(A) Design standards.
(1) All open channels, whether private or public, and whether constructed on private or public land, shall conform to the design standards requirements of the County Surveyor.
(2) The required channel cross-section and grade are determined by the design capacity, the material in which the channel is to be constructed, and the requirements for maintenance. A minimum depth may be required to provide adequate outlets for subsurface drains, tributary ditches, or streams. The channel grade shall be such that the velocity in the channel is high enough to prevent siltation but low enough to prevent erosion. Velocities less than one and one-half feet per second should be avoided since siltation will take place and ultimately reduce the channel cross-section. The maximum permissible velocities in vegetal-lined channels are shown in Table 1. Developments through which the channel is to be constructed shall be considered in the design of the channel section.
(3) Earthen channel side slopes shall be no steeper than two horizontal to one vertical. Flatter slopes may be required to prevent erosion and for ease of maintenance. Where channels will be lined, side slopes shall be no steeper than one and one-half horizontal to one vertical with adequate provisions made for weep holes. Side slopes steeper than one and one-half horizontal to one vertical may be used for lined channels, provided that the sidelining is designed and constructed as a structural retaining wall with provisions for live and dead load surcharge.
Table 1 | |||
Maximum Permissible Velocities in Vegetal-Lined Channels* | |||
Cover | Side Slope Range*** (Percent) | Permissible Velocity** | Permissible Velocity** |
Erosion Resistant Soils (ft. per sec.)**** | Easily Eroded Soils (ft. per sec.)**** | ||
Table 1 | |||
Maximum Permissible Velocities in Vegetal-Lined Channels* | |||
Cover | Side Slope Range*** (Percent) | Permissible Velocity** | Permissible Velocity** |
Erosion Resistant Soils (ft. per sec.)**** | Easily Eroded Soils (ft. per sec.)**** | ||
Alfalfa | 5-10 | 3.4 | 2.5 |
Bahia Buffalo Grass | 0-5 | 7 | 5 |
Bermuda Grass | 0-5 | 8 | 6 |
5-10 | 7 | 5 | |
Over 10 | 6 | 4 | |
Canary Grass | 5-10 | 4 | 3 |
Common Lespedeza***** | ******0-5 | 3.5 | 2.5 |
Grass Mixture Reed | ***0-5 | 5 | 4 |
Kentucky Bluegrass | 5-10 | 6 | 4 |
Lespedeza Sericea | 5-10 | 3.4 | 2.5 |
Red Fescue | 5-10 | 3.4 | 2.5 |
Redtop | 5-10 | 3.4 | 2.5 |
Smooth Brome Blue Grama | Over 10 | 5 | 3 |
Sudangrass***** | ******0-5 | 3.5 | 2.5 |
Weeping Lovegrass | ****0-5 | 3.4 | 2.5 |
Yellow Bluestem | 5-10 | 3.4 | 2.5 |
Notes to table: * From Soil Conservation Service, SCS-TP-61, “Handbook of Channel Design for Soil and Water Conservation.” ** Use velocities exceeding five feet per second only where good channel ground covers and proper maintenance can be obtained. *** Do not use on slopes steeper than 10% except for vegetated side slopes in combination with a stone, concrete, or highly resistant vegetative center section. **** Do not use on slopes steeper than 5% except for vegetated side slopes in combination with a stone, concrete, or highly resistant vegetative center section. ***** Annuals- use on mild slopes or as temporary protection until permanent covers are established. ****** Use on slopes steeper than 5% is not recommended. | |||
(4) (a) Characteristics of a stable channel are as follows.
1. It neither promotes sedimentation or degrades the channel bottom and sides beyond tolerable limits.
2. The channel banks do not erode to the extent that the channel cross-section is changed appreciably.
3. Excessive sediment bars do not develop.
4. Excessive erosion dos not occur around culverts, bridges, outfalls, or elsewhere.
5. Gullies do not form or enlarge due to the entry of uncontrolled flow to the channel.
(b) Channel stability shall be determined for an aged condition and the velocity shall be based on the design flow or the bank full flow, whichever is greater. In no case shall it be necessary to check channel stability for discharges greater than that from a 100-year frequency storm.
(5) Vegetated waterways that are subject to low flows of long duration or where wet conditions prevail shall be drained with a tile system or by other means such as paved gutters. Tile lines may be outletted through a drop structure at the ends of the waterway or through a standard tile outlet.
(6) When the Drainage Board determines it is necessary to establish a new regulated drain, each developer shall provide the necessary information and meet the requirements of the 1965 Indiana Drainage Code, being I.C. 36-9-27, as amended, for the establishment of a new regulated drain. The Drainage Board shall determine necessary easements for adequate maintenance of any new regulated drain.
(7) (a) The design of channels will include provisions for operation and maintenance and the proper functioning of all channels, laterals, travelways, and structures associated with the project. Recessed inlets and structures needed for entry of surface and subsurface flow into channels without significant erosion or degradation shall be included in the design of channel improvements. The design will also provide for necessary flood gates, water level control devices, and any other appurtenance structure affecting the functioning of the channels and the attainment of the purpose for which they are built.
(b) The effects of channel improvements on existing culverts, bridges, buried cables, pipelines, and inlet structures for surface and subsurface drainage on the channel being improved and laterals thereto shall be evaluated to determine the need for modification or replacement. Culverts and bridges which are modified or added as part of channel improvement projects shall meet reasonable standards for the type of structure and shall have a minimum capacity equal to the design discharge or governmental agency design requirements, whichever is greater.
(8) Spoil material resulting from clearing, grubbing, and channel excavation shall be disposed of in such a manner which will:
(a) Minimize overbank wash;
(b) Provide for the free flow of water between the channel and floodplain boundary unless the valley routing and water surface profiles are based on continuous dikes being installed;
(c) Not hinder the development of travelways for maintenance;
(d) Leave the right-of-way in the best condition feasible, consistent with the project purposes, for productive use by the owner;
(e) Improve the aesthetic appearance of the site to the extent feasible; and
(f) Be approved by the IDNR or U.S. Army Corps of Engineers (whichever is applicable), if deposited in the floodway.
(B) Construction and materials.
(1) Specifications shall be in keeping with the proceeding standards and shall describe the requirements for proper installation of the project to achieve its intended purpose.
(2) (a) Materials acceptable for use as channel lining are:
1. Grass;
2. Revetment riprap;
3. Concrete;
4. Hand laid riprap;
5. Precast cement concrete riprap;
6. Grouted riprap;
7. Gabions; and
8. Mattins.
(b) Other lining materials shall receive specific approval of the County Surveyor. Materials shall comply with the latest edition of the State Department of Transportation “Standard Specifications.”
(Ord. 1997-16, passed 12-8-1997; Ord. 2005-01, passed 2-17-2005) Penalty, see § 153.999