310 CMR 10 app 10.00 Wildlife Habitat

• Library: Code of Massachusetts Regulations
• Edition: 2023
• Currency: Current through Register 1511, December 22, 2023
• Citation: 310 CMR 10 app 10.00
• Year: 2023

Note: The following are appendices to, but not part of,( 310 CMRWetlands Protection310 CMR 10.00 ).

PREFACE TO REVISIONS TO THE MASSACHUSETTS WETLANDS

REGULATIONS ( 310 CMRWetlands Protection310 CMR 10.00 )

RELATING TO THE DEFINITION OF "EXTENDED

DROUGHT" AND DISTINGUISHING "PERENNIAL RIVERS"

FROM "INTERMITTENT STREAMS", 2002 REGULATORY REVISIONS

Introduction

The Wetlands Protection Act (M.G.L. c. 131, § 40) was amended in 1996 to provide additional protection for rivers, defined in the Act as "any natural flowing body of water that empties to any ocean, lake, pond, or other river and which flows throughout the year." Since promulgating regulations in 1997, the Department of Environmental Protection (Department) has found that the original regulatory criteria do not clearly distinguish perennial rivers that flow throughout the year from intermittent streams that do not flow throughout the year. Many factors embodied in the original regulations, such as soil types or the presence or absence of macroinvertebrates, cannot practically be used to distinguish between perennial and intermittent streams. Other factors, such as stream gages, have limited usefulness due to their limited geographic extent. Still other factors, such as watershed size, are relevant but need to be modified based upon more recent research.

The Department has also found that the original definition of extended drought, which was based solely on precipitation data, does not accurately reflect the role of groundwater and stream flow during drought conditions. Extremely dry conditions existed in most of Massachusetts in the summer of 1999, leading to some of the lowest river and stream flows ever recorded. Even though many federal and state agencies declared droughts, the Wetlands Protection Act definition was not triggered in most communities because of brief but heavy summer rainstorms - rainstorms that fulfilled the regulatory precipitation numbers but did not provide sufficient recharge to restore groundwater or stream flow levels .

In order to address the issue of perennial rivers and drought, the Department formed a technical advisory committee with representatives from various interest groups, and with research and technical support provided by the United States Geologic Survey (USGS) and the Massachusetts Department of Environmental Management (DEM). The technical advisory committee spent more than two years searching for an approach that was based upon sound science and could also be implemented at the local level. This approach, based primarily on watershed size and surficial geology, is described below and is embodied in the new regulations.

It is also important to note that many intermittent streams still receive protection under the Wetlands Protection Act through applicable resource area performance standards for land under water, bank, land subject to flooding, and often, bordering vegetated wetlands. The distinction between perennial and intermittent flow pertains only to whether the stream has an associated riverfront area.

The Rulemaking Process

Drought conditions across the Commonwealth in late 2001 prompted the Department to adopt changes to the extended- drought provisions as an emergency regulation in December 2 0 0 1 . The Department then conducted four regional public hearings on the emergency-drought provisions as well as the perennial river versus intermittent stream changes. The Department received public comments through March 29, 2002. Thirty-eight parties commented on the proposed amendments. Of those, thirty-one commentators generally supported the proposed amendments or requested clarification of certain provisions. Six parties commented against the proposed amendments, and one party requested additional time to review and comment. Based upon a careful review and consideration of the comments, the Department has made some changes to the public hearing draft as described below.

Summary and Rationale of the New Regulations

A. Perennial Rivers and Intermittent Streams:

1. Watershed Size and Surficial Geology.

The Department and its technical advisory committee concluded field observations alone cannot be used to predict whether a small stream is likely to flow throughout the year. Given permitting time constraints, the Department also concluded that it would be unworkable to devise a system based entirely on stream flow observations made during the late summer or early fall, when water levels are often at their lowest. Aside from the practical difficulties with this approach, observations made during this period may not be definitive when the conditions are unusually wet or unusually dry compared to long-term records.

To explore other options, the Department contracted with the USGS to research watershed characteristics that might be useful in classifying streams, such as drainage area, mean basin slope, length of stream, urbanized land cover, and the percentage of sands and gravels in the watershed. This research revealed that the most important characteristics for predicting whether a river flows throughout the year are watershed size (drainage area) and surficial geology (the percentage of sands and gravel in the watershed). As a result of this research, as well as independent analysis and field-testing by the Department, the Department and its technical advisory committee agreed that watershed size and surficial (subsurface) geology could reliably be used to predict whether a stream will flow year-round. There is a strong correlation between watersheds greater than or equal to one square mile and streams that are predicted to flow 99% of the time. There is also a strong correlation between watersheds with a high percentage of stratified drift (sands and gravels) and streams that flow 99% of the time. These two factors, as well as a fail-safe field observation provision, have been incorporated into the new regulations.

USGS continues to refine its statistical methodology to better predict the probability of a stream flowing year-round. Once completed, the Department plans to use this information to produce stream maps that will eliminate reliance on the USGS topographic maps. Since this process will take several years, the regulatory changes described herein are necessary to address perennial versus intermittent determinations during the interim.

2. USGS Topographic Maps and STREAMSTATS.

The new regulations continue to rely upon an initial review of USGS topographic maps. Although these maps were not specifically developed to delineate perennial rivers from intermittent streams, the Department believes it is important to base initial reviews on maps that are widely available to Conservations Commissions and the regulated community. The regulations then provide for adjustments to stream status based upon watershed size, watershed geology, and field observations of no flow. Under the new regulations, streams that are shown as perennial on USGS topographic maps are classified as perennial. Streams that are shown as intermittent, or not shown at all, are classified based upon watershed size. If the watershed size is greater than or equal to one square mile, the stream is perennial. If the watershed size is less than one square mile, the stream is most likely intermittent.

Some intermittent streams with a watershed size of between one-half and one square mile may be shown to be perennial if the USGS STREAMSTATS model predicts a positive flow or if the watershed contains at least 75% stratified drift. STREAMSTATS is a new statistical tool developed by USGS that can be accessed through the USGS web site at http://ma.water.usgs.gov/streamstats/. This web site provides valuable stream flow information to applicants and regulators alike. STREAMSTATS incorporates watershed size and geology into its calculations, and can be used to analyze the probability that a stream flows on a year-round basis at a particular location. That probability is reported in terms of flow duration statistics. Flow duration statistics indicate the percentage of time stream flows are equaled or exceeded at a given stream location. For example, if a stream's flow at the 99% flow duration is five cubic feet per second, the stream's flow is predicted to be greater or equal to that discharge rate 99% of the time. Streams with a predicted flow rate greater than or equal to 0.01 cubic feet per second at the 99% flow duration rate are considered perennial. The 99th percentile is the best available statistical expression of the statutory language "flows throughout the year."

Some commentators requested that the Department require use of the STREAMSTATS tool exclusively, and abandon reliance on USGS topographic maps. While the Department may take this approach in the future, we are concerned about USGS's ability to handle the high demands this would place on its web site. In addition, STREAMSTATS cannot work if the stream's centerline has not been digitized. Thus, streams located in many southeastern communities (a list of watersheds is included in the regulations), as well as smaller, unmapped streams throughout the state, cannot be analyzed using STREAMSTATS. In those communities, watershed size and surficial geology must be analyzed using available maps.

Other commentators expressed concerns about using STREAMSTATS in small watersheds, particularly those below 1.61...