Climate change impacts on NATURAL EVENTS 3.1 RIVER FLOODS |
FLOOD CONTROLLING FACTORS
Type of knowledge |
Results and interpretation |
Observation and analysis methods |
References |
| Reconstructions | French Alps: However, during the Little Ice Age (LIA), well-documented major environmental changes in the catchment area essentially resulted from climate change and formed basin-wide major flood deposits in Lake Le Bourget. Up to five ‘LIA-like’ Holocene cold periods developing enhanced Rhone River flooding activity in Lake Le Bourget are documented at c. 7200, 5200, 2800, 1600 and 200 cal. yr BP. These abrupt climate changes were associated in the NW Alps with Mont Blanc glacier advances, enhanced glaciofluvial regimes and high lake levels. Correlations with European lake level fluctuations and winter precipitation regimes inferred from glacier fluctuations in western Norway suggest that these five Holocene cooling events at 45°N were associated with enhanced westerlies, possibly resulting from a persistent negative mode of the North Atlantic Oscillation. |
The Holocene evolution of Rhone River clastic sediment supply in Lake Le Bourget is documented by subbottom seismic profiling and multidisciplinary analysis of well-dated sediment cores. Six high-amplitude reflectors within the lacustrine drape can be correlated to periods of enhanced inter- and underflow deposition in sediment cores.
|
Chapron & al 2005 - A |
Observations |
Swiss Alps:
Extreme events such as those which affected the Alpine region in 1987 and 1993 took place towards the end of summer and in autumn. They are caused by rising bodies of moist and warm air from the South/South-West which are transported from the Mediterranean and blocked by the alpine barrier when the 0°C isotherm is very high (>3000m asl, giving many precipitation mainly in the form of rain). The increase in the frequency of extreme flooding in the Alpine region is still within the range of natural variability (as in the case of mountain torrents) and can not be attributed solely to climate change |
Events recorded in the inventory for the last few centuries were only mentioned in terms of the damage caused to public or private property. The information was collected from accounts of past events, archives, monographs or various observations. Based on such an inventory, a database of about 4000 events, divided into different kinds of damage and covering the period 1800-1995, has been drawn up. |
Bader & Kunz 2000b - R: PNR31 |
Europe: During the late boreal summer (July–September), European climatic conditions occasionally favour very severe precipitation episodes, such as those that caused the recent flooding of the rivers Odra (1997), Elbe (2002) and of sub-catchments of the Rhone (2002). |
Christensen & Christensen 2003 - A | ||
|
France: The ground depth and the vegetation (forest cover or other) play a positive rule for the flood protection. Following vegetation disappearance due to fire events, a liquid and solid runoff increase can be expected. The results of experimental river catchments area are helping us to understand better these phenomenon evolutions. For example, after a fire event in 1990 at the Rimbaud river basin (Var, part of Réal Collobrier river system) and the vegetation cover disappearance, the observations (held by the Cemagref since 1967) show an augmentation of the flood peak by a factor 3, and a 30 to 40% increase of the flood volume. The centennial flood reference (before the fire event) has been overrun several time during the months following the fire event. However, after some years, the vegetation covered again the area and this negative effect disappeared. |
Experimental river catchments area observations. | Demirdijan 2004 - A | |
World: There are no significant trends in the floods frequency or intensity: most of the observed precipitation increase concerns the 50-75mm/day range that are not leading to flood event most of the time. There are no proofs of a precipitation pattern increase that typically trigger floods (as >100 mm/day or > 200-400 mm for several consecutive days). |
Lins 2006 - E | ||
World/Europe: Climate variability or climate change is not the only possible factor of variability or changes in hydrological patterns. River development (dams) and consumptions (particularly agricultural consumption) also strongly affect hydrological patterns and some catchment's area transformations affecting the nature of land use (urbanization, deforestation…) can have significant effects and make the detection of changes even more difficult. |
Bibliographic review | Hubert 2007 - P | |
France: The observed climatological evolutions (IMFREX Project) are insufficient to explain the regional extreme hydrometric evolutions, notably because of the strong non-linearity of the rain-temperature-discharge relation. |
Lang & Renard 2007 - P | ||
Modeling |
France: The hydrological models show that the observed discharge evolution (increase of annual maxima and intensification of floods) seems to be coherent with the precipitation behavior for the Northeast region, the rain-discharge transformation being apparently not responsible for this change. For the Alps, a link between the temperature increase and the seasonality modification of stream flows related to melting has been highlighted. |
Comparison of the observed evolution of discharges with that obtained from hydrological model: for the continental region, the pluvial floods evolution was obtained from the GR4J model (Perrin, 2000) and for the Alps, the nival floods evolution was obtained from the MORDOR model (Paquet, 2004). |
Lang & Renard 2007 - P |
Hypothesis |
Swiss Alps:
It is quite impossible to draw up a precise balance sheet of flood-reducing and flood-promoting actions. However, the flood-reducing actions took full effect before 1960, whereas flood-promoting actions have tended to multiply since 1960 and are more dominant in low altitude regions. The link between flodding events and climatic parameters is often obscured by many anthropogenic factors. |
Bader & Kunz 2000b - R: PNR31 | |
| Swiss Alps: A warmer and wetter autumn climate (according to the usual scenario) may lead to more situations of flood triggering in the Viège valley (Swiss Valais). |
Stoffel & Monbaron 2000 - P | ||
| Switzerland: The precipitation patterns modifications will have a stronger impact on the floods than the snow cover melting. The change in the river catchment’s area that will influence the situations leading to floods will be slower than the change in the precipitation patterns. |
OcCC 2003 - R | ||
Global scale: Greenhouse gas-induced climate warming could affect severe precipitation in a number of ways, including changing its frequency, intensity, and timing of occurrence. Given the potential for catastrophic damage and loss of life from subsequent flooding of river systems and further associated hazards, e.g., mud slides, damage to sewage systems, etc., any such changes could have important societal consequences. |
Bibliographic review. |
Christensen & Christensen 2004 - A | |
France: In a general manner, the hydrological cycle intensification would increase flood hazards in winter and spring, as well as the duration of low-water (from June/July to October/November). In most people's opinion meteorologists and hydrologists, it remains impossible to demonstrate a link between the reproduction of the floods and the warming of the climate; numerous anthropological reasons can explain first of all these phenomena (waterproofing of grounds, modalities of use of farmlands, constructions on easily flooded grounds). |
ONERC 2006 - R | ||
German Alps: One of the possible impact of climate change concerns the regional inundation increase and straightening. The precipitation increase and spring snow melting may have huge consequences especially on the torrents, which react immediately to the precipitations. This concerns also the urbanized area because of compact soil and too smal undergound water systems. |
