250 R.I. Code R. 250-RICR-150-15-3.21

Current through November 7, 2024

Section 250-RICR-150-15-3.21 - Specific Criteria for Identifying Freshwater Wetlands and Floodplain Edges

3.21.1Vegetated Freshwater Wetlands

A. The landward edge of vegetated freshwater wetlands (i.e., bogs; marshes; swamps; emergent wetlands; or similar types, including complexes of these types), shall, under normal conditions, be identified as the place where the plant community associated with the vegetated wetland is no longer dominated by hydrophytes/hydrophytic vegetation (i.e., the plant community is composed of less than or equal to fifty percent (50%) hydrophytes/hydrophytic vegetation).

B. Hydrophytes/hydrophytic vegetation includes, but is not limited to:

1. Those typical plant species listed in the Act under R.I. Gen. Laws §§ 2-1-20(3)"bog", (10) "marsh" and (16) "swamp"; or

2. Those plant species listed as having a wetland indicator status of Obligate (OBL) according to the most recent edition of the National Wetland Plant List: State of Rhode Island Wetland Plant List, as prepared by the U.S. Army Corps of Engineers incorporated above at § 3.3(C) of this Part; or

3. Those plant species listed as having a wetland indicator status of Facultative Wetland (FACW), Facultative (FAC) or Facultative Upland (FACU) according to the National Wetland Plant List: State of Rhode Island incorporated above at § 3.3(C) of this Part, where such plants are present along with other clear hydrologic indicators of wetland.

C. Where no distinct edge is apparent based upon examination of vegetation alone (e.g., the plant community is transitional in nature and dominated by species having an indicator status of FACW, FAC or FACU), other hydrologic indicators must be considered before determining the location of the landward edge of vegetated freshwater wetlands. Where such indicators are present, the FACW, FAC, or FACU plant species are considered hydrophytes/hydrophytic vegetation; however, the landward edge of vegetated wetland in such transitional areas is located where other hydrologic indicators are no longer present.

D. Other hydrologic indicators are those characteristics, other than vegetation, which provide evidence that an area is continuously or periodically saturated, inundated, flooded, or ponded; has standing or slowly moving water; or frequently collects surface run-off or drainage. Examples of other hydrologic indicators include, but are not limited to, the following: (Those features in §§ 3.20.1(D)(3), (5), and (7) through (9) of this Part are valid indicators only when at least one (1) additional hydrologic indicator is present.)

1. Morphologic features or properties associated with hydric soils in accordance with the most recent version of the Field Indicators for Identifying Hydric Soils in New England;

2. Visual observation of soil saturation within twelve inches (12") of the soil surface (considering both seasonal and recent weather conditions);

3. Distinct water marks on vegetation or other fixed objects;

4. Sulfitic materials (H2S - rotten egg odor) within twelve inches (12") of the soil surface;

5. Mound and pool microtopography;

6. Patches of peat mosses (Sphagnum spp.);

7. Soil morphologic evidence of recent or periodic flooding (e.g., stratification associated with flood plains);

8. Visual observation of surface inundation (considering both seasonal and recent weather conditions);

9. Dark or water-stained leaves on the ground surface;

10. Drift or wrack lines of water-borne materials;

11. Wetland drainage features or patterns such as scoured channels;

12. Morphological plant adaptations (e.g., buttressed trees trunks, adventitious roots, exposed or shallow root systems);

13. Distinct or prominent pore linings (oxidized rhizopheres) along live roots within twelve inches (12") of the soil surface.

E. For purposes of locating and identifying the edge of vegetated freshwater wetlands for applications submitted to the Department, the Department will accept the methodology described and incorporated within the Corps of Engineers Wetlands Delineation Manual, Technical Report Y- 87-1, January, 1987, Prepared for: Department of The Army, U.S. Army Corps of Engineers and Regional Supplement to the Corps of Engineers Wetlands Delineation Manual Northcentral and Northeast Region, 2012, prepared by the U.S. Army Corps of Engineers, Technical Report 12-0 ERDC/EL under the following conditions:

1. The use of this methodology is intended to facilitate the location and identification of the edge of "vegetated" wetlands, but must not be interpreted as redefining freshwater wetlands regulated under the Act and these Rules.

2. All edge locations and delineations are subject to the Department's review and acceptance under the procedures set forth in § 3.9.2 of this Part for Requests to Determine the Presence of Jurisdictional Area. Accordingly, all requests to verify the edge of these types of wetlands will require onsite inspection and analysis.

3. Areas discovered during the delineation of freshwater wetlands which appear to have altered conditions (e.g., removal of vegetation, ditching, draining, filling or other alterations that have changed or appear to change normal conditions) must be documented.

3.21.2Flowing and Standing Water Freshwater Wetlands

A. The edge of rivers, streams, intermittent streams, ponds, vernal pools, areas subject to storm flowage, areas subject to flooding and other areas dominated by open or flowing water shall be identified as follows:

1. The edge of rivers, streams, intermittent streams, ponds, vernal pools, areas subject to storm flowage, areas subject to flooding and other areas dominated by open or flowing water shall be the ordinary high water mark of standing or flowing water. The ordinary high water mark is the line separating land flooded at high water and land exposed at high water. This line may be determined and documented by using recorded hydrologic data (e.g., data obtained from site specific planning and design documents; in-stream flow studies; stream gauge data; the Department's file data; or flood data), or, in the absence of these, by observing physical characteristics, such as evidence of a clear demarcation line between terrestrial and aquatic conditions as a result of standing or flowing water; shelving; permanent watermarks and stains on woody vegetation or other fixed objects, such as bridges, stones, walls, docks, or piers; changes in the character of the soil; the presence of water-borne natural litter and debris; evidence of surface scouring; or other appropriate means.

