Calculating the Effects of Climate Change Modeling on
Calculating the Effects of Climate Change Modeling on Olsen Creek, WA Bridge Replacement Design Following methodology presented in the WDFW 2016 study, “Incorporating Climate Change into the Design of Water Crossing Structures”
GIS Component Washington Department of Fish and Wildlife (WDFW) Study
WEST Consultants, Inc. Results Introduction
With the development and release of the Washington Department of Fish and Wildlife (WDFW) Final Report regarding the incorporation of climate change into the design of water crossing structures (WDFW 2016), WSDOT asked WEST to determine how the procedures outlined in the report would affect the design process for replacement stream crossings. To do this, we applied the techniques described in the WDFW report to the SR112 Olsen Creek Fish Barrier Removal project, and then investigated how the change in bankfull width and 100-year peak flow would impact the Preliminary Basis of Design (PBoD) report we had previously developed for the Olsen Creek Crossing.
Incorporating Climate Change into the Design of Water Crossing Structures, Final Report. Wilhere, George, Jane Atha, Timothy Quinn, Lynn Helbrecht (WDFW), and Ingrid Tohver (UW Climate Impacts Group, 2016) Introduction Washington State regulations require that water crossing structures (i.e., culverts and bridges) “allow fish to move freely through them at all flows when fish are expected to move” (WAC 220-660-190). Washington State was ordered by federal court to replace approximately 1,000 stream crossings deemed to block fish passage. The Washington Department of Transportation (WSDOT) requires a minimum life expectancy of 50 years for all culverts, indicating that climate change, including increased flows and bankfull widths, must be taken into account. This study seeks to provide tools to help decision makers understand the potential impacts of climate change on the hydrology and hydraulics of western Washington stream crossing structures, particularly in order to weigh uncertainty and risk factors when designing bridges and culverts.
Methods and Results Using the shapefiles provided along with the report, we first duplicated the results from the Big Creek case study to verify that our methodology was correct. Following the same procedure we used to duplicate the Big Creek results from the study, we determined the forecasted changes to bankfull width and the 100-year flow on Olsen Creek (see Figure 2). The analysis resulted in a 12.5% increase in bankfull width, from 24 feet to 27 feet, and a 23.8% increase in 100-year flow, from 306 cfs to 379 cfs.
Methods
University of Washington Climate Impacts Group assembled a suite of 10 Global Climate Models (GCMs) that most reliably simulate 20th Century climate in the Pacific Northwest, listed in Table 1, then “downscaled” them from a resolution of 100-300 km2 to a grid of 570 33 km2 cells covering the State of Washington, as shown in Figure 1.
Table 1. Ten global climate models used by Climate Impacts Group in projecting stream flows in the Pacific Northwest. Model Name
Organization
Country
Ccsm3
National Center for Atmospheric Research
USA
Pcm1
National Center for Atmospheric Research
USA
Cgcm3.1_t47
Canadian Centre for Climate Modeling Analysis
Canada
Cnrm_cm3
Météo-France/Centre National de Recherches Météorologiques
France
Echam5
Max Planck Institute for Meteorology
Germany
Echo_g
Meteorological Institute of the University of Bonn, Korea Meteorological Administration
Germany, Korea
Hadcm
Hadley Centre for Climate Prediction and Research
UK
Hadgem1
Hadley Centre for Climate Prediction and Research
UK
Ipsl_cm4
Institut Pierre Simon Laplace
France
Miroc_3.2
Center for Climate System Research, University of Tokyo
Japan
Figure 1. WDFW divided Washington State into 570 33 km2 cells and calculated flows for each cell in 2040 and 2080 for each of the 10 global climate models listed in Table 1. The results are provided in a shapefile.
PBoD Values
Computed 2080 Values
Difference (%)
Bankfull Width (ft)
24
27
12.5%
100-year flows (cfs)
306
379
23.8%
2-year flows est. (cfs)
96.3
122
26.7%
PBoD Values
Computed 2080 Values
Water Surface Elevation (ft)
10.94
11.04
Velocity (ft/s)
5.36
5.61
Shear Stress (lb/ft2)
2.22
2.40
Freeboard (ft)
2.76
2.66
32
37
Minimum Bridge Span (ft)
Table 2. Adjusted Bankfull Width and 100-year Flow on Olsen Creek.
