Towards more effective strategies to reduce property level flood risk: standardising the use of Unmanned Aerial Vehicles

Effective flood risk management strategies require a detailed understanding of the source, extent and impact of flooding. Unmanned Aerial Vehicles (UAVs) enable detailed and accurate data collection that can be used to determine flood source, extent, impact and the presence of property level flood resistance measures. This paper draws on the practical experience of the authors including the use of UAVs during flood events. We highlight the potential uses of UAVs in flood risk management activities and the associated challenges. The impact of a flooding event will also be dependent on how well an area is prepared in terms of community and property level resistance and resilience measures. We have looked at potential reasons why there is not a greater uptake of property level resistance and resilience measures. It is clear that a standardised approach is required if UAVs are to fulfil their potential within flood risk management activities. We have identified five pillars of standardisation that underpin an overarching, purpose-driven, cost-effective systems-based approach to the use of UAVs in flood risk management. These are as follows: (P1) deployment, data collection and flight-related regulatory requirements; (P2) data processing, data merging and outputs; (P3) the introduction and use of innovative approaches and technological integration; (P4) use of outputs for public engagement and (P5) policy development and governance. We consider that the proposed approach will maximise cost-effective information gathering, standardise the way processed outcomes are generated and provide the basis for comparable and robust flood risk information that is based on a single coherent methodology.


THE FIVE PILLARS UNDERPINNING PURPOSE-DRIVEN FLOOD RISK MANAGEMENT APPROACHES
Such an approach recognises that environmental systems are complex and integrated through interconnected and nested subsystems referred to in the following discussion as Pillars. The use of Unmanned Aerial Vehicles (UAVs) technology in flood risk management activities can be used to test out the overall approach and to determine whether there are generic lessons that can be applied to other situations. UAVs, commonly known as drones, are small aircrafts piloted by remote control or onboard computers. Within the context of flood risk management, they have been used to capture high-resolution data to quantify flood extent and impacts.
A balance has to be struck between continuing technological advances and the development of agreed methodologies that then enable data to be shared and used widely irrespective of who has collected the data or even for what purpose. To that end we have defined five Pillars There is a need (P1) for the development of a standardised monitoring protocol for all the variables that inform data collection, such as flight altitude, resolution and accuracy of the imagery collected, number and location of waypoints, as well as spatial and temporal survey coverage, among others. This should include standards defining a purpose-driven use of UAVs to maximise information gathering for flood management decisions pre-, during and post-event and the platforms and sensors recommended for each application.
There is also a need to identify flight-related regulatory constraints and then propose policy and regulatory changes to address them. In the last few years, there has been a strong push to integrate airspace regulation with UAV operation following the decision of the European Council December 2013 to ensure the progressive integration of UAVs (<7 kg) into airspace as from 2016. The regulatory framework developed by the CAA and summarised in CAP722 and CAP393 positions the UK as a leading country in the areas of UAV deployment and operation with its aim being to enable the full and safe integration of all UAV operations in to the UK's total aviation system. The regulations restrict operations over congested areas and near (<50 m) people, buildings, vehicles (including vessels) or structures.
Although special licences can be granted to overcome these restrictions, this capability has not yet been explored in full within the context of flood extent and damage assessment.
In addition to the need for a standardised approach to data collection (P1), there is a need for an agreed protocol for data processing (P2). This should focus on the tools (e.g. software) used, the selection of approved and trustable processing algorithms, specific uncertainty and accuracy thresholds and workflow repeatability.
There is often resistance to the introduction and use of innovative and disruptive approaches. Sometimes this can be because policy and regulations are based on the outputs from an existing technique. There is also the time and cost associated with demonstrating equivalence and overcoming the barrier of acceptance by the practitioners and decision makers who have always used the traditional approach.
Means of overcoming these barriers and blockers need to be found (P3) demonstrating how UAVs can be used in a proactive and purpose-driven way to deliver clear benefits over the existing approaches.
The actions outlined above will provide the basis for preparing shareable, comparable and robust flood risk information that is based on a coherent methodology. Means by which such information can inform and facilitate the work of flood risk management practitioners and how they can be used to communicate more effectively with decision makers and the public about the flood risks and mitigation approaches need to be developed (P4). The outputs can also be used to explain more clearly accountabilities and responsibilities including actions to reduce flood risk.
This could help inform the decisions made by property owners regarding the measures they can take to reduce their own risks.
There is a need for greater coordination of UAV flights during and after events (P5). This would reduce costs and also provide clarity on why flights are being made.
A distinction may need to be made between flights that are for visual observation or news purposes and those where the data have been collected in accordance with an agreed protocol that enables robust data analysis to be carried out. It would be good to be able to access all the UAV data that is being collected before, during and after an event. There would be a real benefit in having a single curated source of flood data, collected to agreed standards that can be interrogated and used by anyone.
A shared and easily accessible platform that promotes standardised UAV processed outputs to inform management decisions would reduce overall costs and generate greater trust in the interpretation and use of the data. It would enable informed local, regional and national discussions to be had in relation to the levels of risk experienced in different locations, the actions being taken to mitigate the risks and who should be acting to reduce residual risks. This There will be particular challenges where properties are at risk from surface water rather than fluvial or coastal sources. Surface water is not yet as well understood as river flooding and the responsibilities and accountabilities are more widely spread among many local councils. Some of the local councils do not have the necessary skills, experience and resources to address the risk.

