High-Speed Rail (HS2) and Flood Risk: A Comprehensive Report

This report examines the potential impact of the High-Speed 2 (HS2) rail project on flood risk, focusing on the assessment methodologies employed and the strategies for mitigation. The report utilizes Strategic Flood Risk Assessment (SFRA), Sequential Test, and Exception Test to identify high-risk areas and potential flooding problems. It discusses the advantages and disadvantages of the HS2 development in relation to flood risk, considering factors such as cheaper and faster movement, reduced congestion, and potential environmental mitigation, alongside the limited benefits to users and environmental concerns. The methodology involves analyzing data from the Environment Agency and evaluating flood risk using SFRA levels 1 and 2, which include assessing flood zones, sources, and defenses. The report also explores risk minimization plans, referencing existing flood risk management practices in England and the development of national rail, to offer recommendations for managing and mitigating flood risks associated with the HS2 project. The report concludes with a detailed analysis of the application of SFRA in determining suitable site locations and mitigating potential flood risks.

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HIGH-SPEED RAIL 2
Tutor’s Name
Institution’s name
City
Date

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1. OBJECTIVES
The aim of this report is to discover how the construction of HS2 increase/ decrease the risk of flooding
along the development site (and to seek improvement method?) with the following objectives;
 Identify regions of high risk with an explanation and description of following assessment models
in terms of flood risk management;
I. Strategic Flood Risk Assessment.
II. Sequential Test.
III. The Exception Test
 Identify risks of flooding (e.g. flood the surrounding residential area) using the assessment
models mentioned above to identify the flood risk problems that HS2 development is facing.
Discuss the advantage and disadvantage of the HS2 development impact on flood risk
 Determine risk minimization plan (e.g. flood barrier/ defence) looking into the current flood risk
example in England and how the public and government deal with it using the previous
example, such as the development of national rail, as reference
Evaluation of the disadvantages and advantages of HS2 rail
Advantages
• The development of fast rail transport system across the country benefits the train users
by cheaper and faster movement. Also, there is reduced congestion on the streets.
• There will be job provision from the construction of the rail.
• The curation of travelling across the country will be shortened.
• There would be an environmental mitigation due to the building of green tunnels.

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Disadvantages
• There would be benefits only felt by the small train users.
• Benefits of fast travelling to the workplace can be debatable as recent jobs are possible to
be done at home.
• There is no assured guarantee that the passengers would use the train that often.
• The development encourages people to live far from London opting to use the train to
reach London.
• Other alternatives that include further development of existing train length exist.
2. METHODOLOGY
Data were requested from the Environment Agency with the planning of the proposed
government construction site of the HS2 rail and analyzed as per the following described model
methods;
I. Strategic Flood Risk Assessment (SFRA).
II. Sequential Test.
III. The Exception Test.
SFRA
The SFRA has a number of objectives during its undertaking. During the undertaking of the
SFRA, there needs to be a provision of sufficient information and data on the flood risk types
that affect the application of Sequential Test in the determination of the allocation of land use
allocation. Also, if necessary, where the application of exception test. The SFRA has to allow
the planning authority to get a full understanding of flood risk from any source within the area.
Also, there is an understanding of the risks from and to the area surrounding the area of

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development. Another reason for the use of SFRA is to produce an informative sustainability
appraisal in that the flood risk can be able to be considered fully during the preparation for use of
land. The SFRA has the importance of preparing appropriate policies that can manage the flood
risk. A detailed level of identifying assessment of flood risk sites in specific locations. Moreover,
there is a determination of acceptable relation in flood risk relating to the planning capability of
emergency situations (Filho, et al., 2017).
General scope.
Level 1 SFRA has the benefit of showing the flood risked land outside the area of interest but
fails to accommodate the important development in the area of concern and the application of
exception test. The SFRA scope, therefore, needs to be widened to increase its effect therefore
level 2 is more applicable. The document in this model talks more about level 2 application and
its evaluation. SFRA has to be completed fast enough so as to provide information on the options
of development concerning the land being developed for the rail tracks. Changes that may take
place in the planning would mean some activities in the SFRA had to be done later (United,
2016).
SFRA planning role in high-speed rail 2
SFRA has the role of helping in assessing the suitable potential of broadening site-specific
locations for the development of rail as required by the planning authority. As such, there is
informed evidence-based identification that helps in determination of flood risk level.
However, the main role of using the SFRA is to provide a determined potential site suitable for
gradual stages in plan-making. The gradual stages include the use of Sequential Test or the use
of Exception Test in areas where appropriate. In this model, measures of flood risk mitigation

