Stormwater Management Manual

VIII. STREAMS AND CHANNELS

Open channels may have significant advantages in cost, capacity, multiple use, and potential for reducing flood peaks. This chapter provides standards and criteria for the incorporation of open channels in a drainage system, including both natural & artificial channels.

A. Definitions

This chapter identifies three kinds of open channels: natural, grassed channels, and lined channels. Overlap among these categories exists, and criteria from more than one category may apply to a given channel.

1. Natural channels are characterized by irregular section, alignment, vegetative cover and bottom and side materials. Velocities are usually low in the natural channel, resulting in long concentration times and lower downstream peak flows. Natural channels often have an overbank storage capacity which also tends to decrease peak flows.

Maintenance needs are low if the channel is stable. The natural channel often provides opportunities for multiple uses, including fish and wildlife habitat and recreation and has the best aesthetic qualities of the alternatives.

2. Grassed channels are characterized by a more uniform section and a vegetative cover of grass. They are typically used where velocities are low and erosion may therefore be prevented with a cover of grass. Grassed channels may be natural or, more often, artificial. The advantages of a grassed channel include lower cost and positive aesthetic qualities.

3. Lined channels must be used when there are high velocities due to a reduced section or steep slopes: they may be used with subcritical or supercritical flow. Linings include concrete, stone and other permanent material.

4. Bankfull flow is the flow in a channel that creates a water surface at or near the normal ground elevation, or the tops of dikes or continuous spoil banks that confine the flow for a significant length of a channel reach.

B. Policies

1. Natural Channels Preferred Open channel planning and design objectives are often best met by using natural, or natural-type channels. Therefore, as is stated as a policy in Chapter 2, natural channels shall be used for storm runoff whenever possible. Use of natural channels will be consistent with the floodplains and open space requirements of the area and preserve as much as possible the value of the channel for fish and wildlife habitat, recreation and aesthetics.

2. Channelization Channelization of natural waterways will be avoided: channelizing usually speeds up the flow, causing greater peaks and higher drainage costs downstream.

3. 100-year Capacity Open channels should be capable of carrying the 100-year runoff (a one percent chance of occurring in any single year).

4. Alignment Open channels should follow the natural drainage paths as much as possible.

5. Channels Artificial earth channels, that is, either constructed channels or heavily modified natural channels, shall not be used for drainage because of the potential erosion and damage to those downstream.

6. Compliance With FEMA Standards Where appropriate, channel design criteria shall comply with FEMA standards and the 100-year floodplain shall be designated.

C. Criteria

1. General

a. Water Surface Profile Open channel flow is usually non-uniform because of bridge openings, curves, and structures. Except as specified below, this requires the use of backwater computations for all final channel design work.

A water surface profile must be computed for all channels and clearly shown on the final drawings. Computation of the water surface profile should use standard backwater methods, such as the Corps of Engineers HEC-2 computer program, taking into consideration losses due to changes in velocity, drop structures, bridge openings, and other obstructions. Computations begin at a known point and extend in an upstream direction for subcritical flow and downstream for critical flow. The depth of flow in the receiving stream must be consistent with the level of event being considered.

Extensive cross section data taken for flood insurance purposes may be available from the local jurisdiction or FEMA.

b. Manning n Values Wherever possible, Manning n values should be based on calibrations to observed high water marks and known flows for the same or a similar location. Table 8-1 provides general guidelines for estimating n values for streams and channels in cases where observations are not available. Also see Figures 8-2 and 8-3.

c. Drop Structures Drop structures may be used to decrease the bed slope and to control erosion in natural streams and grassed waterways. Drop structures shall be constructed with reinforced concrete, grouted rock or gabions in accordance with best engineering practice. A low-flow notch shall be provided for drainage and, where applicable, to allow passage of fish and other aquatic life.

d. Riprap and Gabions Riprap may be used to prevent damage to channel bottom and bank upstream and downstream from hydraulic structures, at bends, at bridges, and in other channel areas where erosive tendencies exist. Criteria and guidelines for riprap, grouted riprap, and gabions are presented in Chapter IX.

e. Appurtenant structures The channel design shall include all structures required for proper functioning of the channel and its laterals, as well as travelways for operationand maintenance. Inlets and structures needed for entry of surface and subsurface flow into channels without significant erosion or degradation shall be included in the channel design. The design also shall provide for necessary flood gates, water-level-control devices, bays used in connection with pumping plants, and any other appurtenances essential to the functioning of channels and contributing to attainment of the purposes for which they are built. If needed, protective structures or treatment shall be used at junctions between channels to insure stability at these critical locations.

