Transcript Flood Plain Inundation

Flood Plain Modelling
MIKE 11
Flood Plain Modelling
MIKE 11
Flood Plain Model Options:
•1-D:
- Lump River and Flood Plain as Single branch
(Limitation: Same Water Levels in River and Flood Plain)
• Quasi 2-D:
- River and Flood Plain separate Flow Paths
- Requires accurate and detailed Data
- Relevant for:
Flood Mapping,
Flood Plain Inundation and Drainage Modelling
Flood Damage assessments
(a) Low Lying Area Adj acent to Main Riv er Channel
Wa ter surfa ce rema in s h orizon ta l a cross
the river a nd d ep ression
Depression
Lo w lying a rea a djacen t to river is co nn ected d irectly
to the main chan nel. Free exchan ge of water between
river an d depressio n occu rs, b ut no flow takes place
pa ra llel to the river.
(b) Low Lying Area Separated from Main Riv er Channel by Lev ee
Wa ter surfa ce is no t ho rizonta l across the
river an d depressio n
e
Depression
Leve
One
dimensional
flood flows
Flo odin g of lo w lying a rea a djacen t
to river preven ted b y levee. However
excha nge of water between river an d
depressio n o ccurs via spillin g over
the levee b an k. No flo w takes p lace
pa ra llel to the river.
(c) Flood Plain Connected to Main Riv er Channel
Wa ter surfa ce rema in s h orizon ta l
across the river a nd flood plain s
Flo ws take p la ce in both main river
chan nel a nd o n flo od plains, which are
conn ected d irectly to the river
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(a) Unobs tructe d Flood Plain Flow Paralle l to
M ain Rive r Channe l
Drainage back into river
where levee discontinues
Rive r
Le ve e
Spilling over levee onto floodplain
Floodplain separated from
main river channel by levee.
Floodplain flow flow caused
by overtopping of levees and
local rainfall runoff
(b) Obs tructed Flood Plain Flow
High Ground
Drainage back into river
where levee discontinues
Rive r
Spilling over levee
onto floodplain
Floodplain
Floodplain separated from
main river channel by levee.
Floodplain flow interrupted by
road embankment.
Road
Two
dimensional
flood flows
Floodplain
Le ve e
Floodplain
Flow past road occurs via
culverts or by overtopping of
road embankment
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START
N
Does the river spill?
Flood plain model not needed
Y
N
Do the spill areas convey
significant flow discharges ?
Are levees present ?
Y
Y
Flood Cell with
link channel
Are spill flows conveyed
parallel to the river ?
N
Y
Are levees present ?
N
Flood plain
attached to
cross section
N
Additional
Flooded
Area
1-D
Y
Is the flood plain flow frequent
interrupted by roads and other
flow obstructions?
Y
Q 2-D
Interlinked Flood Cells
N
Routing Channels
Flood Plain Modelling
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RIVER MODEL 1D
RIVER CROSS-SECTIONS
Flood Plain Modelling
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SCHEMATIZATION (1 DIMENSION)
LOOPED RIVER
NETWORK
TRIBUTARIES
Flood Plain Modelling
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SCHEMATIZATION OF FLOODPLAINS (QUASI 2D)
PARALLEL RIVERS
FLOODED AREAS
LINK
CHANNELS
Channel Center-Lines
SCHEMATIZATION (1 DIMENSION)
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Non-Channel Flow Axes
SCHEMATIZATION OF FLOODPLAINS (QUASI 2D)
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Inundation Flow Network
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Integrated Flood Plain
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Flood Plain Schematisation
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Flood Plain Description, definitions:
FP1: Ignored
River
FP2: Add. Storage
Flood plain
?
FP3: Part of Cross section
River
Flood plain
River
Flood plain
FP4: Separated from River
River
Flood plain
Link
channel
Flood Plain Schematisation
FP1 :
FP2 :
FP3 :
FP4 :
?
?
•
•
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MIKE 11 Descriptions:
FP2 and FP3
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FP2
Add. Storage area
in processed data
Raw data view
Processed data table
FP3
Relative Resistance
in raw data
MIKE 11 Descriptions: FP4
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River channel and floodplains
modelled separately.
Link channels define flow
exchange properties
Channel 1
Channel 2
Channel 3
Link1
Link Channels
(Network Tabular View)
Link2
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River-Floodplain Flow Exchange
Floodplain
D/S Chainage
Connection to
River Branch
Connection to
Floodplain Cell
or Branch
U/S Chainage
D/S Bed Level
U/S Bed Level
River
Longitudinal Parameters of a Link Structure
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Flood Plain Inundation
High ground
Flood Plain Inundation, definitions:
Khal
No Flooding:
FL1 : Local Rainfall Flooding
FL2 : Flooding via Khals
FL3 : Flooding via Levees
FL1
River
No Flooding
FL2
FL3
Flood Plain Drainage
Flood Plain Inundation,
Drainage, definitions:
definitions:
DR1 : Drainage via Channel
DR2 : Drainage via Levees
River
Flood Plain
Channels
DR1
Flood Plain
River
Levee
DR2
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Storage calculated from
cross section width
dx 1/2
dx 2/2
b2
b1
b3
As=b 2(dx 1/2+dx 2/2)
dx 1
dx2
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User Defined Storage
b1
b2
As=calculated
b3
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Total Surface Storage
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Total surface storage =Storage width . dx + Add. Storage Area
Flooded Area
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