A Stream or a Ditch? What You Need to Know

By: Joe Roy, Project Technician & Rodney Kelshaw, Project Manager/Project Scientist, Stantec

When evaluating a site for purchase or development it is important to understand environmental resources that could affect allowable uses and property value. One factor that should be considered is the presence and location of streams.

Maine is home to over 5,000 named rivers and streams, crisscrossing the state and covering over 37,000 miles. In addition, the unnamed tributaries that feed into the larger streams and rivers are extremely valuable. In these small streams and brooks (terms that can be used interchangeably) are many insects, plants, amphibians, birds, and mammals that contribute to the overall health of the water that flows downstream to the larger streams. These small watercourses that meet the regulatory definition of a stream can be difficult to recognize.

The Maine Natural Resource Protection Act (NRPA) requires that the Maine Department of Environmental Protection (MDEP) regulate activities that may alter—or are adjacent to—rivers, streams and brooks. The MDEP staff recognized the complexity of identifying small streams and in 2018 released the “Natural Resource Protection Act (NRPA) Identification Guide for Rivers, Streams, and Brooks[i]. The intent of this document was “to be a guidance document for the identification of rivers, streams and brooks. The manual is also intended to assist developers and the regulated community in complying with existing state laws and regulations”.

The NRPA statutory definition of river, stream or brook is “a channel between defined banks. A channel is created by the action of surface water and has 2 or more of the following characteristics (emphasis added);

  1. A) it is depicted as a solid or broken blue line on the most recent edition of the U.S. Geological Survey 7.5 minute series topographic map,
  2. B) it contains or is known to contain flowing water continuously for a period of at leas 6 months of the year in most years,
  3. C) the channel bed is primarily composed of mineral material such as sand and gravel, parent material or bedrock that has been deposited or scoured by water,
  4. D) The channel contains aquatic animals such as fish, aquatic insects or mollusks in the water or, if no surface water is present, within the stream bed,
  5. E) The channel contains aquatic vegetation and is essentially devoid of upland vegetation

It also states that “river, stream, or brook does not mean a ditch or other drainage way constructed, or constructed and maintained, solely for the purpose of draining storm water or a grassy swale”.

A channel that is constructed to drain water is not always a ditch. To determine if a channel is a stream or a ditch the water source must be identified.

A channel is considered an altered stream segment if it connects to an upstream waterbody, such as a stream, spring, wetland, or pond. Stream segments that were relocated by human activities (e.g. diverted into a roadside ditch) remain regulated streams. A channel meeting two of the criteria above and originating from a culvert outlet is a regulated stream if the water source is a wetland, waterbody or spring on the inlet side. In contrast, a channel from a culvert outlet would not be a regulated stream if the only water source is stormwater.

When planning to develop property it is important to understand if there are on-site natural resources and how they could affect development. If there are questionable ditch/stream determinations at a site, the best course of action is to consult the MDEP stream identification guide and if the determination remains unclear to contact a professional who can perform a resource evaluation. The benefits are accurate investment valuation, compliance with the MDEP, and protection of our valuable natural resources.


[1] Danielson, T. J. 2018.  Natural Resource Protection Act (NRPA) Streams, Rivers, and Brooks.  Maine Department of Environmental Protection, Augusta, ME.

This entry was posted in Business, Member Articles, MEREDA Resources, People. Bookmark the permalink.