EUROPEAN COMMISSION
WG F Thematic Workshop on Implementation of the Floods Directive 2007/60/EC
“FLASH FLOODS AND PLUVIAL FLOODING”
26th – 28th May 2010, Cagliari, Italy
PLUVIAL FLOODS
FLOOD RISK ASSESSMEN
C. Leeb(1), M. Moser(2) *
(1) Bavarian State Ministry of the Environment and Public Health
Rivers and Lakes
(2) Regierungspräsidium Stuttgart
Abstract
The methodology described in the following is the result of a workshop
held in Karlsruhe on the 12th April 2010. The workshop was participated
by representatives of German
and other institutions involved in the implementation of the European
Floods Directive (EG - FD).
In the south of Germany
local intense rainfall of convective cells
The following part describes
considering those having occurred in the past and an estimation
impacts have to be expected for
conclusion is arrived, that floodings of
precipitation are not significant in the sense of EG
* Corresponding authors:
Christian Leeb – Bavarian State Ministry of the Environment and Public Health
and Lakes
Rosenkavalierplatz 2, 81925 München
E-mail: [email protected]
Markus Moser – Regierungspräsidium Stuttgart
Ruppmannstr. 21, 70565 Stuttgart
E-mail: [email protected]
EUROPEAN COMMISSION – WFD COMMON IMPLEMENTATION STRATEGY
WG F Thematic Workshop on Implementation of the Floods Directive 2007/60/EC
“FLASH FLOODS AND PLUVIAL FLOODING”
May 2010, Cagliari, Italy
PLUVIAL FLOODS – CRITERIA FOR THE PRE
FLOOD RISK ASSESSMENT IN THE SOUTH OF GE
Bavarian State Ministry of the Environment and Public Health - Unit 55
Regierungspräsidium Stuttgart
The methodology described in the following is the result of a workshop
held in Karlsruhe on the 12th April 2010. The workshop was participated
German and Swiss authorities, science, engineering
institutions involved in the implementation of the European
FD).
In the south of Germany pluvial flood incidents are caused
of convective cells.
part describes criteria for the assessment of
having occurred in the past and an estimation
impacts have to be expected for similar events in the future. The
conclusion is arrived, that floodings of surface runoff, due to intense
precipitation are not significant in the sense of EG-FD.
Bavarian State Ministry of the Environment and Public Health - Unit 55
Rosenkavalierplatz 2, 81925 München, Germany
Regierungspräsidium Stuttgart
Ruppmannstr. 21, 70565 Stuttgart, Germany
1 WG F Thematic Workshop on Implementation of the Floods Directive 2007/60/EC
CRITERIA FOR THE PRELIMINARY
T IN THE SOUTH OF GERMANY
Unit 55 - State owned
The methodology described in the following is the result of a workshop
held in Karlsruhe on the 12th April 2010. The workshop was participated
and Swiss authorities, science, engineering
institutions involved in the implementation of the European
caused typically by
of pluvial floods,
having occurred in the past and an estimation if such
similar events in the future. The
surface runoff, due to intense
Unit 55 - State owned Rivers
EUROPEAN COMMISSION
WG F Thematic Workshop on Implementation of the Floods Directive 2007/60/EC
“FLASH FLOODS AND PLUVIAL FLOODING”
26th – 28th May 2010, Cagliari, Italy
1 Introduction
The aim of the EG-FD
human health, the environment, cultural heritage and economic activity
associated with floods. Therefore, all types of floods should be taken into
consideration. Besides floodings along surface water bodies
appearing those caused by surface runoff due to
In the context of the preliminary flood risk assessment, according to
articles 4 and 5 of the EFD, available information on pluvial floods is
analysed for mapping the areas
run-off where appropriate.
2 Surrounding conditions in the south of Germany
Flood incidents are natural appearances having different causes and
characteristics, especially hydro
The south of Germany is located in temperate climate zone, having a
moderate-warm rain climate.
and moderate hot summers.
which provide intense
precipitation cells are at small scale
square-kilometres. They can occur anywhere in the south of Germany
which makes it not possible to map areas with a significant flood risk
For those torrential precipitation incidents in the south of Germany, which
have caused appreciable impacts, where gauged precipitation heights of
240 mm within three hours
mentioned in the statistical convective precipitation analysi
the German state weather service (DWD).
considered as an extreme incident with a very low occurrence probability.
The relief of the south of Germany is highly structured and shaped by the
low mountain ranges, covered of woodlands in a high percentage.
8 % of the territories are sealed.
