Iowa Admin. Code r. 567-72.4 - Levees, floodwalls, and dikes
The following criteria shall apply to levees, floodwalls, and 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 shall be located outside of the floodway or
demonstrate that the construction shall not result in a rise in upstream water
surface elevations.
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)"c" or "d."
(2)
Flood control levees, floodwalls,
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
located outside of the floodway or demonstrate that the construction shall not
result in a rise in upstream water surface elevations.
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.
Notes
State regulations are updated quarterly; we currently have two versions available. Below is a comparison between our most recent version and the prior quarterly release. More comparison features will be added as we have more versions to compare.
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.