MIKE 11Flood Plain ModellingFlood Plain Modelling

MIKE 11Flood Plain ModellingFlood Plain Modelling

Flood Plain Model OptionsFlood Plain Model Options:

• 1 - D :1 - D :- Lump River and Flood Plain as Single branch (Limitation: Same Water Levels in River and Flood Plain)

• Quasi 2-D:Quasi 2-D:- River and Flood Plain separate Flow Paths- Requires accurate and detailed Data- Relevant for:

Flood Mapping,Flood Plain Inundation and Drainage ModellingFlood Damage assessments

MIKE 11

(b) Low Lying Area Separated from Main River Channel by Levee

Depression

Leve

e

Flooding of low lying area adjacentto river prevented by levee. Howeverexchange of water between river anddepression occurs via spilling overthe levee bank. No flow takes placeparallel to the river.

Water surface is not horizontal across theriver and depression

(a) Low Lying Area Adjacent to Main River Channel

Low lying area adjacent to river is connected directlyto the main channel. Free exchange of water betweenriver and depression occurs, but no flow takes placeparallel to the river.

Water surface remains horizontal acrossthe river and depression

Depression

(c) Flood Plain Connected to Main River Channel

Flows take place in both main riverchannel and on floodplains, which areconnected directly to the river

Water surface remains horizontalacross the river and floodplains

One dimensional flood flows

MIKE 11

Floodplain separated frommain river channel by levee.Floodplain flow flow causedby overtopping of levees andlocal rainfall runoff

Spilling over levee onto floodplain

Drainage back into riverwhere levee discontinues

Levee

River

Floodplain

River

Levee

Floodplain separated frommain river channel by levee.Floodplain flow interrupted byroad embankment.

Spilling over leveeonto floodplain

Drainage back into riverwhere levee discontinues

Roa

d

High Ground

FloodplainFloodplain

(a) Unobstructed Flood Plain Flow Parallel toMain River Channel

(b) Obstructed Flood Plain Flow

Flow past road occurs viaculverts or by overtopping ofroad embankment

Two dimensional flood flows

MIKE 11

Do the spill areas conveysignificant flow discharges ?

Does the river spill? Flood plain model not needed

Are levees present ?

Are spill flows conveyed parallel to the river ?

Flood Cell with link channel

Are levees present ?

Additional Flooded

Area

Flood plain attached to

cross section

Is the flood plain flow frequentinterrupted by roads and other

flow obstructions?

Interlinked Flood Cells Routing Channels

1-D

Q 2-D

N

Y

N

N

N

N

Y

Y

Y

Y

Y

N

START

MIKE 11

RIVER MODEL 1D

RIVER CROSS-SECTIONS

Flood Plain ModellingFlood Plain Modelling

MIKE 11

SCHEMATIZATION (1 DIMENSION)

LOOPED RIVER NETWORK

TRIBUTARIES

Flood Plain ModellingFlood Plain Modelling

MIKE 11

SCHEMATIZATION OF FLOODPLAINS (QUASI 2D)

PARALLEL RIVERS

FLOODED AREAS

LINK CHANNELS

Flood Plain ModellingFlood Plain Modelling

MIKE 11Channel Center-LinesChannel Center-LinesSCHEMATIZATION (1 DIMENSION)

MIKE 11Non-Channel Flow AxesNon-Channel Flow AxesSCHEMATIZATION OF FLOODPLAINS (QUASI 2D)

MIKE 11Inundation Flow NetworkInundation Flow Network

MIKE 11Integrated Flood PlainIntegrated Flood Plain

MIKE 11Flood Plain Flood Plain SchematisationSchematisation

Flood Plain Description, definitions:

River Flood plain

River Flood plainRiver Flood plain

River Flood plain

?

FP2: Add. Storage

FP3: Part of Cross section FP4: Separated from River

FP1: Ignored

Linkchannel

MIKE 11Flood Plain SchematisationFlood Plain Schematisation

FP1 :

FP2 :

FP3 :

FP4 :

•

? ?

•

MIKE 11MIKE 11 Descriptions: MIKE 11 Descriptions: FP2 and FP3FP2 and FP3

FP2

Add. Storage area

in processed data

Processed data table

FP3

Relative Resistance in raw data

Raw data view

MIKE 11

Link2

Channel 1Channel

2Channel 3

Link Channels

(Network Tabular View)

River channel and floodplains modelled separately.

Link channels define flow exchange properties

Link1

MIKE 11 Descriptions: MIKE 11 Descriptions: FP4FP4

MIKE 11

River-Floodplain Flow ExchangeRiver-Floodplain Flow Exchange

U/S Bed Level

D/S Bed Level

U/S

Cha

inag

e

D/S

Cha

inag

e

Link Structure

Connection toRiver Branch

Connection toFloodplain Cellor Branch

Longitudinal Parameters of a Link Structure

River

Floodplain

Manning's Coefficient

MIKE 11Flood Plain InundationFlood Plain Inundation

Flood Plain Inundation, definitions:

No Flooding:FL1 : Local Rainfall FloodingFL2 : Flooding via KhalsFL3 : Flooding via Levees

River

Khal

High ground

No Flooding

FL3FL2FL1

MIKE 11Flood Plain DrainageFlood Plain Drainage

Flood Plain Drainage, definitions:

DR1 : Drainage via ChannelDR2 : Drainage via Levees

Flood PlainRiver

Levee

Flood PlainRiver

Channels

DR1

DR2

Flood Plain Inundation, definitions:

MIKE 11Storage calculated from Storage calculated from cross section widthcross section width

dx 1 dx 2

dx 1 /2 dx 2 /2

b1b2

b3

As =b2(dx 1/2+dx 2 /2)

MIKE 11User Defined StorageUser Defined Storage

b1b2

b3

As=calculated

MIKE 11Total Surface StorageTotal Surface Storage

Total surface storage =Storage width . dx + Add. Storage Area

MIKE 11Flooded AreaFlooded Area