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Hydromodification Chapter Factsheet
What Is the Coastal Nonpoint Pollution Program?
Section 6217 of the Coastal Zone Act Reauthorization Amendments of
1990 (CZARA) requires coastal states (including Great Lakes states)
with approved coastal zone management programs to address nonpoint
pollution impacting or threatening coastal waters. States must
submit Coastal Nonpoint Pollution Control Programs for approval to
both the U.S. Environmental Protection Agency (EPA) and the National
Oceanic and Atmospheric Administration (NOAA). Requirements for
state programs are described in a document entitled "Coastal
Nonpoint Pollution Control Program: Program Development and Approval
Guidance" and are summarized in a separate fact sheet.
What are Management Measures?
CZARA requires EPA, in consultation with NOAA and other federal
agencies, to publish guidance specifying "management measures" to
restore and protect coastal waters from specific categories of
nonpoint source pollution. EPA has done so in a document entitled
"Guidance Specifying Management Measures for Sources of Nonpoint
Pollution in Coastal Waters." State Coastal Nonpoint Pollution
Control Programs must provide for implementation of these measures
or alternative management measures in conformity with these measures
in the coastal management area generally. "Management Measures" are
defined by law to be economically achievable measures that reflect
the best available technology for reducing pollutants. States may
select from a wide range of practices or combinations of practices
that will achieve the level of conrol specified in the management
measure. This fact sheet summarizes the management measures
applicable to hydromodification. Other fact sheets summarize the
measures for agriculture, forestry, urban areas, marinas and
recreational boating, and wetlands/riparian areas.
What Are the Nonpoint Source-Related Problems Associated with
Hydromodification?
Hydromodification activities have been separated into the categories
of channelization and channel modification, dams, and streambank and
shoreline erosion.
A frequent result of channelization and channel modification
activities is a diminished suitability of instream and streamside
habitat for fish and wildlife. They can also alter instream patterns
of water temperature and sediment type, as well as the rates and
paths of sediment erosion, transport, and deposition. Hardening of
banks along waterways has increased the movement of NPS pollutants
from the upper reaches of watersheds into coastal waters.
Dams can adversely impact the hydraulic regime, the quality of the
surface waters, and habitat in the stream or river where they are
located. A variety of impacts can result from the siting,
construction, and operation of these facilities.
The erosion of shorelines and streambanks is a natural process that
can have either beneficial or adverse impacts on the creation and
maintenance of riparian habitat. Excessively high sediment loads can
smother submerged aquatic vegetation, cover shellfish beds and tidal
flats, fill in riffle pools, and contribute to increased levels of
turbidity and nutrients.
MANAGEMENT MEASURES SUMMARY
Management Measures for Channelization and Channel Modification
PHYSICAL AND CHEMICAL CHARACTERISTICS OF SURFACE WATERS -- This
measure ensures that the planning process for new channelization
projects includes an evaluation of the potential effects on the
physical and chemical characteristics of surface waters that may
occur as a result of the proposed work. The measure encourages
planning and design of new projects to reduce undesirable impacts.
The operation and maintenance programs for existing modified
channels should identify and implement any available opportunities
to improve the physical and chemical characteristics of surface
waters in those channels.
INSTREAM AND RIPARIAN HABITAT RESTORATION FOR CHANNELIZATION AND
CHANNEL MODIFICATION -- This measure ensures that the planning
process for new channelization projects includes an evaluation of
the potential effects on instream and riparian habitat that may
occur as a result of the proposed work. The measure encourages
planning and design of new projects to reduce undesirable impacts.
The operation and maintenance programs for existing modified
channels should identify opportunities to restore instream and
riparian habitat in those channels. The habitat characteristics
that may be influenced by channelization and channel modification
include: elimination of stream bank vegetation, reduced freshwaer
availability, and accelerated delivery of pollutants.
Management Measures for Dams
These management measures apply to dams 25 feet or more in height
and greater than 15 acre-feet in capacity, or to dams six feet or
more in height and greater that 50 acre-feet in capacity. The
measures also apply only to those projects and activities that fall
outside of existing jurisdiction of the National Pollutant Discharge
Elimination System permit program.
EROSION AND SEDIMENT CONTROL -- This measure provides for reducing
erosion and retaining sediment onsite, to the extent practicable,
during and after construction of dams. An approved erosion and
sediment control plan, or similar administrative document that
contains erosion and sediment control provisions, should be prepared
and implemented prior to land disturbance.
CHEMICAL AND POLLUTANT CONTROL -- This measure ensures the proper
storage and disposal of certain chemicals, substances, and other
materials that are used in construction or maintenance activities at
dams. These include construction chemicals such as concrete
additives, petrochemicals, solid wastes, cement washout, pesticides
and fertilizers. The measure limits the application, generation,
and migration of toxic substances, and ensures their proper storage
and disposal. The measure also ensures that nutrients are applied
at rates necessary to establish and maintain vegetation without
causing significant nutrient runoff to surface waters.
PROTECTION OF SURFACE WATER QUALITY AND INSTREAM AND RIPARIAN
HABITAT -- This measure ensures that the operation of dams will be
assessed for impacts to surface water quality and instream and
riparian habitat, and that the potential for improvement will be
evaluated. Significant nonpoint source pollution problems that
exist from excessive surface water withdrawals will also be assessed
and evaluated.
Management Measure for Streambank and Shoreline Erosion
STREAMBANK AND SHORELINE EROSION -- Eroding streambanks and
shorelines should be stabilized, where streambank and shoreline
erosion is a nonpoint source problem. Vegetative methods such as
marsh creation and vegetative bank stabilization ("bioengineering")
are the preferred methods. The measure also ensures that streambank
and shoreline features such as wetlands and riparian areas with the
potential to reduce NPS pollution are protected. Streambanks and
shorelines should also be protected from erosion due to uses of
either the shorelands or adjacent surface waters.
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