Evaluation

The qualitative evaluation of the adaptation strategies is based on expert judgement using a number of indicators, which have been selected to represent various impacts that can be expected. A brief description of these indicators and some considerations concerning key adaptation aspects is given below. Table 7.2 illustrates an assessment matrix of the five adaptation strategies.

People at risk

Flood protection measures aim to reduce the number of people at risk. The most effective way is to reduce peak flows by upstream storage and efficient discharge. Traditional measures of dyke strengthening and heightening will on one hand reduce the frequency of flooding but at the same time potentially increase the magnitude of a flooding event (depth and extent). The flood protection measures in the 'Safety' strategy will reduce risk in the short term (2039) but possibly increase risk in the long term (2099), especially since the frequency and magnitude of extreme events will increase during that period.

Economic losses

Economic losses are defined as direct and indirect damage to property and income. Without protective measures (flood proofing, etc.) even relatively small events (in terms of flood depth, extent and duration) can result in considerable direct and indirect damage. Typical examples are the pollution by fuel oil from flooded oil tanks for household heating situated in the basement of buildings and damage to electrical and other equipment in the basement or ground floor of private, commercial or public buildings (e.g. as occurred in Dresden in 2002; www.dw-world.de). Possible interruptions of normal trade through blockage or disruption of communication and transport will result in considerable economic losses as well. The latter can be the result of floods and extreme weather events, but also of very high or very low flows in the river that interfere with shipping.

Fish diversity

The main impact on fish diversity will be the loss of habitat due to further canalization of the river in the 'Industrial' strategy. Introduced species may profit from new conditions directly through a more favourable environment (e.g. temperature) or through a reduced resilience of native species. In general the risk of introduction of new species will be a determining factor, although some 'pockets' of special conditions will allow the continued survival and potential spreading of deliberately or accidentally introduced exotic species (e.g. local population of tropical fish Poecilia reticulata in cooling water of power plants in Ijmuiden, The Netherlands).

Upstream forest

One of the measures to influence peak flow levels is to increase the upstream retention of rainwater. In the Rhine Basin this is of special concern in periods when the evapotranspiration of agricultural crops is low.

Table 7.2. Expected effect of the five strategy options in the period up to 2039 and the period up to 2099.

Strategy

Adaptation Environment Industry

Safety Integrated

Indicators

2039 2099 2039 2099 2039 2099 2039 2099 2039 2099

Indicators

2039 2099 2039 2099 2039 2099 2039 2099 2039 2099

Human

People at risk (no.)

-

— —

+ +

+

0

0

+

+(—)

+

+ +

Economic losses

+

+

+

+ +

+

0/—

+ +

+ +

Ecosystem related

Fish diversity

0

0

+

+

0

0

+

+

Upstream forest (ha)

0

0

+

+ +

0

0

0

0

+

+

Floodplain forest and

wetlands (ha)

0/+

+

+

+ +

0

0

0

0

+

+

BOD

0

0

+ /—

0

0

0

0

0/+

0/+

Fertilizer

0

0

0

+

0

0

0

0

0

0/+

Lateral and

0

0/+

+

+

— —

— —

0

0

+

+

longitudinal

freedom (%)

Food production

Total production

0

0

0

0

0

0

Average yield

+

+

+ +

++

+

+

+

+

+

+

Variation in yield

+/—

+/—

0/—

0/—

Food security

Variation in farm income

0/—

0/—

—/0

— /0

Water productivity

0

0

0

0

0

0

0/—

0/—

Industry

Weirs (no.)

0

0

0

0

+

+

0

0

0

0

kW produced

— —

0/—

0

+

+ +

0

0

0

0

(hydropower and

cooling water)

Un-navigable

days (no.)

0

0/+

+

+

0

0

0

0/+

+ , positive effect of the strategy on this indicator (quantitative effect can be an increase or a decrease!); negative effect of the strategy on the indicator; 0, no effect of the strategy on this indicator. +/-: .. + + : ...

More extensive land use will help to improve infiltration, while (evergreen) trees will maintain evapotranspiration and also will intercept a considerable amount of water. An increase in upland forest is therefore a management measure as well as an element of the Environmental strategy.

