Modelling of Urban Drainage and Wastewater Collection systems

8/10/2019 Modelling of Urban Drainage and Wastewater Collection systems

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Modelling of urban drainage andwastewater collection systems

by

Berislav Tomicic, MSc.

Ole Mark, PhD., MSc.

DHI Water Environment Health

And now Birgitte Lilholt Srensen


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Approach to learning ?

To make it efficient / easy but

You learn by doing (no pain no gain !) I expect questions I expect self-learning


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WHAT IS YOUR EXPERIENCE WITH

MODELS ?


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WHAT DO YOU EXPECT TO GET FROM

THIS COURSE ?


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WHAT WILL YOU LEARN ?

To understand, identify and solve problems within

urban drainage and wastewater

To choose and apply urban drainage models

Good modelling practice

Esmaeil will teach the numerical mathematics


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COURSE PROGRAMME

Dynamic modelling of sewage transport

Rationale: To provide applied knowledge of hydrology and hydraulics toprincipal of design, function, planning and management of stormwater drainagein urban area.

Catalogue Description: Weather and hydrology, element of urban stormwaterrunoff, stormwater facilities and detention/retention, computer models in urbandrainage, planning and management.

Course Outline:I IntroductionII Weather and Hydrology

1.Hydrologic cycle in urban area

2.Rainfall and runoff relationship3.Infiltration and groundwater flowIII Element of Urban Stormwater Runoff

Design storms Rainfall excess

Design storm frequency Design duration and distribution


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COURSE PROGRAMME

2. Dry weather flow

Wastewater Self cleaning of pipes Hydraulic capacity

3. Overland flow Hydrographs

Effect of infiltration4. Hydraulics of channel flow

Flow routing Hydraulic Capacity

Backwater (tidal) effects from rivers and seas


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Mathematical Modelling, e.g. a River

PHYSICAL SYSTEM

River Network

Flood Plains

Structures

PHYSICAL LAWS

Conservation of MassConservation of

Momentum

SCHEMATIZE

Represent by a simpleEquivalent System

DISCRETIZE

Express as e.g. a FiniteDifference Relation

NUMERICAL MODELBOUNDARIES OUTPUTS


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Mathematical Modeling

Any computer program for mathematical

modeling of unsteady flow is based onfundamental elements like:

A differential relationship expressing thephysical laws

A numerical scheme (e.g. finite difference)

producing a system of algebraic equations

An algorithm to solve these equations


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Urban Flooding Problems MIKE FLOOD


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Street

Infiltration to soil

Street

Runoff ~ 100%

Catchment

Runoff


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Sewer and roads modelled

simultaneously in 1D


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Areas next to the road are

included

h

Figure : 2 layers with surface storage model


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Red:Observed flooded

Computed and observed flood map for Dhaka, 1996


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Flood Indundation Maps & Applications


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Bangkok April 2002


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The flood mitigation cycle

1. Prepardness forPrevention and

mitigation

3. Emergency

response

4. Recovery and

rehabilitation

DisasterImpact

Before

impact

During

impact

After

impact

2. Flood warning


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The Bangkok model, 2001


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In the past the modelwas a copy of the sewer

system.


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Initial elevation grid

Grid with streets

Final grid with streets

and buildings

Lowering by 20 cm places

where there are streets

Raising by 5 m places

where there are buildings

Today, the model is a copy of the city


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Results from Bangkok


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How can computer

models help us ?


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To understand the

reasons for the present

situation and ...


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To test a new design

before it is implemented...


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To test -

What happens if...


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Argentina - sometime around 1990


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T

P

Sewers /Klongs

Sea

TreatmentPlant

Part of the Solution

1

1.2

1.4

1.6

1.8

2

2.2

2.4

14.30 14.50 14.70 14.90 15.10 15.30

Time (decimal day)

Wate

rLevel(m)River

Integrated

Modelling


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TP

MIKE 11/21

WEST

Integrated Modelling

MOUSE

MIKE SHE


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1. Evaluate the waterquality at the beach

2. Estimate the

improvements fromthe new WWTP

The Challenge at Pattaya

Pattaya Beach


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CSO into the river


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A mix of sewage and rain is pumped onto the

beach !


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A recreational place


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Pattaya, Thailand 2001


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The Model of Pattaya Beach

1. Model of the sewers

2. Model of the bay


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Lisbon Harbour, Portugal - Summer 1999


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Danger level

Warning level

24-hour water level forecasts at Bhadrachalam


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Yangtze flood, August 1998

250 mill people affected

2500 dead5 bill. $ damages

Juijiang main street


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What is ?

Urban drainage model for pipe flow and surface flow

MOUSE TRAP - Water Quality & Sediment Transport

MOUSE RTC - Real Time Control

MIKE URBAN - Data management and resultpresentation

MOUSE


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MOUSE - Part of a Family

MIKE 11 and MIKE 21 for modelling of thequality of the receiving waters

MIKE SHE for modelling of surface water /groundwater / sewer system interaction

MIKE 21 for modelling of 2D flows in

flooded urban areas

WEST for modelling of sewage treatment

facilities


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MOUSE Classic


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The ICS model for Barcelona, Spain

MOUSE MIKE URBAN


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MOUSE - Modelling ofUrban Sewers

Water Quality

Sediment Transport

Hydrodynamic

Rainfall-Runoff

Advection-Dispersion


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SUMMARY Models are approximations!

Models are never 100% correct replications of nature,but they may not be wrong or better: they may beright for the purpose!

Calibration requires understanding, systematicapproach and reliable data

Its not magic - just do it!

Th C lib i P


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Disturbances

Minimise

Disturbances

Input Catchment Data

Physical

System Model

Recorded Output Model OutputError

Differences

Statistical MeasuresParameter

Adjustment

The Calibration Process

Make a simple runoff model of


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Make a simple runoff model of

Faculty of Engineering

Copyright: COWI


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Definition of a Rainfall Runoff Model forFaculty of Engineering

1. Which data do you need ?

2. Which physical equations have you got ?

3. How do you want to solve the equations ?


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The Kinematic Wave Model

V = flow velocity (m/s)

M = The Manning Number (m1/3/s)

R = Hydraulic Radius (m)

I = Slope

R = Flow area/wetted perimeter Water depth

IRMV 2/3


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AVQ

IYWMQ 5/3

Q = (m3/s)

M = The Manning Number (m1/3/s)

Y = Water depth

W = The flow width = the width catchment

I = Slope


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Pros: Fast & Easy Widely applied - sooner or later you will meet this

model Applied for simple river modelling Also applicable for 2-D surface runoff modelling

Cons: No hydrological memory No Back water i.e. no flooding....

IRMV 2/3

Exercise: Kinematic Rainfall Runoff Model


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Exercise: Kinematic Rainfall Runoff Model

If possible, calibrate the model by changing: Manning no. Slope

Catchment Width Reduction factor

Answer the questions:1. Do you consider you model calibrated ?2. Explain your answer above.

Modelling of Urban Drainage and Wastewater Collection systems

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