Storm surges: Phenomena,

modelling and scenariosHans von Storch

Institute of Coastal ResearchHelmholtz-Zentrum Geesthacht

Germany

19-24 August, 2012 Mini-symposium "Mechanics of natural disasters" at the 23rd International Congress of Theoretical and Applied Mechanics, Beijing

Who is this?

Hans von Storch

Director of Institute for Coastal Research, Helmholtz Zentrum Geesthacht (HZG), near Hamburg,

Professor at the Meteorological Institute of Hamburg University

Works also with social and cultural scientists.

Overview

1. Storm surges – global phenomenon, with regional manifestation.

2. Physics of storm surges: The kid in the bathtub

3. The case of the German Bight

4. Modelling storm surges

5. Examples for attribution of causes for changing storm surge risk

Overview

1. Storm surges – global phenomenon, with regional manifestation.

2. Physics of storm surges: The kid in the bathtub

3. The case of the German Bight

4. Modelling storm surges

5. Examples for attribution of causes for changing storm surge risk

Midlatitude storms

The Netherlands and UK, 1953German Bight and Hamburg 1962Baltic Sea – Germany and Denmark, 1872

Storm Nargis, 2008Bhola, 1970

Bangladesh cyclone, 1991Katrina, 2005

Spatial distribution of storm surge risks according to Munich Re

Scientific Issuesa)Physics of storm surges

b)Prediction of storm surges

c)Coastal defense – new options

d)Disaster management – new options

e)Changing risks – Climate change and other factors

Overview

1. Storm surges – global phenomenon, with regional manifestation.

2. Physics of storm surges: The kid in the bathtub

3. The case of the German Bight

4. Modelling storm surges

5. Examples for attribution of causes for changing storm surge risk

Meteorological component of anomalous sea level(Storm, waves, seiches)

Regional sea levelOcean currents, filling of marginal seas (Baltic Sea),Regional affects of changing mass distributions

Global sea levelVolume of the ocean (thermal expansion, melting of ice sheets, glaciers etc.)

Graphics: Michael Schrenk

Graphics: Michael Schrenk

Graphics: Michael Schrenk

Graphics: Michael Schrenk

Graphics: Michael Schrenk

Coastal Defense: acceptable wave overtopping

Niemeyer & Kaiser 2008, NLWKN

presently accepted3% of all waves – Lower Saxony (Germany)2 l/(m∙s) – Schleswig-Holstein (Germany)0,1-1,0 l/(m∙s) – The Netherlands

Niemeyer & Kaiser 2008, NLWKN

Coastal Defense: acceptable wave overtopping

Tests with elevated wave overtopping in Delfzijl (The Netherlands)

• No damages at the grass surface with overtopping of up zo 50 l/(m s)∙

• Functionality maintained even in case of pre-set surface damages up to 50 l(m s)∙

Cascading flood compartmentsExample Hamburg

Erik Pasche, TU HH

Cascading flood compartmentsExample Hamburg

Erik Pasche, TU HH

Cascading flood compartmentsExample Hamburg

Erik Pasche, TU HH

Overview

1. Storm surges – global phenomenon, with regional manifestation.

2. Physics of storm surges: The kid in the bathtub

3. The case of the German Bight

4. Modelling storm surges

5. Examples for attribution of causes for changing storm surge risk

Albrecht et al., 2010

[m]Increase of sea level in the German Bight

Temporal development of intra-seasonal 99%ile of high tide levels AFTER subtraction of annual mean high tide

and mean annual high tide

in Cuxhaven (Germany)

until 2005.

Case of German Bight

Overview

1. Storm surges – global phenomenon, with regional manifestation.

2. Physics of storm surges: The kid in the bathtub

3. The case of the German Bight

4. Modelling storm surges

5. The case of Hamburg – assessment and options

Tidal modelling: hydraulic vs. numerical

1

shallow water equation of vertically averaged movement

von Storch, H., 2001: Models. In: H. von Storch and G. Flöser (Eds): Models in Environmental Research. Springer Verlag, 17-33

Aspelien, T., 2006: The use of long-term observations in combination with modelling and their effect on the estimation of the North Sea storm surge climate. PhD thesis, Hamburg, 106pp

Operational modelling by assimilation of „upstream“ data Trygve Aspelien, pers. comm

Trygve Aspelien, pers. comm

Trygve Aspelien, pers. comm

Inter-annual variability (1958-2001)Cuxhaven

After nudging:

• Better reproduced inter-annual variability

• Linear long-term trends are closer to the observed trends

Black curve: observed values

Blue curve: Aberdeen nudged (ABE)

Red curve: Control experiment (CTL)

• Improvement from CTL in the percentiles (1,5,10,90,95,99) of surge when Aberdeen is nudged (Brier skill score):

Cuxhaven: 58-80%

Borkum: 10-76%

Trygve Aspelien, pers. comm

Overview

1. Storm surges – global phenomenon, with regional manifestation.

2. Physics of storm surges: The kid in the bathtub

3. The case of the German Bight

4. Modelling storm surges

5. Examples for attribution of causes for changing storm surge risk

http://www.loicz.org/imperia/md/content/loicz/stormsurges/15_syvitski.pdf

Hamburg – storm surges

Difference of water level maxima at the mouth of the estuary (Cuxhaven) and in Hamburg (St. Pauli)

Scenarios 2030, 2085

Only the effect of anthropogenic climate change (A2, B2)

- No effect of water works.

Conclusions• Storm surges are a serious issue• Storm surges are an interesting issue.• Storm surges is a global phenomenon but usually considered

on a regional or even local scale.• Issues relate to the phenomenon, prediction, risk

management, disaster management and dealing with changing conditions

• The phenomenon allows for efficient description (risk statistics, forecast) by numerical modeling

• Risks are changing due to geophysical conditions (sea level, wind statistics), delta sinking (resource extraction) and water works (dredging shipping lanes, coastal protection)

• Storm surges is a societal issue, which needs transdis-ciplinary attention.

Hans von Storchhvonstorch@web.de