Seiler 2006 - P* |
Type of knowledge |
Results and interpretation |
Observation and analysis methods |
References |
| Reconstructions | Large alpine valleys and their piedmont to the Mediterranean Sea: An extension of the active minor bed during the Little Ice Age has been identified on several sections of the Rhone river and its tributaries; some experienced a clear progradation of a “sedimentary wave” (bedload transport), accompanied or not with a river metamorphosis (from a meandering river to a braided river). These events, classified according to their increasing scale, began in the 14th century for the Rhone river in Lyon, which is under influence of the sedimentary contributions of the Ain river. Note that the Isère river metamorphosis is more premature downstream Grenoble (Drac influence) than upstream the city, which is less influenced by sedimentary flux of the Isère and Arc high watersheds due to greater distance. The phenomenon also concerns the Camargue at the beginning of the 18th century. It seems that the phenomenon reached its peak in the 18th century, although the 19th century is known for its high floods and alpine torrential events. The relative respite of the 19th century might be linked to the effect of the embankment or simply a progressive return to calmer period after the very active 18th century. |
Studies of river paleo-dynamics performed for about fifteen years on the basis of old maps and archives have been analysed. |
Bravard 2000 - P |
Southern France: |
Benito 2003 - P | ||
French Alps – Isère river (Grésivaudan): According to the qualitative chronology of the Isère floods for the 1600-1950 period, established following three classes of events (low or moderate; high; exceptional), the eight strongest known events occurred in 1651, 1673, 1711, 1733, 1740, 1764, 1778 and 1859. During the last five centuries, exceptional Isère floods all concentrate between the mid-17th century and the mid-19th century. The climatic degradation of the Little Ice Age appears rather clearly (Grove, 1987). Before 1600, the only known event is the 1524 one, which can be considered as a class 3 event. It is especially the Drac river that experienced large floods, from the end of the 16th century and during the 17th century. The Isère river experience a paroxystic phase between 1730 and 1780 (with four class 3 floods) then a slight calmer period during the earlier 19th century (before 1840-1850s). The November 1859 flood corresponds to the last large flood in Grenoble. |
Detailed historic assessment (within the framework of the “Historisque” program) based on a General State of Sources, computing seizure of Isère hydrometric data and analysis of archives with a methodological purpose (history of services responsible for measures, methods and measurement equipments, as well as events occurring in the watershed). Qualitative chronology of Isère floods for the 1600-1950 period, according to three classes of events (low or moderate; high; exceptional), history of the evolution of the announcement service of Isère floods and inventory of all available data for the 19th and 20th centuries). The analysis of Isère floods historic data allowed to list 91 major floods in Grenoble (quotations available for the 1600-1950 period). The estimation of the flood discharge has been carried out for some of these floods. |
Lang & al 2003 - E | |
Rhone River - French Alps: During the Little Ice Age (LIA), well-documented major environmental changes in the catchment area essentially resulted from climate change and formed basin-wide major flood deposits in Lake Le Bourget. Up to five ‘LIA-like’ Holocene cold periods developing enhanced Rhone River flooding activity in Lake Le Bourget are documented at c. 7200, 5200, 2800, 1600 and 200 cal. yr BP. These abrupt climate changes were associated in the NW Alps with Mont Blanc glacier advances, enhanced glaciofluvial regimes and high lake levels. In the long term, the increase in the frequency and intensity of Rhone River flooding activity in Lake Le Bourget after the Holocene climatic optimum may be attributed to onset of the Neoglacial around 5600 cal. yr BP (Steig 1999). |
The Holocene evolution of Rhone River clastic sediment supply in Lake Le Bourget is documented by subbottom seismic profiling and multidisciplinary analysis of well-dated sediment cores. Six high-amplitude reflectors within the lacustrine drape can be correlated to periods of enhanced inter- and underflow deposition in sediment cores. |
Chapron & al 2005 - A | |
|
Observations |
Swiss Alps: At the moment, no significant trend can be recorded, the extreme values remaining in the statistical limits uncertainties for the last two decades. |
Stoffel & Monbaron 2000 - P | |
Rhone
catchment: In the last 15 years, severe floods occurred in the Upper Rhone downstream Geneva (1990 was the 1 on 100 years flood), and in the lower Rhone (for instance: 1993, 1994, 2003) |
Sauquet & Haon, 2003 in Bravard 2006 - P | ||
France: The statistical study of river discharges in France did not detect any significant change in the number and the intensity of floods since the mid-XXth c. Also, it is impossible to confirm any change in low discharges, mostly because of heavy human impacts on rivers. |
|
Lubès-Niel & Giraud 2003 ; Lang et al. 2005 in Bravard 2006 - P |
|
Southern
Germany:
Long-term behaviour
of flood runoffs:
In summary, it can be
established that only in the last 30 to 40 years do the examined runoff
time series demonstrate regional increases in flood runoffs. The long-term behaviour of the highest runoffs can be characterised as follows: • When examining the annual series from 70 to 150 years duration, the majority of annual highest runoff levels do not show significant changes. • When examining the last approx. 30 years the highest runoffs show increasing trends at many gauges. • The frequency of winter floods has increased since the 70s with the exception of Southern Bavaria. • The monthly flood runoffs in the winter half year since the 70s are higher than in the time before the 70s. |
Investigations of long series of hydrometeorological
and hydrological measurements available were systematically carried
out for Baden-Württemberg and Bavaria on the basis of a large data
set within the context of KLIWA Project. The long-term behaviour of the flood
runoffs, the mean runoffs, the regional and heavy precipitation, the
air temperature, the evaporation and the snow cover period were analysed
for time periods in the 20th century. The investigation of the long-term behaviour [of flood runoffs] included determination of any linear trends present in the time series of the annual and monthly highest runoffs. The annual and monthly highest runoff values at 107 gauges, which have long observation series since at least 1931, formed the basis for the trend investigations. Furthermore 51 gauges with shorter time series, i.e. with observation start after 1932, were included in the analysis. |
Hennegriff & al 2006 - A | |
World: There are no significant trends in the floods frequency or intensity: most of the observed precipitation increase concerns the 50-75mm/day range that are not leading to flood event most of the time. There are no proofs of a precipitation pattern increase that typically trigger floods (as >100 mm/day or > 200-400 mm for several consecutive days). |
|
Lins 2006 - E | |
World:
Most of the maximum annual runoff values recording (70%) show no statistically significant trends. The other recording trends are divided between increase and decrease of the values. There is a lack of unequivocal proofs of a long term increase of the river flood intensity. |
Long term trends studies based on 195 stations measures all over the world
|
Svenson & al.2006 - P | |
| German Alps: During the late 20th century, the bad weather and meteorological extreme increase led to inundations increase, damaging more and more people. |