Table 3. HEC-RAS Model Results at the Olsen Creek Crossing (100-year Flows).
Figure 3. HEC-RAS Model Results
As part of the process to determine the increase in bankfull width, we also determined the increase in bankfull flow, which we estimated to approximately equal the increase in 2-year flow. These results are listed in Table 2. Using the adjusted values, we ran the HEC-RAS model of the Olsen Creek crossing to determine how the increased flow and width would affect crossing hydraulics. This was done by increasing both the cross section width within the HEC-RAS model to account for the computed increase in bankfull width and the peak discharges. Figure 3 shows the results in HEC-RAS Mapper. We determined that a minimum bridge width of 37 feet was required to pass the 100-year flow without constricting the flow, an increase of five feet over the previous model. Results are summarized in Table 3.
They then input the data into the Variable Infiltration Capacity (VIC) hydrologic model and determined the future bankfull discharge for each cell. With the bankfull discharge data, they estimated bankfull width for each of the 10 models in each of the grid cells for three time periods: historical, 2040s, and 2080s. Finally, they calculated 100-year flood discharge and the percent change for the two future time periods between historic flows and the mean of the 10 projected future flows.
To access the WDFW Climate Change paper, go to wdfw.wa.gov/publications/01867/wdfw01867.pdf Or scan the QR code to the right
Katie Messick, Dan Eggers and Keelan Jensen, WEST Consultants, Inc.
Figure 2. WEST applied the methodology laid out by WDFW to calculate increases in flows and bankfull width at the State Route 112 crossing of Olsen Creek on the Olympic Peninsula. To do this, the watershed area above the crossing was delineated using the StreamStats website (streamstats.usgs.gov); then the area of intersection between the drainage and each climate grid cell was calculated; projected bankfull flow was calculated as a weighted average; and the percent change in bankfull flow was calculated for each of the 10 global climate models. These results were then input into WEST’s HEC-RAS model.
112
N
Elevation NAVD 88 100 Year Flood Inundation Extent Existing Conditions Climate Change 2080 Scenario 1 inch = 50 feet
GIS Component Washington Department of Fish and Wildlife (WDFW) Study
WEST Consultants, Inc. Results Introduction
With the development and release of the Washington Department of Fish and Wildlife (WDFW) Final Report regarding the incorporation of climate change into the design of water crossing structures (WDFW 2016), WSDOT asked WEST to determine how the procedures outlined in the report would affect the design process for replacement stream crossings. To do this, we applied the techniques described in the WDFW report to the SR112 Olsen Creek Fish Barrier Removal project, and then investigated how the change in bankfull width and 100-year peak flow would impact the Preliminary Basis of Design (PBoD) report we had previously developed for the Olsen Creek Crossing.
Incorporating Climate Change into the Design of Water Crossing Structures, Final Report. Wilhere, George, Jane Atha, Timothy Quinn, Lynn Helbrecht (WDFW), and Ingrid Tohver (UW Climate Impacts Group, 2016) Introduction Washington State regulations require that water crossing structures (i.e., culverts and bridges) “allow fish to move freely through them at all flows when fish are expected to move” (WAC 220-660-190). Washington State was ordered by federal court to replace approximately 1,000 stream crossings deemed to block fish passage. The Washington Department of Transportation (WSDOT) requires a minimum life expectancy of 50 years for all culverts, indicating that climate change, including increased flows and bankfull widths, must be taken into account. This study seeks to provide tools to help decision makers understand the potential impacts of climate change on the hydrology and hydraulics of western Washington stream crossing structures, particularly in order to weigh uncertainty and risk factors when designing bridges and culverts.
Methods and Results Using the shapefiles provided along with the report, we first duplicated the results from the Big Creek case study to verify that our methodology was correct. Following the same procedure we used to duplicate the Big Creek results from the study, we determined the forecasted changes to bankfull width and the 100-year flow on Olsen Creek (see Figure 2). The analysis resulted in a 12.5% increase in bankfull width, from 24 feet to 27 feet, and a 23.8% increase in 100-year flow, from 306 cfs to 379 cfs.
