N.D. Admin. Code 89-14-01-03

Current through Supplement No. 395, January, 2025

Section 89-14-01-03 - Design flood frequency

The following table provides the minimum design standard recurrence interval of the event for which each type of stream crossing must be designed. Nothing contained in this chapter is intended to restrict an entity from providing greater capacity.

Type of Crossing	State Highway System						County
	Urban System		Rural System				Rural System
	Regional	Urban Roads	Principal Arterial		Minor Arterial	Major Collector	Major Collector	Off⁴ System
	Regional	Urban Roads	Interstate	Other	Minor Arterial	Major Collector	Major Collector	Off⁴ System
Bridges & Reinforced Concrete Boxes	25 year²	25 year²	50 year²	50 year²	50 year²	25 year²	25 year^{2, 3}	15 year^{2, 3}
Roadway Culverts	25 year²	25 year²	50 year²	25 year²	25 year²	25 year²	25 year^{2, 3}	15 year^{2, 3, 5}
Storm Drains	10 year¹	5 year¹	10 year²	10 year²	10 year²	10 year²
Underpass Storm Drains	25 year¹	25 year¹	50 year²	25 year²	25 year²	25 year²

¹Discharges must be computed using the rational method or other recognized hydrologic methods.

²Discharges must be computed using United States geological survey report 2015-5096 or other recognized hydrologic methods.

³If an overflow section is provided, the pipes and the overflow section, in combination, must pass the appropriate design event within the headwater limitations provided in this chapter.

⁴Off system roads include all nonmajor collector public roads open for public travel.

⁵For public roads open for public travel under the jurisdiction of a board of township supervisors of a civil township, the recurrence interval is 10 years.

N.D. Admin Code 89-14-01-03

Effective May 1, 2001; amended effective July 27, 2001.

Amended by Administrative Rules Supplement 2015-355, January 2015, effective 1/1/2015.

Amended by Administrative Rules Supplement 2022-387, January 2023, effective 1/1/2023.

Amended by Administrative Rules Supplement 2024-393, July 2024, effective 7/1/2024.

General Authority: NDCC 24-02-01.1, 24-02-01.5, 61-03-13

Law Implemented: NDCC 24-03-06, 24-03-08, 24-06-26.1