david whyte - a comparison of 1d 2d modelling

7/29/2019 David Whyte - A Comparison of 1d 2d Modelling

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Comparing 1D and 2D modelling implications of outcomes for

development planning and appro

David WhyteSenior Engineer, Aurecon

Nina BarichProgram Leader, Develop Works,Waterways, Melbourne Water


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INTRODUCTION


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A brief discussion of some of the available 1D

flood modelling software Required data input, the model set-up and

assumptions

The importance of good data

Differences in defining flood model extents

Case Study comparison

Assessing impacts of development


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FLOOD MODELLING BASICS


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Flood

Hydrology model and a Hydraulic model

Catchment routing hydrology software

RORRAFTS, WBNM, URBS

1D hydraulic software HEC-RAS, MIKE-11, X

SWMM, DRAINS

2D and 1D-2D coupled hydraulic software M

(MIKE Flood), TUFLOW, XP-2D, SOBEK, RMA-


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Importance o

Models are an approximation. The more accurate th

the closer the simulation will be to representing rea

Common Issues

Inaccurate LiDAR/survey

Poor identification or definition of important

Lack of calibration data

Unknown dimensions for hydraulic structure

Lack of stage-storage information for dams


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Example of good and poor survey definition

Well defined

levee

Poorly d

embank

road

Well de

channe


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Comparing 1D, 2D and 1D-2D couple

1D models

well defined channel and floodplain

flow predictable and predominantly in one direction

2D models

complex interactions between main channel and floodplain

multi-directional and numerous flowpaths within the floodplai

1D-2D coupled models

allows a 1D representation of channels and pipes with a 2D mo

floodplain topography


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1D (left) and

(right)

Representat

Open Chann

(Source: USACE Enginee

River Hydraulics 1994)


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The choice of model will depend on:

The purpose of and desired outcome of the s The level of accuracy required

The available data

Available budget; and Available skills to use or interpret the softwa


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CASE STUDY


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C

Rural catchment in western

Melbourne

Several dams, grassed channels androad culverts

Catchment Area = 3.2km2

Hydrology Modelled using RORB

Hydraulics Modelled using HEC-RAS

Comparison Model using MIKE

FLOOD


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C

Catchment

Overview


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C

1D Model

Network


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C

88

114

88Br

Down stream

1119

1105

1081

1046

1020

958930 841

807777

721

672

635

547 407

381235

6030

Main

Stream 65

65

Up stream

2988

2932 2872 2812 27522633

2551

25142357

2306

2276

2238

22052169

21192076

202319511884

1855

MainS

tr

eam6565

Resevoir

0 50 100 150 200 250245

246

247

248

249

250

251

Station (m)

Elevation(m)

Legend

EGPF#1

WSPF#1

Crit PF#1

Ground

Bank Sta

.05 .05 .05

0 100 200 300235.2

235.4

235.6

235.8

236.0

236.2

236.4

236.6

236.8

Station (m)

Elevation(m)

.05 .05


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C

2D Model Grid


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C

1D Network -

2D Model Grid

Coupled


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C

1D Model

Flood Extents

Results


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C

1D 2D

Coupled

Model Flood

Extents


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C

Comparison

of FloodExtents

E l ti d l


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Evaluating developme

and/or flood mitigatio

1D alter a portion of the cross-section

2D

insert the footprint of the design in the

grid

Whether 1D or 2D - the ability to accurately

represent the development proposal will ulti

depend on the resolution of the model set-u

E l i d l


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Evaluating develop

and/or flood mitig

Example Development Area 1D Model Setup

114

88

Down stream

1119

1105

1081

1046

1020985

958

930

900870841

807777

753

721

700

672

635

578522441 407

38

0 200 400 232.4

232.6

232.8

233.0

233.2

233.4

233.6

233.8

234.0

Station (m)

Elevation(m)

.05 .05

Evaluating developm


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Evaluating developm

and/or flood mitigat

Larger 1D cross-section spacing 2D Model Setup


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CONCLUSION


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C

Good data is important

Choice of model must be fit for purpose Model set-up and resolution is importa

Future use of the model should be cons

Greater understanding leads to better

outcomes


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Question And Answer

david whyte - a comparison of 1d 2d modelling

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