Floodplain forest and wetland area

An increase in wetland and floodplain areas is considered as an environmental benefit, since it could attract more species and enrich existing ecosystems. Increasing vegetation densities in the floodplains has an adverse impact on flood risks by increasing roughness and hydraulic resistance, thereby reducing the conveyance capacity during peak flows.

A reduction in pollution loads will in principle result in an improved water quality. If flows are reduced at the same time (due to climate change effects and/or by upstream retention/utilization), the actual water quality could still deteriorate by lack of dilution.

Fertilizer

The modifications in land use to increase water retention and groundwater infiltration in the upstream parts of the catchment will result in a reduction of the area used for agriculture and therefore in a reduction in the total amount of fertilizer used.

Lateral and longitudinal freedom

Land use changes due to floodplain development and retention areas will positively affect the degree of lateral freedom in the river system and could contribute to the (re)establishment of 'ecological connection zones'. Impacts on longitudinal freedom would only result from the additional weirs that are part of the 'Industry' strategy. These impacts could partially be mitigated by the inclusion of fish ladders in the design of the weirs.

Total production

As a result of the increased CO2 levels, combined with an increase in temperature and net increased precipitation, the average yield of crops is expected to increase considerably. As such this is independent of any adaptation intervention. The overall result of the developments in agriculture is that areas with a reduced suitability (regarding soils, slope, exposure, etc.) are taken out of production.

Average yield

As mentioned above, the average yield of crops is likely to increase as a result of potentially more favourable climate conditions in combination with improved agricultural practices. In the 'Environment' scenario, it is assumed that the more marginal agricultural areas will be used for nature development. Concentration of agriculture in the most suitable locations will have an additional positive effect on average yield (per unit area).

Variation in yield

Although the increased climate variability is a factor that will add to the yield variation, the concentration of agricultural production in the most suitable areas will help to mitigate yield variation.

Variation in farm income

This aspect is directly linked to total production and yield variation but would also depend on the (new) role of farmers in nature conservation, management and recreation. This will ameliorate the negative impacts of climate variability on farm income, at least for some of the farms in some parts of the catchment.

Water productivity

Climate change in the Rhine Basin is associated with an increase in rainfall, together with an increase in evapotranspiration as a result of the rise in average temperature. Although (biomass) productivity will increase, this will be associated with a more or less equivalent increase in evapotranspiration. Water productivity as kg/m3 will therefore be more or less constant (assuming no or only a limited water stress during the growing season).

Weirs

If water depth becomes a limiting factor for navigation, the construction of additional weirs would serve to maintain the necessary depth in critical river stretches. It has to be noted that the reduced capacity of the fairway may be a more critical factor than the actual water depth. This concerns in particular the waiting times at shipping locks needed when weirs are constructed and reduced passage heights under bridges with changing peak flow regimes.

kW produced

For the production of electricity, the discharge of the river can be a limiting factor. The discharge determines the capacity of hydropower production. In the River Rhine the only major hydropower plants are located in Switzerland. The thermal power plants in the downstream areas of the Rhine depend on the river as a source of cooling water

(and the transport of coal). Adaptations to times of low flow are the maintenance of the minimum base flow through upstream storage or the development of cooling water reservoirs. A reduction of the need for cooling water can be achieved by constructing cooling towers or by the use of alternative energy sources (solar, wind) without cooling requirements. Energy crops are not part of the solution of the problem, as they would be used as fuel in thermal power plants (requiring cooling water).

Un-navigable days

Both during periods of peak flows and periods of low flows, navigation on the Rhine and its tributaries will be impeded. This can be caused by physical limitations or regulatory constraints. An increase in extreme high or low flows will increase the frequency of reduced navigability. Most strategies aim at reducing peak flows by upstream storage, allowing release of water during periods of low flows. Navigation will benefit to a certain (limited) extent from this levelling of extremes, but only the specific measures in the Industry scenario will have a positive effect.

