Iowa Admin. Code r. 567-72.4

Current through Register Vol. 47, No. 5, September 4, 2024

Rule 567-72.4 - Levees or dikes

The following criteria shall apply to levees or dikes.

(1)Agricultural levees or dikes.

a.Level of protection. The permanent height of agricultural levees or dikes normally shall be limited so that overtopping will occur due to discharges from Q10 to Q25 with the more comprehensive levee system being permitted the greater degree of protection.

b.Additional protection. Where it can clearly be shown that loss of valley storage caused by construction of the levee will not increase peak flood stages and discharges, the level of protection provided by the agricultural levee or dike may be increased beyond the Q10 to Q25 range.

c.Alignment. The location and alignment of agricultural levees or dikes shall be compatible with existing encroachment limits so that minimum flood protection levels will not be increased and said levee or dike alignment otherwise shall be consistent with the rules governing the location of encroachment limits set out in 567-754. (455B).

d.Maximum effect. The maximum increase in the flood profile resulting from the construction, operation, and maintenance of an agricultural levee or dike shall be 1 foot. Equal and opposite conveyance as defined in 567-Chapter 70 shall be used in determining the maximum increase in flood profile resulting from such levees or dikes.

e.Interior drainage. All agricultural levees or dikes shall be provided with adequate interior drainage facilities.

f. Offset. A minimum offset equal to 100 feet or twice the width of a river or stream measured from top of bank to top of bank, whichever distance is less, shall be required for all agricultural levees unless a greater offset is dictated by 72.4(1), paragraph"c" or"d."

(2)Flood control levees or dikes.

a.Design level. The minimum design flood protection level for flood control levees or dikes shall correspond to the flood profile for Q100.

b.Freeboard. The levee or dike height shall provide for at least 3 feet of freeboard above the design flood profile.

c.Alignment. The alignment of a flood control levee or dike shall be consistent with the rules governing the location of encroachment limits set out in 567-754. (455B).

d.Interior drainage. Flood control levees or dikes shall provide for adequate interior drainage and ponding.

e.Design and specifications. The structural design and construction of flood control levees or dikes must be undertaken in accordance with accepted engineering and construction procedures and practices.

Iowa Admin. Code r. 567-72.4