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need to be taken into account as portions of solving the constraints of flood risk (Transport,
2004).
The scope of Level 1 and its approach
An SFRA level 1 has to be sufficient for allowing the use of Sequential Test together with the
identification of whether the site development can be put in medium and high areas of flood risk,
taking consideration of the flooding sources. The flooding sources need not only be coastal and
rivers. Also, the identification need not be for the possibility of use of Exception Test.
Information from the level 1 can principally be studied from the desk that makes the better of
existing data (Great Britain: H.M. Treasury, 2011).
The level 1 has its constituents being;
 Flood map that covers the tidal and river flooding.
 Areas that are more prominent to flooding of their surfaces.
 Data coming from other consultees affected by floods like the local authorities. ‘
 Soil and geological maps that ease the implementation of techniques to be implemented.
 Events involving floods that occurred in the past. May come from the newspaper,
community groups or local residents.
Outputs from level 1
There are key outputs that come from SFRA level 1. Plans form the local authority have an
indication of the flood zones and the ordinary watercourses that include the floodplain.
Moreover, there is an indication of the existing plan on the locality and the previous site
development allocation on the considered on the site in the future. An included implication
assessment of the change in climate for the flood risk allocation site development, this is done

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for the appropriate period of time in case it lacks in the plans that were proposed. Areas that are
at risk from flooding sources that include groundwater flooding and the surface water flooding.
Level 1 has the pleasure of informing on the management measures concerning the flood risk
that includes the standard and the location of infrastructure warning systems. A guidance on the
assessment in flood risk preparation for the allocation of development sites is included (Wilson
& Piper, 2010).
This information needs to be sufficient so as to allow the application of additional tests such as
the Sequential Test and to allow the informing of subsequent planning policies and sustainability
appraisal. Level 2, however, needs to be carried out in the field. Level 2 will, therefore, entail
collection of data and their analysis.
SFRA scope of level 2
In level 2, there is an increased level of scope in that there is a higher possibility of later
inclusion of Exception and Sequential Tests. Level 2 has the characteristic of requiring more
information in the areas that have the risk of either medium or high tendency to flood with
lacking alternatives to the application of Sequential Test for development. Such a detailed study,
therefore, requires equally detailed nature in the flood hazard that takes into account the
existence of management measures in flood risks. Such techniques would allow sequential
approach in site allocation that can be adopted in the flood zone areas. Level 2 SFRA also allows
the practices and policies required for ensuring development in areas affected by floods to satisfy
the requirements for the Exception Test. A detailed scope that considers a detailed nature in the
areas rampant with the flood is (Anon., 2016);
 Flood depth.

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 Flood probability.
 The rate of flood onset.
 Flood velocity.
Such factors are heavily affected by flood defences presence or any relevant infrastructure.
Flooding that may occur in the infrastructure of such nature may be due to;
 Rising of water level to exceed the defence level (overtopping)
 Operational or constructional defence failure either in part or whole.
 An overload of the surface water system of drainage, this can be due to an own limited
capacity.
Flooding defence information
Information in the level 2 portion of the SFRA has data on the standard, location, and condition
of flood defences of the area under scrutiny for rail building needs to be obtained from the
individuals operating and marinating such assets. More policies that come in the future also need
to be reviewed.
The Environment Agency has a provisioned guidance concerning the assessment of risks that
may occur to people behind the flood defence system. This research suggests three options that
assess the increasing complexity of flood risk. They include simple, intermediate and complex
approaches. Using SFRA is suitable for implementing intermediate and simple methods. The
choice of these approaches heavily depends on the pathways, flood risk and receptor
vulnerability in the region located behind the flood defence. Level 2 analysis is sufficiently
allowing flood defence assessment with the design appropriate to the standard (Hall, et al.,
2016).

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Level 2 outputs in SFRA
The results in the SFRA level 2 needs to build on the information source that can be
compromised in level 1 by containing;
 Current condition appraisal of the flood defence in infrastructure together with likely
future management policy in floods taking into consideration the upgrade and
maintenance.
 Consequences and probability appraisal in the failure or overtopping in management if
the infrastructure of the flood that includes allowing climate change possibility.
 Mapping and definition of floodplain functionality in the locations that require such
features.
 Maps that indicate the flood risk distribution across any flood zone from any source of
flood considering climate change.
 Appropriate policy guidance that can satisfy requirements on the flood risk planning and
exception test.
 Preparation guidance on the assessment of the flood risk sites that vary in risks across the
flood zones. More information can be added to make use of the techniques in sustainable
drainage.
 An identification of the areas and locations of critical drainage as well as the
identification of the plans of management of surface water.
 Important recommendations to the informative policy controlled development and
technical issues.
An output of the SFRA aims at providing clear guidance on appropriate measures in risk
management for the zones prone to flooding risks for protection from flooding by the use of

