Lesson 2-Hydraulics and Hydrology Methods, Exercises of Hydrology

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Lesson 2: Hydraulics and Hydrology

Methods (HM Chapter 2)

....~WSDOT

H&H Methods

-^ What is the difference between Hydraulics and Hydrology? •^ What are the different methods used by WSDOT to calculateflow? •^ What tools and software models does WSDOT require forHydraulic and Stormwater design on WSDOT

projects?

-^ How do I design: -^ a roadway culvert? –^ a roadway ditch? –^ a pipe network including inlet/Catch Basin/Manhole spacing?

....~WSDOT

H&H Methods

What’s the difference between Hydraulics and Hydrology anyways? Hydrology -

The study or science of transforming rainfall amount

into quantity of runoff. Hydraulics –

The study or science of the motion of liquids in

relation to disciplines such as fluid mechanics and fluid dynamics. It rains and roadway surface runoff flows into the roadway ditch = hydrology Determining the water level in the ditch and how fast thewater is moving = hydraulics

Hydrology Methods: Flow rates can be determined using:•^ Santa Barbara Urban Hydrograph Method (SBUH) •^ Continuous Simulation Method (western WA

for stormwater

design) • United States Geological Survey (USGS) Regression Equations(StreamStats) • USGS Streamflow Gages - Published Flow Records • Rational Formula • FEMA

Flood Studies

Hydrology Methods

-^ Documented Testimony –

used to

back up assumptions

Hydraulic Software/Tools

We take flow rates from the

hydrology methods

and use the

following tools for

hydraulic calculations

:

-^ StormShed3G –

conveyance (storm sewer, culvert, pipe,

and ditch) design statewide and stormwater BMP design ineastern WA • MGSFlood - stormwater Best Management Practice (BMP)design and temporary construction stream bypass designin western WA • FHWA

HY-8 –

culvert design

-^ HEC-RAS (one dimensional) and SRH2D (twodimensional) flow modeling to determine water surfaceprofiles, scour design, fish passage design •^ WSDOT inlet spacing and sag inlet spreadsheets •^ WSDOT pipe sizing spreadsheet using Manning’s

equation

Hydraulics Manual Policies

We use thissoftware fordesign andsizing theculvert

We use thisto developthe flow rateto theculvert

We wantto designa culvert

One Stop Shopping!

MGSFlood (western WA

only) and StormShed3G (statewide) are

hydraulic models that also develop hydrology for the basin ofinterest MGSFlood is used for stormwater BMP sizing in western WA

only

StormShed3G is used for conveyance design statewide StormShed3G is used for stormwater BMP sizing in eastern WA only

....~WSDOT

MGSFlood

Here’s what you will need to run the model for stormwater BMP design: •^ Precipitation for your project area using mean annualprecipitation maps or latitude and longitude coordinates •^ Drainage basin sizes and land covers for predeveloped andpost developed condition

-^ Forest, Pasture, Grass, Saturated Soils, Impervious •^ Use MGSFlood Inputs Spreadsheet on HRM Revisionswebpage -^ Set up Basin to BMP links •^ Use MGSFlood to size your BMP •^ Use MGSFlood to design a temporary construction streambypass when doing a fish passage or culvert replacementproject.

MGSFlood Simulate Tab is whereMGSFlood runs thesimulation for developinghydrology and sizing

Project Locationand ScenarioTabs requiredifferent data

PredevelopedandPostdevelopedScenarios =input basin andstructure dataand link datatogether

....~WSDOT

StormShed3G

Here’s what you will need to run the model for conveyancedesign: •^ Precipitation for your project area using isopluvial

maps

-^ Drainage basin sizes and land covers -^ Curve Numbers (CN) represent forest (CN= 70) toimpervious land covers (CN = 98) •^ Time of concentration needs to be developed using sheet,shallow, and channelized flow inputs -^ Pipe and/or ditch locations, elevations, and geometry to lay outconveyance network •^ Define any downstream tail water conditions There are StormShed3G classes that walk though detailedanalysis method and examples

StormShed3G

Nodes = CB/MH/GI

Layout = wherewe link datatogether DATA

TREE =

where we inputinformation – CB/MH/PIPE/Ditch/ Basin Information

Reach =Pipe/Ditch

Rain on Snow Design

-^ Snow Depth Chart (

WRCC Data)

-^ Average Snow Depth > 2 inches/day •^ Equation •^ Max of 1.5 inches •^ Additional considerations (Roadside drainage,retention ponds, frozen ground)

H&H Methods

Hydrology: Rational Method

RATIONAL METHOD FUN FACTS FOR WSDOT

DESIGNS

-^ Generally overestimates flow rates but requires minimal input •^ Is suitable for new facility designs since it incorporates a levelof safety into the design •^ May not be suitable for determining the existing condition orexisting capacity of hydraulic structure

-^ Limitations •^ C for different return intervals (Figure 2-5.2 applicable for10-year frequency) -^ Increase C by 10% for 25-year frequency –^ Increase C by 20% for 50-year frequency –^ Increase C by 25% for 100-year frequency

Hydrology: Rational Method

Rainfall Intensity

-^ m and n (HM Figure 2-5.4A) •^ Coefficient assumptions

Hydrology: Rational Method

Time of Concentration - Tc

-^ K (Figure 2-5.3) •^ T

= 5 minute minimumc

Hydrology: Rational Method

Rational Method Spreadsheet

http://www.wsdot.wa.gov/Design/Hydraulics/ProgramDownloads.htm

Hydrology: Rational Method

....~WSDOT

USGS Regression Equations

(StreamStats)

-^ Used for large rural or non-urban basins to develop flows forfish passage design and culvert design •^ StreamStats Web Application - Uses USGS RegressionEquations to develop flow rates at a certain point^ –

Point and click and StreamStats gives basin information,flow rates, drainage area, etc.

-^ New regression equations and new 2 versions of StreamStatsavailable

StreamStats

HY-

-^ Developed by FHWA •^ Based on FHWA’s Hydraulic Design Series (HDS) 5 andHydraulic Engineering Circular (HEC) 14 •^ Preferred method for culvert design •^ Multiple culverts

HY-8

W

SDOT Hydraulic Spreadsheets

-^ Most use Rational Method and Manning’s Equation for sizing -^ Culvert Corrosion/Pipe Angle Calculation Worksheet –^ Storm Drain Design –^ Inlet Spacing and Sag Design –^ Short Duration Rainfall Depth Converter –^ Pond Hydraulics (orifice, wet pond, volume) –^ Biofiltration Swale (basic, wet, continuous) –^ CAVFS LID Calculator –^ MFD Underdrain –^ Slotted Pipe Flow Spreader

http://www.wsdot.wa.gov/Design/Hydraulics/ProgramDownloads.htm http://www.wsdot.wa.gov/Environment/WaterQuality/Runoff/HighwayRunoffManual.htm

^ Rational Method flows

-^ Design Frequency (10 year vs 50 year) –^ Coefficient (m, n, and C values) ^ Inlet sizes ^ Allowable spread width Z

d

^ Inlet Spacing Spreadsheet ^ Sag Inlet Worksheet

Inlet Spacing (Curb and Gutter)

Inlet Spacing Spreadsheet

Inlet Spacing (Curb and Gutter)

Sag Inlet Design Worksheet

Sag Inlet Design