Seiler 2006 - P* | ||
World/Europe: If some authors propose an increase of the average flows during the XXth century (Labat and al. 2004), numerous recent studies dedicated to the study of instrumental and historic series available at the global scale (Kundzewicz 2004; Svensson and al. 2004; Svensson and al. 2006) or regional, for central Europe (Mudelsee and al. 2003) or France (Lang and al. 2002; Fox 2006) did not notice any significant trend for floods and particularly the most extreme of them and this, even for very long series, in spite of climatic turned out fluctuations (Small glacial age marked by a cooling from the XVth to the XIXth century). |
Bibliographic review. | Hubert 2007 - P | |
France: At the French scale, no coherence in the spatial distribution of the detected anomalies, or generalised evolution of discharges or floods, have been found. No coherent and generalised climatic trend has been detected in the evolution of the hydrometric extremes pattern. Evolutions have been detected for only 5 of the 15 hydro-climatic regions: • weaker low water levels in the Alps and the nival wave seems to be more premature in the Northern Alps; • increase of the nival module of the glacial stations and earlier occurrence of the maximum basic discharge; • Stronger low water in Pyrenées and Basque country. Pluvial floods also seem to decrease in Pyrenées; • increase of annual maxima in the Northeast region; • Stronger floods in oceanic region (Northern France), apparently related to the filling of the fluvial water tables. In the Northern Alps, changes concern snow cover floods and low waters. The melting wave occurs earlier and the melting peak decreases. Low waters are less severe, with a significant increase of the annual daily minima and a significant decrease of the volume deficit. The duration of low waters also seems to decrease, although not significantly. |
Set of 192 long series of daily discharges, only with series considered as not influenced, covering at least 40 years of observation. Around thirty samples were extracted for every station from descriptive variables of high-waters, low-waters and water pattern. Every sample was subjected to a stationnarity test chosen according to the series autocorrelation, the expected type of distribution and the sample length. A series of 15 hydro-climatic regions was established (Renard, 2006) by crossing a classification based on floods and low waters seasonality with a pluviometric zoning of Météo France. The regional coherence was studied by using regional variable, from the regional version of the Mann and Kendall test (Douglas et al., 2002; Yue and Wang, 2002), or with the regional test of deviation proposed by Renard. |
Lang & Renard 2007 - P | |
French Alps: In the Northern Alps, the detected changes concern nival floods and low waters. The melting wave occurs earlier and the melting peak decreases. In the Southern Alps, the nival melting wave does not show coherent changes for the five tested stations. Three glacial regime stations show a decrease of the basic discharge during the melting peak, and a rather clear increase of the nival season total module. This last result is coherent with the glacier retreat in the French Alps (Vincent, 2002). |
A statistical analysis of 200 long hydrometric series has been carried out within the framework of a PNRH national project and the B. Renard's doctoral thesis (2006). 13 hydrometric stations were studied for the French Alps sector. |
Lang 2007 - C1 | |
|
Modeling |
World / extratropical basins larger than 200,000
km² : Under idealized CO2 quadrupling, relative change in annual mean discharge range from -12% to +76%, with a median value of +30%. Relative changes in the 100-yr monthly maximum discharge generally are smaller and less variable, with a median of +15%. Between 1865 and 2089, the flood rate could be 2 to 8 times greater than its value during the historical period of observations. The recent emergence of a statistically significant positive trend in risk of great floods is consistent with resutlts from the climate model, and the model suggests that the trend will continue. Danube basin (station : Orsova, Romania), after quadrupling of atmospheric CO2 : - Relative change change in annual mean discharge (dq) : -3%. - Relative change in 100-yr annual maximum monthly discharge (dQ) : +16%. |
To assess flood-risk sensitivity to radiative forcing, they used a 300-yr 'idealized CO2 quadrupling' experiment with a 1%-per-year growth (for 140 yr) of atmospheric CO2 concentration from the control level to a stable, quadrupled level (maintened for 160 yr). Modelled changes in annual mean discharge (relative to the control experiment) provide a measure of intensification of the water cycle as a result of idealized CO2 quadrupling [...] [They] used the 100 yr of model output that begins 60 yr after stabilization of CO2 concentration at the quadrupled level. Post-quadrupling distributions of annual maximum monthly flows were fitted to Pearson's type III distribution, which was then used to determine the probability of the control 100-yr flood. [They] examined the detectability of flood-risk change in five transient 'scenario' climate experiments (225 yr, 1865-2089) that shared common estimates of historical and projected future changes in radiative forcing by greenhouse gases and direct effects of sulphate aerosols, each with a distinct initial condition. |
Milly & al. 2002 - A |
French Alps: The Isère catchment area should experience a 30 to 50% decrease of the maximum snow accumulation and an almost complete disappearance during summertime. The winter runoff value for the entire area would increase, in correlation with the precipitation increase and the melting peak a month earlier. The spring runoff value should be reduced in most of the cases. At the annual scale, the scenario propose a slightly increase or decrease of the runoff. The impact of climate change on the snow covers in the catchment’s area of the Haute Durance should be similar, with a lighter reduction due to the lower altitude. The annual runoff value would decrease faster than in North Alps (from 0 to 20%). The rivers flows would increase significantly in winter and autumn and would decrease during summer. The spring runoff would occur a month earlier, the magnitude would remain the same or decrease (10 to 25%), depending on the scenario used. |
Using SAFRAN / MODCOU / CROCUS model and ISBA surface scheme of Météo France. |
Etchevers & Martin 2002 - P |
|
French Alps: For the Rhône, as well as for the Saône and Ardèche, the medium waters and the low water tend to decrease whereas the high water tend to increase. For the Durance (nival pattern), the melting peak decrease is observed (the conclusion are linked to the scenario chosen: the flood increase of 12% with the CNRM model while they slightly decrease with the LMD model). |
Hydrological model with 6 climatic scenarios (combining observations with results from simulations). |
GICC-Rhône 2005 - R | |
Southern
Germany: The results predict a marked increase in mean flood levels (MHQ), and also in the extreme runoff. Although the results of the model chain (global model – regional climate model – water balance models) and the model assumptions contain uncertainties, the results all point in the same direction. Thus for the period considered up to the year 2050 it can be assumed that floods will intensify due to climate change in Baden-Württemberg and Bavaria. [An increase in the duration and frequency of rain-laden west weather conditions (especially west condition cyclonic), which is important for flood formation in winter, is to be expected]. |
In the framework of the KLIWA Project, the
data of the regional climate scenarios were employed as input quantities
for the water balance models (WHM), in order to make statements on the
impact of climate change on water balance (e.g. runoffs into flowing waters).
