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CTC 440 Review

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

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Title: CTC 440 Review


1
CTC 440 Review
  • Determining peak flows
  • Rational method
  • QCIA
  • Intensity determined from IDF curves
  • Set time of concentrationstorm duration

2
CTC 440 Sizing Structures
  • Hydraulic Devices
  • Pipes
  • Culverts
  • Inlets
  • Ditch /or gutter flow
  • Storm drainage systems
  • Detention structures

3
Subjects
  • Open Channel Flow
  • Ditch flow
  • Gutter flow
  • Pipe flow (non-pressurized)

4
Objectives
  • Know how to use Mannings equation for uniform
    flow calculations
  • Know how to calculate Normal Depth

5
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

6
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

7
Mannings 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
    search22manning20irish20engineer22

8
Mannings Equation-Metric
  • QAV(1/n)(A)(Rh)2/3S1/2
  • Where
  • Qflow rate (cms)
  • Awetted cross-sectional area (m2)
  • RhHydraulic RadiusA/WP (m)
  • WPWetter Perimeter (m)
  • Sslope (m/m)
  • nfriction coefficient (dimensionless)

9
Mannings Equation-English
  • QAV(1.486/n)(A)(Rh)2/3S1/2
  • Where
  • Qflow rate (cfs)
  • Awetted cross-sectional area (ft2)
  • RhHydraulic RadiusA/WP (ft)
  • WPWetter Perimeter (ft)
  • Sslope (ft/ft)
  • nfriction coefficient (dimensionless)

10
Mannings Friction Coefficient
  • http//www.lmnoeng.com/manningn.htm
  • Typical values
  • Concrete pipe n.013
  • CMP pipe n.024

11
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).
  • A5 sf WP7 Rh0.714 ft
  • S.05
  • Q38 cfs

12
Example-Find S
  • A 3-m wide rectangular irrigation channel
    carries a discharge of 25.3 cms _at_ a uniform depth
    of 1.2m. Determine the slope of the channel if
    Mannings n.022
  • A3.6 sm WP5.4m Rh0.667m
  • S.0414.1

13
Triangular/Trapezoidal Channels
  • Must use trigonometry to determine area and
    wetted perimeters

14
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

15
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16
Using Mannings equation to estimate pipe size
  • Size pipe for Q39 cfs
  • Assume full flow
  • Assume concrete pipe on a 2 grade
  • Put Rh and A in terms of Dia.
  • Solve for D2.15 ft 25.8
  • Choose a 27 or 30 RCP
  • Velocity is approx. 9.8 ft/sec

17
Using Mannings equation to estimate pipe size
  • Size pipe for Q220 cfs
  • Assume full flow
  • Assume concrete pipe on a 2 grade
  • Put Rh and A in terms of Dia.
  • Solve for D4.1 ft 49.5
  • Choose a 54 RCP
  • Velocity is approx. 13.8 ft/sec high

18
Normal Depth
  • Given Q, the depth at which the water flows
    uniformly
  • Use Mannings equation
  • Must solve by trial/error (depth is in area term
    and in hydraulic radius term)

19
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
  • N0.013

20
Normal Depth Example 7-3
Assumed D (ft) Area (sqft) Peri. (ft) Rh (ft) Rh.66 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
21
Inlets
  • Capacity usually estimated using orifice or weir
    equations

22
Froude Number
  • FVel/(gD).5
  • FFroude
  • VVelocity (fps or m/sec)
  • Dhydraulic deptha/T (ft or m)
  • ggravitational constant
  • F1 (critical flow)
  • Flt1 (subcritical tranquil flow)
  • Fgt1 (supercritical rapid flow)

23
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

24
History
  • Water Quality Act-1987
  • 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 gt 5 acres (Phase I)
  • Phase II Stormwater Regulations-1999
  • Apply to Construction Projects gt 1 acre

25
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

26
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

27
Commonly Used SWPPP Measures
  • Construction Entrance
  • Mulching/Seeding
  • Silt Fences
  • Straw Bale Dikes
  • Drop Inlet Protection
  • Stone Check Dams
  • Prefabricated Check Dams

28
Construction Entrance
http//pasture.ecn.purdue.edu/sedspec/sedspec/ima
ges/construction.jpg
http//www.harfordcountymd.gov/dpw/engconst/Water
Resources/Images/Sedimentcont2.jpg
29
Erosion Control (Mulching/Seeding)
http//www.terra-mulch.com/photos/11-11.JPG
http//www.ssseeds.com/ecb/photos/WS05/images/WS05
202-120Over20Mulch.jpg
30
Silt fences
www.acfenvironmental.com/ bmp_siltfence.htm
www.forestry.state.ar.us/ bmp/appn_soil.html
31
Straw Bale Dikes
http//www.salmonhabitat.org/images/v3f52b.gif
http//www.forester.net/images/ec_0103_p78_top.jpg
32
Drop Inlet Protection
http//unix.eng.ua.edu/rpitt/Class/Erosioncontrol
/Module8/Module8_files/image050.gif
http//www.greatamericantec.com/images/inlet.jpg
33
Stone Check Dams
http//www.ncc-swnpdes.com/images/stone_creek_dam.
jpg
http//www.dfr.state.nc.us/images/wq/glossary/rock
checkdam.jpg
34
Other Check Dams
http//www.lakemac.infohunt.nsw.gov.au/erosion/ima
ges/09051.gif
http//www.wsdot.wa.gov/NR/rdonlyres/BA478915-1B80
-4188-BB59-37358244CBDF/0/CheckDam_Jan05.jpg
35
Detention Structures
  • Designed for water quality, attenuation of peak
    flows, infiltration, aesthetics

36
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