Graeme Vass of Northwest Hydraulic Consultants (NHC) was the presenter for the "methods of climate change assessment for infrastructure projects" session at the Association of Consulting Engineering Companies (BC) transportation conference, held Jan. 26 in downtown Vancouver.
Vass started by detailing work on the Gamma Creek Replacement Project. The culvert is quite damaged and infilling, due to it being undersized and a shallow slope, which leads to sediment settlement.
A rainfall intensity and frequency tool was used to provide estimates of future rainfall intensity based on projection from 39 different general circulation model runs for three representative concentration pathways.
The Salmon River Bridge Replacement, located in Prince George, B.C., is susceptible to climate change, due to projected increases in seasonal temperatures, low relief in the watershed, and banks consisting of gravel and fine materials that "tend to meander."
Rate of meandering has increased following a 1997 flood event, and for this site a more robust climate change assessment was required. A variable infiltration capacity hydrologic model was used to make future projections of streamflow.
It was found the lowest per cent change was a decrease of 29 per cent. But an increase could be eight per cent.
Bridge soffit elevation and bank protection used this 8 per cent measurement when building.
The South Peace Region Hydrology Assessment was undertaken after extensive flooding in the summer of 2016.
More than 100 tributaries were assessed, and the method used for small tributaries was the same rainfall and intensity and frequency tool used for gamma creek. Non-stationary analysis was used, which looks at how peak flows change over time.
The flow increases due to climate change affect sizing and placement of protection elements, soffit elevation of bridges and sizing of culverts. Different degrees of climate change assessments can be used for different phases of the project, Vass said.