The water balance models on the basis of LARSIM are available as a 1-km
grid for the whole of Baden-Württemberg; in Bavaria the model system
ASGi has, up to now, been adapted for the river regions north of the Danube.
The modelling of water balance focused at first on the possible future
changes in runoff, with initial consideration of the effects of flood
runoff. For this purpose the runoff values obtained from water balance
modelling were analysed with methods of extreme value statistics. |
Hennegriff & al 2006 - A | |
World/Europe: Despite results concerning the evolution of the precipitation which are sometimes contradictory at the regional scale regarding the direction of the changes, all models insist on a likely intensification of the hydrological cycle (IPCC, on 2001; Leblois and Margat, on 2000), which would be translated by increased floods in winter and stronger low-water events during summer. |
Bibliographic review. | Hubert 2007 - P | |
Rio Ridanna/Mareiter Bach (South Tyrol Italian Alps): The analyses of the possible impacts of climate changes showed that the flooded areas of a design event with a return period of 30 years representing the assumed future climate conditions (scenario +20%) have a larger extent than the flooded areas of a design event with a return period of 100 years representing the actual climate conditions (scenario 2000). The hazard zones delimited and classified following the guidelines for hazard zone mapping show remarkable changes if considering the assumed changes in precipitation intensities due to climate changes. The hazard zones representing the assumed future climate conditions show a shift from the yellow zones (hazards with low intensities prevail) to the blue zones (the construction of new buildings is regulated), which have significantly increased extent. The potential shifts from blue hazard zones to red hazard zones (the construction of new buildings is restricted) do not show significant consequences for buildings. The expected damages of a flood event with a return period of 30 years (scenario +20%) increased up to 1700% (in comparison to the scenario 2000). The expected damages of a flood event with a return period of 100 years increased up to 207% and up to 117% for an event with a return period of 200 years. |
On the basis of a literature review, a possible increase of 20% (by 2050-2100) of the precipitation intensity for each design event (reoccurrence interval 30, 100, 200 years) was assumed. The Rio Ridanna/Mareiter Bach basin lies in the north of the Province. The catchment area is 210 km2. This study area is a representative example for an alpine river with hazard potential for settlements. For the assessment of the present flood hazard situation, this procedure was followed: – statistical analyses of the precipitation time series of the measurement stations in the study area and calculation of the characteristics of precipitation events relevant for the hazard scenarios with a return period of 30, 100 and 200 years; – preparation and calibration of the rainfall-runoff model; – simulation of the inundation processes for each return period; – delimitation of the hazard zone map; – analysis of the exposed buildings. The statistical analysis of the precipitation time series was based on the measurement stations of Ridanna/Ridnaun. The precipitation values of a rainfall event with a duration of 24 hours representing reoccurrence intervals of 30, 100 and 200 years have been calculated. For the discharge prediction, the rainfall-runoff model Hec-HMS and the SCSapproach was used. For the simulation of the inundation process, the simulation model SOBEK of WL Delft Hydraulics was used. |
Staffler & al. 2008 - A | |
|
Hypothesis |
World : An implication of simulated changes in streamflow is that riverine flood risk generally would increase across much of Europe [...].As the glacier melts as a result of global warming, flows would be expected to increase during summer—as water is released from long-term storage—which may compensate for a reduction in precipitation. As the glacier gets smaller and the volume of melt reduces, summer flows will no longer be supported and will decline to below present levels. The duration of the period of increased flows will depend on glacier size and the rate at which the glacier melts; the smaller the glacier, the shorter lived the increase in flows and the sooner the onset of the reduction in summer flows. |
IPCC
2001 - R |
|
Europe:
Even as summers become drier, the incidence of severe precipitation [on summertime flooding] could increase. |
Christensen & Christensen 2003 - A | ||
Switzerland:
The major apparent risk is linked to increased flood hazards. If winter floods occurring on rivers in Switzerland have negative influences on discharges in downstream countries, then these countries may ask for improved retention in the Swiss lakes and reservoirs, along with political consequences. |
Schädler, 2003 in Bravard 2006 - P | ||
Rhone
catchment:
In the last 15 years, severe floods occurred in the Upper Rhone downstream Geneva (1990 was the 1 on 100 years flood), and in the lower Rhone (for instance: 1993, 1994, 2003). As stated above (Sauquet & Haon, 2003), they may be just a cycle of high discharges as many occurred in the past. Also, they may be the first signals of changed climate towards higher peak floods. Anyhow, they revealed the strong vulnerability of the Rhone valley to flooding. |
Sauquet & Haon, 2003 in Bravard 2006 - P | ||
Switzerland: There should be winter runoff acceleration and a heavy precipitation event intensity increase. The changes in the precipitation patterns should have a stronger impact on floods than the snow cover melting. |
OcCC 2003 - R | ||
Europe/France: In France, more frequent and more intense floods in winter and stronger low-water events summer are to be expected (CRUMBS 2000). According to Petit (2001), "the Southern and Arctic Europe are more vulnerable than the rest of Europe. Particularly in summer, the runoff, the available water and the soil moisture will decrease in the Southern Europe, increasing its current drought vulnerability. On the other hand, in winter, an increase of these same quantities should affect both the North and the South; the risk of catastrophic river floods will probably increase. " |
ONERC 2005 - R | ||
Europe: In mainland Europe, vulnerability to flooding seems to be increasing because of such factors as the occupation of floodplains by more people and the engineering structures, and unusually severe floods affected much of the continent during the 1990s and early 2000s (Mitchell, 2003). Therefore, a major question is the extent to which future flooding may be exacerbated by climate change. |
Goudie 2006 - A | ||
France: In a general manner, it is confirmed that the intensification of the hydrological cycle would increase the risk of floods in winter and in spring, as well as the duration of low-water events (from June / July to October / November). |
ONERC 2006 - R | ||
German Alps: One of the possible impact of climate change concerns the regional inundation increase and straightening. The precipitation increase and spring snow melting may have huge consequences especially on the torrents, which react immediately to the precipitations. This concerns also the urbanized area because of compact soil and too smal undergound water systems. |
Seiler 2006 - P* |
Type of knowledge |
Results and interpretation |
Observation and analysis methods |
References |
| Reconstructions | Swiss
Alps:
During the last 500 years, there have been two periods with very little flooding: 1641-1706 and 1927-1975, and two periods with a great deal of flooding: 1550-1580 and 1827-1875. Such inventories are based on "report of damage" and may not reflect the tendency for the event itself. During the 1641-1706, the whole Alpine region was spared any serious flooding; even Lago Maggiore did not overflow its banks. Considering the similarity of results from all regions, it can be explained by a gap in the inventories but by a pause in the flooding cycle. This pause conicides with the "Maunder Minimum", a period of reduced solar activity. The period 1827-1875 is marked by a sharp increase in flooding events following a series of extremely wet autumns. Lago Maggiore overflows its banks almost every 4 years. The decrease of flooding between 1927 and 1975 is possibly related to the planning and protective measures undertaken. Flooding events appears to be on the increase again since 1975. The general tendency for the 1800-2000 period is an annual increase in flood damage since 1800. This is explained by an increase in potential hazards. The increase in the frequency of extreme flooding in the Alpine region is still within the range of natural variability (as in the case of mountain torrents) and can not be attribute solely to climate change. |
Events recorded in the inventory for the last few centuries were only mentioned in terms of the damage caused to public or private property.
