Infrastructure: Flood management

Introduction

The winter’s floods brought back firmly into focus the risk faced by UK businesses and residents from multiple sources of flood damage. Ten per cent of UK property is located on flood plains, and housing continues to be developed on at-risk locations.

According to the Met Office, winter 2013/14 saw the most prolonged period of winter rainfall in England and Wales in 248 years, and rivers such as the Thames saw their highest levels and most extended period of peak flow since the 1880s. Unfortunately, these events are increasingly common.In its 32 year operational life, the Thames Barrier has been raised 150 times. 100 of these lifts took place after 2000, and over 50 have occurred since the 2007 floods.  While the Met Office has not isolated climate change as the cause of recent extreme events, it is widely accepted that sea levels are rising and that global warming is associated with more intense patterns of rainfall - placing growing strain on surface water drainage systems as well as rivers and tidal defences. At the same time, population growth in London, the South-east and other growth areas drives more development - increasing the risk and the consequences of flooding in many areas, irrespective of the effects of climate change. It is little surprise that the UK is ranked seventh in the world with respect to economic risk of flooding.

The UK has an extensive network of existing flood defences, with 24,000 miles of linear flood defences and 46,000 structures. These are managed by a range of stakeholders including local authorities and the Environment Agency. The aftermath of the 2013/14 winter floods has opened up a debate about the balance between expenditure on new assets and maintenance of the existing infrastructure, as well as the equitable prioritisation of schemes to manage high and low impact flood events. Both considerations point to the potential adoption of “totex” - based integrated management of capital and revenue expenditure similar to that which will be used by many regulated utilities in their next control periods.

Despite the extensive damage and the genuine hardship experienced by businesses and homes that were directly affected by the floods, evidence points to most aspects of the UK flood protection system having met their objectives. In all, 1.3 million properties were protected, while 7,000 properties were actually flooded. By contrast, during the 2007 floods, 100,000 properties were successfully protected from flooding, but over 60,000 properties were damaged - leading to a £3bn insurance bill.  This is evidence that some of the recommendations of the 2008 Pitt Review have been implemented effectively - such as the enhanced flood warning system. However, public reaction to the impact of flooding on rural farming communities demonstrated that assumptions that underpin current investment priorities on high impact areas may be less politically acceptable when floods do occur.

Sources of flooding risk

Flooding is caused by a wide range of factors which might affect a particular catchment. The floods of 2013/14 illustrate how these causes combine, and the different measures which might be needed to mitigate flood risk in a particular area. Catchment-based flood management approaches enable these interactions to be accounted for in the design of mitigation measures. The key sources of risk are:

• River flooding. Fluvial flooding was the cause of a great deal of the damage seen in the 2013/14 floods. River flooding is closely related to the degree of rainfall, the ability of a catchment to retain water where it causes least harm and the capacity of a river system to transport water away from areas of risk. Mitigation measures associated with river flooding include the creation of retention measures as well as work to increase watercourse capacity such as “re-meandering”. Passive measures that use features of the catchment to slow water flows are increasingly the preferred option.
• Surface water flooding. Pluvial flooding occurs when the capacity of a drainage system is exceeded. The factors that increase surface water flooding risk include rainfall patterns, speed of run-off, drainage capacity and river levels. Pluvial flooding caused most of the damage during the 2007 floods in locations such as Hull. The risk of pluvial flooding increases in line with urbanisation and growth in the total area of impermeable paving surfaces that accelerate surface run-off. Greater surface water run-off will potentially contribute to river flooding, so the preferred solution is to retain water in-situ, using a range of sustainable urban drainage solutions.
• Groundwater flooding occurs when the capacity of a catchment to absorb water is exceeded. High levels of ground water were a factor in the recent flooding on the River Thames.
• Coastal flooding. Coastal flooding is caused by peak tides, storm surges or damage to flood defence structures. Coastal flooding was another key risk during the 2013/2014 winter and many defence structures were damaged during the storms. The overall success of the coastal flood risk management strategy is demonstrated by the successful defence during the winter of the largest storm surge recorded since 1953, with only limited flood damage to property.

All of these flood risk causes interact within a single catchment. Increased surface water flows resulting from new housing or infrastructure will inevitably find their way into rivers - which could cause flooding downstream. Similarly, measures taken to hold water upstream in order to reduce the flood risk for urban development in a flood plain, may actually increase the frequency of upstream floods. Tidal waters interact with high river flows of course, and the Thames Barrier was closed 28 times during the 2013/14 floods so that low tidal water levels could be used to make room for abnormally high river flows. However, responsibility for flood management is split: the Environment Agency is responsible for the overall strategy and looks after rivers, reservoirs and coasts; the Highways Agency looks after drainage from strategic roads; while local authorities are responsible for drainage from public spaces and roads as well as smaller watercourses.  Water companies have a role in connection with their drainage networks, and landowners adjacent to water courses have responsibilities for their upkeep and maintenance. Stakeholders are being required to work ever more closely together in the management of catchment area flood risk and the delivery of jointly funded schemes.

However, this complexity adds further challenges to the delivery of a capital programme comprised in the main of small, self-contained capital and revenue-funded projects.

