RICHLAND COUNTY
DEPARTMENT OF BUILDING REGULATIONS
1495 WEST LONGVIEW AVENUE
MANSFIELD, OHIO 44906
•
SUITE 202A
Phone • (419) 774-5517
Fax • (419) 774-6317
www.richlandcountyoh.us/c&p.htm
Richland County Courthouse
Requirements for Channel Modifications in Unnumbered A Zones
The attached forms are provided to help clarify the data requirements for engineering studies within FEMA Unnumbered
(Approximate) A Zones. The forms address engineering requirements necessary to evaluate the impact of proposed
developments on flooding. This form is to be used for structural and non-structural activities that modify channels located
with Special Flood hazard Areas (SFHA’s) as defined by the Richland County Special Purpose Flood Damage Prevention
Resolution (Regulations) as adopted May 28, 1987.
Building standards for protection of structures from flood damage are not addressed by the forms.
Reference material:
The USDA Forest Service publication referenced in the forms and the presentation (General Technical Report RM-245,
Stream Channel Reference Sites: An Illustrated Guide to Field Technique) can be downloaded via the Internet at the
following address: http://www.stream.fs.fed.us/publications/PDFs/RM245E.PDF
Note: Fill out one form for each flooding source studied
Community Name:
Flooding Source:
Project Name/Identifier:
1. REACH STUDIED
Describe the limits of the reach being studied or submit a workmap with the study area clearly highlighted. If the reach
has been identified by FEMA as a Special Flood Hazard Area, a highlighted FIRM or FHBM should be attached depicting
the area of study.
Copy of highlighted FIRM or FHBM attached?
Yes
No
Downstream limit:
Upstream limit:
Page 1 of 3
Riverine Hydraulic Analysis Form
(Models required - FEMA Zone A - no BFE provided) updated 08/05/2010
2. MODELS REQUIRED - FEMA ZONE A – NO BFE PROVIDED
Purpose of study:
Determine Base Flood Elevation data for “Subdivisions and Large Developments” (as defined by Regulations Section
5.2-6)
Indicate models submitted below and complete Section 3. Full input and output listings along with files on
diskette for items A, B, and C listed below and a summary of the source of input parameters used in the models
must be provided. The summary must include a description of any changes made from the Existing or PreProject Conditions model to the Revised or Post-Project Conditions model. Delineation of a floodway is
recommended, but may not be required.
Models Required:
A. Existing or Pre-Project Conditions Model
Natural
Floodway
(File name)
(File name)
The Existing or Pre-Project Conditions model represents existing conditions at the time the flood study was
conducted.
B. Revised or Post-Project Conditions Model
Natural
Floodway
(File name)
(File name)
The Existing or Pre-Project Conditions model is revised to reflect revised or post-project conditions. This model
must incorporate any physical changes to the floodplain resulting from the project. When the request for approval
is for the proposed project this model must reflect proposed conditions.
C. Other
Please attach a sheet describing all other models submitted along with the file names.
Natural
Floodway
Perform an impact analysis for alteration of a watercourse
Computer model not required. Complete Section 3.
Other
Please contact Richland County for information on data requirements for flood studies completed for purposes
other than those listed above.
3. ALTERATION OF WATERCOURSE
3.1. Field Determination of Watercourse Geometry:
The horizontal extent of the watercourse must be determined by field observation. It is recommended that bankfull
stage, as described in the USDA Forest Service General Technical Report RM-245, Stream Channel Reference Sites:
An Illustrated Guide to Field Technique, be used to define the watercourse. Provide a site plan clearly indicating the
location of cross-sections where the watercourse geometry has been determined.
Provide a plot of all cross-sections used to determine the bankfull watercourse. Any of the following bankfull
indicators that are present, as described in the above referenced report, should be clearly labeled on the crosssection:
1) Top of Pointbars
2) Change in Vegetation
3) Change in Slope
4) Change in Bank Materials
5) Bank Undercuts
6) Stain Lines
Page 2 of 3
Riverine Hydraulic Analysis Form
(Models required - FEMA Zone A - no BFE provided) updated 08/05/2010
The following information should be determined at multiple cross-sections to ensure proper evaluation of the channel
bankfull geometry:
1. Bankfull width
2. Bankfull depth/stage
3. Water surface elevation at bankfull stage
Note: Provide a summary table for the information listed above. If bankfull indicators disagree, please attach an
explanation for how bankfull determination was made.
3.2. Flood Carrying Capacity:
3.2.1. Does the proposed work encroach upon the bankfull watercourse determined above?
No
Yes
If “No”, the proposed work will not diminish the flood carrying capacity of the watercourse.
If “Yes”, an engineering analysis must be performed that determines the following information for each crosssection:
Existing conditions
Bankfull water surface elevation (as determined above)
Bankfull discharge capacity
Proposed conditions
Using the existing conditions bankfull discharge capacity, compute the water surface elevation for the
proposed channel configuration.
Note: Provide a summary table and supporting calculations for the information listed above.
3.2.2. Does the proposed channel configuration convey the bankfull discharge without increasing the water
surface elevation?
Yes
No
If “Yes”, the proposed work will not diminish the flood carrying capacity of the watercourse.
If “No”, the proposed work will diminish the flood carrying capacity of the watercourse.
3.3. Maintenance of Watercourse:
3.3.1. Does the proposed channel design incorporate concepts/elements intended to prevent increased erosion
or sedimentation?
Yes
No
If “Yes”, please attach plans and an explanation describing how the design elements work to prevent increased
erosion or sedimentation.
If “No”, has a maintenance agreement been signed between the permit requestor and an authoritative
government entity, so that the flood carrying capacity of the altered or relocated watercourse will not be
diminished?
Note: It is recommended that a maintenance agreement between the permit requestor and the appropriate
government entity be required that indicates the specific maintenance responsibilities of the requestor.
Page 3 of 3
Riverine Hydraulic Analysis Form
(Models required - FEMA Zone A - no BFE provided) updated 08/05/2010