The information was collected from accounts of past events, archives, monographs or various observations for the 1800-1995 period. |
Bader & Kunz 2000b - R: PNR31 |
Rhine catchment’s area (Central Europe):
Important flood variations have been observed for the Rhine river. They have been rare between 1641 and 1706 and between 1882 and 1994. But strong floods and inundation in the whole alpine arc occurred between 1828 and 1876: the 6 “extreme” floods recorded between 1808 and 1994 occurred between 1817 and 1882, excepting the 1994 one. The Rhine flood frequency has been established: July is in the first rank because of the combination of intense precipitation and snow melting from the Alps. December follows with floods linked to persistent frontal precipitations from SW track, combined with fast snow melting at middle altitude. The flood rarity for 110 years since 1882 can be partially explained by a change in the synoptic meteorological situation, especially higher summer blocking anticyclone frequency. Important inundation events have been found in the Ticino canton during the last centuries. The 1927-1975 period shows high occurrence. The end of summer and autumn floods increase since 1975 on the Southern flank of the Alps seems to lie within natural fluctuations; it is premature to see a human influence in this process. |
An objective typology of flood categories has been established depending on 4 magnitude levels for the damage and 3 spatial extension levels (local, regional and interregional). The most damaging floods have been compared with lakes levels (Lago Magiorre and Leman) using “strong” and “extreme” as standard deviation threshold for the 1901-1960 series.
|
Paul 2002 - A | |
French Alps – Isère river (Grésivaudan): According to the qualitative chronology of the Isère floods for the 1600-1950 period, established following three classes of events (low or moderate; high; exceptional), the eight strongest known events occurred in 1651, 1673, 1711, 1733, 1740, 1764, 1778 and 1859. The historic assessment confirms and clarifies the chronology generally proposed by geomorphologists to define the “river metamorphosis” period (Peiry, 1997). During the last five centuries, exceptional Isère floods all concentrate between the mid-17th century and the mid-19th century. The climatic degradation of the Little Ice Age appears rather clearly (Grove, 1987). Before 1600, the only known event is the 1524 one, which can be considered as a class 3 event. It is especially the Drac river that experienced large floods, from the end of the 16th century and during the 17th century. The Isère river experience a paroxystic phase between 1730 and 1780 (with four class 3 floods) then a slight calmer period during the earlier 19th century (before 1840-1850s). The November 1859 flood corresponds to the last large flood in Grenoble. |
Detailed historic assessment (within the framework of the “Historisque” program) based on a General State of Sources, computing seizure of Isère hydrometric data and analysis of archives with a methodological purpose (history of services responsible for measures, methods and measurement equipments, as well as events occurring in the watershed). Qualitative chronology of Isère floods for the 1600-1950 period, according to three classes of events (low or moderate; high; exceptional), history of the evolution of the announcement service of Isère floods and inventory of all available data for the 19th and 20th centuries). The analysis of Isère floods historic data allowed to list 91 major floods in Grenoble (quotations available for the 1600-1950 period). The estimation of the flood discharge has been carried out for some of these floods. |
Lang & al 2003 - E | |
Swiss Alps: During the last 500 years, in the Swiss Alps, there has been two periods with few flooding events: 1641-1706 and 1927-1975 and two periods with many flooding events 1550-1580 and 1827-1875. Such inventory are based on “damage reports” and do not reflect the flood event trend on itself. For example, the decrease of the flood events number between 1927 and 1975 is possibly linked to the planning and prevention measures implemented at this time. The general trend is an annual increase of the damage due to flooding since 1800. This is explained by the stake vulnerability increase. There has been no extreme floods on the North side of the Alps from 1882 to 1992. The extreme floods frequency increased during the last 15 years, in comparison with the 20th century (August 1987, September 1993 and October 2000). |
Such inventories are based on damage reports and do not reflect any trends for the event itself. For example, the flood decrease between 1927 and 1975 is probably linked to prevention measures implemented.