2. The edge of any pond and incoming or outgoing flowing body of water shall be that location where characteristics associated with a lentic ecosystem and a lotic ecosystem are both present.

3.21.3Floodplain

A. The edge of any floodplain shall be identified as the maximum horizontal extent of flood water which will result from the statistical one hundred (100) year frequency storm event.

B. The one hundred (100) year floodplain elevation shall be determined by the most recently available flood profile data prepared under the National Flood Insurance Program of the Federal Emergency Management Agency (FEMA); or

C. In instances where FEMA has not established the elevation of the one hundred (100) year floodplain, the floodplain elevation and floodplain edge shall be determined through calculations completed by a Registered Professional Engineer. These calculations shall be based upon the following:

1. Calculation of one hundred (100) year flood discharge based on a one hundred (100) year rainfall event identified in the Stormwater Management, Design and Installation Rules, Subchapter 10 Part 8 of this Chapter, and a generally accepted hydrologic model including, but not limited to, TR-20, TR-55 or commercially available software based on TR-20 or TR-55. In certain cases involving very large watersheds an acceptable regression equation methodology may be used, such as a U.S.G.S regression for Rhode Island.

2. Using the flood discharge established as described in § 3.21.1(C)(1) of this Part along with detailed topography mapping, prepare a determination of peak one hundred (100) year flood elevation using a widely accepted hydraulic model such as the U.S. Army Corps of Engineers' Hydrologic Engineering Center River Analysis System (HEC-RAS). Once this elevation is established the edge of the one hundred (100) year floodplain must be plotted on a detailed site topography map.

D. The flood plain edge must coincide with the flood plain elevation and topographic contour elevations as depicted on submitted plans. Transposing flood boundaries from FEMA maps by using horizontal scaling is not acceptable for plans submitted to the Department. Identification of the one hundred (100) year flood elevation must be expressed as North American Vertical Datum 1988 (NAVD88).

3.21.4Floodway

A. The edge of floodway for all rivers and streams will be depicted and recognized as follows:

1. Where FEMA has designated a floodway for any river or stream on a FEMA Flood Insurance Rate Map (FIRM), the Department will recognize the same floodway; or

2. Where no FEMA floodway has been established for a river or stream, the edge of the channel as identified in § 3.21.2(A) of this Part shall also be considered the edge of the floodway.

3.21.5Criteria for Identification of Freshwater Wetlands for Farmers Conducting Normal Farming and Ranching Activities

A. For the purpose of R.I. Gen. Laws § 2-1-22(k), identification of the edges of vegetated freshwater wetlands, flowing and standing water freshwater wetlands, and floodplains shall be consistent with the criteria specified in §§ 3.21.1, 3.21.2, and 3.21.3 of this Part.

B. The "area of land within fifty feet (50')" shall be identified as the line measured landward horizontally, without regard for topography, fifty feet (50') from the edge of any bog; marsh one (1) acre or greater; swamp three (3) acres or greater; or pond not less than one quarter (1/4) acre in size as those freshwater wetlands are defined herein.

C. The area of land within two hundred feet (200') of a flowing body of water greater than or equal to ten feet (10') wide and the area of land within one hundred feet (100') of a flowing body of water less than ten feet (10') wide shall be referred to as riverbank. The edge of riverbanks along a river, stream, intermittent stream, or flowing body of water shall be determined by the method described herein:

1. The Department may compile designated riverbank widths (one hundred feet (100') or two hundred feet (200')) for flowing water body segments and maintain this information on file. Such designations shall be based upon currently available maps, aerial photographs, observations, and past determinations by the Department. All applicants may consult with the Department regarding the availability of designated riverbank widths along any flowing bodies of water segments in the project area. If a riverbank width has been determined by the Department, this designation can be used to preclude the need for the applicant to undertake field measurements or observations.

2. When designated riverbank widths are not available, the identification and assignment of a riverbank width shall, if the width is not obvious, be conducted using the following method, without regard to topography:

a. The width of the flowing body of water shall be measured along the channel's length at a minimum of five (5) locations upstream and at a minimum of five (5) locations downstream from a measured midpoint within the project area or area of concern.

b. The measurements shall be taken at the midpoint, and at approximately equal intervals along the channel's length with the minimum distance between intervals not less than twenty feet (20') and the maximum distance between intervals not exceeding fifty feet (50').

c. The midpoint of the measurements shall be near the midpoint of the project area or area of concern.

d. The measurements shall be taken between the edges of the flowing body of water or channel as delineated according to § 3.21.2(A)(1) of this Part.

e. All measurements shall be taken at locations that are representative of the water body segment, must be documented as to the locations, and must be able to be reproduced. Measurements taken at any human-induced restrictions which are less than the natural conditions or within sections of the flowing body of water subject to unauthorized alterations are not applicable or acceptable.

3. The arithmetic average or mean of the channel width measurements shall serve as the average channel width for the purposes of assigning riverbank. The mean shall be calculated using the formula:

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4. When the mean channel width is less than ten feet (10'), the riverbank shall be one hundred feet (100'). When the mean channel width is ten feet (10') or more, the riverbank shall be two hundred feet (200').

250 R.I. Code R. 250-RICR-150-15-3.21

Adopted effective 1/13/2022
Amended effective 7/15/2022