FLOOD00850

• Designation Number: 31
• County: Arapahoe
• Community: Unincorporated Arapahoe County
• Title: Major Drainageway Planning - Little Dry Creek, Report, Volume I
• Date: 2/1/1974
• Designation Date: 6/1/1974
• Floodplain - Doc Type: Floodplain Report/Masterplan

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flood plain zoning. This could take the form of an ordinance requiring

that no new buildings be constructed within a delineated lOO-year flood plain.

To make the ordinance more effective in preserving the natural environment,

an added requirement could be that no large trees be removed within the deline-

ated flood plain without written authorization from the city or county, and

that no fences or other man-made obstacles be constructed within the deline-

ated flood plain.

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Most flood plain ordinances require that no construction be permitted

within a delineated flood channel coinciding with the streambed itself

and that construction within the delineated flood plain outside the

flood channel is permitted provided certain requirements are met for

flood-proofing structures and retaining the currently available volume

of flood backwater storage. Such an ordinance can still serve to some

extent to preserve the natural condition of a streambed.

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In jurisdictions where relocating and straightening a stream channel are

permitted, destruction of the natural environment can be total. However,

a reasonably satisfactory new environment for a residential setting can

be created by laying stream banks back to stable slopes that are easily mowed

(4:1 or flatter) and re-establishing vegetation to prevent erosion. Straighten-

ing and shortening a streambed will have the effect of increasing its slope and

thereby increasing velocities of flow in the stream; and drop structures may be

required to prevent erosion. To provide protection where developers

are permitted to straighten and relocate streambed channels, the govern-

mental agency having jurisdiction should require that re-establishment of

suitable vegetation including an adequate sprinkling system (if the

vegetation requires it) be completed along with the water, sewer and

street systems, and prior to permitting sale of lots. To protect the

general public, some means of charging annual channel maintenance costs

to the developer also should be agreed on prior to permitting sale of lots.

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Detention Dams

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Improving existing Englewood Dam on Willow Creek in Arapahoe County and

addition of five other detention dams are proposed in this report. Four

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