10/4/ slide sample of Presentation. Key Principles to Current Stormwater Management

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ASLA 2012 Annual Meeting and EXPO ASLA 2012 Annual Meeting and EXPO ASLA 2012 Annual Meeting and EXPO ASLA 2012 Annual Meeting and EXPO

40 slide sample of Presentation

• Please contact [email protected] if you would like the complete presentation

Key Principles to “Current”

Stormwater Management

Distributed Control Distributed Control Distributed Control Distributed Control

Measures MeasuresMeasures

Measures Integrated PlanningIntegrated PlanningIntegrated PlanningIntegrated Planning Multiple Objective / Multiple Objective / Multiple Objective / Multiple Objective / Function Function Function Function

Urbanization Impacts to Surface Runoff Hydrology

• Increased runoff volume

• Increased peak flowrate

• Reduced time of concentration

• Increased flow frequency

• Reduced infiltration

• Modified flow patterns

• Loss of surface storage

• Increased temperature

• Reduced sediment sources

• Stormwater pollutants /bacteria

• Non-stormwater discharges

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What is Hydromodification - “Hydromod”?

• Focus on changes to the downstream streams that changes in hydrology causes

• Urban Related Hydromodification – Increase Imperviousness

– Changes in runoff volume and frequency – Changes in sediment supply

– Direct channel changes

• Hydromodification Impacts – Increase Erosion

– Sediment Changes – Habitat Loss / Degradation – Bio/ecological Impacts

Development Hydromodification Impacts

Urbanization Changes Watershed Hydrology

Changes in Urban Storm Runoff and Stream Flow

Observed Stream Channel Responses

to Hydrologic Changes

• Increased Imperviousness

• Efficient conveyance

• Vegetative cover

• Topography

• Landuse

• Flow diversions

• Riparian encroachment

• Increased peak runoff rates

• Faster Response

• More frequent runoff events

• Higher flow velocities

• Sediment supply change

• Increased stream erosion

• Enlarged channels

• Deeper/wider

• Flooding problems

• Habitat damage

• Increase sedimentation / erosion

• Sediment size change

Stormwater Pollution Impact from Urbanization

• EPA estimates the No. 1 source of surface water pollution is caused by stormwater runoff and caused pollution of nearly 40% of US waterbodies

• Non-point source pollution

• Initial “first flush” runoff washes off 85% of pollutants within first 15minutes of storm

– Generally first ½-inch runoff from impervious area - Small portion of storm runoff but large percentage of all pollutant loading

Federal CWA - NPDES Permit Program

• National Pollutant Discharge Elimination System (NDPES) part of the 1972 Clean Water Act (CWA)

• Administered by the EPA

• Point source

• Non-point source (i.e. stormwater)

• Originally excluded from NPDES but environment groups sued

• Stormwater targets

• Industrial

• Municipal Separate Stormwater Systems (MS4)

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Recent Changes in Federal NPDES / State Implementation Requirements

Requirement Existing Changes

Site Design None Infiltration control

measures (LID) to maximum extent

onsite Infiltration /

Hydromodifiaction / Groundwater

Recharge

None Volumetric Controls / Maintain Annual recharge / Duration

flow control Water Quality Treatment of Water

Quality Control Volume

Infiltration controls measures

Erosion Control Erosion Control Standard Practices

Water Quality Monitoring Numeric

Standards Limits

Surface Runoff Hydrology Fundamental Concepts

• Surface Runoff is excess rainfall not abstracted

• Basics of surface hydrology are simple – Moving volumes (water) over time

• Volume = Area x Depth

– Rainfall depth is considered a volume

• Velocity = Distance / Time

• Rate of Flow = Q = Volume /Time – Also is Q = (Area)x(Velocity)

– Volume delivered over time = (rate)x(time) V= Q x t

Area Depth

Flowrate Volume

Volume Volume

Volume

Precipitation and Storm Events

• Rainfall varies in time and area where it falls

• Storm events characterized by total volume,

intensity, and duration (inches, in/hour,

minutes, or hours)

Precipitation and Storm Events

• Rainfall events are random

– Analysis of long historical records will provide statistical pattern of the rainfall occurrence

– Probability (p) and Recurrence Interval (T) used to define storm magnitude/severity where p=1/T

• Example: 10-year storm P= 0.10

• Storm that will be reached or exceeded on average once every 10-years

Orange County (Example) – 10-year 24-hour rain = 3.7 inches – 10-year 1-hour rainfall = 0.78 inches – 100-year 24-hour rainfall 5.6 inches

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• Important method facilitates evaluating benefits of sustainable design practices quickly on stormwater runoff

• SCS Curve Number Method provides number from 1 to 100 that indicates the runoff potential conversion of rainfall

• SCS curve number function of soil type, vegetative cover, and impervious area.

• Procedure found in TR-55 published by SCS (NRCS) and calculator and tables

• http://www.wsi.nrcs.usda.gov/products/W2 Q/H&H/Tools_Models/other/TR55.html

Simplified Method to Determine “Runoff Potential”

SCS (NRCS) TR-55 Method – Simple Hydrology Equations – Site Design

• General Equation Gives Runoff Depth:

• Knowing That I=0.2S, the Equation Becomes:

• PMust Be Greater Than or Equal to 0.2S

Where:

Q = Precipitation excess (inches) P = Cumulative Rain (inches) S= Soil - water retention potential CN = SCS Curve Number

( )

(

^P^P ^I^I

)

^S

Q

a a

+

−

= −

2

( )

S P

S Q P

8 . 0

2 .