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OcCC 2003 - R | |
Rhone River - French Alps: In the long term, the increase in the frequency and intensity of Rhone River flooding activity in Lake Le Bourget after the Holocene climatic optimum may be attributed to onset of the Neoglacial around 5600 cal. yr BP (Steig 1999). |
The Holocene evolution of Rhone River clastic sediment supply in Lake Le Bourget is documented by subbottom seismic profiling and multidisciplinary analysis of well-dated sediment cores. Six high-amplitude reflectors within the lacustrine drape can be correlated to periods of enhanced inter- and underflow deposition in sediment cores. |
Chapron & al 2005 - A | |
Switzerland: A phase of high flooding activity in major Swiss rivers has been observed after 1827 and until the late 19th century. After 1835 (and until the mid-1890s), considerable above-average precipitation sums in summer and fall are noted for the Swiss Alps. Low flooding frequencies were recorded between 1927 and 1975. |
Archival data on flooding between June and October. |
Stoffel & al. 2005a - A | |
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Observations |
Swiss Alps: The flood and inundation number seems to increase significantly during the two last decades (1978, 1987, 1993 and 1994). In the studied area (Ticino and Viège valley) sheltered from precipitations but influenced by the same pluvial patterns, similar evolution can be found. At the moment, no significant trend can be recorded, the extreme values remaining in the statistical limits uncertainties. |
Stoffel & Monbaron 2000 - P | |
Alps: The 1927-1975 period shows high occurrence. The end of summer and autumn floods increase since 1975 on the Southern flank of the Alps seems to lie within natural fluctuations; it is premature to see a human influence in this process. But that would be interesting to examine if the post 1994 catastrophic higher frequency contribute to invalidate this remark. Some recent research works on 133 Swiss stations highlight an increase of the days with heavy precipitations (> 50 mm/day) since 1973 for the whole country, that could be explained by cyclonic situation increase. |
An objective typology of flood categories has been established depending on 4 magnitude levels for the damage and 3 spatial extension levels (local, regional and interregional). The most damaging floods have been compared with lakes levels (Lago Magiorre and Leman) using “strong” and “extreme” as standard deviation threshold for the 1901-1960 series. |
Paul 2002 - A | |
| World
/ extratropical basins larger than 200,000 km² : The frequency of great floods increased substantially during the twentieth century (1865-1999). The frequency of flood having return periods shorter than 100 yr did not increase significantly. |
Here, [they] consider 29 basins larger than 200,000 km² in area for which discharge observations span at least 30 yr. [They] analyse annual maximum monthly-mean flows. This investigation has a global scope and focuses on extreme events; they analyse the 100-yr flood. |
Milly & al. 2002 - A | |
Southern Europe : |
Duband 2003 - P | ||
France:
The statistical study of river discharges in France did not detect any significant change in the number and the intensity of floods since the mid-XXth c. Also, it is impossible to confirm any change in low discharges, mostly because of heavy human impacts on rivers. |
Lubès-Niel & Giraud 2003 ; Lang et al. 2005 in Bravard 2006 - P |
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| Swiss Alps: There have been no floods on the North flank of the Alps between 1882 and 1992. The extreme inundations frequency increased during the last 15 ears, compared to the 20th century mean (August 1987, September 1993 and October 2000). |
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OcCC 2003 - R | |
| World: There are no significant trends in the floods frequency or intensity: most of the observed precipitation increase concerns the 50-75mm/day range that are not leading to flood event most of the time. There are no proofs of a precipitation pattern increase that typically trigger floods (as >100 mm/day or > 200-400 mm for several consecutive days). |
Lins 2006 - E | ||
World/Europe: Numerous recent studies dedicated to the study of instrumental and historic series available at the global scale (Kundzewicz 2004; Svensson and al. 2004; Svensson and al. 2006) or regional, for central Europe (Mudelsee and al. 2003) or France (Lang and al. 2002; Fox 2006) did not notice any significant trend for floods and particularly the most extreme of them and this, even for very long series, in spite of climatic turned out fluctuations (Small glacial age marked by a cooling from the XVth to the XIXth century). |
Bibliographic review. | Hubert 2007 - P | |
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Modeling |
World: In all but one of the basins, the control 100-yr flood is exceeded more frequently as a result of idealized CO2 quadrupling. The probability of exceeding this control flood changes by a factor that ranges from 0.90 to 46; in half of the basins, the factor exceeds 8 (implying a deacrease in return period from 100 yr to shorter than 12.5 yr). These experiments [1865-2089, with projected future changes in radiative forcing by greenhouse gases and direct effects of sulphate aerosols] show an increase in extratropical flood frequency that generally is apparent early in the twenty-first century. Therafter, the flood rate is 2 to 8 times greater than its value during the historical period of observations. Values of extratropical Z [the flood-frequency trend] were computed for each scenario with exactly the same gauging scheduke as in the observations. Four of the experiments (all except scenario 4) had positive values of Z; the largest of these (scenario 3) was slightly smaller than the observed value. For Extratropical basins, [Between 1865 and 2089] the flood rate could be 2 to 8 times greater than its value during the historical period of observations. The recent emergence of a statistically significant positive trend in risk of great floods is consistent with resutlts from the climate model, and the model suggests that the trend will continue. |
To assess flood-risk sensitivity to radiative forcing, they used a 300-yr 'idealized CO2 quadrupling' experiment with a 1%-per-year growth (for 140 yr) of atmospheric CO2 concentration from the control level to a stable, quadrupled level (maintened for 160 yr). Modelled changes in annual mean discharge (relative to the control experiment) provide a measure of intensification of the water cycle as a result of idealized CO2 quadrupling [...] [They] used the 100 yr of model output that begins 60 yr after stabilization of CO2 concentration at the quadrupled level. Post-quadrupling distributions of annual maximum monthly flows were fitted to Pearson's type III distribution, which was then used to determine the probability of the control 100-yr flood. [They] examined the detectability of flood-risk change in five transient 'scenario' climate experiments (225 yr, 1865-2089) that shared common estimates of historical and projected future changes in radiative forcing by greenhouse gases and direct effects of sulphate aerosols, each with a distinct initial condition. |
Milly & al. 2002 - A |
|
Hypothesis |
Swiss Alps: A warmer and wetter autumn climate (according to the usual scenario) may lead to more situations of flood triggering in the Viège valley (Swiss Valais). |
Stoffel & Monbaron 2000 - P | |
| World
: Low-flow frequency generally will increase across most of Europe, although in some areas where the minimum occurs during winter the absolute magnitude of low flows may increase because winter runoff increases. An implication of simulated changes in streamflow is that riverine flood risk generally would increase across much of Europe [...]. Floods and droughts are likely to become more frequent in mountainous area. |
IPCC
2001 - R |
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Southern Europe: We can still consider the reasonable hypothesis for pseudo stationary distribution of extreme rainfalls and flood hazard, in reference to the last centuries, for the next twenty or forty future years. However, we remain aware of the opportunity that a global climate change can happen in the second part of the 21st century. |
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Duband 2003 - P | |
Switzerland: The medium and big rivers would experience more floods because of more important precipitations and the precipitations falling rather as rain than snow on the “Plateau” and the Pre Alps. |
OcCC 2003 in Frei & Widmer 2007 - E | ||
Swiss Alps:
The medium and big rivers would experience more floods because of more important precipitations and the precipitations falling rather as rain than snow on the “Plateau” and the Pre Alps. The floodless periods because of low temperature would decrease. The changes in the catchment’s area that would influence the process leading to floods would be slower than the precipitation changes. |
OcCC 2003 - R | ||
Global scale: Greenhouse gas-induced climate warming could affect severe precipitation in a number of ways, including changing its frequency, intensity, and timing of occurrence. Given the potential for catastrophic damage and loss of life from subsequent flooding of river systems and further associated hazards, e.g., mud slides, damage to sewage systems, etc., any such changes could have important societal consequences. |
Christensen & Christensen 2004 - A | ||
France: In France, more frequent and more intense floods in winter and stronger low-water events summer are to be expected (MIES, 2000). |
ONERC 2005 - R | ||
German Alps:
One of the possible impact of climate change concerns the regional inundation increase and straightening. The precipitation increase and spring snow melting may have huge consequences especially on the torrents, which react immediately to the precipitations. This concerns also the urbanized area because of compact soil and too smal undergound water systems. |
Seiler 2006 - P* |
Type of knowledge |
Results and interpretation |
Observation and analysis methods |
References |
| Reconstructions | Rhine catchment's area:
The Rhine flood frequency has been established: July is in the first rank because of the combination of intense precipitation and snow melting from the Alps. December follows with floods linked to persistent frontal precipitations from SW track, combined with fast snow melting at middle altitude. |
An objective typology of flood categories has been established depending on 4 magnitude levels for the damage and 3 spatial extension levels (local, regional and interregional). The most damaging floods have been compared with lakes levels (Lago Magiorre and Leman) using “strong” and “extreme” as standard deviation threshold for the 1901-1960 series.