EUROPEAN COMMISSION – WFD COMMON IMPLEMENTATION STRATEGY
WG F Thematic Workshop on Implementation of the Floods Directive 2007/60/EC
“FLASH FLOODS AND PLUVIAL FLOODING”
May 2010, Cagliari, Italy
is the reduction of the adverse consequences for
human health, the environment, cultural heritage and economic activity
associated with floods. Therefore, all types of floods should be taken into
consideration. Besides floodings along surface water bodies
appearing those caused by surface runoff due to intense rainfall.
In the context of the preliminary flood risk assessment, according to
articles 4 and 5 of the EFD, available information on pluvial floods is
analysed for mapping the areas with a significant flood risk by surface
off where appropriate.
urrounding conditions in the south of Germany
Flood incidents are natural appearances having different causes and
, especially hydro-meteorological and geomorphologic ones
The south of Germany is located in temperate climate zone, having a
warm rain climate. The oceanic influence provides mild winters
and moderate hot summers. In the warm season, convective cells occur,
intense precipitation of large height. These convective
precipitation cells are at small scale – in most cases less than a few
kilometres. They can occur anywhere in the south of Germany
not possible to map areas with a significant flood risk
ial precipitation incidents in the south of Germany, which
have caused appreciable impacts, where gauged precipitation heights of
240 mm within three hours or less. These values exceed far those
statistical convective precipitation analysi
the German state weather service (DWD). For this reason, they have to be
extreme incident with a very low occurrence probability.
The relief of the south of Germany is highly structured and shaped by the
covered of woodlands in a high percentage.
8 % of the territories are sealed. Water storage capacity in the area can
2 WG F Thematic Workshop on Implementation of the Floods Directive 2007/60/EC
is the reduction of the adverse consequences for
human health, the environment, cultural heritage and economic activity
associated with floods. Therefore, all types of floods should be taken into
consideration. Besides floodings along surface water bodies, there are also
rainfall.
In the context of the preliminary flood risk assessment, according to
articles 4 and 5 of the EFD, available information on pluvial floods is
with a significant flood risk by surface
Flood incidents are natural appearances having different causes and
meteorological and geomorphologic ones.
The south of Germany is located in temperate climate zone, having a
provides mild winters
In the warm season, convective cells occur,
These convective
in most cases less than a few
kilometres. They can occur anywhere in the south of Germany,
not possible to map areas with a significant flood risk.
ial precipitation incidents in the south of Germany, which
have caused appreciable impacts, where gauged precipitation heights of
These values exceed far those
statistical convective precipitation analysis (KOSTRA) of
they have to be
extreme incident with a very low occurrence probability.
The relief of the south of Germany is highly structured and shaped by the
covered of woodlands in a high percentage. Only 5-
Water storage capacity in the area can
EUROPEAN COMMISSION
WG F Thematic Workshop on Implementation of the Floods Directive 2007/60/EC
“FLASH FLOODS AND PLUVIAL FLOODING”
26th – 28th May 2010, Cagliari, Italy
be considered as high, according to the rank vegetation and the
abundantly covered soil. Due to the highly structured relief and the
ramified water distribution network the drainage capability can be
regarded as convenient. During torrential rainfall, the surface runoff can
easily reach the next water body within a short range. Therewith the sub
basins to survey in the context o
This also means, that accumulations of surface runoff have only little
adverse impact.
3 Summary of previous incidents
Within the research project “Forecasting and management of pluvial floods
in urban areas (URBAS)” previous pluvial flood incidents in Germany have
been analysed. The database of URBAS contains 422 incidents within a
period of rather 30 years. The given sum
uncertain estimations, mixing different kinds of damages. Mainly, there
are documented singular incidents with relatively high damage sums, with
an average of 160 million
such torrential rainfalls are located in very small areas. Often only a
district of a municipality is affected.
reactions of areas due to convective precipitation with short durations and
large precipitation heights respectively i
ramified water distribution network and the relatively small sub basins,
precipitation incidents of middle (return period 100 years) or high (return
period 10 years) occurrence probability do not cause noteworthy
damages. Only extreme incidents cause higher damages.
4 Assessment of future flood incidents in Baden
In addition to Bavaria and Rhineland
incidents of pluvial were surveyed, Baden
analysis for the assessment of future incidents. The model is based
EUROPEAN COMMISSION – WFD COMMON IMPLEMENTATION STRATEGY
WG F Thematic Workshop on Implementation of the Floods Directive 2007/60/EC
“FLASH FLOODS AND PLUVIAL FLOODING”
May 2010, Cagliari, Italy
be considered as high, according to the rank vegetation and the
abundantly covered soil. Due to the highly structured relief and the
ramified water distribution network the drainage capability can be
regarded as convenient. During torrential rainfall, the surface runoff can
easily reach the next water body within a short range. Therewith the sub
basins to survey in the context of surface runoff are comparatively small.
