According to a recent study by strategic consulting firm ICF, much of the flooding in Maryland occurs outside Federal Emergency Management Agency designated flood zones.
The report, Flooding Impacts on Maryland’s Transportation System and Users, examines how flooding affects nearly 15,000 lane miles of state-maintained roadways. Approximately 20 percent of lane miles were in Maryland.
Researchers reviewed 2,771 flood-related incidents and discovered 78 percent occurred outside the 100- or 500-year flood zones, although most occurred within 0.3 miles of the mapped flood areas.
Researchers also identified state highways that are especially flood-prone. Seven locations had at least 30 incidents collectively. More than 100 locations experienced at least five flood events within about 1,000 feet of one another.
In Maryland, flooding disrupts traffic an average of 66 days annually on state-maintained roadways, with 16 percent of the disruptions lasting longer than 12 hours.
These disruptions cost approximately $15 million annually in delayed deliveries and lost work time and totaled more than $230 million during the study period.
Each flood incident cost approximately $80,000 on average in user delay costs.
The Maryland Department of Transportation provided researchers with data for the years 2006 to 2020.
The department has used climate data to assess the vulnerability of more than 8,500 structures.