Strategic Flood Risk Management Research Articles

Strategic flood risk management over time. Applying a temporal lens to see how flood risk management measures are (or are not) implemented

ABSTRACT Strategic flood risk management of river catchments involves significant increases in the complexity both of the contents (e.g. the aims and measures) of a given strategy and also its social, spatial, and temporal scales. Conceptually, flood risk management research to date has underestimated the importance of time and temporality. This paper, which is based on ‘historical Institutionalism,’ introduces a temporal lens to focus on strategic flood risk management; it highlights issues of duration and timing as well as tempo and change in tempo with respect to the implementation of measures to reduce flood risk at catchment level. The application of a temporal lens is illustrated through empirical research into strategic flood risk management for the medium-sized Aist river catchment in Austria. The paper uses a longitudinal qualitative research design to analyze the changes in strategic flood risk management in the catchment. The analysis shows that strategy efforts in reaction to an extreme flood event in the catchment in August 2002 can be differentiated into three phases. Phase 1 is characterized by the design of ambitious catchment-wide management; Phase 2 by struggles to implement the strategy due to institutional conditions and protests by citizens; and Phase 3 by redesign of the initial strategic plan to make it less ambitious and by changes to the actor constellation supporting the plan. The present paper offers a process-oriented institutional explanation for this pattern of phases, and it highlights issues of timing and tempo. It concludes with general suggestions for enhancing the temporal dimension in flood risk management.

Conclusions

Is it possible to define an integrated method for strategic flood risk management and spatial quality enhancement, in which spatial quality is a decisive ex-ante criterion, and what would be the key elements and steps in such a method? This constitutes the primary research question. The publications that together form this dissertation describe such a method and thus provide a positive answer to the primary research question. A key principle in the approach is the inclusion of multiple interchangeable (effective) flood risk reduction interventions at varying locations, so that the criteria of spatial quality can become decisive in flood risk management strategy development. The ability to assess the impact of different interventions on spatial quality is essential. In order to do so, an assessment framework was developed; it combines the approach of a spatial quality criteria checklist with expert judgement. The checklist supports expert judgement in that it keeps a wide, open perspective while assessing the spatial quality of a conceptual intervention, and thus allows verifiable and reproducible assessments. The method developed employs research-by-design to systematically test different interventions at different locations. It includes the following steps: An inventory of current and potential flood risk protection strategies An inventory of a region’s spatial characteristics, challenges, and potentials A qualitative assessment of existing situations and a spatial impact assessment of reference flood risk strategies, if any exist Systematic research on how flood risk management interventions at different scales can shift the location of a flood risk intervention; this includes qualitative assessments of interventions at various locations Systematic research on how flood risk management interventions in different flood risk layers can shift the location of a flood risk assignment; this includes qualitative assessments of interventions at various locations Selection of a combination of interventions that are preferred from a spatial quality objective

Experiences in developing and applying decision support systems for strategic flood risk management

ABSTRACTDecision support systems (DSSs) have been developed for many years. Their main goal was originally to support decision-makers. Reviews show, however, that the actual use of most DSSs did fall short of these ambitions. The goal of DSSs has gradually shifted to enhancing stakeholder engagement for better informed and societally supported decisions. In this paper, we present and discuss a DSS which has been extensively used by a large and diverse group of stakeholders. This so-called Planning Kit Room for the River did successfully support the development of alternative strategies for flood risk management of the riverine area in the Netherlands. Based on these strategies a major investment programme was developed, which has been implemented recently, within time and budget. In the paper, we explore the key factors for its successful application. Based on this analysis and our experience with both interactive planning processes and DSSs, we propose a typology of DSSs for strategic planning of flood risk management. We outline three types of DSSs with different set-ups and associated users, including a DSS based on an integrated model system. The paper concludes with a discussion of the main characteristics and the potential and limitations of these types of DSSs from both a user and a hydro-informatics perspective.

Large-scale application of the flood damage model RAilway Infrastructure Loss (RAIL)

Abstract. Experience has shown that river floods can significantly hamper the reliability of railway networks and cause extensive structural damage and disruption. As a result, the national railway operator in Austria had to cope with financial losses of more than EUR 100 million due to flooding in recent years. Comprehensive information on potential flood risk hot spots as well as on expected flood damage in Austria is therefore needed for strategic flood risk management. In view of this, the flood damage model RAIL (RAilway Infrastructure Loss) was applied to estimate (1) the expected structural flood damage and (2) the resulting repair costs of railway infrastructure due to a 30-, 100- and 300-year flood in the Austrian Mur River catchment. The results were then used to calculate the expected annual damage of the railway subnetwork and subsequently analysed in terms of their sensitivity to key model assumptions. Additionally, the impact of risk aversion on the estimates was investigated, and the overall results were briefly discussed against the background of climate change and possibly resulting changes in flood risk. The findings indicate that the RAIL model is capable of supporting decision-making in risk management by providing comprehensive risk information on the catchment level. It is furthermore demonstrated that an increased risk aversion of the railway operator has a marked influence on flood damage estimates for the study area and, hence, should be considered with regard to the development of risk management strategies.