Methods
University of Washington Climate Impacts Group assembled a suite of 10 Global Climate Models (GCMs) that most reliably simulate 20th Century climate in the Pacific Northwest, listed in Table 1, then “downscaled” them from a resolution of 100-300 km2 to a grid of 570 33 km2 cells covering the State of Washington, as shown in Figure 1.
Table 1. Ten global climate models used by Climate Impacts Group in projecting stream flows in the Pacific Northwest. Model Name
Organization
Country
Ccsm3
National Center for Atmospheric Research
USA
Pcm1
National Center for Atmospheric Research
USA
Cgcm3.1_t47
Canadian Centre for Climate Modeling Analysis
Canada
Cnrm_cm3
Météo-France/Centre National de Recherches Météorologiques
France
Echam5
Max Planck Institute for Meteorology
Germany
Echo_g
Meteorological Institute of the University of Bonn, Korea Meteorological Administration
Germany, Korea
Hadcm
Hadley Centre for Climate Prediction and Research
UK
Hadgem1
Hadley Centre for Climate Prediction and Research
UK
Ipsl_cm4
Institut Pierre Simon Laplace
France
Miroc_3.2
Center for Climate System Research, University of Tokyo
Japan
Figure 1. WDFW divided Washington State into 570 33 km2 cells and calculated flows for each cell in 2040 and 2080 for each of the 10 global climate models listed in Table 1. The results are provided in a shapefile.
PBoD Values
Computed 2080 Values
Difference (%)
Bankfull Width (ft)
24
27
12.5%
100-year flows (cfs)
306
379
23.8%
2-year flows est. (cfs)
96.3
122
26.7%
PBoD Values
Computed 2080 Values
Water Surface Elevation (ft)
10.94
11.04
Velocity (ft/s)
5.36
5.61
Shear Stress (lb/ft2)
2.22
2.40
Freeboard (ft)
2.76
2.66
32
37
Minimum Bridge Span (ft)
Table 2. Adjusted Bankfull Width and 100-year Flow on Olsen Creek.
Table 3. HEC-RAS Model Results at the Olsen Creek Crossing (100-year Flows).
Figure 3. HEC-RAS Model Results
As part of the process to determine the increase in bankfull width, we also determined the increase in bankfull flow, which we estimated to approximately equal the increase in 2-year flow. These results are listed in Table 2. Using the adjusted values, we ran the HEC-RAS model of the Olsen Creek crossing to determine how the increased flow and width would affect crossing hydraulics. This was done by increasing both the cross section width within the HEC-RAS model to account for the computed increase in bankfull width and the peak discharges. Figure 3 shows the results in HEC-RAS Mapper. We determined that a minimum bridge width of 37 feet was required to pass the 100-year flow without constricting the flow, an increase of five feet over the previous model. Results are summarized in Table 3.
They then input the data into the Variable Infiltration Capacity (VIC) hydrologic model and determined the future bankfull discharge for each cell. With the bankfull discharge data, they estimated bankfull width for each of the 10 models in each of the grid cells for three time periods: historical, 2040s, and 2080s. Finally, they calculated 100-year flood discharge and the percent change for the two future time periods between historic flows and the mean of the 10 projected future flows.
To access the WDFW Climate Change paper, go to wdfw.wa.gov/publications/01867/wdfw01867.pdf Or scan the QR code to the right
Katie Messick, Dan Eggers and Keelan Jensen, WEST Consultants, Inc.
Figure 2. WEST applied the methodology laid out by WDFW to calculate increases in flows and bankfull width at the State Route 112 crossing of Olsen Creek on the Olympic Peninsula. To do this, the watershed area above the crossing was delineated using the StreamStats website (streamstats.usgs.gov); then the area of intersection between the drainage and each climate grid cell was calculated; projected bankfull flow was calculated as a weighted average; and the percent change in bankfull flow was calculated for each of the 10 global climate models. These results were then input into WEST’s HEC-RAS model.
112
N
Elevation NAVD 88 100 Year Flood Inundation Extent Existing Conditions Climate Change 2080 Scenario 1 inch = 50 feet