0 ²

+

= −

1000 10

−

= CN S

What is a Runoff Hydrograph? – Watershed Response from Storm

• Illustrates how flowrate varies in time

• Time is a key

characteristics of the watershed

• Runoff Volume is area under hydrograph

Small Site Rational Method Hydrology for Flowrate

• Simplified hydrology formula for determination of flowrate from small site

• Applicable to less than 640 acres Q = Peak flowrate (cfs) = C x I x A C = runoff coefficent

I = intensity (in/hr) A = acres

• For Parking Lot Example:

Q = 1.0 x 1.0 in/hr x 1.0 ac = 1.0 cfs

1.0 acre

inlet

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What is stormwater Detention?

• Stormwater “detention” is the temporary storage of runoff and released at lower rate than it entered the storage

reservoir/pond

• Primary benefit to attenuate peak flow rate

Storm Water Quality - Design Storm Capture Volumes

• Examples:

– 6 month, 24 hour (Wa) – 0.5 in runoff (Fl) – 1 inch of runoff (Mn) – 0.5 inches from

impervious area (Md)

• Recommended:

– 85th percentile runoff event, Average Annual 24-hour

• Mass Balance – Storage = Inflow – Outflow

– Inputs = Rainfall+Runoff+Urban Dry Flows – Output=Evaporation+Irrigation Use+Infiltration

Water Harvesting – Water Balance Analysis

Conventional Stormwater

Treatment BMPs – Detention Storage

Dry Detention Dry DetentionDry Detention

Dry Detention Wet DetentionWet DetentionWet DetentionWet Detention

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Conventional Stormwater Treatment BMPs – Infiltration

Infiltration Trench Infiltration Trench Infiltration Trench

Infiltration Trench BioretentionBioretentionBioretentionBioretention Infiltration BasinInfiltration BasinInfiltration BasinInfiltration Basin

Conventional Stormwater Treatment BMPs – Vegetative

Treatment Wetland Treatment Wetland Treatment Wetland

Treatment Wetland BiofilterBiofilterBiofilterBiofilter

Conventional Stormwater

Treatment BMPs – Mechanical/Chemical

Hydrodynamic Separation Hydrodynamic SeparationHydrodynamic Separation

Hydrodynamic Separation Media Filtration Media Filtration –––– Perlite/ZeoliteMedia Filtration Media Filtration Perlite/ZeolitePerlite/ZeolitePerlite/Zeolite

What is “Low Impact Development” (LID)?

– LID is a stormwater management technique that mimics nature (runoff)

– LID manages rainfall at the source by mimicking site

“pre-development” hydrology

– Utilizes techniques that infiltrate, filter, store, evaporate, and detain stormwater close to the sources – Stormwater is treated in small cost effective landscape features through the site instead of just at the “end of pipe”

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High performance Low performance

Measuring Sustainability

Measuring Sustainability Measuring SustainabilityMeasuring Sustainability Measuring Sustainability

Measuring Sustainability

Water Quality Treatment

Low performance High performance

New Technologies Present New Opportunities for Artful Expression

Measuring Sustainability

High performance Low performance

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“Value Added” Evolution of Stormwater Management

Stormwater Infrastructure

Stormwater Treatment

Landscape

Techniques Art /

Aesthetics

• Urban Urban Urban Urban Drainage DrainageDrainage Drainage

• DetentionDetentionDetentionDetention

• Flood Flood Flood Flood Control ControlControl Control

• Structural Structural Structural Structural BMPsBMPsBMPs BMPs

• LID FeaturesLID FeaturesLID FeaturesLID Features

• Eco LandscapingEco LandscapingEco LandscapingEco Landscaping

• Green Green Green Green Infrastructure InfrastructureInfrastructure Infrastructure

• Sustainable Sustainable Sustainable Sustainable Design DesignDesign Design

• Environmental Environmental Environmental Environmental Site Design Site DesignSite Design Site Design

• Structural Structural Structural Structural BMPs BMPs BMPs BMPs

• NonNonNonNon---- structural structural structural structural BMP BMP BMP BMP

Techniques to Provide Art / Creative Form with Stormwater

Allow public to touch and interact with water / stormwater systems

Create interesting pathways for destinations points of stormwater systems

Techniques to Provide Art / Creative Form with Stormwater

Focal points of stormwater visual interest

Contrast different materials natural vs manmade and imbed artistic forms

Techniques to Provide Art / Creative Form with Stormwater

Recreate natural water features which Recreate natural water features which Recreate natural water features which Recreate natural water features which use natural forms and water movement use natural forms and water movement use natural forms and water movement use natural forms and water movement and motion

and motionand motion and motion Create visual interest in

water through unique shape and change in direction

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Techniques to Provide Art / Creative Form with Stormwater

Stormwater basins/ponds have visual interest different themes / geometry

Use unique conveyance (flumes/bioswales) to emphasize water path – interest / curiosity

Techniques to Provide Art / Creative Form with Stormwater

Use sounds of water and different rhythms falling different height and materials

Emphasize water movement with waterfalls/pools

Modular Modular Modular Modular

Resides Above Roof System, Not Integral to It, Less Likely to Impact Warranty Pre-Grown Off-Site, Easy to Install, Provides Instant Visual Impact Module Dimensions Limit Root Mass and Available Moisture Reservoir Rigid Module Doesn’t Always Work with Curvelinear Design Concepts

Green Walls

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Below-Ground Modular Tank

Frees Up Programmable Space Reliable

No Evaporation Loss No Vector Breeding

Secure

Less Costly, Configurable to Odd Shapes, Requires More Pumping

Bio Bio Bio

Bio----Swale Swale Swale Swale

Potential Landscape Amenity Habitat Potential, Filtration Function Adds to Aquifer More Costly, Less Capacity Some Evapotranspiration Loss

Below-Grade Infiltration Chamber

Frees Up Programmable Space No Evaporation Loss Adds to Aquifer

More Costly

No Habitat, but No Vector Breeding Ground Either