wind event. The wind and wave effects extend 40 m shoreward to delineate the expected limit of wave effects. Beyond this limit the FCL (or COFCL) is based on inundation of the flood event without wave effects. Wave effects have been calculated based on generalized shoreline profile and roughness for each shoreline reach. Site specific runup analysis by a Qualified Registrant may be warranted to refine the generalized wave effects shown, which could increase or decrease the FCL (or COFCL) by as much as a metre.7. Underlying hydraulic analysis assumes channel and shoreline geometry is stationary. Erosion, deposition, degradation, and aggradation are expected to occur and may alter actual observed flood levels and extents. Obstructions, such as log-jams, local storm water inflows or other land drainage, groundwater, or tributary flows may cause flood levels to exceed those indicated on the maps.8. The Okanagan floodplain is subject to persistent ponding due to poor drainage. Persistent ponding is not covered by the flood inundation mapping.9. For flood level maps (water level and inundation extents):a. Layers for each flood scenario describe inundation extents, water surface elevations, and depths.b. The calculated water level has been extended perpendicular to flow across the floodplain; thus mapping inundation of isolated areas regardless of likelihood of inundation; whether it be from dike failure, seepage, or local inflows. Distant isolated areas may be conservatively mapped as inundated. Site specific judgement by a Qualified Professional is required to determine validity of isolated inundation.c. Filtering was used to remove isolated areas smaller than 100 m2. Holes in the inundation extent with areas less than 100 m2 were also removed. Isolated areas larger than 100 m2 are included in GIS data layers and are shown on maps if they are within 40 metres of direct inundation or within 40 metres of other retained polygons.d. Okanagan Dam breach, dam overtopping, or overtopping and breaching of Penticton Beach were not modelled. Inundation downstream of the Okanagan Dam on the left bank floodplain is based on river modelling with the assumption that Okanagan Lake levels will not overtop Lakeshore Drive and adjacent high ground. For the design flood scenarios, inundation mapping on the right bank of the Okanagan River from the Okanagan Dam downstream to the Highway 97 bridge and Burnaby Avenue is based on additional lake and river modelling. For other flood scenarios, river and lake inundation has been mapped separately and has not been integrated on the right bank. Inundation mapping on the right bank is based on river modelling as far as the most upstream modelled river cross section.10. For flood hazard maps (depth and velocity):a. Layers describe flood water depths and velocities. Depths and velocities are based on the maximum values from three modelled scenarios: all dikes removed, left bank dikes removed, and right bank dikes removed. Depths do not include freeboard.b. All hazard layers were modelled with the same parameters and boundary conditions as the design flood.11. Flood modelling and mapping is based on a digital elevation model (DEM) with the following coordinate system and datum specifications: Universal Transverse Mercator Zone 11-N (UTM Zone 11-N), North American Datum 1983 Canadian Spatial Reference System epoch 2002.0 (NAD83 CSRS (2002.0)), Canadian Geodetic Vertical Datum 2013 (CGVD2013), Canadian Gravimetric Geoid model of 2013 (CGG2013). FCL values are presented on the maps in both CGVD2013 and CGVD1928 vertical datums. CGVD1928 values are based on the following specifications: NAD83 CSRS (2002.0), CGVD1928, Height Transformation version 2.0 epoch 1997 (HTv2.0 (1997)). COFCL and COFCL values are presented only in CGVD2013.12. The accuracy of simulated flood levels is limited by the reliability and extent of water level, flow, and climatic data. The accuracy of the floodplain extents is limited by the accuracy of the design flood flow, the hydraulic model, and the digital surface representation of local topography. Localized areas above or below the mapped inundation maybe generalized. Therefore, floodplain maps should be considered an administrative tool that indicates flood elevations and floodplain boundaries for a designated flood. A qualified professional is to be consulted for site-specific engineering analysis.13. Industry best practices were followed to generate the