|
Paul 2002 - A |
| Observations |
Alps:
Extreme events such as those that affected the Alpine region in 1987 and 1993 happened in the end of summer and autumn. |
|
Bader & Kunz, 2000b - R |
Southern Europe: Actually no significative trend has been detected in historical date (year, season, day) of rains and discharges hundred years old and more, in France, West Europe and other countries. |
Duband 2003 - P | ||
France: Evolutions have been detected for only 5 of the 15 hydro-climatic regions: • weaker low water levels in the Alps and the nival wave seems to be more premature in the Northern Alps; • increase of the nival module of the glacial stations and earlier occurrence of the maximum basic discharge. |
Set of 192 long series of daily discharges, only with series considered as not influenced, covering at least 40 years of observation. A series of 15 hydro-climatic regions was established (Renard, 2006) by crossing a classification based on floods and low waters seasonality with a pluviometric zoning of Météo France. |
Lang & Renard 2007 - P | |
|
Modeling |
French Alps: The Isère runoff values should increase significantly in autumn and in winter and would decrease in summer. The spring runoff would happen a month earlier, their value should remain the same or slightly decrease (10 to 25%), depending on the scenarios chosen. |
SAFRAN-MODCOU-CROCUS model chain used with six different “2*CO2” scenarios to estimate the impact of climate change on nival hydrology of certain watershed with nival regime. Four models were used among which two supplied scenarios with low (LR) and high (HR) resolution. |
Etchevers et Martin 2002 - P |
French Alps:
The runoff may decrease from May to November but the winter evolution depends on the scenario chosen. The spring runoff decrease, consequence of the nival pattern is the most marked effect given by the study. The snow cover melting happening a month earlier and the solid precipitation decreasing, the strong spring runoff decrease and happen a month earlier. The winter runoff increases perceptibly (more precipitation) whereas the summer decreases of up to 50% (ground drying more important). These general trends are found for all the scenarios, with more or less intensity. |
Hydrological model with 6 climatic scenarios (combining observations with results from simulations). |
GICC-Rhône 2005 - R | |
|
Hypothesis |
World: Low-flow frequency generally will increase across most of Europe, although in some areas where the minimum occurs during winter the absolute magnitude of low flows may increase because winter runoff increases: The season of lowest flow shifts toward summer. An implication of simulated changes in streamflow is that riverine flood risk generally would increase across much of Europe and that in some areas, the time of greatest risk would move from spring to winter. |
IPCC
2001 - R |
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Switzerland: The time without floods would decrease because low temperature duration would be shortened in the future. |
OcCC 2003 - R | ||
France: In a general manner, it is confirmed that the intensification of the hydrological cycle would increase the risk of floods in winter and in spring, as well as the duration of low-water events (from June / July to October / November). |
ONERC 2006 - R |
Type of knowledge |
Results and interpretation |
Observation and analysis methods |
References |
Reconstructions |
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Observations |
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Modeling |
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Hypothesis |
Experiences feed-back |
Objectives |
Learnings |
References |
In 1995, the French government launched a large study called “Global Rhône study”, combining hydraulics, sediment transport and land occupation, as these different topics having been recognized as complementing each other. The 2003 flood, approximately the 1 in 100 years flood for the downstream gauging stations, motivated the French government to launch the so-called “Rhône Masterplan” (2005) which includes a series of measures to mitigate the human consequences of flooding, the reduction of hydrological hazards being recognized as quite impracticable. The expected risk explicitly refers to the largest past floods (1856), to extremal scenarios combining several meteorological origins (the so-called “general flood” in the sense of Pardé, 1925), and to the negative impacts of the occupation of the floodplain. It is thus worth noting that the possible effects of climate change on the intensity of large flood is not taken into account, despite the possible increase in extreme winter events. Also, to face the expected changes, the French Ministry of Environment and Sustainable Development recommended to extend the number of the “Plans de Prévention des Risques” and to improve forecasting procedures (Redaud et al., 2002). |
Bravard 2006 - P | ||
Adaptation of flood protection planning: The use of the load case climate change for flood protection conceptions, where the implementation has already started or had already been completed, is currently not planned.