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flooding defences. Such measure allows minimized the extent of the various developers
undertaking separate studies of like problems. Some instances allowed improvement of the flood
defences that existed to the management of flood risk residue. In times that the flood defence is
to be considered, the use of SFRA has to include an extent of appraisal of required works that
raise or provide appropriate flood defence (Brebbia, 2014).
Level 2 SFRA provided the necessary information about the risk variation in flood zones having
protection by infrastructure flood defence with the appropriate conclusions drawn to make
recommendations on the potential site development (Thorne, et al., 2007).
Issues that were related to the provision of SFRA
Areas defended
Practice and policy in the management of the areas in particular risks in the planning had to be
included in SFRA. This planning helped in the knowledge of the future development in the plan
of maintenance or management of flood defences as well as the drainage infrastructure. Another
consideration that was to be included in the climate change that has influence over the durability
of the rail development.
It is a recommendation that in case of any allocation of land in the flood defended area, there
needs to be a consideration of the impact of the cumulative impact potential of loss in storage at
the site of allocation within the blood cell. Assessing such a recommendation needed to be
inappropriate scale as well as the nature of the development being proposed together with any
flood risk. If the potential risk has an unacceptable impact, there needs to be the provision of
mitigations or rejection. Such planning is suitable since the impact to the areas being defended

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might have a negative or positive flood risk. The circumstances were dependent on such factors
making it essential hydraulic and robust modelling.
Areas with undefended floodplain functionality.
In cases where there is a proposal on the development of areas with undefended floodplains,
these are the areas that are found outside the floodplain functionality, this development had to be
done under compliance with the policies of the local authority. These areas were to remain safe
and maintain their features of not increasing the food risk thereby reducing risks. More issues
that include appropriate guidance provision to developers and the careful consideration are some
of them.
The hierarchy in managing flood risk was used before the coming up of solutions that included
new defences construction and ground raising. The flood defence was possible to be provided in
various ways that included; flood storage and embarked defences on the site. These are the
options in the SFRA.
In cases of coastal areas, that was majorly undefended, if one were to raise the ground, there
would be less impact on the water level emanating from flooding in the tidal sea. Also, providing
compensatory storage might fail. Contrasting this to the undefended areas in the estuaries,
ground raising is possible to impact the tidal levels, therefore, making it necessary for
compensatory storage. Compensatory storage majorly used along with this project as few
instances did not require it in the areas having undefended floodplains. This came handy as the
single development plans had minimal impact on the cumulative impact of many developments.
Compensation plan had to be aiming at provision with levelled basic floodplain mimic features
before the development of the proposed rail development (Schanze, et al., 2006).

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Conveyance or flood storage compensatory
In times where there is a need for the proposal of development in flood-susceptible areas, there
might be an establishment of compensatory conveyance that can reduce or prevent an increase in
flood risk. Level 2 SFRA had to provide a feasible flood storage compensation in the area close
to the site of development. In the conveyance routes, the local authority had to consider the
absence of compensatory flood storage since there was no possibility of future application of
Exception Test.
Rates of run-off and the new development volume.
The used SFRA had to provide baseline information on the flooding areas with surface water and
susceptible run-off with a possible future change in climate. The outputs coming from the SFRA
were used identifying the areas that had critical issues in drainage hat involved the determination
of measures that ensured safe managing of risks. Safe management was either done by
investment or development of operating authorities. One specific investment is the sewage
undertakers. Consulting the local authority is one way to realizing this development. Ideas from
the local authority drainage system may be used. Ideas were also possible to be taken from the
environment agency. Lastly, areas that were susceptible to the issues in drainage were identified
before plans were commissioned to seeking ways of managing the flooding of future areas
(Vojinovic, 2015).
The local authority came up with plans that coordinated sub-regional, regional and local levels.
Such a plan enabled;
 The undertaking of a comprehensive assessment of flooding by surface water as a method
of strategic assessment in flood risk as well as prediction of the place of occurrence.

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 Making of informed land use decision in planning with the aim of such assessment.
 Clarification of coordination and responsibilities in drainage systems in managing the
risk ineffective and great systems of drainage.
 Improving emergency of plans for flooding by surface water by the production of an
approach that is risk-based and pro-active and therefore making deliverable resources that
are required most.
The initial stage of the SFRA entailed the production of guidance to developers on the
management of surface water together with the potential for the use of sustainable drainage
measures. The policies involved in the SFRA state that the volumes and rates of the run-off of
developments being made should not be greater than the rates of the previously proposed
development, however, specific off-site can be made to come up with a similar net effect. Such
can produce significant developments where developers will have to include the early
development stages of any project (Punter, 2009).
THE SEQUENTIAL TEST
The use Sequential Test is the use of a simpler tool in decision making that is designed to
facilitate no risk or little flooding development in areas of high risk. The developers are urged to
use the most of land appropriately minimizing flood risk. Substitution of land use in that the
areas that are more vulnerable to flooding have lower risks. This test also urges the developers to
use any opportunity that would mean reduction of flood risk that includes; flood pathways
development and creation of flood storage.