Protecting Roads From Flood Damage
MnDOT knows what kind of damage flooding can do to our transportation system and the efforts required to repair that damage. With the impacts of climate change increasing, new approaches are needed to understand vulnerabilities across the transportation system and what actions can be taken to minimize expanding risks.
MnDOT has multiple research projects and initiatives addressing this topic.
MnDOT Slope Vulnerability Assessments
MnDOT conducted four slope vulnerability assessments to identify, map and categorize slopes vulnerable to failure with the potential to affect state trunk highways in MnDOT Districts 1, 2, 3, 4, 6, 7, 8, and Metro. Researchers developed a model for assessing slope failure risks near roadways that can be used in MnDOT's geographic information system (GIS) platform. The model maps slope failure vulnerability within a half-mile of a road based on slope characteristics and proximity to risk factors, and then generates PDFs and physical maps of roadways and the slopes alongside. The slope vulnerability maps point inspectors to areas that require investigation and will help MnDOT plan for and prevent slope failures, reducing the damage caused by failures and the expense related to their repair.
- MnDOT Slope Vulnerability Assessments - Phase 1
- MnDOT Slope Vulnerability Assessments - Phase 2
- MnDOT Slope Vulnerability Assessments - Phase 3
- MnDOT Slope Vulnerability Assessments - Phase 4
- MnDOT Slope Vulnerability Assessments - Phase 5
Slope Stabilization Guide for Minnesota Local Government Engineers
Slope failures must be repaired to prevent damage to roadways and embankments. When slope damage is severe, a geotechnical engineering firm must step in at some expense. But when damage is less severe, a county can often stabilize the slope using local materials and simple techniques.
A guidebook provides eight cost‐effective stabilization techniques that local government engineers can undertake to stabilize slopes using local materials and equipment. It includes a simple, three-step flowchart that helps engineers quickly select the most appropriate repair technique.
The methods are the result of a research effort that analyzed recent slope failures in Minnesota. Researchers examined 14 destabilized sites, analyzing soil samples from each. They identified 12 potential stabilization techniques from a literature search; and used computer modeling to examine the viability of various techniques at sites where soil was sandy, fine-grained or rocky. They also interviewed local engineers about what practices have worked well.
- Slope Stabilization Guide for Minnesota Local Government Engineers. (Report 2017-17)
Storm-Induced Slope Failure Susceptibility Mapping
Researchers identified risk factors that inform slope failure and then collected topographic, soils and rainfall data to use in mapping areas for certain slope characteristics. They produced geographic information system (GIS) maps of two Minnesota counties that rank the failure potential of each slope in each county. County road crews can use the maps to anticipate potential failure response needs at roadways alongside slopes. Highway agencies can use the maps to plan preventive action on slopes that appear susceptible to failure in significant storm events.
- Storm-Induced Slope Failure Susceptibility Mapping (Report 2018-05)
Design Considerations for Embankment Protection During Road Overtopping Events
Roadway overtopping is a major safety concern for Minnesota transportation managers because of the potential for rapid soil erosion and mass wasting resulting in partial or complete failure of the roadway embankment. This multi-year research study focused on various aspects of the roadway embankment overtopping.
A robust literature survey was performed to identify research, reports and other published knowledge that would inform the project. A field-based research campaign was developed with the goal of collecting data on the hydraulics associated with full-scale overtopping events.
The St. Anthony Falls Laboratory (University of Minnesota) conducted a series of laboratory experiments to study the hydraulic and erosional processes associated with embankment overtopping and three slope protection techniques for overtopping flow. The largest component of the research project was the laboratory hydraulic testing, which focused on bare soil (base case) and three slope protection technologies. A full-scale laboratory facility was constructed to carry out the testing.
- Design Considerations for Embankment Protection During Road Overtopping Events.
- Extreme Flood Vulnerability Analysis (PowerPoint)
MnDOT Flash Flood Vulnerability and Adaptation
Minnesota’s climate is changing. Temperatures are on the rise and extreme precipitation events and associated flooding are becoming more frequent and severe. As the earth continues to warm, these events are projected to become even more common since a warmer atmosphere is capable of holding more water vapor.
Recognizing this, MnDOT planners and engineers have long considered minimizing the risk of flash flooding in the siting and design of the state’s roadway network. However, as has been the standard practice worldwide, they have traditionally assumed that future climate conditions will be similar to those recorded in the past. Climate change challenges this assumption. MnDOT must develop new approaches to understanding vulnerabilities across the highway system and at specific transportation facilities so that appropriate actions can be taken to minimize expanding risks.
This project is one of 19 Federal Highway Administration (FHWA) climate vulnerability pilot studies nationwide looking at the effects of climate on the transportation system. It represents a starting point for developing new approaches. The focus of this pilot study was on flash flood risks to the highway system. While flooding is not the only threat to the state’s highway system posed by climate change, it is likely to be one of the most significant and has already caused extensive disruptions to the transportation system in many areas.