TABLE 8-1 MANNING N FOR STREAMS AND CHANNELS (24) UNIFORM CHANNELS
Description		n
Concrete Earth Grass Rock, Rubble		0.012 - 0.016 0.017 - 0.022 0.020 - 0.025 0.025 - 0.045
NATURAL STREAMS-CHANNELS Channel n is a composite computed from the component n and k values in the table as follows: n=k (n1+n2+n3+n4 )
Component	Condition	n
Material involved (n1)	Earth Rock Cut Fine Gravel Course Gravel	0.020 0.025 0.024 0.028
Degree of Irregularity (n2)	Smooth Minor Moderate Severe	0.000 0.005 0.010 0.02
Relative effect of Obstructions (n3)	Negligible Minor Appreciable Severe	0.000 0.010 - 0.015 0.020 - 0.030 0.040 - 0.060
Vegetation (n4)	Low Medium High Very High	0.005 - 0.010 0.010 - 0.025 0.025 - 0.050 0.050 - 0.100
Degree of Meandering (k)	Minor Appreciable Severe	1.000 1.150 1.300

TABLE 8-1 (CONTINUED) MANNING N FOR NATURAL STREAMS - FLOODPLAIN
Description	Condition	n
Pasture	Short Grass High Grass	0.025 - 0.035 0.030 - 0.050
Cultivated Areas	No Crop Mature Row Crops Mature Field Crops	0.020 - 0.040 0.025 - 0.045 0.030 - 0.050
Brush	Scattered brush, heavy weeds Light brush/trees, winter Light brush/trees, summer Medium to dense brush, winter Medium to dense brush, summer	0.035 - 0.070 0.035 - 0.060 0.040 - 0.080 0.045 - 0.110 0.070 - 0.160
Trees	Dense willows, summer, straight Cleared land with tree stumps, no sprouts Same as above, but with heavy growth of sprouts Heavy stand of timber,a few down trees, little undergrowth, flood stage below branches As above, but with flood stage reaching branches	0.110 - 0.200 0.030 - 0.050 0.050 - 0.080 0.080 - 0.120 0.100 - 0.160

The effect of channel work on existing culverts, bridges, buried cables, pipelines, irrigation flumes, and inlet structures shall be evaluated to determine the need for modification or replacement.

f. Culverts and Bridges Culverts and bridges that are modified or added as part of channel projects shall meet reasonable standards for the type of structure and shall have a minimum capacity equal to the design discharge or state agency design requirements, whichever is greater. Capacity of some culverts and bridges may need to be increased above the design discharge.

g. Disposition of spoil Spoil material from clearing, grubbing, and channel excavation shall be disposed of in a manner that will:

- Not confine or direct flows so as to cause instability when the discharge is greater than the bankfull flow.

- Provide for the free flow of water between the channel and flood plain unless the valley routing and water surface profile are based on continuous dikes being installed.

2. Natural Channels Natural waterways are important in conveying storm runoff in Placer County. The objectives of the following criteria are to provide discharge capacity and stability in these channels. The criteria below are intended to provide for other purposes, such as fish and wildlife habitat and recreation.

a. Stability The main difficulties in the use of natural channels result from the effects of increased flows on the stability of the channel. Natural streams have an equilibrium in which the watershed, length, slope, width and depth of the channel, floodplain, and channel bedforms evolve in relationship with each other. This equilibrium determines the nature of the eroding, transporting, sorting, and depositional processes. The equilibrium can be upset by land use changes, channelization or other modifications. Channel adjustments which typically occur as a result of increased peak discharge or increased volume of storm runoff are widening and relocation of the channel, within the floodplain.