floodplain maps. However, actual flood levels and extents may vary from those shown. OBWB and NHC do not assume any liability for variations of flood levels and extents from that shown.Data Sources Design flood events are based on hydrologic modelling of the Okanagan River watershed. The hydraulic response is based on a combination of 1D and 2D numerical models developed by NHC using HEC-RAS software, and NHC SWAN models. The hydraulic models are calibrated to the 2017 flood event and validated to the 2018 flood event; due to limits on data availability the hydrologic model is calibrated using data from 1980-2010. The digital elevation model (DEM) used to develop the model and mapping is based on Lidar data collected from March to November 2018 and provided by Emergency Management BC (EMBC), channel survey conducted by WSP in March, April, and June 2019, and additional survey data. See accompanying report for details NHC (2020).DisclaimerThis document has been prepared by Northwest Hydraulic Consultants Ltd. for the benefit of Okanagan Basin Water Board, Regional District of North Okanagan, Regional District of Central Okanagan, Regional District of Okanagan-Similkameen, Okanagan Nation Alliance for specific application to the Okanagan Mainstem Floodplain Mapping Project, Okanagan Valley, British Columbia, Canada (Ellison, Wood, Kalamalka, Okanagan, Skaha, Vaseux, and Osoyoos lakes and Okanagan River from Okanagan Lake to Osoyoos Lake). The information and data contained herein represent Northwest Hydraulic Consultants Ltd. best professional judgment in light of the knowledge and information available to Northwest Hydraulic Consultants Ltd. at the time of preparation, and was prepared in accordance with generally accepted engineering practices.Except as required by law, this document and the information and data contained herein are to be treated as confidential and may be used and relied upon only by Okanagan Basin Water Board, Regional District of North Okanagan, Regional District of Central Okanagan, Regional District of Okanagan-Similkameen, Okanagan Nation Alliance, its officers and employees. Northwest Hydraulic Consultants Ltd. denies any liability whatsoever to other parties who may obtain access to this document for any injury, loss or damage suffered by such parties arising from their use of, or reliance upon, this report or any of its contents.Data Layer List and Descriptions<!--· River / Lake Model Boundary -River / Lake Model Boundary (NHC): Boundary between Okanagan River and Okanagan Lake modelling and mapping areas for design and flood mapping.Recommended Design Flood (gates open): Ellison, Skaha, Vaseux, and Osoyoos lakeso Lake Shoreline Flood Construction Level (FCL) Zone – Recommended Design Flood with Freeboard and Wave Effect (NHC): Zone defined based on approximate shoreline and the wave breaking boundary plus a buffer; FCLs defined by zone along shoreline; shoreline FCLs take precedence over lake inundation FCLs.o Lake Flood Construction Level (FCL) Zone (Inundation Extent) – Recommended Design Flood with Freeboard (NHC): Design flood inundation extent with freeboard. Design event varies by lake, plus wind setup, plus mid-century climate change; plus freeboard 0.6m.o Lake Inundation Extent – Recommended Design Flood without Freeboard (NHC): Design flood inundation extent without freeboard. Design event varies by lake, plus wind setup, plus mid-century climate change.o Depth Grids§ Ellison Lake Depth – Recommended Design without Freeboard (NHC): ELLISON LAKE: 200-YEAR MID-CENTURY. Design flood depth

This data layer is part of a collection of GIS data created for the Okanagan Mainstem Floodplain Mapping Project. Notes below apply to the entire project data set.General Notes1. Please refer to the Disclaimer further below.2. Please review the associated project reports before using the floodplain maps: Northwest Hydraulic Consultants Ltd. (NHC). 2020. ‘Okanagan Mainstem Floodplain Mapping Project’. Report prepared for the Okanagan Basin Water Board (OBWB). 31 March 2020. NHC project number 3004430. Northwest Hydraulic Consultants Ltd. (NHC). 2021. ‘Okanagan Mainstem Floodplain Mapping Project – Development of CGVD1928 Floodplain Mapping’. Letter report prepared for the Okanagan Basin Water Board (OBWB). 30 March 2021. NHC project number 3006034.Northwest Hydraulic Consultants Ltd. (NHC). 