Flood Risk Management Strategies in Europe

Disastrous floods cause tragic mortality and economic losses on a large scale. Being a natural disaster, it is quite implausible to reduce the flood losses to zero, but appropriate measures can reduce the likelihood and limit the impact of floods. In addition to social and economic damage, floods can have a severe impact on the environment, for example when installations holding large quantities of toxic chemicals are neutralized or wetland areas are destroyed. Europe has identified the looming flood risk in European region and to support the transition from traditional flood defense strategies to a flood risk management approach to a basin scale, it has adopted a new Directive in 2007 (2007/60/EC). One of the major tasks of these directives is where the member states involved in carrying out flood risk management plans. To comply with the directives, mapping of flood hazards and risk in each territory is necessary which forms the basis of flood risk management plans. This paper gives an overview of detailed functions off stages of a flood risk directive with respective illustrations and the measures taken to accomplish the EU wide regulation for flood risk in Europe.

Through the ages, the problem of flooding has acquired a particularly notorious reputation for itself. With global warming and increased rate of urbanization the severity of the problem has grown exponentially. Nevertheless, the social, legal and scientific studies on the trans-boundary flood risk management are sparse, fragmented and restricted in scope. At the same time, the collaborative measures and strategies for trans-boundary floods i.e., floods that originate in one country and then propagate downstream to another are poorly understood. In general terms, a flood event is generally where water overflows outside its normal confines and temporarily covers land bodies. Similar to any event, a flood event also breaks down into two high level components: (1) Probability of an event occurring (2) Impacts associated with the event. This paper aims to explain the EU directive step by step plan, process and the measures undertaken to mitigate the prospective flood risks which Europe could face in the future.

Flooding is normally caused by natural events such as prolonged excessive rainfall and thunderstorms over a short period of time, high tide combined with storm conditions, ice jams and poor insufficient drainage networks and inadequate maintenance of watercourses. The reason behind these causes can be explained under three categories as follows:

a) Overflow due to heavy rains:

After heavy rain, the river bursts its banks and the water engulfs the entire valley far from its precipitation zone. The other tributaries add to the flow of water causing a flood event.

b) Water accumulation in basins:

In normal weather conditions, water is absorbed into grounds and merges with the water table. When the ground is saturated, the water builds up in low line areas. Runoff quickly fills the valley in heavy rain condition resulting in a flood.

c) Urbanization in flood-prone areas:

Excess water passing through drainage system accumulates in low line zones. It is now in bad shape due to excessive land use, coverage of land due to buildings and impermeable surface like concrete.

Although flood itself is a unique phenomenon, it is further classified into different types based on their causes, namely:

a) Coastal flood or surge flood:

Coastal floods occur in areas which lie in the coast of the sea, ocean or other large bodies of open water. Extreme weather conditions lead to unstable tidal conditions when a hurricane and other storms push water onto the shore. This is often the greatest threat associated with a tropical storm. Various factors like strength, size, speed and the direction of the storm help determine the extremity of the resulting coastal flood. The coastal flood models consider this information along with the data from historical storms of the affected area to estimate the likelihood and the effectiveness of a storm.

b) Fluvial flood or river flood:

Excessive rainfall over an extended period causes a river to overflow, leading to fluvial flood. This is also caused due to snow melts and ice jams. The damage from river flood can be widespread as the overflow affects smaller river downstream often causing dames and dikes of rivers to break open and swamp the adjacent areas. The severity of river floods is measured by the amount of precipitation in an area, duration of the precipitation, previous saturation records of soil and the terrain surrounding the river system. The flood water accumulation depends on regions. In hilly areas, floods can occur in minutes after a heavy rain whereas in flat areas flood water rises slowly and often remain for days. To determine the probability of river flooding, it is necessary to consider the past and forecasted precipitation, current river levels, and temperature.

c) Pluvial flood or surface flood

Surface water flood is caused when heavy rainfall creates flood event which is independent of an overflowing waterbody. It is commonly believed that one must be near a waterbody to be at risk. Pluvial flooding debunks the myth, as the urban areas are also prone to flooding. Intense rain saturating urban drainage system and runoff water from rain on hillsides that are unable to absorb water are few examples. Pluvial flooding generally occurs in combination with coastal and fluvial flooding. These floods are capable of significant property damage.

Disastrous floods cause tragic mortality and economic losses on a large scale. In addition to social and economic losses, these floods also have severe impact on the environment, for example when installations storing large quantities of toxic chemicals are submerged. Since 2000, floods in Europe has resulted in at least 700 deaths, displacement of about half a million people and approximately EUR 25 billion in insured economic losses. The following figure shows the flood impact in Europe from 1950-2005.

Figure 1: Major flood disasters in EU, Bulgaria and Romania 1950-2005

Numbers in the map represent each flood event. During this period 3539 floods of all types occurred globally, of which 298 of them took place in the current EU member states. This cost around 5500 lives and resulted in about US$ 106 billion in damage. 01-23 being flush floods, 24-44 being river floods and 45-47 which is storm surge floods. The triangulated features on the map represent very large regional events.

Many floods have consistently ravaged Europe throughout the centuries, making urban planning a serious challenge. The coming decades are likely to see a flood risk in Europe and greater economic damage. Fluvial flooding is the most common type of flood in Europe. The following figure represents the recurrence of a flood in Europe between 1998 and 2005.

Certain areas are more affected than others. Between 1998 and 2005 north-western Romania, northern Italy, central and southern Germany, south-eastern France and eastern England struggled with frequent flooding.

Many measures are undertaken like constructing rive dikes and using sandbags. But these are just measures to avoid and encounter flooding up to an extent. For the estimated probability of prospective flood events, thee measures do not suffice to reduce the impacts associated with floods. Hence EU flood risk directives came into existence in 2007.