Therefore, where it is necessary to modify a natural channel or create a new open channel to accommodate increased flows from development channel design must consider not only the effects of peak flows, but also the effects of base flow hydrologic conditions on sediment transport, channel stability, erosion control, water quality, and vegetation, wildlife and aquatic resources.

In order to assure a successful design, the components of a natural system in channel improvements should be included. These components include a relatively narrow low flow channel to increase velocities and flow depths; a flat terrace between the low flow channel and the bank to accommodate peak flows; meander and pool and riffle sequences to accommodate sediment transport; and riparian vegetation on the terrace and shade trees on the banks to maintain lower water temperatures and discourage vegetative growth in the channel. Figure 8-1 illustrates these components.



All channel construction and modification including clearing and snagging shall be according to a design that can be expected to result in a stable channel that can be maintained at reasonable cost.

Vegetation, riprap, revetments, linings, structures, or other measures shall be used if necessary to insure stability. Characteristics of a stable channel are:

• The channel neither aggrades nor degrades beyond tolerable limits.
  
• The channel banks do not erode to the extent that the channel cross section is changed appreciably at critical sections.
  
• Excessive sediment bars do not develop.
  
• Gullies do not form or enlarge because of the entry of uncontrolled surface flow to the channel.

To evaluate the stability of a natural channel, it is generally necessary to estimate velocities under design conditions and to assess the bed and bank material for erosion potential with the velocities indicated. Velocities computed in the backwater analysis are suitable for this evaluation.

Channels must be stable under conditions existing immediately after construction (as-built condition) and under conditions existing during effective design life (aged condition). Channel stability shall be determined for discharges under these conditions as follows:

(1) As-built condition Bankfull flow, design discharge, or 10-year-frequency flow, whichever is smallest, but not less than 50 percent of design discharge. The allowable as-built velocity in the newly constructed channel may be increased by a maximum of 20% if irrigation is provided to establish a vegetative cover before October 15.

For newly constructed channels in fine-grained soils and sands, the n values shall not exceed 0.025. The n value for channels to be modified by clearing and snagging only shall be determined by reaches according to the expected channel condition upon completion of the work.

(2) Aged condition Bankfull flow or design discharge, whichever is larger, except that it is not necessary to check stability for discharge greater than the 100-year frequency.

b. Capacity Channel and overbank capacity shall be adequate for 100-year fully-developed runoff if possible. Design flows shall be determined by the basin master planning model, if available. The water surface profile or hydraulic gradeline for design flow shall be determined with HEC-2. The n value shall reflect the expected vegetation at the level of maintenance prescribed in the operation and maintenance plan.

c. Velocity Permissible velocities are shown in Table 8-2. In addition, velocities for any section shall not exceed critical velocity for that section.

d. Supercritical Flow Supercritical flow usually does not exist in natural channels and frequent checks should be made during the course of the backwater computations to insure that the computations do not reflect supercritical flow.

TABLE 8-2 PERMISSIBLE VELOCITIES FOR EARTH-LINED CHANNELS
Soil Type or Lining (earth, no vegetation)	Permissible Velocity (fps)
Find Sand (noncolloidal) Sandy Loam (noncolloidal) Silt Loam (noncolloidal) Ordinary Firm Loam Fine Gravel Stiff Clay (very colloidal) Graded, Loam to Cobbles (noncolloidal) Graded, Silt to Cobbles (noncolloidal) Alluvial Silts (noncolloidal) Alluvial Silts (colloidal) Coarse Gravel (noncolloidal) Cobbles and Shingles Shales and Hard Pans	2.5 2.5 3.0 3.5 5.0 5.0 5.0 5.5 3.5 5.0 6.0 5.5 6.0

e. Storage Effects on Downstream Flows Filling of the flood fringe reduces valuable storage capacity and tends to increase downstream runoff peaks. The evaluation of storage capacity and effects of proposed changes shall be evaluated using appropriate engineering standards and guidelines. Acceptable alternatives includes use of Modified Puls or a widely accepted unsteady-flow model.

