Flood risk management measures can be used to prepare for floods


Flood risk assessment and management measures can be used to prepare for floods and the damage they cause. Various types of flood maps are vital to the effective management of flood risks. In the event of a flood, damages are reduced through measures taken by authorities, but it is crucial that citizens also take the initiative in preparing for floods and protecting their property from the flood damage.

Climate change increases flooding

Normally dry land covered temporarily by water is called a flood. Flooding may be the result of a rise in the water level of watercourses (rivers and lakes) or the sea, or it can be caused by the accumulation of storm water runoff from for example heavy rain or melt water on land (figure 1) [1] .

Floods are estimated to increase in Finland as a consequence of climate change. The autumn and winter flooding of watercourses will become more frequent and increase in volume, while spring floods will decrease and occur earlier. The water levels in large central lakes will rise higher in the winter, and the risk of slush floods may increase by higher winter flow rates (discharge) of their outlets, such as Kokemäenjoki River, Kymijoki River, and Oulujoki River. However, change depends on the location and features of a given watercourse. In some parts of Finland river and lake flooding will decrease, while in others it will increase. [2], [3]

The risk of sea floods will also possibly increase along with the predicted sea level rise [4], [3]. In summer, more intense heavy precipitation events will increase urban floods caused by storm water runoff if drains and flood routes cannot channel flood water away quickly enough [2], [3].

Flood damages can be reduced by managing flood risks

Without preparation, floods may pose a hazard to health, safety, the environment, infrastructure (for example transportation and energy systems), economic activity, and cultural heritage. These damages can be reduced by flood risk management measures [1], [5].

Flood risk management involves a set of measures which aim to assess and reduce flood risks as well as prevent or reduce the damages caused by floods [6], [1]. In Finland, flood risks are traditionally managed by flood protection measures, such as regulating watercourse levels, dredging rivers and streams, and embanking shorelines.

Flood damages can be significantly reduced by taking floods into consideration in land use planning [6]. For example, urban floods can be most effectively managed by reserving adequate catchment areas and flow routes for storm water runoff. Land use planning is supported by systematic flood mapping. Flood maps are used to provide authorities and citizens with information on flood areas. [7] Using flood forecasts and warnings, it is possible to guide rescue operations during a flood and reduce flood damage.

Figure 1. Päntäneenjoki River in Kauhajoki flooded in the autumn of 2012.

© Unto Tapio, Etelä-Pohjanmaan ELY-keskus

Flood risk management is governed by legislation

In Finland, the management of flood risks is regulated by the Flood Risk Management Act and Decree which implement the Floods Directive of the European Union (EU) [8] at the national level. The purpose of Finnish flood risk management legislation is to reduce flood risks, prevent and reduce the adverse consequences caused by floods and promote the preparedness for floods. [9], [10]

Statutory flood risk management involves a preliminary flood risk assessment, the identification of significant flood risk areas, flood mapping and flood risk management planning for watercourses or coastal areas with at least one major flood risk area. The Act covers river and lake floods, sea floods, and urban floods. [9], [10]

ELY Centres and municipalities are responsible for the management of flood risks

The agency responsible for flood risk management depends on the type of flood. The planning of flood risk management for watercourses and coastal areas is the local Centre for Economic Development, Transport and the Environment (ELY Centre). Municipalities are responsible for the planning of urban flood risk management. [11], [9]

Finland has 22 significant flood risk areas

As part of implementation of the flood risk legislation, the Ministry of Agriculture and Forestry have identified the areas where the risks posed by watercourse or sea floods are considered significant. For the first time, these significant flood risk areas were designated in 2011. The review and designation of these areas for 2018–2024 took place in 2018. There is a total of 22 of these significant flood risk areas, five of which are located on the sea coast and the rest along inland watercourses (figure 2). No urban flood areas are included among them. Three new significant flood risk areas were designated and two areas removed based on the review of 2018. [12], [13]

The significant flood risk areas are chosen based on preliminary flood risk assessments conducted by the regional ELY Centres. ELY Centres reviewed all flood risks from watercourses or sea floods in 2018 using uniform criteria. In the assessment of the significance of flood risk, the likelihood of the flood event and the adverse consequences from the general perspective were taken into account. In addition,  the impacts of climate change, past floods and implemented flood risk measures were taken into account together with more precise spatial and other information. [12], [13]

Figure 2. 22 significant flood risk areas have been identified in Finland [13].

