Facility

Designer’s First Priority
Roadway Base or
Bridge Low Chord Clearance

Designer Must Check
Shoulder Break Point Clearance or

Bridge Low Chord Clearance

Required  Clearance

Design Flood Frequency

Required
Clearance

Design Flood Frequency

Interstate

2-ft.

50-year

1-ft. below shoulder break point

100-year

Hurricane Evacuation Routes

2-ft.

50-year

1-ft. below shoulder break point

100-year

Roads Designed as State Routes

2-ft.

50-year

1-ft. below shoulder break point

100-year

Roads Not Designed as State Routes

ADT:  0 – 99

2-ft.

5-year

1-ft. below shoulder break point

10-year

ADT:  100 – 399

2-ft.

10-year

1-ft. below shoulder break point

25-year

ADT:  400 – 1,499

2-ft.

25-year

1-ft. below shoulder break point

50-year

ADT:  1,500 or more

2-ft.

50-year

1-ft. below shoulder break point

100-year

Driveways

2-ft.

25-year

Shoulder break point not overtopped

50-year

Temporary Detours

2-ft.

10-year

Shoulder break point not overtopped

25-year

Permanent Bridges

2-ft.

50-year

1-ft. low-chord clearance

100-year

Temporary Bridges

Local Road with ADT < 400

2-ft.

2-year

Low-chord not overtopped

5-year

All Other Roads

2-ft.

10-year

Low-chord not overtopped

25-year