Future Flooding Impacts on Transportation Infrastructure and Traffic Patterns Resulting from Climate Change

Climate change in the Pacific Northwest of America is likely to bring more frequent, heavier winter precipitation as temperature rises. These changes in precipitation patterns have significant implications in hydrology and socioeconomic sectors that could be affected by changes in hydrology. Transportation infrastructure and travel patterns are also vulnerable to potential changes in runoff regimes and stream geomorphology. The 2006 and 2007 winter storms resulted in massive flooding, causing several major road failures in Oregon. While the probability of these extreme events is projected to rise under the global warming scenarios, there is no study investigating this issue in Oregon.…

Climate change in the Pacific Northwest of America is likely to bring more frequent, heavier winter precipitation as temperature rises.  These changes in precipitation patterns have significant implications in hydrology and socioeconomic sectors that could be affected by changes in hydrology.  Transportation infrastructure and travel patterns are also vulnerable to potential changes in runoff regimes and stream geomorphology.  The 2006 and 2007 winter storms resulted in massive flooding, causing several major road failures in Oregon.  While the probability of these extreme events is projected to rise under the global warming scenarios, there is no study investigating this issue in Oregon.

The objectives of the project are threefold.
(1) To investigate the changes in the timing and magnitude of winter runoff under climate change scenarios;
(2) To determine the lag time of streams to adjust to changes in the discharge regime;
(3) To quantify the operational and economic impacts of these changes on transportation chokepoints and damage related to flooding.

We will examine two representative urban streams in the Portland Metro area.  Johnson Creek and Fanno Creek were chosen because both creeks have historical flow data and exhibit high flooding potential; each also has high road density with high traffic volume. The hydrological processes of the two watersheds, however, are different (Fanno – highly urbanized and steep slope; Johnson Creek – mixed land use with gentle slope); thus, each serves as a good model for other urban watersheds in Oregon.

The following methodology will be used to conduct the proposed work.
(1) Hydro-climate modeling: We will apply downscaled climate change scenarios for our study sites to predict the anticipated changes in winter precipitation amount and intensity.  The USGS MMS hydrologic model, together with a statistical model, will be used to estimate runoff changes and resultant changes in flood frequency.
(2) Stream geomorphology survey: We will survey channel profiles, patterns, and dimensions at the multiple cross sections of our study sites.  We will also determine bankful discharge level for each site and relate that to channel flood capacity and possible channel adjustments. 
(3) Vulnerability analysis: We will use GIS and statistics to delineate flood vulnerable road intersections by overlying road layer and river levels. In addition, we will determine vulnerable transportation infrastructure (e.g., bridges) as a result of changes in runoff regime.
(4) Traffic analysis: We will use Metro’s travel forecast model to determine the potential impacts of road failure and congestion resulting from flooding. The model has long been applied in the Portland metro area and serves as a reasonable and accurate assessment of the outcomes due to traffic disruption.  The economic impact of the disruptions on workers, freight, and businesses will be estimated. 

The outcomes of this research will include (1) maps showing potentially vulnerable roads to different magnitudes of flooding, (2) socioeconomic damage of trip disturbance resulting from road closures, and (3) papers that could be presented at professional conferences and submitted to peer-reviewed journals. In addition, the research will potentially lead to MS student theses in Geography and Civil Engineering.