damping of tsunami and storm waves by ......parameterization based on easily measurable/observable...
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Leichtweiß-Institute für Wasserbau (LWI)
Abteilung Hydromechanik und KüsteningenieurwesenTechnische Universität Braunschweig
DAMPING OF TSUNAMI AND STORM WAVES BY COASTAL FORESTS –
PARAMETERIZATION AND HYDRAULIC MODEL TESTS
S. Reimann
S. Husrin
A. Strusińska
H. Oumeraci
FZK Kolloquium, Hannover, 26. March 2009
FZK Kolloquium, Hannover, 26. March 2009S. Reimann
2. Parameterization of mangroves
3. Laboratory experiments on hydrodynamic performance of mangrove forest
1. Motivation and objectives
4. Outlook
POSITION OF THE PROBLEM
1. Motivation and objectives FZK Kolloquium, Hannover, 26. March 2009S. Reimann
MULTI DEFENCE LINE STRATEGY (Oumeraci, 2006)
> 500 m ?
250 - 500 m ?
Damped
TsunamiHWL
MWLLWL
1
2 45
Artificial reefs
Sea wallsDunes
Raised buildings
Mobile defence systems
FOREST
50 - 100 m ?
Tsunami resistant Building
• Damping performance of forest• Structural integrity of single tree
3
OBJECTIVES
1. Motivation and objectives FZK Kolloquium, Hannover, 26. March 2009S. Reimann
Generate knowledge base for better insight into physical processes involved in interaction of tsunami/storm waves with coastal forests, incl. subsequent energy attenuation
Develop generic methodology for coastal forest parameterization based on easily measurable/observable parameters
Develop and validate/verify prediction models (analytical/ numerical, semi-empirical) for hydraulic performance of coastal forests as a protection against tsunami/storm waves.
FZK Kolloquium, Hannover, 26. March 2009S. Reimann
2. Parameterization of mangroves
3. Laboratory experiments on hydrodynamic performance of mangrove forest
1. Motivation and objectives
4. Outlook
REAL MANGROVE TREE AND ITS DIMENSIONS
2. Parameterization of mangroves FZK Kolloquium, Hannover, 26. March 2009S. Reimann
after Dinar et al. (2004)
bB = 3.0 - 3.2 m
hB = 3.5 - 4.0 m
hTR = 0.5 - 1.0 m
hR = 1.3 - 1.5 m
Ø root = 4 - 6 cm
Ø trunk = 12 - 18 cmMHWL
Rhizophora sp.
density of trunks = 0.8 - 1.0 trunks/m²number of prop roots = 72 - 152 roots/trunk
hM = 5.0 - 5.5 m
Ø branch = 5 - 6 cm
PARAMETERIZATION OF MANGROVE TREE
Reference Model Parameterised Models
Model Scale 1 : 20
2. Parameterization of mangroves FZK Kolloquium, Hannover, 26. March 2009S. Reimann
SELECTED RESULTS OF PARAMETERIZATION TESTS
2. Parameterization of mangroves FZK Kolloquium, Hannover, 26. March 2009S. Reimann
FZK Kolloquium, Hannover, 26. March 2009S. Reimann
2. Parameterization of mangroves
3. Laboratory experiments on hydrodynamic performance of mangrove forest
1. Motivation and objectives
4. Outlook
EXEMPLARY MODEL SET-UP FOR FOREST WIDTH B=0.75m (1)
h=0.415m
10.0m
WG1
WG2
WG3
WG4
23.64m
13.64m 8.33m
8.33m
2.01m B=0.75m
WAVE
MAKER WG5
ARRAY1
SWL
PLATFORM
Bf=
2.0
m
WA
VE
MA
KE
R
ADV1 ADV2
WG6
WG7
WG8
WG9
WG10
WG11
WG12
ARRAY2 ARRAY3
FOREST
WG13 WG14 WG15
WG16
WG17
WG18
WG19
PLATFORM
GLAS WINDOW
~1:20
WG1
WG2
WG3
WG4
WG5
WG6
WG7
WG8
WG9
WG10
WG11
WG12
WG16
WG17 WG19
WG13 WG14 WG15
P1 P2
WG18
PT1 PT2
WA
VE
MA
KE
R
Bf=
1.0
m
~1:20PLATFORM
WG8
WG9 WG11
WG10P2PT2WG1
WG2
WG3
WG4
FT
FT
10.0m 0.40m
0.755m
1.095m 0.40m 1.08m 0.42m 1.08m
0.775m 0.76m
1.03m0.375m0.375m0.495m
0.5m
0.495m
0.539m
FOREST
WG6 WG7
PT1