f. Drop Structures Drop structures may be used at regular intervals to decrease the bed slope and to control erosion.

g. Other Improvements Improvements to natural channels to provide more capacity or protect the channel from erosion, other than those listed above, are beyond the scope of this manual. Criteria and guidelines for these improvements may be found in references 2,8,9,10,15,17,20,21. Many of these references are available in the Placer County Flood Control District library.

h. Environmental Features Environmental features may be desirable or necessary to provide for or enhance multiple uses or to mitigate for significant adverse impacts. Criteria and guidelines for environmental features are beyond the scope of this manual but may be found in references 2,8,9,10,12,15,17,20,21. Many of these references are available in the Placer County Flood Control District library.

3. Grassed Channels Grassed channels feature a uniform cover of grass to protect the channel from erosion where low velocities make this possible. Grass lined channels may be a desirable alternative because of its stability and aesthetic qualities. The criteria specified below also may apply to natural channels where appropriate.

a. Capacity

(1) Uniform Section and Slope The capacity for a grassed channel with uniform section and slope may be calculated at normal depth using Manning's formula with an appropriate n value.

(2) Irregular Section and Slope The capacity for a grassed channel with an irregular section or slope must be calculated with a backwater model as described above.

(3) Overbank Flows When the channel slope is less than 0.01 feet/feet, overbank flow may be allowed if such flow will not cause excessive erosion or damage to structures.

b. Design Velocities Maximum permissible velocities for various grasses and soils are presented in Table 8-3.

Design velocities for all linings should not fall below 2 fps for the 10-year runoff to minimize sediment depositional problems.

If the natural channel slope would cause excessive velocity, drop structures, checks, riprap, or other suitable channel protection shall be employed.

c. Roughness Coefficients The hydraulic roughness of grass lined channels depends on the length of cutting, if any, the type of grass, and the depth of flow. Roughness coefficients are determined using Figure 8-2 based on the retardance values of Table 8-4.



d. Grass Lining The grass lining used should be capable of surviving without irrigation, and have a thick root structure for keeping the bank soils in place.

e. Planting Considerations The most critical time in successfully installing grassed waterways is when vegetation is being established. Special protection such as mulch anchoring, straw or hay bale dikes, or other diversion methods are warranted at this critical period. Supplemental irrigation may also be warranted. The vegetation should be timed so plants will be established before flows occur in the channel.

f. Irrigation Where irrigation water is available for establishment and maintenance, dense, sod-forming perennial grass can be used that will permit higher velocities compared with bare earth. Where no irrigation water is available, a longer establishment period is required for perennial cover.

Annual grasses are generally shallow-rooted so safe velocities cannot exceed those for bare earth and drop structures may be required.

g. Low-Flow Channel A low-flow channel shall be used and shall provide a capacity of 0.5 to 1.0 percent of the major design flow.

The low-flow channel shall be protected from erosion with rock lining. Flows must enter the low-flow channel without flowing parallel to the channel, or bypassing the inlets.

h. Cut-off Walls The use of cut-off walls at regular intervals in a grassed channel is desirable for erosion control since a small level of erosion is otherwise unavoidable. Cut-off walls are also useful in containing the low flow channel.

Erosion control cut-off walls are usually of reinforced concrete, approximately 8 inches thick and from 18 inches to 2 feet deep, extending across the bottom of the channel. They can be shaped to fit a slightly sloped bottom to help direct water to the low-flow channel or to an inlet.