The measures in the Industry strategy prevent economic losses from reduced working days and reduced capacity. The projected economic losses would be higher due to a combination of increased climate variability and climate change trends. By implementing the specified measures, economic benefits increase after all. Increasing the heights of dykes and levees in the Safety strategy implies an increased protection factor, but the number of people potentially at risk and the magnitude of potential damage will increase as well. The use of emergency storage areas could result in considerable economic losses. This is more likely to occur in the later part of the century. In that case the economic benefits of protection would be partly eliminated. With an increasing risk factor, combined with a growing population and ongoing investments in flood-prone areas, the benefits of protective measures will increase, although the measures themselves may not be changing.

Due to a more sustainable approach, the Integrated strategy is expected to have a positive effect on the economy. Increasing base flows in summer will enhance dilution, although the pollution level (load) itself is not affected by this strategy. The increased forest area will reduce the amount of fertilizer used, but due to the soil reservoir this is only a long-term effect. Retention measures upstream, combined with appropriate operation schemes, will result in a higher base flow in summer. This will be especially important in the latter half of the century and the forestation may only be required after the 2039 period.

Finally, maintenance of flows for (hydro)power production could also benefit navigation.

Preferable strategy and key indicators

Obviously the number of people at risk and potential economic losses are two core indicators in the evaluation of the five strategies. Given the number of people at risk, it is perhaps surprising that the safety strategy has not been allocated the highest score. The main reason for this is that the amelioration of extreme flows in the Environment

Table 7.3. Quantitative comparison of scenarios against the five adaptation strategies.

Strategy

2039

2099

BAU

-4.5

-7.5

Environment

6

9

Industry

0

2

Safety

1

-1.5

Integrated

6

8

and Integrated strategies, combined with a limitation or even reduction of the population in flood-prone areas for ecosystem development, results in the highest score for these two strategies. Economic losses are reduced by the Industry strategy, but here also the Environment and the Integrated strategy score nearly as well, or even better.

The 'natural' condition of the floodplain is best described by the indicator 'lateral and longitudinal freedom'. Additional weirs and canalization in the Industry scenario obviously will have a clear negative effect, while the Safety scenario does not affect this indicator, as this scenario does not include significant interventions in the flood-plain itself.

The indicators kW produced and number of un-navigable days are specific for the industrial interests. Only the specific measures in the Industry scenario have a positive effect. In the other cases the result is mostly neutral, although again the reduction of the duration and magnitude of the highest and lowest flows in the Environment and Integrated scenarios will have some influence.

As discussed earlier, the productivity of the agricultural sector is predominantly determined by political considerations at the EU level. In the evaluation of the climate adaptation scenarios the food production and food security indicators therefore do not play an important role.

By allocating values to the indicators scores in Table 7.3 a quantitative comparison can be made, although it has to be stressed that in this case it has been assumed that all indicators have an equal weight. In practice the selection of a strategy would depend to a large extent on the weighing of the different impacts.

Table 7.3 shows that the BAU strategy has very undesirable results, which will increase after 2039. The opposite applies for the Environment and the Integrated strategy, whereas the Industry and Safety strategy have a low score, with a negative score for the Safety strategy in the long term. The reason for this low score is partly due to their limited scope with hardly any positive spin-off in the other sectors.

The difference between the Environment and Integrated strategy is mainly due to differences in the agricultural sector, while the economic losses are lower in the Integrated strategy. Taking into account that socio-economic considerations will be of major importance, an integrated strategy is the most likely choice.

Cost and benefits

Apart from estimates of maximum potential damage, it is difficult to compare the financial benefits of the different strategies. The (Dutch) Emergency Flooding Areas

Commission (Commissie Noodoverloopgebieden, 2002) estimated a possible reduction of flooding damage of about €54 billion through the development of emergency flooding areas at a cost of around €1 billion. In the same report, the total investment costs of installing all potential emergency storage areas is estimated at between € 1.7 and 2.3 billion. This would provide a storage capacity of 1—1.2 billion m3. Actual flooding of these areas would, however, result in collateral damage of a maximum of €7.4 billion. It should be noted, however, that the social aspects are by far the most important factor in implementing these measures, as it would involve huge efforts from the regional population (capital losses, movement of companies) to develop these areas.

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