No matter how good flood defences are, they can always fail under extreme conditions. Therefore it is recommended to also develop the capacity to absorb flood events: to minimise damage and casualties in case of a flood. Many instruments to do so can be found in the domain of spatial planning. However, there is a general tension between the economic development interest in flood prone areas, and the interest to minimise flood risk. This tension is higher in countries with a lot of flood prone areas, like the Netherlands. In spatial planning all those interests collide. An often heard complaint from the flood risk management community is that too many developments in flood prone areas are allowed. Yet, in the end it should be a societal or political choice which developments in flood prone areas are accepted and which are not.
Spatial planning instruments can largely be divided in two categories. One is to prohibit development in flood prone areas, another is to develop planning conditions that minimise the potential damage caused by flooding by flood-proofing buildings.
France has a particularly strong spatial planning policy, with zoning that prohibits development of the highest risk areas. Belgium, England and Sweden have spatial planning policies that aim to direct development away from the highest risk areas, with the possibility of exceptions under certain circumstance (such as a lack of available land at lower risk). In Belgium and the Netherlands water managers are involved in spatial planning to check the impact of new developments on water and flood management and to give advice. Insurance mechanisms can also be used to discourage development in flood prone areas, e.g. by charging higher premiums for properties in flood prone areas (see §7.2).
In many countries spatial planning rules to prevent or mitigate flood risk are in place. A recurring issue is, however, the lack of enforcement of these rules. This may require a system with multiple checks and balances.
The good examples described below are the water assessment and signal areas in Flanders, construction and permitting in Sweden and the link between spatial planning and flood risk in Nice (France).
With increasing urbanisation, there is an increase of paved and impervious land surfaces leading to a decrease of water infiltration and storage. This increases the chance and number of flood events with the subsequent effect of more damage to residential properties. In order to decrease future damage, Flanders has two tools that influence spatial planning procedures: the Water Assessment and the Signal Areas address the decrease of room for water and the increase of imperviousness. With these instruments the Flemish government hopes to avoid a substantial increase of potential flood risk.
The Water Assessment tool is an obligation for authorities to ask advice from the water manager on the impact of a permit, plan or programme on the water system (applicable to all building permits). The advice is non-binding but authorities have to motivate the reasons for deviating from it in the final permit, plan or programme. This can prevent further decrease of room for water in places where water storage is important and can prevent further imperviousness of the soil. With this advice, the awareness among authorities of the impact of planned developments increases.
By controlling the activities and development on undeveloped land, the Flemish government aims to avoid a substantial increase of potential risks. Signal areas are mainly areas with a ‘construction’ destination (e.g. residential) in flood-prone areas. Potential futures for these areas range from an innovative flood-proof within the current destination to a re-destination of the area with flanking measures, as arranged in the Circular LNE/2015/2 of 19 May 2015.
The Signal Area approach is connected to the Water Assessment instrument and the duty to inform that is described in §5.7.2. Together these instruments influence developments in flood prone areas. They address the lack of attention paid in the past to water issues in Flemish spatial planning and oblige planners and governmental institutions to focus more on this. Similar instruments could also be applied to prohibit or steer developments in flood prone areas in other countries (STAR-FLOOD Deliverable 3.4, see §8.2.1).
In the new National Guidelines (2016) from the Swedish Water Organisation, it is stated that the location of new urban developments has to be safe from both fluvial and pluvial flooding of a 1/100 year rain event. The plans have to be formally approved at many different stages in the planning process, minimizing the risk of projects that significantly increase flood risk slipping trough.
Building permits, which may involve restrictions for building in certain areas, come from the municipal level, which has a complete overview of the local situation. The municipality is also responsible for detailed area planning and has to evaluate the risk of both pluvial and fluvial flood risk. In addition, the County Administrative Boards have an important function in checking the municipalities. If the County Administrative Board does not agree with the municipality on the decision of permitting the construction of buildings because of the flood risk, they can stop the detailed plan referring to the flood risk STAR-FLOOD Deliverable, WP 3.5, see §8.2.1).
Since the creation of the Department for Risk Prevention in the Ministry of the Environment at the end of the 1980s, risk prevention has been an independent (and multi-dimensional) field of action dominated by the State. It is part of a broader planning culture that is dominated by the principle of rigorous restrictions on construction in risk areas.
Municipalities also play an important role, as they are responsible for land planning and issuing building permits. It is worth noting that the principle of independence of the law leads to a separate implementation of risk policy and urban planning policy. The two main planning tools (the Risk Prevention Plan (PPRi) and the Local Land-Use Plan) are thus used by two independent public authorities. The Flood Risk Prevention Plan is elaborated by the State and sets overarching rules for spatial planning and construction in flood prone zones. The State imposes its vision on flood risk management on local authorities, by prohibiting construction, or by limiting or regulating it with obligations to adopt building mitigation measures. In this way, local authorities are obliged to take the flood risk into account in their land use plans.
The case of Nice illustrates the progressive evolution process that leads locally to a softening of the restrictive flood legislation and makes local development viable. It challenges the national approach and framework. The relationship between the State and local authorities has evolved over fifteen years.
In 1999, the first proposal of a very restrictive flood zoning plan for the area of Nice was issued. It finally got approved in 2013, with a softening of the zoning regulations. The evolution process took place in the specific legal framework of a National Interest Operation (OIN) launched in 2008 to promote the Eco-Valley project. It led to a master plan in which the State and local authorities control local land use plans. The aim of the plan is to launch four major projects (a business centre and multimodal transport hub, a technological centre called, a food and horticultural platform, and an eco-district).
Besides the Flood Risk Prevention Plan, other instruments play a role in flood management and spatial planning in Nice as well, involving several stakeholders. Among these, the public Development Organisation (Etablissement Public d’Amenagement – EPA) is the operational body for the new pro-development coalition. Gathering various public and private partners, the Development Organisation implements the Eco-Valley project.
In 2012 the Development Organisation elaborated a specific study for the planning of the Grand Arenas sector, business centre and multimodal transport hub: the SCHAE study. It assessed the possibility to build without increasing the level of risk exposure on both the Grand Arenas sector and adjacent districts, bringing to light that it can be done. This constituted an important step in the process towards softening the restrictive flood legislation in the Risk Prevention Plan.
At the same time, two Actions Plans for Flood Prevention (PAPI 1 2009-2014 and PAPI 2 2012-2018, see also §4.3.2) have been implemented, principally to guarantee the funding of the major protection works. The formal uptake of dikes in these plans opens up the way to development projects.
At the end of this process, the role of the State changes from a provider of regulations and controller to an actor involved, inter alia, in the bargaining game to attempt to combine development and flood prevention. Each with their own interests, but in dialogue, the involved authorities explored which developments are still possible in the flood prone area without increasing flood risk (STAR-FLOOD Deliverable 3.7, see §8.2.1).
 The National Interest Operation status is given by the State to projects with scopes of national interest.