This also means, that accumulations of surface runoff have only little
Summary of previous incidents
Within the research project “Forecasting and management of pluvial floods
in urban areas (URBAS)” previous pluvial flood incidents in Germany have
The database of URBAS contains 422 incidents within a
period of rather 30 years. The given sums for the adverse impacts base on
uncertain estimations, mixing different kinds of damages. Mainly, there
are documented singular incidents with relatively high damage sums, with
an average of 160 million € per year in Germany. Almost all damages of
orrential rainfalls are located in very small areas. Often only a
district of a municipality is affected. Pluvial floods are hydrological
reactions of areas due to convective precipitation with short durations and
large precipitation heights respectively intensities. According to the widely
ramified water distribution network and the relatively small sub basins,
precipitation incidents of middle (return period 100 years) or high (return
period 10 years) occurrence probability do not cause noteworthy
. Only extreme incidents cause higher damages.
Assessment of future flood incidents in Baden-Württemberg
In addition to Bavaria and Rhineland-Palatinate, where only previous
incidents of pluvial were surveyed, Baden-Württemberg has done a further
for the assessment of future incidents. The model is based
3 WG F Thematic Workshop on Implementation of the Floods Directive 2007/60/EC
be considered as high, according to the rank vegetation and the
abundantly covered soil. Due to the highly structured relief and the widely
ramified water distribution network the drainage capability can be
regarded as convenient. During torrential rainfall, the surface runoff can
easily reach the next water body within a short range. Therewith the sub-
f surface runoff are comparatively small.
This also means, that accumulations of surface runoff have only little
Within the research project “Forecasting and management of pluvial floods
in urban areas (URBAS)” previous pluvial flood incidents in Germany have
The database of URBAS contains 422 incidents within a
s for the adverse impacts base on
uncertain estimations, mixing different kinds of damages. Mainly, there
are documented singular incidents with relatively high damage sums, with
Almost all damages of
orrential rainfalls are located in very small areas. Often only a
Pluvial floods are hydrological
reactions of areas due to convective precipitation with short durations and
ntensities. According to the widely
ramified water distribution network and the relatively small sub basins,
precipitation incidents of middle (return period 100 years) or high (return
period 10 years) occurrence probability do not cause noteworthy
Württemberg
Palatinate, where only previous
Württemberg has done a further
for the assessment of future incidents. The model is based
EUROPEAN COMMISSION
WG F Thematic Workshop on Implementation of the Floods Directive 2007/60/EC
“FLASH FLOODS AND PLUVIAL FLOODING”
26th – 28th May 2010, Cagliari, Italy
available data for soil, geologie, topography and soil
surface runoff and infiltration by using physical equations.
The essential results of this analysis are:
- In slope areas the water depths of surface runoff are less then 5 cm.
- The duration of surface runoff is very short.
- Floodings with depths more than 50 cm appear only in the flood plains
in the bottom of the valley; due to fluvial floods.
- Asserted damages in slope areas
alluvial sedimentation.
5 Assessment of the potential significant flood risk
As described above, intense rainfall appears at small scale and does only
activate appreciable surface runoff at incidents with a return perio
considerable over 100 years. Such events can occur anywhere in the
south of Germany, so that areas with a significant higher risk can not be
identified. Previous incidents have shown, that adverse impacts to the EG
FD subjects of protection occur only in
In Germany, the assessment of the significance of flood risks, is also
linked to the public interest in flood protection infrastructure. Measures of
public interest are required, where human lives or health are affected in a
larger number or economic activities are impacted in a regional scale.
Flood protection against pluvial floods can easiliy be realised by indiviuals.
For this reasons, in our point of view, for floodings of surface runoff a
potential significant flood risk does not exist
likely to occur.
Acknowledgements
The authors thank Mrs. Merz (
Hennegriff (LUBW, Baden
EUROPEAN COMMISSION – WFD COMMON IMPLEMENTATION STRATEGY
WG F Thematic Workshop on Implementation of the Floods Directive 2007/60/EC
“FLASH FLOODS AND PLUVIAL FLOODING”
May 2010, Cagliari, Italy
available data for soil, geologie, topography and soil-sealing. It displays
surface runoff and infiltration by using physical equations.
The essential results of this analysis are:
the water depths of surface runoff are less then 5 cm.
The duration of surface runoff is very short.
Floodings with depths more than 50 cm appear only in the flood plains
in the bottom of the valley; due to fluvial floods.
Asserted damages in slope areas are mostly related to soil erosion or
alluvial sedimentation.