Since grass will not grow under a bridge, a cut-off wall should be used at the downstream edge of the bridge, or the area under the bridge deck should be stabilized with soil-cement.

i. Drop Structure Drop structures may be necessary to maintain an appropriate channel slope. Riprap or gabions shall be used at drop structures to prevent erosion downstream.

j. Design Slopes Grass lined channels function well with slopes from 0.2 to 0.6 percent. Steeper slopes shall be reduced with drop structures.

k. Channel Cross Sections The channel shape may be any type suitable to the location and to the environmental conditions provided they meet all other criteria.

l. Side slopes The minimum maintainable side slope is 2:1. Flatter slopes are more desirable.

m. Alignment Sharp curves shall not be used. Centerline curves should not have a radius of less than twice the design flow top width, but not less than 100 feet.

n. Freeboard Required freeboard varies according to the size of the channel and stability of proposed improvements. In general, a minimum freeboard of 3 feet is required beneath bridge and utility crossing and where a levee contains the flow. Exceptions will be allowed when justified.

TABLE 8-3 PERMISSIBLE VELOCITIES FOR WELL MAINTAINED GRASS CHANNELS
Permissible Velocity (fps)
Cover1	Slope Range (percent)	Erosion Resistant Soils	Easily Eroded Soils
Annual Ryegrass Blando Brome Zoro Fescue Luna Wheatgrass Topar Wheatgrass Hardingrass	0-5 5-10 over 10	4 NR3 NR3	3.5 NR3 NR3
Bermudagrass (hybrid)	0-5 5-10 over 10	8.02 7.02 6.02	6.02 4.02 3.02
Alta or Fawn Fescue	0-5 5-10 over 10	5.0 4.0 3.0	4.0 3.0 NR3
Reed Canarygrass4	0-5 5-10 over 10	5.0 4.0 NR3	4.0 3.0 NR3

1. The permissible velocities are for dense stands of grasses. The species chosen must be compatible with climatic and soil conditions.Check with the local Soil Conservation Service office for planting mix recommendations.
2. For channels with flow velocities greater than 5 fps, a synthetic erosion liner, jute, or anchored straw mattings are required for seeded or sprigged plantings. Sod may be used without cover but requires irrigation.
3. Not recommended. Use grade control structures or other types of lining.
4. Requires irrigation, but tolerates flooding and standing water

TABLE 8-4 FLOW RETARDANCE CLASSES FOR GRASSED CHANNELS
Retardance	Cover Type	Stand	Condition
A B B C C C D D D D E E E E	Reed Canarygrass Alta or Fawn Fescue Reed Canarygrass Harding Grass Luna or Topar Wheatgrass Read Canarygrass Annual Ryegrass Blando Brome Zoro Fescue Bermudagrass Bermudagrass (Hybrid) Annual Ryegrass Blando Brome Zoro Fescue	Excellent Good Good Good Good Good Good Good Good Good Good Good Good Good	36" Tall Uncut Mowed 18" Uncut Uncut Mowed 12" Uncut Uncut Uncut 3 - 6" Tall Mowed 1.5" Mowed 6" Mowed 6" Mowed 6"

Note:

A stand is considered "good" if 75 percent of the ground is covered by the plants. Reduce retardance one group for 50 percent ground cover.

o. Depth The maximum design depth of flow is 4.0 feet.

p. Bottom width The bottom width shall be at least 6 to 8 times the depth of flow, but shall not exceed 100 feet.

q. Maintenance A maintenance program shall be established to maintain waterway capacity, vegetative cover, and the outlet. Vegetation damage must be repaired promptly. The watershed above the channel must be treated to prevent sheet and rill erosion to keep sediment from damaging the vegetation.

4. Lined Channels Lined channels or channel segments may be used where natural or grassed channels provide inadequate capacity given space constraints or where erosion is a problem.

a. Roughness Coefficients Roughness coefficients for lined channels are:

TABLE 8-5 ROUGHNESS COEFFICIENTS FOR LINED CHANNELS
Lining	n
Trowel Finish	0.013
Float Finish	0.015
Unfinished	0.017
Shotcrete, troweled, Not wavy Wavy	0.018 0.020
Shotcrete, unfinished	0.022
Flagstone	0.022
Riprap See Figure 8-3

b. Design Velocities Maximum design velocity shall be as shown in Figure 8-4. Except for short transition sections, velocities at or near critical should be avoided. Velocities exceeding critical shall be restricted to straight reaches.

