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Service Description: GIS Layers
• Lake shoreline zones – polygons (include flood construction level (FCL))
• Lake inundation, various flood scenarios – extent polygons (design extents include FCL), water surface elevation (WSE) rasters, depth rasters
• River inundation based on 1D modelling, various scenarios – extent polygons, FCL isolines for design extent, WSE rasters, depth rasters
• River cross sections – lines including WSE values
• River/lake modelling and mapping boundaries – lines
• River hazard layers based on 2D modelling – depth raster, velocity points
• 2017 water extents layer - polygons
General Notes
1. These floodplain mapping layers delineate flood inundation extents under the specific flood events. Tributaries are not included in mapping. Please review the associated report before using the floodplain mapping layers, NHC (2020).
2. 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.
3. 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.
4. Where noted, the FCL 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 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 Professional may be warranted to refine the generalized wave effects shown which could increase or decrease the FCL by as much as a metre.
5. 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. 6. The Okanagan floodplain is subject to persistent ponding due to poor drainage. Persistent ponding is not covered by the flood inundation mapping.
7. 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 is required to determine validity of isolated inundation.
c. Isolated inundated areas less than 100 m2 have been mapped as dry consistent with surrounding ground. Similarly, isolated islands less than 100 m2 have been mapped as inundated. d. Okanagan Dam breach and dam overtopping 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. 8. 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.
9. 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. 10. Industry best practices were followed to generate the floodplain maps. However, actual flood levels and extents may vary from those shown. The Okanagan Basin Water Board and Northwest Hydraulic Consultants Ltd. (NHC) do not assume any liability for variations of flood levels and extents from that shown.
Data Sources
1. Design flood events are based on hydrologic modelling of the Okanagan 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.
2. 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). Reference
NHC (2020). Okanagan Floodplain Mapping. Final Report. Prepared for Okanagan Basin Water Board. Disclaimer
This document has been prepared by Northwest Hydraulic Consultants Ltd. for the benefit of the Okanagan Basin Water Board 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 the Okanagan Basin Water Board, 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.
Map Name: OBWB_FloodMapping
Legend
All Layers and Tables
Dynamic Legend
Dynamic All Layers
Layers:
Description: GIS Layers
• Lake shoreline zones – polygons (include flood construction level (FCL))
• Lake inundation, various flood scenarios – extent polygons (design extents include FCL), water surface elevation (WSE) rasters, depth rasters
• River inundation based on 1D modelling, various scenarios – extent polygons, FCL isolines for design extent, WSE rasters, depth rasters
• River cross sections – lines including WSE values
• River/lake modelling and mapping boundaries – lines
• River hazard layers based on 2D modelling – depth raster, velocity points
• 2017 water extents layer - polygons
General Notes
1. These floodplain mapping layers delineate flood inundation extents under the specific flood events. Tributaries are not included in mapping. Please review the associated report before using the floodplain mapping layers, NHC (2020).
2. 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.
3. 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.
4. Where noted, the FCL 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 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 Professional may be warranted to refine the generalized wave effects shown which could increase or decrease the FCL by as much as a metre.
5. 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. 6. The Okanagan floodplain is subject to persistent ponding due to poor drainage. Persistent ponding is not covered by the flood inundation mapping.
7. 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 is required to determine validity of isolated inundation.
c. Isolated inundated areas less than 100 m2 have been mapped as dry consistent with surrounding ground. Similarly, isolated islands less than 100 m2 have been mapped as inundated. d. Okanagan Dam breach and dam overtopping 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. 8. 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.
9. 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. 10. Industry best practices were followed to generate the floodplain maps. However, actual flood levels and extents may vary from those shown. The Okanagan Basin Water Board and Northwest Hydraulic Consultants Ltd. (NHC) do not assume any liability for variations of flood levels and extents from that shown.
Data Sources
1. Design flood events are based on hydrologic modelling of the Okanagan 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.
2. 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). Reference
NHC (2020). Okanagan Floodplain Mapping. Final Report. Prepared for Okanagan Basin Water Board. Disclaimer
This document has been prepared by Northwest Hydraulic Consultants Ltd. for the benefit of the Okanagan Basin Water Board 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 the Okanagan Basin Water Board, 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.
Copyright Text: NHC and OBWB
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Document Info:
Title: FloodStoryRevamp_ArcPro.aprx
Author:
Comments: GIS Layers
• Lake shoreline zones – polygons (include flood construction level (FCL))
• Lake inundation, various flood scenarios – extent polygons (design extents include FCL), water surface elevation (WSE) rasters, depth rasters
• River inundation based on 1D modelling, various scenarios – extent polygons, FCL isolines for design extent, WSE rasters, depth rasters
• River cross sections – lines including WSE values
• River/lake modelling and mapping boundaries – lines
• River hazard layers based on 2D modelling – depth raster, velocity points
• 2017 water extents layer - polygons
General Notes
1. These floodplain mapping layers delineate flood inundation extents under the specific flood events. Tributaries are not included in mapping. Please review the associated report before using the floodplain mapping layers, NHC (2020).
2. 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.
3. 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.
4. Where noted, the FCL 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 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 Professional may be warranted to refine the generalized wave effects shown which could increase or decrease the FCL by as much as a metre.
5. 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. 6. The Okanagan floodplain is subject to persistent ponding due to poor drainage. Persistent ponding is not covered by the flood inundation mapping.
7. 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 is required to determine validity of isolated inundation.
c. Isolated inundated areas less than 100 m2 have been mapped as dry consistent with surrounding ground. Similarly, isolated islands less than 100 m2 have been mapped as inundated. d. Okanagan Dam breach and dam overtopping 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. 8. 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.
9. 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. 10. Industry best practices were followed to generate the floodplain maps. However, actual flood levels and extents may vary from those shown. The Okanagan Basin Water Board and Northwest Hydraulic Consultants Ltd. (NHC) do not assume any liability for variations of flood levels and extents from that shown.
Data Sources
1. Design flood events are based on hydrologic modelling of the Okanagan 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.
2. 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). Reference
NHC (2020). Okanagan Floodplain Mapping. Final Report. Prepared for Okanagan Basin Water Board. Disclaimer
This document has been prepared by Northwest Hydraulic Consultants Ltd. for the benefit of the Okanagan Basin Water Board 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 the Okanagan Basin Water Board, 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.
Subject: NHC Flood Modeling
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Keywords: NHC,FLC,FLood
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