CHALLENGES FOR EFFECTIVE IMPLEMENTATION OF THE FIVE PILLARS OF STANDARDISATION
A wide range of challenges will curtail the implementation of the five pillars of standardisation. P1 (data collection) will be resource-intensive as it will require (i) substantial From a systems engineering perspective, a wider range of processing possibilities is preferable; uncertainty estimation and error propagation analysis will facilitate that approach.
In turn, this will require additional efforts to address the challenges presented under P3 (technological integration).
The pace at which technological changes are occurring is unprecedented; a robust approach to standardisation (P1data collection; P2processing) and integration (P3technological integration) will depend upon iterative system engineering approaches that rapidly highlight strategies for technological uptake, social acceptance and adaption.
Such approaches may be time-consuming and will require dedicated resource within government departments and the associated arms-length bodies on their successful implementation via policy, guidelines and regulations as appropriate.
The challenges identified here are not insurmountable impediments to the development and implementation of the five pillars system engineering approach. On the contrary, the beneficial outcomes that can be achieved highlight the need for the standardisation across the multiple overarching domains identified. We illustrate and justify the need for the five pillars of standardisation in the following sections. Much of our work and thinking has been facilitated by the development and deployment of UAVs over recent years in various aspects of flood risk management activities including flood modelling, flood extent and impacts assessment and during the emergency response.

THE BENEFITS OF UAVS
UAVs enable detailed and accurate data to be collected more readily than was previously possible. For example, current methods used to assess flood extent and impact tend to rely on satellite or aircraft imagery that often fails to provide sufficiently detailed information for that purpose (Cihlar  Figure 3 shows the direct tangible losses Within the specific context of flooding, these sources of bias interact. An assessment of the biases helps provide a better understanding of why the majority of people do not proactively introduce resistance and resilience measures within their properties. In general, people believe that it is unlikely their house will be flooded and therefore do not need to take any action to reduce the risk of this happening.
Not surprisingly, homeowners that have recently been affected by flooding take the risk of future flood events more seriously than homeowners that live in a high-risk area but have not yet experienced a flood. However, the seriousness with which this risk is perceived, for those who have experienced a flood event, fades with time.
The way that risk is presented and communicated also has an impact on the decision whether or not to put in place property level flood resistance and resilience measures. For example, the use of return periods, such as a flood being a 1 in 100-year frequency event, leads to a lower perception of the risk and a lower uptake of flood protection measures. Similarly, the usual framing of insurance products in which an immediate cost in relation to purchasing a policy is traded for an uncertain longer-term gain discourages uptake of such products (Oakley et al. ).
Overall, the communication strategy needs to consider carefully how risk is presented to homeowners and significant effort needs to be invested in explaining the benefits, possible mitigations, the imperative of taking action and the potential emotional and economic costs of not implementing measures (Oakley et al. ).
The overall perception of risk is conditioned by all of the factors outlined above which then affects the uptake of property level resistance and resilience measures. These findings (Oakley et al. ) were used to develop the Adapted Protection Motivation Theory (Figure 4). This provides a rationale for more structured discussions with potentially affected property owners.
It is important to address peoples' perceptions so that these can then be answered in a way that enables progress to be made on the introduction of more property level resistance and resilience measures thereby reducing the impact and upset caused by future flooding events.
Such communications also need to be informed by objectively agreed data and information presented in an easily understood way. This will need to take account of all sources of flooding. For example, in Cockermouth, both fluvial and surface water flooding need to be addressed and will require an integrated approach between the different authorities including the EA for fluvial flooding and the local council for surface water flooding. Motivation Theory helps identify the key areas (processed outcomes) within which UAV derived products (e.g. visualisation tools) can be used to address change risk perception and inform policy and regulation. This in turn helps prioritise UAV data collection efforts pre-, during and post-event. To date, UAVs have generally been used within the context of news coverage and flood extent and impact assessment. The use of UAVs to inform risk perception will require a tailored surveying strategy (P1data collection). The Adapted Protection Motivation Theory could provide the first steps towards defining the logistics (e.g. flight plan, camera configuration) of such UAV missions. In time, this information will be incorporated to the UAV decision matrix outlined in Figure 2.