Waterways or outlets with velocities exceeding critical shall discharge into an energy dissipator to reduce velocity to less than critical.

c. Cross Section The cross section shall be triangular, parabolic, or trapezoidal. Cross sections made of monolithic concrete may be rectangular.

d. Side slope The steepest permissible side slopes, horizontal to vertical, shall be as shown in Table 8-6:

TABLE 8-6 PERMISSIBLE SIDE SLOPES FOR LINED CHANNELS
Non-reinforced Concrete
Hand-placed, formed concrete, Height of lining 1.5' or less	Vertical
Hand-placed screened concrete or mortared in-place flagstone
Height of lining less than 2' Height of lining more than 2'	1 to 1 2 to 1
Slip Form Concrete
Height of lining, less than 3' Rock riprap	1 to 1 2 to 2

e. Freeboard The minimum freeboard for lined waterways or outlets shall be 0.25 ft above design high water in areas where erosion-resistant vegetation cannot be grown adjacent to the paved side slopes. No freeboard is required if vegetation can be grown and maintained.

f. Lining thickness Minimum lining thickness shall be:

Concrete..................4 in. (In most problem areas,minimum thickness shall be 5 in. with welded wire fabric reinforcing.)
Rock riprap..........Maximum stone size plus thickness of filter or bedding
Flagstone............4 in., including mortar bed

g. Related structures Side inlets, drop structures, and energy dissipators shall meet the hydraulic and structural requirements for the site.

h. Filters or bedding Filters or bedding shall be used to prevent piping. Drains shall be used to reduce uplift pressure and to collect water, as required. Filters, bedding, and drains shall be designed according to generality accepted. Weep holes may be used with drains if needed.

i. Concrete Concrete used for lining shall be proportioned so that it is plastic enough for thorough consolidation and stiff enough to stay in place on side slopes. A dense durable product shall be required.

Specify a mix that can be certified as suitable to produce a minimum strength of at least 3,000 lb/in.2. Cement used shall be Portland cement. Types I, II, or if required, Type IV or V. Aggregate used shall have a maximum size of 1-1/2 in.



j. Mortar Mortar used for mortared in-place flagstone shall consist of a workable mix of cement, sand, and water with a water-cement ratio of not more than 6 gallons of water per bag of cement.

k. Contraction joints Contraction joints in concrete linings, if required, shall be formed transversely to a depth of about one-third the thickness of the lining at a uniform spacing in the range of 10 to 15 ft. Provide for uniform support to the joint to prevent unequal settlement.

l. Rock riprap or flagstone Stone used for riprap shall be dense and hard enough to withstand exposure to air, water, freezing, and thawing. Flagstone shall be flat for ease of placement and have the strength to resist exposure and breaking.

m. Maintenance Provisions must be made for timely maintenance to insure that lined waterways function properly.

n. Supercritical Flow Criteria

(1) Curvature It is generally not possible to have any curvature in a supercritical channel.

(2) Stability Flow at Froude numbers near 1 is unstable and should be avoided. Careful attention must be taken to insure against excessive oscillatory waves which may extend down the entire length of the channel from only minor obstructions upstream. The design must take care to insure that hydraulic jumps do not form.

(3) Cross Section There shall be no diminution of wetted area cross section at bridges or culverts. Freeboard shall be adequate to provide a suitable safety margin, the safety margin being at least 2 feet or an additional capacity of approximately one-third of the design flow.

(4) Linings All channels carrying supercritical flow shall be lined with continuously reinforced concrete linings, the reinforcing being continuous both longitudinally and latterally.



The linings must be protected from hydrostatic uplift forces which are created by a high water table or momentary inflow behind the lining from localized flooding. Generally a perforated underdrain pipe will be required under the lining and designed to be free draining.

Imperfections at joints may rapidly cause a deterioration of the joints, in which case a complete failure of the channel can readily occur. In addition, high velocity flow entering cracks or joints creates an uplift force which can damage the channel lining.

The roughness of lined, supercritical channels is a particularly critical element in their performance. The construction of supercritical channels must be rigorously inspected to insure that the design roughness is obtained. Because of field construction limitations the designer should not use a Manning n roughness coefficient any lower than 0.013 for a well-troweled concrete finish.

