Adapting Stormwater Infrastructure to Extreme Precipitation
Increases in precipitation intensity raise the question of how to adapt stormwater infrastructure. We developed a model to simulate the effects of increasing flows on roadway culverts, which are typically constructed to convey certain flow volumes. Key model inputs include when and how to modify stormwater infrastructure as climate changes and culvert failures become more likely. By the end of this reporting period WWA Graduate Student Adam McCurdy successfully produced several adaptation simulations using the model for a testbed of selected Colorado culvert emplacements. McCurdy presented on the results at the Adaptation Futures conference in May, 2016 in Rotterdam, Netherlands. That presentation and two articles prepared for submission, available as working papers in the WWA website, convey the key findings related to different rates of climate change and four different adaptation strategies: Nominal, Anticipatory, Reactive, and Concurrent. The Nominal Strategy assumes no change in culvert replacement strategy over the entire simulation; in the event that a crossing’s lifespan is reached, or the crossing is destroyed by a runoff event, it is replaced with a crossing of the same capacity. Under the Anticipatory Strategy, all crossings are replaced with higher capacity crossings prior to the end of their normal lifespans. Under the Concurrent Strategy the capacity of each crossing is increased at the time of normal replacement. The Reactive Strategy begins with the Nominal Strategy and switches to the Concurrent Strategy when a crossing is replaced following damage by an extreme event. Results indicate that aggressive anticipatory replacement of culverts is economically inefficient even under rather large climate change scenarios. This is due to the sunk investment of culverts and the traffic disruption caused by construction. The most efficient adaptation pathway under climate uncertainty appears to be to invest more effort to evaluate the vulnerability of each culvert no matter what its life-cycle status, and adapt only those likely to failure in the near term.