FLOOD PLAIN OR FLOODWAY DEVELOPMENT: WHEN APPROVAL IS REQUIRED
Dams
When Department Approval is Required Per Chapter 71
Approval by the department for construction, operation, or maintenance of a dam in the floodway or flood plain of any water source shall be required when the dimensions and effects of such dam exceed the thresholds established by this rule. EXCEPTION: Public road embankments with culverts which impound water only in temporary storage are exempt from the requirements of this rule and shall be reviewed under rules 567-71.1(455B) and 567-72.1(455B). Approval required by this rule shall be coordinated with approval for storage of water required by 567-Chapter 51. Approval by the department shall be required in the following instances:
71.3(1) Rural areas. In rural areas:
- Any dam designed to provide a sum of permanent and temporary storage exceeding 50 acre-feet at the top of dam elevation, or 25 acre-feet if the dam does not have an emergency spillway, and which has a height of 5 feet or more.
- Any dam designed to provide permanent storage in excess of 18 acre-feet and which has a height of 5 feet or more.
- Any dam across a stream draining more than 10 square miles.
- Any dam located within 1 mile of an incorporated municipality, if the dam has a height of 10 feet or more, stores 10 acre-feet or more at the top of dam elevation, and is situated such that the discharge from the dam will flow through the incorporated area.
71.3(2) Urban areas. Any dam which exceeds the thresholds in 71.3(1) "a," "b" or "d."
71.3(3) Low head dams. Any low head dam on a stream draining 2 or more square miles in an urban area, or 10 or more square miles in a rural area.
71.3(4) Modifications to existing dams. Modification or alteration of any dam or appurtenant structure beyond the scope of ordinary maintenance or repair, or any change in operating procedures, if the dimensions or effects of the dam exceed the applicable thresholds in this rule. Changes in the spillway height or dimensions of the dam or spillway are examples of modifications for which approval is required.
71.3(5) Mill dams. Rescinded IAB 2/20/91, effective 3/27/91.
71.3(6) Maintenance of preexisting dams. Approval shall be required to maintain a preexisting dam as described in 567-Chapter 73 only if the department determines that the dam poses a significant threat to the well-being of the public or environment and should therefore be removed or repaired and safely maintained. Preexisting dams are subject to the water, air and waste management dam safety inspection program as set forth in 567-Chapter 73. This rule is intended to implement Iowa Code sections 455B.262, 455B.264, 455B.267, 455B.275 and 455B.277.
Application Forms, Checklists & Guidance:
| Application Form(s) |
*.pdf |
| Joint Application Form |
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| Application for Permit to Store Water for Beneficial Use |
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| Application Guidance | *.pdf |
| Climatology of Iowa Series 2, Revised |
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| Bulletin No. 16, Design Criteria and Guidelines For Iowa Dams |
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| Maintenance Manual for Dam Owners |
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| Application Checklist(s) | *.pdf |
| Project Information Checklist for Earth Embankment Dams |
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Aerial photographs can be obtained online at:
http://ortho.gis.iastate.edu/search.html.
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