Flood risk management solutions

As flood risk has become more acute, and the challenges associated with balancing economic development, cost of defences and the consequences of flood damage have become more complex, a more joined-up approach to flood management strategy has been developed for the UK. The latest ICE State of the Nation report (June 2014) calls for long term (longer than the current six year funding plans) capital and maintenance programmes to support a fully integrated approach to flood management and deliver a resilient system.

Increasingly flood managers aim to work with natural forces rather than against them, so rather than investing in hard defences at specific at-risk locations, strategies based on increasing the overall flood resilience of a watercourse are being developed.

Holistic, multi-layer approaches to flood management have been used in flood-prone countries such as the Netherlands for many years, combining high levels of investment in hard flood defences, spatial planning to prevent building in at-risk places and a sophisticated and dynamic flood response plan - ensuring that communities are prepared for flood events, should all else fail. In the UK, the current emphasis is on risk-based management, supported by improved information flow and underpinned by enhanced early warning systems.

The latest ICE State of the Nation report (June 2014) calls for long term (longer than the current six year funding plans) capital and maintenance programmes to support a fully integrated approach to flood management and deliver a resilient system.

Stakeholder and community awareness and engagement with flood prevention strategy is a critical starting point. One of the successes of recent floods was the effectiveness of flood warning systems. However, engagement needs to extend to the agreement of prioritisation of flood defence investment - which may involve increasing flood risk in low impact areas of a catchment so that downstream settlements are protected. Negotiating these agreements is a major element of catchment management activity.

Recent developments in coastal flood protection are a good example of how strategies to increase resilience are evolving. Historically, solutions based on hard sea-wall defences and beach replenishment have involved high running costs. New approaches involving “managed realignment” and the creation of coastal wetlands to form a flood barrier proved highly successful during the recent storms, and are also contributing to the creation of new habitat.

A similar approach is being adopted for river flood management - which can be summarised as “making space for water”. The aim is to reduce peak water flows, and to keep surplus water in locations where it will do least harm.  Physical barrier defences are only part of the range of solutions involving capital investment. Flood defences in a catchment will include a range of features which contribute to different aspects of flood management:

• Enhancement of natural water retention capacity - slowing the flow of water into rivers in the first place. This is done by increasing soil capacity, blocking drains in upland areas or through managed planting. This work will be undertaken by landowners.
• Managing surface water run-off from new development. Typical sustainable urban drainage (SUDs) solutions include green roofs, permeable pavings, swales and retention tanks.  SUDs are a key aspect of the 2010 Flood and Water Management Act, typically funded by developers as part of the planning requirement. Under the act, SUDs will be approved and adopted by the local authority, creating a long-term maintenance liability. New national SUDs standards are in the process of being signed off.
• Increasing water course capacity - including engineered flood plain storage features such as meanders, washlands or temporary storage ponds. This work is typically initiated by the Environment Agency, working in partnership with other bodies including local authorities and landowners.
• Managing surplus surface water when drainage capacity is exceeded - using surface car parks, playgrounds and even pathways as temporary storage facilities.
• Providing temporary or demountable flood defences. Temporary defences have high whole-life costs and the risk of failure is greater than for permanent work, so are not an ideal solution.
• Landowners in locations that are vulnerable to flooding, including some utilities companies, have invested in defences independently of the Environment Agency and local authorities.
• Providing permanent hard flood protection measures including embankments and sluices.
• Making property resilient to flooding, known as property level protection, potentially using measures such as water-resistant finishes, raised electrical fittings and simple flood barriers. 

Interestingly, research undertaken in flood-affected areas show that very few homeowners think that it is worthwhile investing in these measures, with 46% considering that it is not their responsibility.

Watercourse and coastal flood management has an important role in the creation and management of habitat including wetlands and the encouragement of natural fish stocks.  As a result, flood protection works will often include elements of habitat enhancement including planting, ponds or the introduction of fish passes. 

Interestingly, research undertaken in flood-affected areas show that very few homeowners think that it is worthwhile investing in these measures, with 46% considering that it is not their responsibility.

The importance and sensitivity of the environmental agenda can be seen in the complexity of recent debates associated with river dredging, which increases water course capacity, but which also damages river habitat and makes river banks vulnerable to future erosion. The significant impact on habitat of recent dredging on the River Parrott in Somerset illustrates the conflicting pressures that flood management strategy aims to resolve.

Stakeholders and funding

The management of all aspects of flood risk in England and Wales was overhauled following the publication of the Pitt Review in 2008, held to review the lessons learned from the 2007 floods. Overall strategy is set out in the National Flood and Coastal Erosion Management Strategy, published in 2011 as part of the implementation of the 2010 Flood and Waterway Management Act.

