Board Meeting 10/01/1987

• Board Meeting Date: 10/1/1987
• Description: CWCB Meeting
• Board Meetings - Doc Type: Meeting

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Rule 6.

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Standards for
Information:
information.
consideration
subject to
respectively.

Delineation of Approximate Floodplain
To qualify as approximate floodplain
the standards of this rule with
of the effects of dams and levees being
the criteria of rules 7 and 8.
must be met.

A. Topographic Base Mapping.

1. Work Map. The best available topographic
base map shall be used to develop approximate
floodplain information. Such work map shall.
at a minimum. be the most recent edition of a
7.5 minute quadrangle as published by the U.S.
Geological Survey (USGS).

B. Hydrologic Analysis

1. Frequency. The hydrologic analysis for the
preparation of approximate floodplain
information shall include. at a mlnlmum.
calculation of the lOO-year frequency flood
peak discharge.

2. Other Requirements. The hydrology for
approximate floodplain information shall. at a
minimum. meet the hydrology standards in rule
5.B.2 through 5.B.6. for detailed floOdplain
information.

C. Hydraulic Analysis

1.

Floodplain
area maps
floodplain

Boundaries. Approximate flooded
shall show. at a mlnlmum. the
boundary for the lOO-year flood.

2. MethodoloQY. Approximate flooded area maps
shall be based on the following simplified
methods. or any other method approved by the
Board. either individually or in combination.
as appropriate:

a. Assumed Depth Method. An assumed flood
depth above the channel may be used in
conjunction with the best available
topographic map. The assumed depth may be
determined from a regional regression
analysis of depth-frequency relations or
from the slope-area-conveyance calculation
at representative cross sections. Where

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