Assessment of the potential significant flood risk
As described above, intense rainfall appears at small scale and does only
activate appreciable surface runoff at incidents with a return perio
considerable over 100 years. Such events can occur anywhere in the
south of Germany, so that areas with a significant higher risk can not be
identified. Previous incidents have shown, that adverse impacts to the EG
FD subjects of protection occur only in a local scale.
In Germany, the assessment of the significance of flood risks, is also
linked to the public interest in flood protection infrastructure. Measures of
public interest are required, where human lives or health are affected in a
r economic activities are impacted in a regional scale.
Flood protection against pluvial floods can easiliy be realised by indiviuals.
For this reasons, in our point of view, for floodings of surface runoff a
potential significant flood risk does not exist nor could it be considered
Mrs. Merz (Bavarian Environment Agency
Hennegriff (LUBW, Baden-Württemberg) and Mr. Schernikau (Ministry for
4 WG F Thematic Workshop on Implementation of the Floods Directive 2007/60/EC
sealing. It displays
the water depths of surface runoff are less then 5 cm.
Floodings with depths more than 50 cm appear only in the flood plains
are mostly related to soil erosion or
As described above, intense rainfall appears at small scale and does only
activate appreciable surface runoff at incidents with a return period
considerable over 100 years. Such events can occur anywhere in the
south of Germany, so that areas with a significant higher risk can not be
identified. Previous incidents have shown, that adverse impacts to the EG-
In Germany, the assessment of the significance of flood risks, is also
linked to the public interest in flood protection infrastructure. Measures of
public interest are required, where human lives or health are affected in a
r economic activities are impacted in a regional scale.
Flood protection against pluvial floods can easiliy be realised by indiviuals.
For this reasons, in our point of view, for floodings of surface runoff a
nor could it be considered
Bavarian Environment Agency), Mr.
Württemberg) and Mr. Schernikau (Ministry for
EUROPEAN COMMISSION
WG F Thematic Workshop on Implementation of the Floods Directive 2007/60/EC
“FLASH FLOODS AND PLUVIAL FLOODING”
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the environment, forestry and consumer protection Rhineland
for their support.
References
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Starkniederschlagshöhen für Deutschland (1951
2005
- Bundesministerium für Bildung und Forschung
und Management von
Aachen; 2008
- University of Padova
Resources and Technologies for Effective Flash Flood Forecasting
(HYDRATE Project).: Post Flood Event Analysis : Report on the Starzel
River Flash Flood; 2008
- Weiler, M., Steinbrich, A.: „Integrative Ausweisung von
Abflussbildungsprozessen zur räumlichen und zeitlichen
Bewirtschaftung von Wassermenge und Wassergüte“ Institut für
Hydrologie, Universität Freiburg, Vortrag zum „Tag der Hydrologie
2010“ am 25./26. März 2010 in Braunschweig
EUROPEAN COMMISSION – WFD COMMON IMPLEMENTATION STRATEGY
WG F Thematic Workshop on Implementation of the Floods Directive 2007/60/EC
“FLASH FLOODS AND PLUVIAL FLOODING”
May 2010, Cagliari, Italy
the environment, forestry and consumer protection Rhineland
Deutscher Wetterdienst [Hrsg.].: KOSTRA
Starkniederschlagshöhen für Deutschland (1951-2000)
Bundesministerium für Bildung und Forschung [Hrsg.].:
und Management von Sturzfluten in urbanen Gebieten (URBAS)
University of Padova et. al. [Hrsg.] Hydrometeorological Data
Resources and Technologies for Effective Flash Flood Forecasting
: Post Flood Event Analysis : Report on the Starzel
2008
Weiler, M., Steinbrich, A.: „Integrative Ausweisung von
Abflussbildungsprozessen zur räumlichen und zeitlichen
Bewirtschaftung von Wassermenge und Wassergüte“ Institut für
Hydrologie, Universität Freiburg, Vortrag zum „Tag der Hydrologie
5./26. März 2010 in Braunschweig
5 WG F Thematic Workshop on Implementation of the Floods Directive 2007/60/EC
the environment, forestry and consumer protection Rhineland-Palatinate)
KOSTRA-DWD-2000
2000); Offenbach;
[Hrsg.].: Vorhersage
in urbanen Gebieten (URBAS);
Hydrometeorological Data
Resources and Technologies for Effective Flash Flood Forecasting
: Post Flood Event Analysis : Report on the Starzel
Weiler, M., Steinbrich, A.: „Integrative Ausweisung von
Abflussbildungsprozessen zur räumlichen und zeitlichen
Bewirtschaftung von Wassermenge und Wassergüte“ Institut für
Hydrologie, Universität Freiburg, Vortrag zum „Tag der Hydrologie