WG5
P1
?m 8.33m
1.0m
hr=0.415m
ARRAY4
ADV1
3. Laboratory experiments on hydrodynamic performance of mangrove forest FZK Kolloquium, Hannover, 26. March 2009S. Reimann
TREE NUMBER: N=62
SIZE OF SINGLE TREE MODEL: 15x15cm
FOREST WIDTH: B=0.75mT
2
FTS7
FTS4 FTS5 FTS6
FTS1 FTS2 FTS3
Bf=
2.0
m
1.9
5m
1.8
m
B=0.75m
~1:20
2.0m
BE
AC
H S
LO
PE
PT2PT1
DIRECTION OF WAVE
PROPAGATION
FTS8 FTS9
P1 P2
ADV2ADV1
WG13WG14
WG15
Measuring devices:
Wave gauge
Propeller
Acoustic Doppler Velocimeter (ADV)
Pressure Transducer
Force Transducer for single tree
WG
P
ADV
PT
FTS
ARRANGEMENT OF TREE MODELS AND INSTRUMENTATION
3. Laboratory experiments on hydrodynamic performance of mangrove forest FZK Kolloquium, Hannover, 26. March 2009S. Reimann
3. Laboratory experiments on hydrodynamic performance of mangrove forest FZK Kolloquium, Hannover, 26. March 2009S. Reimann
EXEMPLARY MODEL SET-UP FOR FOREST WIDTH B=0.75m (2)
1. STAGE: Mangrove Forest
• MODEL SCALE: 1:25
• MODEL STIFFNESS: MANGROVE FOREST - stiff tree models (submergence depth up to canopy)
MANGROVE & PINE FOREST - stiff/flexible tree models (submergence depth up to canopy)
• FOREST WIDTH: B=0.0, 0.75, 1.5, 2.25, 3.0 … m
• WATER DEPTH: h=0.415, 0.465, 0.515, 0.565, 0.615m
• WAVE TYPES: storm waves (regular and irregular waves), tsunami (solitary waves and bore)
• WAVE PARAMETERS: wave height H=0.04-0.20m; wave period T=1.0-6.0s
2. STAGE: Pine Forest
3. Laboratory experiments on hydrodynamic performance of mangrove forest FZK Kolloquium, Hannover, 26. March 2009S. Reimann
EXPERIMENTAL PROGRAMME
MEASUREMENTS OF FORCE TRANSDUCERS FOR A SINGLE TREE (FTS)
3. Laboratory experiments on hydrodynamic performance of mangrove forest FZK Kolloquium, Hannover, 26. March 2009S. Reimann
REGULAR WAVES:
h=0.565m, H=0.04m, T=1.0s
FTS2
FTS1 (in front of forest)
FTS2 (in the middle of forest)
FTS1
MEASUREMENTS OF FORCE TRANSDUCER FOR ENTIRE FOREST (FT)
3. Laboratory experiments on hydrodynamic performance of mangrove forest FZK Kolloquium, Hannover, 26. March 2009S. Reimann
REGULAR WAVES:
h=0.565m, H=0.04m, T=1.0s
FT
MEASUREMENTS OF WAVE GAUGES (WG)
3. Laboratory experiments on hydrodynamic performance of mangrove forest FZK Kolloquium, Hannover, 26. March 2009S. Reimann
REGULAR WAVES:
h=0.565m, H=0.04m, T=1.0s
WG12 (in front of forest)
WG19 (behind forest)
WG19WG12
FZK Kolloquium, Hannover, 26. March 2009S. Reimann
2. Parameterization of mangroves
3. Laboratory experiments on hydrodynamic performance of mangrove forest
1. Motivation and objectives
4. Outlook
4. Outlook FZK Kolloquium, Hannover, 26. März 2009S. Reimann
Preparation of equipments required for performance of the experiments (e.g. coastal pine models, gate for a bore generation in twin wave flumes)
performance of laboratory experiments on mangrove effectiveness on wave energy reduction for varying water depths and wave conditions
performance of laboratory experiments on Casuarina effectiveness on wave energy reduction for varying water depths and wave conditions
determination of hydraulic performance of both types of forest (wave transmission, reflection and energy dissipation)
Use of experimental results for the development of numerical model
THANK YOU FOR YOUR ATTENTION !
FZK Kolloquium, Hannover, 26. März 2009S. Reimann
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