[Code of Federal Regulations]

[Title 40, Volume 24]

[Revised as of July 1, 2006]

From the U.S. Government Printing Office via GPO Access

[CITE: 40CFR230.45]



[Page 270]

 

                   TITLE 40--PROTECTION OF ENVIRONMENT

 

         CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)

 

PART 230_SECTION 404(b)(1) GUIDELINES FOR SPECIFICATION OF DISPOSAL SITES 

FOR DREDGED OR FILL MATERIAL--Table of Contents

 

          Subpart E_Potential Impacts on Special Aquatic Sites

 

Sec.  230.45  Riffle and pool complexes.



    (a) Steep gradient sections of streams are sometimes characterized 

by riffle and pool complexes. Such stream sections are recognizable by 

their hydraulic characteristics. The rapid movement of water over a 

coarse substrate in riffles results in a rough flow, a turbulent 

surface, and high dissolved oxygen levels in the water. Pools are deeper 

areas associated with riffles. Pools are characterized by a slower 

stream velocity, a steaming flow, a smooth surface, and a finer 

substrate. Riffle and pool complexes are particularly valuable habitat 

for fish and wildlife.

    (b) Possible loss of values: Discharge of dredged or fill material 

can eliminate riffle and pool areas by displacement, hydrologic 

modification, or sedimentation. Activities which affect riffle and pool 

areas and especially riffle/pool ratios, may reduce the aeration and 

filtration capabilities at the discharge site and downstream, may reduce 

stream habitat diversity, and may retard repopulation of the disposal 

site and downstream waters through sedimentation and the creation of 

unsuitable habitat. The discharge of dredged or fill material which 

alters stream hydrology may cause scouring or sedimentation of riffles 

and pools. Sedimentation induced through hydrological modification or as 

a direct result of the deposition of unconsolidated dredged or fill 

material may clog riffle and pool areas, destroy habitats, and create 

anaerobic conditions. Eliminating pools and meanders by the discharge of 

dredged or fill material can reduce water holding capacity of streams 

and cause rapid runoff from a watershed. Rapid runoff can deliver large 

quantities of flood water in a short time to downstream areas resulting 

in the destruction of natural habitat, high property loss, and the need 

for further hydraulic modification.



    Note: Possible actions to minimize adverse impacts on site or 

material characteristics can be found in subpart H.