Undersized Culverts

Image Credit: Scott Craig

Culverts carry streams under roads, and most were sized for storms that are no longer the biggest ones. In July 2023 Vermont's floods damaged more than 800 culverts and bridges, and the state keeps both a culvert inventory and records of what failed. We will train a model to predict which culverts washed out from the size and steepness of the land draining to them, how much of it is paved, and how much rain fell, then score every culvert in the inventory for the next storm. The output is a ranked list for the state transportation agency and a map of which washouts would cut off a town.

Research questions

1. Which features of a culvert and the land draining to it best predict whether it washed out in July 2023?

2. Which culverts in the inventory look most like the ones that failed, and which of those sit on a town's only road?

Datasets

• Vermont culvert and bridge inventory, with pipe size and location

• Vermont Agency of Transportation and town records of July 2023 washouts, as the labels

• Hourly rainfall for the storm from NOAA's gridded products

• FABDEM elevation and National Hydrography Dataset catchments, for drainage area and slope

• Sentinel-2 and NAIP imagery, for the paved fraction of each catchment

• OpenStreetMap roads, for which crossings sit on a single access route; WorldPop population

Machine learning

• A gradient boosting classifier that predicts washout from drainage area, slope, paved fraction, storm rainfall and pipe size where recorded, tested on counties held out of training

GIS

• Place each inventoried culvert on the stream network and delineate the land draining to it from the elevation model

• Compute slope, paved fraction and storm rainfall for each catchment

• Flag crossings that sit on a town's only access road using the road network, and count the people behind them

• Aggregate to counties for the public map

References

• Vermont Agency of Transportation (January 2024). Flood recovery and resilience work, presentation to the Senate Transportation Committee; 94 culverts replaced and 839 cleaned, culvert design standards by road class, and the Resilience Improvement Plan. (LINK ERROR)

• Vermont Agency of Transportation (September 2023). July 2023 flooding impacts and response activities, presentation to the Joint Transportation Oversight Committee; 832 culverts, bridges and multi-plates impacted.

• Segale, Vermont Agency of Transportation (February 2015). Local road bridge and culvert inventories, presentation to the House Transportation Committee; the statewide inventory tool holds about 98,000 culverts and 2,700 bridges. (LINK ERROR)