2022. ‘Supplemental to the Okanagan Mainstem Floodplain Mapping Project – Current Operations Flood Construction Levels for Okanagan and Wood-Kalamalka Lakes’. Report prepared for the Okanagan Basin Water Board (OBWB). Final. 16 August 2022. NHC project number 3006613.3. These floodplain mapping layers delineate flood inundation extents under the specific flood events. Tributaries are not included in mapping.4. The mapped inundation is based on the calculated water level. Freeboard, wind effects, and wave effects have been added to the calculated water level where noted.5. Where noted, a freeboard allowance of 0.6 m has been added to the calculated flood water level. It has been added to account for local variations in water level and uncertainty in the underlying data and modelling.6. Where noted, the FCL (or COFCL) included in lake mapping layers includes an allowance for wind setup and wave runup based on co-occurrence of the seasonal 200-year wind event. The wind and wave effects extend 40 m shoreward to delineate the expected limit of wave effects. Beyond this limit the FCL (or COFCL) is based on inundation of the flood event without wave effects. Wave effects have been calculated based on generalized shoreline profile and roughness for each shoreline reach. Site specific runup analysis by a Qualified Registrant may be warranted to refine the generalized wave effects shown, which could increase or decrease the FCL (or COFCL) by as much as a metre.7. Underlying hydraulic analysis assumes channel and shoreline geometry is stationary. Erosion, deposition, degradation, and aggradation are expected to occur and may alter actual observed flood levels and extents. Obstructions, such as log-jams, local storm water inflows or other land drainage, groundwater, or tributary flows may cause flood levels to exceed those indicated on the maps.8. The Okanagan floodplain is subject to persistent ponding due to poor drainage. Persistent ponding is not covered by the flood inundation mapping.9. For flood level maps (water level and inundation extents):a. Layers for each flood scenario describe inundation extents, water surface elevations, and depths.b. The calculated water level has been extended perpendicular to flow across the floodplain; thus mapping inundation of isolated areas regardless of likelihood of inundation; whether it be from dike failure, seepage, or local inflows. Distant isolated areas may be conservatively mapped as inundated. Site specific judgement by a Qualified Professional is required to determine validity of isolated inundation.c. Filtering was used to remove isolated areas smaller than 100 m2. Holes in the inundation extent with areas less than 100 m2 were also removed. Isolated areas larger than 100 m2 are included in GIS data layers and are shown on maps if they are within 40 metres of direct inundation or within 40 metres of other retained polygons.d. Okanagan Dam breach, dam overtopping, or overtopping and breaching of Penticton Beach were not modelled. Inundation downstream of the Okanagan Dam on the left bank floodplain is based on river modelling with the assumption that Okanagan Lake levels will not overtop Lakeshore Drive and adjacent high ground. For the design flood scenarios, inundation mapping on the right bank of the Okanagan River from the Okanagan Dam downstream to the Highway 97 bridge and Burnaby Avenue is based on additional lake and river modelling. For other flood scenarios, river and lake inundation has been mapped separately and has not been integrated on the right bank. Inundation mapping on the right bank is based on river modelling as far as the most upstream modelled river cross section.10. For flood hazard maps (depth and velocity):a. Layers describe flood water depths and velocities. Depths and velocities are based on the maximum values from three modelled scenarios: all dikes removed, left bank dikes removed, and right bank dikes removed. Depths do not include freeboard.b. All hazard layers were modelled with the same parameters and boundary conditions as the design flood.11. Flood modelling and mapping is based on a digital elevation model (DEM) with the following coordinate system and datum specifications: Universal Transverse Mercator Zone 11-N (UTM Zone 11-N), North American Datum 1983 Canadian Spatial Reference System epoch 2002.0 (NAD83 CSRS (2002.0)), Canadian Geodetic Vertical Datum 2013 (CGVD2013), Canadian Gravimetric Geoid model of 2013 (CGG2013). FCL values are presented on the maps in both CGVD2013 and CGVD1928 vertical datums. CGVD1928 