Implementing sustainable drainage systems for urban surface water management within the regulatory framework in England and Wales

The UK 2007 floods resulted in damages estimated to exceed over £4 billion. This triggered a national review of strategic flood risk management (Pitt, 2008) with its recommendations informing and implemented by the Flood and Water Management, Act (FWMA, 2010). Estimating that up to two-thirds of properties flooded in the 2007 event as a direct result of overloaded sewer systems, the FWMA set out an ambitious overhaul of flood risk management approaches including identifying bodies responsible for the management of local flood risk (local municipalities) and the development of over-arching Lead Local Flood Authorities (LLFAs) at a regional level. LLFAs duties include developing local flood risk management strategies and, aligned with this, many LLFAs and local municipalities produced sustainable drainage system (SUDS) guidance notes. In parallel, changes to the national planning policy framework (NPPF) in England give priority to the use of SUDS in new major developments, as does the related Town and Country Planning Order (2015). However, whilst all three pieces of legislation refer to the preferential use of SUDs, these requirements remain “economically proportionate” and thus the inclusion of SUDS within development controls remain desirable - but not mandatory - obligations. Within this dynamic policy context, reignited most recently by the December 2015 floods, this paper examines some of the challenges to the implementation of SUDS in England and Wales posed by the new regulatory frameworks. In particular, it examines how emerging organisational procedures and processes are likely to impact on future SUDS implementation, and highlights the need for further cross-sectoral working to ensure opportunities for cross-sectoral benefits– such as that accrued by reducing stormwater flows within combined sewer systems for water companies, property developers and environmental protection – are not lost.

Developing a strategic flood risk management framework for Bangkok, Thailand

This study explains deficiencies in Bangkok’s current floodplain management and demonstrates improvements that are possible using a strategic flood risk management framework. The flood that occurred in 2001 in Bangkok is described with the aim of highlighting the deficiencies of the metropolis’ flood management. A preliminary assessment of flood risks was conducted in each of 50 districts of Bangkok. The flood risk estimation over a 12-year period (1999–2009 and 2011) revealed that 10, 3, 6, and 31 districts of the metropolis were categorized as areas with very high (>30 %), high (>20–30 %), moderate (10–20 %), and low (<10 %) flood risks, respectively. This assessment provides quantitative insight, to compliment the observations made in the 2011 flood, and highlights the motivation behind Bangkok’s current flood management practice. The major findings obtained are as follows. First, the existing flood risk management practices for Bangkok are inefficient and need improvement. Second, the districts having different flood risks reflect the land values and the current flood protection procedures. Third, community participation in processes under the flood risk management framework is important to eliminate conflicts and garner public support and acceptance. Fourth, land use planning and development controls should be integrated with floodplain management plans to properly manage future flood risk. Fifth, a further study should be conducted to determine the uncertainties of future flood risks related to future development expansion and land values across Bangkok.

Briefing: Impacts of Victorian engineering on a modern flood risk study

A strategic flood risk management (SFRM) study was undertaken for the heavily urbanised reaches of the River Medlock through Manchester, UK. Many of the buildings and structures on this reach date back to the Victorian era and the industrial revolution, when rapid growth of cities often focused on areas around sources of water for industrial and transportation needs. Key structures on the modelled reach include the Medlock Cloughs, a group of structures designed by Victorian engineers to actively manage water levels in the Bridgewater Canal and the Medlock. Further downstream at Potato Wharf, Giants Basin allows overflow from the canal to spill back into the river. A one-dimensional hydrodynamic model to represent the study reaches was built. Hydraulic modelling of the Medlock Cloughs and Giants Basin proved challenging for several reasons. It was not possible to verify existing survey data or to obtain new survey data because of health and safety issues. The study team was also unable to establish maintenance procedures on the structures or determine whether they now operate as intended by the Victorian engineers who built them. These obstacles were overcome by using old survey drawings, historic data and photographs in modelling the structure. The Medlock Cloughs component of the model proved crucial to obtaining accurate level and flow results for the modelled reaches, as the split in flows between the canal and river controlled the water levels upstream. The lessons learnt from this study may have application in assessing flood risk in other similar situations, and included the requirement for credible, accurate data for structures, and the importance of accurately representing, in a computational model, old structures that are no longer operating as intended.

A methodology for regional-scale flood risk assessment

Sound flood risk management decision making is underpinned by flood risk analysis. Current methods applied at regional and local scales are often limited in their consideration of the potential for defences to fail. Ultimately this can lead to underestimates of the true risk and subsequent difficulties in justifying mitigation measures such as maintenance and replacement of defences. A methodology has been developed for assessing flood risk arising from fluvial and coastal sources that explicitly considers defence failures represented through fragility curves. This method requires consideration of flooding scenarios involving multiple defence section failures and flood events ranging in severity. It has therefore been necessary to develop a purpose-specific flood spreading method that is capable of simulating many flood events in practical timescales. The method has been applied to the Thames Estuary, where outputs including spatial maps of flood risk and defences attributed with residual risk have been used to support decisions relating to strategic flood risk management over the coming century.