(5) Anchorage of Crossings Bridges or other structures crossing the channel must be anchored satisfactorily to withstand the full dynamic load which might be imposed upon the structure in the event of major trash plugging.

o. Subcritical Flow Criteria

(1) Radius of Curvature Generally centerline curves should not have a radius of less than twice the design flow top width, but not less than 100 feet.

(2) Freeboard Bridge deck bottoms and utility crossings may control the freeboard. Where they do not, a minimum freeboard of 2 feet should be allowed.

(3) Depth The depth of flow at the design discharge will be between 3 to 4 feet deep insofar as reasonably practical.

(4) Bottom Width The bottom width shall be at least 6 to 8 times the depth of the flow insofar as reasonably practical.

(5) Low Flow Channel Low flow channels (trickle channels or underdrain pipes) are required to prevent standing water in the channel.

(6) Bottom Width The bottom width shall be at least 6 to 8 times the depth of the flow insofar as reasonably practical.

REFERENCES

1. Agricultural Research Service, Stability Design of Grass- Lined Open Channels, Agriculture Handbook Number 667, 1987.
2. American Fisheries Society, Stream Obstruction Removal Guidelines, 1983.
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4. Chow, Ven Te, Open-Channel Hydraulics, McGraw-Hill, 1959.
5. City & County of Denver, Criteria for Storm Sewer Design, Department of Public Works, Denver, Colorado, 1963.
6. Colby, Ardis V., Kenneth J. Kieker and Arnold Lenz, Storm Drainage Practices of Thirty-two Cities, A.S.C.E. National Meeting on Water Resources Engineering. New York, NY, October 16-20, 1967.
7. Federal Aviation Agency, Airport Drainage, Washington, D.C., 1966.
8. Gray, Donald H, and Andrew T. Leiser, Biotechnical Slope Protection and Erosion Control, Van Nostrand Reinhold, 1982.
9. Henderson, Jim E., and F. Douglas Shields, Environmental Features for Streambank Erosion Projects, U.S. Army Corps of Engineer Waterways Experiment Station, Report E-84-11, 1984.
10. Heyson, James R., et al, Environmental Features for Streamside Levee Project, US Army Corps of Engineers Waterways Experiment Station, Report E-85-7, 1985.
11. Institute of Transportation and Traffic Engineering, Street and Highway Drainage, Volumes 1 & 2 University of California, Berkeley, California, 1982.
12. Jackson, William, ed., Engineering Considerations in Small Stream Management, American Water Resources Association Bulletin, Vol 22, No. 3, 1986.
13. King, Horace W. and Ernest F. Brater, Handbook Hydraulics, McGraw-Hill, 1976.
14. Metcalf & Eddy, Inc., Wastewater Engineering: Collection, Treatment, and Disposal, McGraw-Hill, 1972.
15. Ministry of Environment, Stream Enhancement Guide, Canada, March, 1980.
16. National Association of County Engineers Action Guide Series, Drainage Volume XIV, National Association of Counties Research Foundation, 1972.
17. Nunally, Nelson R. and F. Douglas Shields, Incorporation of Environmental Features in Flood Control Channel Project, U.S. Army Corps of Engineers Waterways Experiment Station, Report E-85-3, 1987.
18. Portland Cement Association, Handbook of Concrete Culvert Pipe Hydraulics, Chicago, Illinois, 1964.
19. Rouse, Hunter, John Wiley and Sons, Inc., Elementary Mechanics of Fluids, New York, New York, 1946.
20. Schiechtl, Hugo, Bioengineering For Land Reclamation and Conservation, University of Alberta Press, 1980.
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22. Soil Conservation Service, Engineering Division, Design of Open Channels, Technical Release No. 25, 1977.
23. Taylor, Edward H., Flow Characteristics at Rectangular Open-Channel Junctions, Transactions A.S.C.E., Vol. 109, 1944, p. 893.
24. Walesh, Stuart, Urban Surface Water Management, John Wiley & Sons, 1989.