Glossary
§401/404 Permit
A permit issued jointly by the Army Corps of Engineers and the Tennessee Department of Environment and Conservation for any work or activity (e.g., road construction, ditching/filling) that can impact “waters ofthe U.S.” (including streams and wetlands); 401 and 404 refer to sections of the Clean Water Act intended to protect water quality and minimize the loss of wetlands in the U.S.
Aquatic Resources Alteration Permit (ARAP)
Permit required by Tennessee Department of Environment and Conservation (TDEC) for any alteration of state waters, including wetlands, that do not require a federal permit.
Bankfull
Corresponds to the discharge (typically 1.5 yr), at which channel maintenance is most effective, that is, the discharge at which moving sediment, forming or removing bars, forming or changing bends and meanders and generally doing work that results in the average morphic characteristics ofchannels.
Buffer
An area adjacent to a stream where development and certain activities are restricted, limited or prohibited. These areas are managed as stream-side zones where vegetation and soils act as filters for runoff pollutants and wildlife habitat corridors.
Channelization
The alteration of stream channels including but not limited to straightening, deepening, widening or enlarging.
Compensatory Mitigation
Action taken to compensate for stream impacts associated with 404/401 permitted projects or projects authorized under and Individual ARAP. Mitigation is required so that any authorized impact results in "no net loss" of the natural resource.
Conservation Easement
A voluntary agreement between a landowner and a conservation organization that limits a portion of the land's uses. Landowners still retain ownership of the land granted in the Conservation Easement.
Degradation
The alteration of the properties of waters by the addition of pollutants or the elimination of habitat.
Ecoregion
An area defined by a similarity of climate, landform, soil, potential natural vegetation, hydrology or other ecologically relevant variables.
Enhancement
The improvement to one or more of the structural or functional attributes of a stream.
Fluvial Geomorphology
The study of landforms associated with river or stream channels and the processes that form them.
Hydrologic Unit Code (HUC)
A method of identifying all of the drainage basins in the United States. Each drainage basin, or hydrologic unit, is identified by a unique hydrologic unit code (HUC) consisting of 2 to 14 digits. These codes describe the relation of the hydrologic units to each other to represent the way smaller watersheds drain areas that together form larger watersheds.
In-Stream Habitat
Natural structures or structures constructed using natural materials within stream channels that provide habitat for aquatic life.
Priority I Stream Restoration
A stream restoration approach where the primary objective is to establish a bankfull stage at the historical floodplain elevation. This is typically accomplished by excavating a new channel with the appropriate dimension, pattern and profile, based on reference reach data, to fit the watershed and valley type.
Priority II Stream Restoration
A stream restoration approach where the primary objective is to create a new floodplain and stream pattern with the stream bed remaining at the present elevation. This is typically accomplished by excavating a newfloodplain and stream channel at the elevation of the existing incised stream.
Priority III Stream Restoration
A stream restoration approach where the primary objective is to widen the floodplain at the existing bankfull elevation. This is typically accomplished by excavating a floodplain bench on one or both sides ofthe existing stream channel at the elevation of the existing bankfull stage.
Priority IV Stream Restoration
A stream restoration approach where the primary objective is to stabilize the existing stream banks in place. This type of restoraion does notattempt to correct problems with pattern, profile or dimension. Bioengineering techniques such as cross vanes, root wads or j-hooks may be used.
Reference Reach
A stream segment that represents a stable channel within a particular valley morphology. The reference reach is used to develop natural channel design criteria based upon measured morphological relations associated with the bankfull stage for a specific stable stream type.
Replacement
Removing a previously encapsulated stream and returning it to the surface in a natural, stable channel with a riparian zone.
Restoration
The process of returning a significantly degraded, disturbed, or totally altered stream, including adjacent riparian zone and flood-prone area, to a natural stable condition based on reference conditions. Restoration will typically include rebuilding the appropriate channel pattern, profile, dimensions, and riparian zone to the extent that watershed conditions will allow.
Riparian Zone
Vegetated area along streams and rivers that provides canopy, bank stabilization, pollution buffering, and wildlife habitat.
Sedimentation
Process whereby eroded soils are deposited in streams, rivers, lakes; accelerated by any activity that disturbs the land surface or removes vegetation (e.g., road construction, agriculture/forestry, urban development); sediment source areas include upland sites, intermediate slopes, riparian zones, and streambanks and channel scour areas.
Watershed
The land area that drains into a stream; the watershed for a major river may encompass a number of smaller watersheds that ultimately combine at a common point.