Form 81-89E Alluvial Fan Flooding Form

DEPARTMENT OF HOMELAND SECURITY
FEDERAL EMERGENCY MANAGEMENT AGENCY

O.M.B. NO. 1660-0016
Expires August 31, 2007

ALLUVIAL FAN FLOODING FORM

PAPERWORK BURDEN DISCLOSURE NOTICE
Public reporting burden for this form is estimated to average 1 hour per response. The burden estimate includes the time for reviewing
instructions, searching existing data sources, gathering and maintaining the needed data, and completing, reviewing, and submitting the form. You
are not required to respond to this collection of information unless a vaild OMB control number appears in the upper right corner of this form.
Send comments regarding the accuracy of the burden estimate and any suggestions for reducing this burden to: Information Collections
Management, Department of Homeland Security, Federal Emergency Management Agency, 500 C Street, SW, Washington, DC, 20472,
Paperwork Reduction Project (1660-0016). Submission of the form is required to obtain or retain benefits under the National Flood Insurance
Program. Please do not send your completed survey to the above address.
Flooding Source:
Note: Fill out one form for each flooding source studied.
A. THREE-STAGE ANALYSIS (Based on FEMA Guidelines dated February 23, 2000)

1. Stage 1 Analysis
a. The landform is composed of (check one)

alluvial

debris flow deposits

b. Source of data used to determine composition, morphology, and location of the landform:

Yes

c. Is there an NRCS soils survey and soil survey map available?

No

If Yes, please include a copy of the map and any pertinent sections of the soil survey
2. Stage 2 Analysis
a. The alluvial fan exhibits

active

inactive

a combination of active and inactive alluvial fan flooding

b. Approximate age of inactive fan surfaces (thousands of years):

yrs

c. Is there an opportunity for avulsions that could lead channels or sheetfloods across th older fan surfaces?
d. Is there evidence of headcutting that could lead to stream piracy?

Yes

No

e. Is ther geomorphic evidence of past avulsions during the Holocene epoch?

Yes

No

Yes

No

f. The fan exhibits the following types of flooding (check one):
Flooding along stable channels
Sheetflow
Debris flow
Unstable flow path flooding

3. Stage 3 Analysis
The boundaries of the 1%-annual-chance floodplain have been determined using (check one):
Risk-Based Analysis
FEMA Fan Program (if discharge at the apex is different than that given in the effective FIS, then attach MT-2, Form 2 along with a plot of the flood
frequency curve on long-normal probability paper and include the drainage area above the hydrographic apex, and the mean, standard deviation, and
skew coefficient of the curve)
Sheetflow Methods
Hydraulic Analytical Methods
Geomorphic Data, Post-Flood hazard Verification, and Historical Information
Composite Methods

FEMA Form 81-89E, JAN 07

MT-2 Form 6 Page 1 of 2

B. STRUCTURAL FLOOD CONTROL MEASURES

1. The following structural flood control measures are proposed or built (check one):
channelization

Levee/Floodwall

Yes

Sedimentation

2. Do the constructed or proposed structural measures affect flood hazards (including velocity, scour, and sediment deposition), on other areas of
the fan?
Yes
No
3. Attach completed Form 3 (Riverine Structures Form)
4. Sediment Transport Considerations:
Was sediment transport considered?

Dam

No

If Yes, then fill out Form 3, Section F (Sediment Transport). If No, then attach your explanation for why sediment transport was not
considered.
5. Please attach a copy of the formal Operations and Maintenance Plan.
C. MAPPING REQUIREMENTS

Attach a certified topographic work map showing the following:
- The boundaries of the alluvial fan including: toe, topographic and hydrologic apexes, and lateral boundaries
- The delineation of the active and inactive portions of the fan as determined by the Stage 2 Analysis
- The revised 1%-annual-chance floodplain boundaries, as determined by the Stage 3 Analysis, that tie into the effective floodplain
boundaries
- The correct alignment of all structural features
- The map scale

FEMA Form 81-89E, JAN 07

MT-2 Form 6 Page 2of 2