CTC 440 Review Determining peak flows Rational method Q=CIA Intensity determined from IDF curves Set time of concentration=storm duration

CTC 440 Sizing Structures Hydraulic Devices Pipes Culverts Inlets Ditch &/or gutter flow Storm drainage systems Detention structures

Subjects Open Channel Flow Ditch flow Gutter flow Pipe flow (non-pressurized)

Objectives Know how to use Manning’s equation for uniform flow calculations Know how to calculate Normal Depth

Open Channel Flow Open to the atmosphere Creek/ditch/gutter/pipe flow Uniform flow-EGL/HGL/Channel Slope are parallel velocity/depth constant Varied flow-EGL/HGL/Channel Slope not parallel velocity/depth not constant

Uniform Flow in Open Channels Water depth, flow area, Q and V distribution at all sections throughout the entire channel reach remains unchanged The EGL, HGL and channel bottom lines are parallel to each other No acceleration or deceleration

Manning’s Equation Irish Engineer On the Flow of Water in Open Channels and Pipes Empirical equation See more: http://manning.sdsu.edu/\ http://el.erdc.usace.army.mil/elpubs/pdf/sr10.pdf#search=%22manning%20irish%20engineer%22

Manning’s Equation-Metric Q=AV=(1/n)(A)(Rh)2/3S1/2 Where: Q=flow rate (cms) A=wetted cross-sectional area (m2) Rh=Hydraulic Radius=A/WP (m) WP=Wetter Perimeter (m) S=slope (m/m) n=friction coefficient (dimensionless)

Manning’s Equation-English Q=AV=(1.486/n)(A)(Rh)2/3S1/2 Where: Q=flow rate (cfs) A=wetted cross-sectional area (ft2) Rh=Hydraulic Radius=A/WP (ft) WP=Wetter Perimeter (ft) S=slope (ft/ft) n=friction coefficient (dimensionless)

Manning’s Friction Coefficient http://www.lmnoeng.com/manningn.htm Typical values: Concrete pipe: n=.013 CMP pipe: n=.024

Example-Find Q Find the discharge of a rectangular channel 5’ wide w/ a 5% grade, flowing 1’ deep. The channel has a stone and weed bank (n=.035). A=5 sf; WP=7’; Rh=0.714 ft S=.05 Q=38 cfs

Example-Find S A 3-m wide rectangular irrigation channel carries a discharge of 25.3 cms @ a uniform depth of 1.2m. Determine the slope of the channel if Manning’s n=.022 A=3.6 sm; WP=5.4m; Rh=0.667m S=.041=4.1%

Triangular/Trapezoidal Channels Must use trigonometry to determine area and wetted perimeters

Pipe Flow Hydraulic radii and wetted perimeters are easy to calculate if the pipe is flowing full or half-full If pipe flow is at some other depth, then tables, figures, or software (flowmaster) are usually used

Using Manning’s equation to estimate pipe size Size pipe for Q=39 cfs Assume full flow Assume concrete pipe on a 2% grade Put Rh and A in terms of Dia. Solve for D=2.15 ft = 25.8” Choose a 27” or 30” RCP Velocity is approx. 9.8 ft/sec

Using Manning’s equation to estimate pipe size Size pipe for Q=220 cfs Assume full flow Assume concrete pipe on a 2% grade Put Rh and A in terms of Dia. Solve for D=4.1 ft = 49.5” Choose a 54” RCP Velocity is approx. 13.8 ft/sec ===high

Normal Depth Given Q, the depth at which the water flows uniformly Use Manning’s equation Must solve by trial/error (depth is in area term and in hydraulic radius term)

Normal Depth Example Find normal depth in a 10.0-ft wide concrete rectangular channel having a slope of 0.015 ft/ft and carrying a flow of 400 cfs. Assume: N=0.013

Normal Depth Example 7-3 Assumed D (ft) Area (sqft) Peri. (ft) Rh (ft) Q (cfs) 2.00 20 14 1.43 1.27 356 3.00 30 16 1.88 1.52 640 2.15 21.5 14.3 1.50 1.31 396

Inlets Capacity usually estimated using orifice or weir equations

Froude Number F=Vel/(g*D).5 F=Froude # V=Velocity (fps or m/sec) D=hydraulic depth=a/T (ft or m) g=gravitational constant F=1 (critical flow) F<1 (subcritical; tranquil flow) F>1 (supercritical; rapid flow)

Stormwater Definitions SWPPP-Stormwater Pollution Prevention Plan NPDES-National Pollutant Discharge Elimination System SPDES-State Pollutant Discharge Elimination System MS4-Municipal Separate Storm Sewer System NOI-Notice of Intent Blue Book-”New York Standards and Specification for Erosion and Sediment Control”

History Water Quality Act-1987 Phase I Stormwater Regulations-1990 First regulations dealing with discharge of stormwater Phase I Stormwater Regulations-1990 NYSDEC is local permitting authority NYSDEC issued 2 general permits-1993 Industrial Site Runoff Construction Projects > 5 acres (Phase I) Phase II Stormwater Regulations-1999 Apply to Construction Projects > 1 acre

SWPPP-Contents Standards for Construction Activities Background project info Site Map Soil Description Construction Phasing Plan Pollution Prevention Measures Description of Construction and Waste Materials Temporary and Permanent Structural and Vegetative Measures

SWPPP-Contents (contents) Map showing control measures Details of control measures Identify temporary measures to be converted to permanent control measures Maintenance Schedule Name of receiving water Description of structural practices used to divert flows Description of existing data that describes the stormwater runoff characteristics at the site

Commonly Used SWPPP Measures Construction Entrance Mulching/Seeding Silt Fences Straw Bale Dikes Drop Inlet Protection Stone Check Dams Prefabricated Check Dams

Construction Entrance http://pasture.ecn.purdue.edu/~sedspec/sedspec/images/construction.jpg http://www.harfordcountymd.gov/dpw/eng&const/WaterResources/Images/Sedimentcont2.jpg

Erosion Control (Mulching/Seeding) http://www.terra-mulch.com/photos/11-11.JPG http://www.ssseeds.com/ecb/photos/WS05/images/WS05%202-1%20Over%20Mulch.jpg

Silt fences www.acfenvironmental.com/ bmp_siltfence.htm www.forestry.state.ar.us/ bmp/appn_soil.html

Straw Bale Dikes http://www.salmonhabitat.org/images/v3f52b.gif http://www.forester.net/images/ec_0103_p78_top.jpg

Drop Inlet Protection http://unix.eng.ua.edu/~rpitt/Class/Erosioncontrol/Module8/Module8_files/image050.gif http://www.greatamericantec.com/images/inlet.jpg

Stone Check Dams http://www.ncc-swnpdes.com/images/stone_creek_dam.jpg http://www.dfr.state.nc.us/images/wq/glossary/rockcheckdam.jpg

Other Check Dams http://www.lakemac.infohunt.nsw.gov.au/erosion/images/09051.gif http://www.wsdot.wa.gov/NR/rdonlyres/BA478915-1B80-4188-BB59-37358244CBDF/0/CheckDam_Jan05.jpg

Detention Structures Designed for water quality, attenuation of peak flows, infiltration, aesthetics