Increase in the design runoff: Increased design runoff has to be taken as the basis for the load case climate change. This is carried out with a supplement (“climate change factor“) to the currently valid design value. In Baden-Württemberg, the climate change factors for the runoffs differ between regions depending on the recurrence time. In order to assess the magnitude of the climate change factors, the results of the regional climate scenarios established in the context of KLIWA, were employed as input quantities for water balance models and the runoff determined in water balance modelling was evaluated using extreme value statistics. The results for the future scenarios were compared with those of the current state. This was used to determine regional climate change factors for runoff for different recurrence intervals (five areas for Baden-Württemberg). The runoff resulting from flood regionalisation or hydrological model calculation can be directly increased with the climate change factor for the runoff in the load case climate change. Examples: The following examples should explain how plans can be implemented in case of increased design values, i.e. taking into consideration the load case climate change. • Planning of a flood protection dam: The dam is built according to current guidelines. However, additional measures are taken, which would not be required according to previous planning regulations. For example, an additional strip of ground on the valley side is reserved, enabling a future increase of the dam, if necessary, without additional problems. • New constructions where a future alteration or adaptation is not possible or is only very expensive (e.g. bridges), should immediately be planned to take account of future increased calculation parameters relating to the level of water, if necessary. • New constructions where a future adaptation is less difficult (e.g. river walls) should in view of the construction features (e.g. statics) be planned to a higher specification than currently required so that any further adaptation necessary (e.g. increase in height using stationary or mobile elements) would be possible without high costs. |
[Framework: KLIWA Project] | Hennegriff & al 2006 - A |
Recommendations
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Remarks |
Object |
References |
The development of methods to calibrate reconstructed data with series of recent reliable climatic measures improves the assessment of warm or cold sequences and drought or flood episodes that occurred during the last 500 years. Thus it is possible to highlight random climatic fluctuations and trends. Their consideration could contribute to improve the probabilistic evaluations concerning long return periods of natural extreme phenomena, which trigger contemporary natural disasters. The transfer of such results would help land planners and policy makers to improve their understanding of natural hazards threatening populations and to have relevant information for regional and local policies of environmental conservation. Finally, the crossing of more numerous and coherent climatic series of indications for historic periods before instrumental measures would help to understand if extreme climatic events can be explained by the natural variability of climate or if there are recent trends related to the actual global changes. |
Paul 2002 - A | ||
In terms of the hydrological effects of climate change, future global circulation model projections incorporate too much uncertainty to accurately specify expected patterns of precipitation change, and even less the frequency and magnitude of extreme storm and flood events. Predictions can be improved by incorporating long-term flood records (several millennia) in climatic modelling and statistical analysis. The study of temporal variability of past climate-flood links can establish short-and long-term relationships at regional levels and in areas within different climatic zones (Benito et al., in press). Regional studies of long-term climate-flood links involve calibrating the relationships, detecting trends (where they exist) and revising estimates of return periods. This integration will greatly advance our understanding of flood frequency and magnitude in the context of changing climates where the assumption of stationarity (implicit in most current flood risk models) is being questioned. European palaeoflood studies can take advantage from long documentary records (last 1000 years) which describe extreme flood occurrence (exact dates) and produced damages. The best scenario combines palaeoflood discharge estimates from bedrock canyons with documentary description and quantification of flood impacts on past socities, including economic losses, recovery strategies and flood management at different periods. The history of past floods [...] provide a unique opportunity to understand the flood hydrology and the social impact of “catastrophic floods” with magnitudes far beyond the ones recorded at gauge stations. This, in turn, means gaining an understanding of individual extreme events not available and perhaps not predicted by the instrumental record, as well as to gain a new dimension on socio-economic impacts and perception of extreme events, which needs to be evaluated according to different historical contexts. Flood damage exerted on riverside societies during centuries is very valuable information to be used in risk education tasks directed to Civil Protection technicians, volunteer bodies and in schools. In the investigation of the environmental effects and risks associated with fluvial systems in natural and anthropogenic disasters, the participation of multidisciplinary groups made up of geomorphologists, sedimentologists and hydrologists, mathematicians and environmental mangers is increasingly called for. The appropriate analysis of hydrological risks is dependent upon the development of new methods in the field of palaeoflood hydrology as a complement and/or alternative to instrumental hydrology. These should allow the standardization of discharge estimation procedures and flood risk assessment using non-systematic data for small watersheds devoid of gauging stations, and also improve the estimation of peak discharges for floods of long return periods (500 and 1000 years) aimed at increasing the safety of dams. |
Benito 2003 - P | ||
Already in the present situation, communities have to learn to modify or adapt new life styles in regard to their activities and behaviour in the case of extreme floods. Of course, nothing can change unless clear and necessary information could be provided in the sense of optimising the prevention actions taken with the object of reducing the vulnerability on a medium term, and, developing modern and efficient organisation of alert and hydrometrological forecasting to improve the protection in a short term. In this scientific, technical, social, economical context, the collective memory of the historical is absolutely fundamental. It is necessary to collect systematical observations from 1850 until 1950 on atmospheric pressure-air temperature, rainfall-discharge (height level) and on a daily basis with critical analysis of the data; from 1950 to 2000, the same collection and analysis can be made, completed by more detailed observations (hourly) and new parameters (radiosounding, satellites, radars....). Then it would be very important and useful to elaborate a database of this information concerning local and extensive rainfall-flood events, between 50 to 100 perhaps, available to all communities in Europe (scientific, historic, social, political, public...). Applications will be: - optimising prevention actions and improving rainfall and flood forecast, - testing the hypothesis of climatic modification in regional /local extreme hydrological risks. |
Duband 2003 - P | ||
It is necessary to protect populations from extreme events, even without considering climate change, because of the increasing concentration of vulnerable properties and stakes and the increasing safety demand. In a climate change context, threats, protection objectives and accepted residual risks should be periodically adapted to changing conditions. Very flexible solutions should also be envisaged. In the medium term, evaluation and planning methods must be developed, in order to quantify the danger resulting from a changing climate. Current simulations calculate an increase of the heavy precipitation intensity and an acceleration of river discharges during the winter half of the year. They should be considered in the risk evaluation, the planning of protective measures (reforestation, protective buildings, buffer area…) and the land planning. It is also necessary to take into account changes which could occur by the end of the planned measure. The same initiative should be applied to estimate zones subject to landslides. |
Policy makers | OcCC 2003 - R | |
It would be useful to improve the collaboration between the hydrology historians and the community of archaeologists and geo-archaeologists because their combined contributions would have a stronger potential. A “macro-regionalization” based on the climate, but nuanced by topography is proposed. This has value for the practical determination of the flood potential; the precise zoning presents a directly applied end. This work implicitly underlines the necessity to make a data base at the European scale. |
Bravard 2004 - A | ||
France: One of the most urgent priorities for the adaptation concerns the planning and the development of large infrastructures, such as new buildings and transport networks. The cost of climate change adaptation will be reduced if it is immediately taken into account in the following cases: • during the improvement or the extension of existing infrastructures; • when revising previous plans; • when examining a project in a sustainable development point of view; • before the community has to react to a sudden event or following an increase of maintenance costs. (1) Be sure that the planning takes into account the future trends of flooding events. Look at the possible options for the flooding management, for example, the implementation of well dimensioned and sustainable protections or the possibility to implement the development area outside of the maximum risk regions. (2) Include the landscape planning that could compensate the floods effects and the water excess. (3) Be sure that the emergency procedure and equipment are sufficient to face the identified risk increase. (4) Examine the possibility to limit the new housing development in floodable area, promote the flood protection measure for the existing buildings. (5) Examine the flood protection possibilities or change the location. (6) Strengthen the monitoring and cleaning of the shoulder and bridge pier as well as the gutter to limit clogging events. |
Policy makers: thematical recommendations: land planning, housing, transort, public health, public information... | ONERC 2004 - R | |
The policy makers are not really aware of the climate change induced necessities which requires urgent actions to identify and implement Society protection measures; such as measures to assure the water resource during summertime by creating artificial lakes, more efficient water use and protecting the mountain forest in a way to increase the buffer effect of soils and improve the avalanche protection. |
Seiler 2006 - P* | ||
Adaptation of flood protection planning: |