values are based on the following specifications: NAD83 CSRS (2002.0), CGVD1928, Height Transformation version 2.0 epoch 1997 (HTv2.0 (1997)). COFCL and COFCL values are presented only in CGVD2013.12. The accuracy of simulated flood levels is limited by the reliability and extent of water level, flow, and climatic data. The accuracy of the floodplain extents is limited by the accuracy of the design flood flow, the hydraulic model, and the digital surface representation of local topography. Localized areas above or below the mapped inundation maybe generalized. Therefore, floodplain maps should be considered an administrative tool that indicates flood elevations and floodplain boundaries for a designated flood. A qualified professional is to be consulted for site-specific engineering analysis.13. Industry best practices were followed to generate the floodplain maps. However, actual flood levels and extents may vary from those shown. OBWB and NHC do not assume any liability for variations of flood levels and extents from that shown.Data Sources Design flood events are based on hydrologic modelling of the Okanagan River watershed. The hydraulic response is based on a combination of 1D and 2D numerical models developed by NHC using HEC-RAS software, and NHC SWAN models. The hydraulic models are calibrated to the 2017 flood event and validated to the 2018 flood event; due to limits on data availability the hydrologic model is calibrated using data from 1980-2010. The digital elevation model (DEM) used to develop the model and mapping is based on Lidar data collected from March to November 2018 and provided by Emergency Management BC (EMBC), channel survey conducted by WSP in March, April, and June 2019, and additional survey data. See accompanying report for details NHC (2020).DisclaimerThis document has been prepared by Northwest Hydraulic Consultants Ltd. for the benefit of Okanagan Basin Water Board, Regional District of North Okanagan, Regional District of Central Okanagan, Regional District of Okanagan-Similkameen, Okanagan Nation Alliance for specific application to the Okanagan Mainstem Floodplain Mapping Project, Okanagan Valley, British Columbia, Canada (Ellison, Wood, Kalamalka, Okanagan, Skaha, Vaseux, and Osoyoos lakes and Okanagan River from Okanagan Lake to Osoyoos Lake). The information and data contained herein represent Northwest Hydraulic Consultants Ltd. best professional judgment in light of the knowledge and information available to Northwest Hydraulic Consultants Ltd. at the time of preparation, and was prepared in accordance with generally accepted engineering practices.Except as required by law, this document and the information and data contained herein are to be treated as confidential and may be used and relied upon only by Okanagan Basin Water Board, Regional District of North Okanagan, Regional District of Central Okanagan, Regional District of Okanagan-Similkameen, Okanagan Nation Alliance, its officers and employees. Northwest Hydraulic Consultants Ltd. denies any liability whatsoever to other parties who may obtain access to this document for any injury, loss or damage suffered by such parties arising from their use of, or reliance upon, this report or any of its contents.Data Layer List and Descriptions<!--· River / Lake Model Boundary -River / Lake Model Boundary (NHC): Boundary between Okanagan River and Okanagan Lake modelling and mapping areas for design and flood mapping.Recommended Design Flood (gates open): Ellison, Skaha, Vaseux, and Osoyoos lakeso Lake Shoreline Flood Construction Level (FCL) Zone – Recommended Design Flood with Freeboard and Wave Effect (NHC): Zone defined based on approximate shoreline and the wave breaking boundary plus a buffer; FCLs defined by zone along shoreline; shoreline FCLs take precedence over lake inundation FCLs.o Lake Flood Construction Level (FCL) Zone (Inundation Extent) – Recommended Design Flood with Freeboard (NHC): Design flood inundation extent with freeboard. Design event varies by lake, plus wind setup, plus mid-century climate change; plus freeboard 0.6m.o Lake Inundation Extent – Recommended Design Flood without Freeboard (NHC): Design flood inundation extent without freeboard. Design event varies by lake, plus wind setup, plus mid-century climate change.o Depth Grids§ Ellison Lake Depth – Recommended Design without Freeboard (NHC): ELLISON LAKE: 200-YEAR MID-CENTURY. Design flood depth without freeboard. Design