For the significant flood risk areas flood maps and flood risk management plans are prepared. First flood hazard and risk maps were made in 2013 and management plans in 2015. Management plans will be prepared or updated 2021 taking into account likely impacts of climate change [14]. Flood risk assessment, flood maps and flood risk management plans are updated every six years. Work related to flood risk management is also done in flood areas other than those listed as significant flood risk areas. Municipal and state authorities must take flood risk management plans into consideration in their own activities. [9], [10]

Flood hazard and flood risk maps can be used as tools for flood risk management

In Finland, there are two types of flood maps made for flood risk management: flood hazard maps and flood risk maps. Both maps can be used as tools for, among others, land use planning, rescue operations, and communications. [7], [15] The maps are available on a web-based Flood Map Service which was launched in 2014 [16]. Flood hazard and flood risk maps will also be prepared or updated for areas other than flood risk areas, resources permitting. [15]

A flood hazard map uses a map template to indicate the probable extent and degree of severity of a flood. The degree of severity is usually expressed as water depth. [7], [17] Flood hazard maps are primarily made for river and lake floods, but also for sea floods and floods caused by ice. Some maps also take into consideration the impact of climate change. In Finland, flood hazard maps have been made for over 100 areas, also including areas other than significant flood risk areas. [16]

In addition to flood hazard maps, flood risk maps have also been made for significant flood risk areas. They are used to indicate flood inundation as well as flood-related risk factors: information on the number of people at risk of being flooded; key functions; buildings difficult to evacuate, such as hospitals and nursing homes; and areas that may pose adverse consequences to people or the environment during a flood. [15]

Damage prevention measures are presented in flood risk management plans

Flood risk management plans have been prepared for significant flood risk areas. These plans contain the objectives and measures for reducing and preventing the damage caused by flooding. The array of proposed measures ranges from the self-initiated protection of property to land use and from forecasting to operative flood prevention. [11]

Plans address, for example, flood forecasting and warning as well as land use and rescue operation planning. These plans analyse needs and possibilities for flood water retention, developing watercourse regulations or dredging, and embanking, among other things. They also take into consideration the objectives of water management. [11]

Regional ELY Centres and flood management groups are responsible for the preparing of flood risk management plans. First plans were published in December of 2015. [11]

Flood risks can be avoided with proper land use planning

It is essential to prevent the formation of new flood risk areas in flood risk management. This can be most effectively done by taking flood hazards into consideration in land use planning. The National land use guidelines of 2017 state that the new building should be located outside flood hazard areas or management of flood risks must be secured by other means [18]. In principle, these objectives are very clear but conflicts often arise in their practical implementation, for example, there is also a need to increase the density of the community structure. The complementary building of old areas within a flood hazard area also often creates conflicts due to the different foundation elevations of new and old buildings. [15]

Regional recommendations exist for minimum building heights

ELY Centres and their predecessors, regional environment centres, have issued recommendations on the minimum building heights for their respective areas. Many municipalities also have their own recommendations. A revised guide on the specification of lowest building elevations is also available. [19]

Citizens should also take their own initiative in preparing for floods

In the event of a dangerous situation, so under a threat of flooding or during a flood, each citizen is responsible for the protection of their own property. [15], [20], [21] The authorities will make every effort to assist the citizens (table 1).

Table 1. Division of responsibilities with regard to floods [20]
Residents are responsible for taking their own measures to protect themselves and their property.
Rescue services are responsible for operational planning and guidance in the event of a flood as well as for rescue operations.
  • General supervision of flood prevention if multiple agencies are involved in the rescue operations as well as forming a situational overview
  • Protection of areas and key sites based on the situational overview (such as floodwalls, sandbags, the making of temporary embankments and dams)
  • Specifying measures for the protection of personal property (such as breaking roads or embankments)
ELY Centres are responsible for informing the public of any flood hazard, making advance preparations for a flood and overseeing watercourse use.
  • Monitoring the water situation and issuing flood warnings
  • Preventive measures (for example ice cutting, sanding, regulatory control)
  • Expert assistance for rescue authorities/organisations protecting their property or private persons in the following flood prevention measures: breaking up ice dams, making temporary embankments and dams, and directing water to temporary areas and channels
Municipalities are responsible for protecting their own buildings and functions as well as for providing support to rescue authorities in flood protection.
  • Protection of municipal structures (such as water supply, health centres, schools, daycare centres) and telecommunications
  • For example, evacuation and organising emergency shelter
  • Providing manpower and equipment for the rescue authorities, when necessary

Information and practical instructions on what to do in the event of a flood threat are available on different websites [22], [23], [24]. Some rescue departments have also published and distributed flood preparation guides for home-owners [22]. Flood forecasts and the manner in which information is presented are crucial to the success of self-initiated measures. The Flood Centre forecasts floods and issues flood warnings as well as constantly monitors the flood situation. [25]