Directives 2007/60/EC, assessment and management of flood risk or also called Flood risk directives entered into force on 26 November 2007. Unlike a regulation it does not set rules on how the objective must be achieved, which means the directives does not set any priority. Each member state (MS) can set a goal collaboratively and decide what national measures are needed. This gives the MS lot of room to choose their own approach. The flood risk directives work in coordination with the water framework directive. Flood action program where the Flood risk management plans and the river basin management plans are coordinated through Public participation procedures (ns, 2013 June). These reinforce the rights of the public to access flood risk information and to have a say in the planning process.

The FD requires that wherever a significant flood risk is identified, maps must be drawn to show its potential extent and consequences of flooding. Based on the maps generated, the MS's must establish a Flood risk Management plan with an aim to reduce the risk associated with an acceptable level. Within this plan, a wide range of measures is considered to achieve the goal, which is dependent on the nature and scale of the issues. To aid this process, the FD has a 3-phase approach. The detailed action plan measures are explained in the following phases.

Phase 01: Preliminary flood risk assessment

This is the first stage of FD where a preliminary flood risk assessment must be conducted by MS's for each river basin districts. MS were requested to complete the assessment by 22 December 2011. The assessment conducted was based on readily available information such as records and studies based on long-term developments. According to Art 13.1, the FD has an exception to this obligation (ns, 2013 June). The MS’s may not undertake the flood risk assessment under two cases:

1. If the area has already been identified earlier before 22 December 2010 as a significant flood risk zone.
2. If it has been already decided before 22 December 2010, to prepare flood risk and hazard maps for the specified area.

The risk assessment must be reviewed and to be updated if required by 22 December 2018 and further subjected for reviews every six years thereafter.

Phase 02: Development of flood hazard maps and flood risk maps

Phase 02 involves drafting of flood hazards maps for the regions where there is a potential flood risk. For the first cycle deadline was set as 22 December 2013. The flood hazard maps categorizes the geographical regions into three separate categories - low probability or extreme event scenarios, medium probability (whose return period is likely ≥100 years) and high probability where appropriate.

Various external parameters are considered when it comes to mapping flood hazards. Parameters such as flood depth, velocity, flood extent, duration, the rate of rising water and the propagation are considered important depending on the region. Interesting examples of such maps are maps which show the water upsurge rate in Austria and Luxembourg which consequently help in mapping the flow velocity. Similarly, in Hungary and the Netherlands tracking water propagation through the low lying lands help in mapping the propagation pattern. Shown below is an illustration of different parameters for flood mapping:

a) Historical flood map.

b) Flood extent map.

c) Flood depth map.

d) Flood danger map.

e) Qualitative risk map.

f) Quantitative (damage) risk map.

Maps showing other parameters always take a single return period in consideration at a time, as it is practically not possible to depict parameters like velocities of several return period on a single map. De Moel et al. (2009) state that several countries have made commendable initial progress in mapping their national flood hazards, but most of them lack detailed information about aftermath of flooding. Currently available maps are mostly used for emergency and spatial planning, and flood zones in these maps serve primarily as guidelines (ns, 2013 June). Countries like France and Poland, where floodplain development can be legally regulated still struggle as the practical problems nullify the beneficial effects of the legislation in place to a good extent.

Also, mapping flood risk zones is an expensive and a data intensive process. Thus the quality of flood risk maps differs from country to country.

Phase 03: Flood risk management plans

Phase 03 required the plans to be completed and published by 22 December 2015. Also it instructs to have a review plan in place, and if necessary the flood risk management plan must be updated by 22 December 2021, every six years thereafter. MS should have a risk management plan for each river basin district, which should be in sync with the respective flood hazard and risk maps.

A single international flood risk management plan needs to be drafted for international river basin districts (IRDBs) falling entirely within the territory of the EU. In case where the complete IRDB area cannot be covered, MSs should fabricate a set of plans covering parts of IRDB located within their territory. Any plan drafted as part of this process should be coordinated at the level of the IRDB (Art. 8.2 of the FD) (ns, 2013 June).

OTHER BINDINGS

According to article 10, FD states that “In accordance with applicable Community legislation, Member States shall make available to the public the preliminary flood risk assessment, the flood hazard maps, the flood risk maps and the flood risk management plans”. The other bindings include:

1. Catchment basin approach: Entire catchment basin should be mapped in terms of flood risk.
2. Safety chain: Before and after flood measure should be in place in order to reduce the likelihood, risks and also to boost the readiness.
3. Risk approach: Plan of action must be based on ‘real’ facts – thorough analysis of the likelihood and the outcome of flood in any region.</li
4. Sustainability: Flood risk management plans must be built considering other EU directives and must look ahead in the future in terms of climate change.
5. Solidarity or non-transference of risk: All the measures should be harmonious and considerate.

There are many flood mappings in the European countries. Most of the illustrations identified in this paper were initiated in the recent decades. Even though a conceptual framework exists, an international standard to create flood hazard and risk maps is still not in place. Approximately 80% of nations use flood extent maps, making it the most frequently used type of flood map. Absence of a common international standard leads to different methodologies among different countries, and this could lead to an extensive range of risk maps which will be difficult to compare. This creates a problem while setting up management plans. However, few countries in Europe must make a step towards hazard maps as most of the other countries comply with EU Flood Directive (2007/60/EC). Climatic changes and increasing urbanization make the 69 trans-boundary catchments in Europe more prone to be flooded in the future. To mitigate the impact level in a short period of time, it is necessary to have directives or its jurisdiction from each country. The way flood management is approached is hence firmly dependent on approaches taken by the member states in Europe. Not being on the same page will severely hamper the Flood risk management in Europe.