The strategy sets out a partnership approach to flood risk management, with a number of bodies taking a lead role:

• The Department for Environment, Food & Rural Affairs sets the National Policy and distributes central government funding
• The Environment Agency is responsible for managing flood risk from rivers, reservoirs and the sea, and for providing national information on current and future flood risk through the production of catchment flood management plans
• Local Lead Flood Authorities are responsible for managing flood risk from “ordinary” watercourses, surface water and ground water.  They work closely with council planning authorities in managing the flood risk impact of new development
• Regional Flood and Coastal Committees provide a forum for wider engagement with local stakeholders. RFCCs can raise levies from local authorities to supplement capital funding from DEFRA and third party sources and are a key means of securing community buy-in to catchment-wide plans.

Partnership working is inevitably challenging, as is the task of co-ordinating the plans of multiple stakeholders. The National Audit Office has, for example, identified 19 different sets of plans that need to be accounted for in a flood risk management strategy.

One key group of stakeholders on most flood defence schemes are the residents and landowners directly affected by a risk management investment. Issues that might be of concern could cover the degree of risk that is mitigated as a result of the investment, as well as the impact of the creation of new flood defence features such as washlands on landowners. These consultations are a key aspect of the capital projects process.

DEFRA’s total funding for flood and coastal erosion risk management will total £3.2bn between 2010 and 2015.  £210m of additional funding was announced after the 2013/14 floods, which will take total spend in 2014/15 to £795m.  Capital investment has been allocated on an annual basis, but from 2015/16 there is a commitment to a six-year funding settlement, totalling £370m in year 1. Grant in Aid for capital spending is split 50:50 between the Environment Agency and local bodies.

Partnership funding is increasingly important as a source of additional funding for projects that are supported by a wider group of local stakeholders.  Partnership funding is expected to have contributed nearly £150m to projects over the period 2010 to 2015, and increasingly only projects delivering exceptional benefits will be 100% funded by central funds.

Although the requirement for partnership funding might bias project selection towards well-funded schemes, the outcome measures used by the Environment Agency focus on whole-life benefit, reduction to household flood risk and habitat creation - emphasising the broader holistic approach that is required for effective strategic flood management.

Capital projects procurement

Procurement processes associated with Flood and Coastal Erosion Risk Management (FCERM) investments are deceptively complex. While the components used and structures built to manage flood risk are relatively simple, the need to tailor solutions to the characteristics of the catchment and the site require a large survey and initial design input into feasibility studies and employer’s requirements.

Flood risk capital investment is focused on the delivery of outcomes - such as the reduction of households at risk of flooding and the achievement of a target whole life benefit relative to whole life cost. It is challenging to be able to demonstrate the achievement of outcomes without investment in up-front design work. As a result, quite a lot of the Environment Agency’s capital investment has been let on the basis of traditional, separate appointments, with modelling and mapping, engineering design and asset delivery all being let under separate competitively tendered appointments. Design and build procurement has become more common albeit that the production of employer’s requirement documentation needs a degree of initial design and survey work to identify the preferred solution and to provide a basis for a realistic target price.

With the shift to a six year spend period from 2015/16 onwards; the Environment Agency is transitioning to a programme-based procurement strategy - aiming to reduce transaction costs and to generate further savings through standardisation, innovation and the sharing of solutions across the programme. Options for bundling the work to drive efficiency include packaging by location, or by work-type. The first example of this approach is a long-term programme management appointment to deliver the initial phases of the Thames 2100 Plan - designed to maintain and improve existing defences and to plan future investment in response to risks from climate change and rising sea levels.

Some of the initial findings of reviews into the 2013/14 floods have focused on the split of expenditure between capex and opex. Many flood risk management require regular maintenance and there is concern that cost reduction measures that followed the 2010 Comprehensive Spending Review fell disproportionately onto operations, including maintenance. Lessons learned from the recent floods could potentially accelerate the transition to a totex-based approach to spend - giving the Environment Agency and its partner organisations further flexibility with respect to targeting spend on optimum outcomes.

Summary

The UK’s approach to flood management will need to evolve as climate change increases the likelihood of extreme weather events and as economic growth increases pressure on land use. At the same time, the need to manage risks within constrained budgets will mean that the search for the most cost effective solutions will rely on high levels of cooperation between all stakeholders involved in flood management processes. Long term funding should facilitate the development of innovative solutions to flood risk management which will be essential as the risks associated with extreme events increase.

Capital projects procurement

The commercial management of flood control and coastal protection works is very challenging due to the wide range of performance requirements that a structure might be designed for as well as a wide variation of conditions at the workface that might affect the construction method, logistics or programme. Accurate estimating of project budgets based on a full consideration of site specific is however essential so that business cases are based on a well-founded assessment of delivery cost, and so that target prices provide an appropriate level of challenge and incentive to the supply chain.

Sources of cost variation that affect delivery costs include:

• Variations in the water course/tidal condition - flow rates, high and low water levels
• Site alignment, including exposure to prevailing winds and other weather variables
• Site topography and geology
• Proportion of work undertaken in or above water
• Boundary condition & substrate (eg river banks)
• Requirements for builder’s work (e.g. surrounds to sluices, fish passes, etc)
• Presence and condition of existing structures
• Access and other logistics requirements
• Programme and access constraints associated with protected habitats, breeding seasons.

As a result of these and other variables, the base cost of flood control structures and features will be subject to a wide variation in final cost associated with the work process rather than quantum of work.