Date post: | 17-Jan-2017 |
Category: |
Documents |
Upload: | truongtuyen |
View: | 218 times |
Download: | 0 times |
Dundee Coastal Study Stage 2
Draft Plan - Options Report
May 2011
Dundee City Council
260186 BNI SNI 002 *
PiMS
09 April 2011
Dundee Coastal Study Stage 2
Draft Plan - Options Report
May 2011
Dundee City Council
Mott MacDonald, Caledonian Exchange, 3rd Floor, 19a Canning Street, Edinburgh EH3 8EG, United Kingdom
T +44(0) 131 221 2300 F +44(0) 131 221 2399, W www.mottmac.com
Dundee City Council Tayside House, 28 Crichton Street Dundee DD1 3RB
Dundee Coastal Study Stage 2
Mott MacDonald, Caledonian Exchange, 3rd Floor, 19a Canning Street, Edinburgh EH3 8EG, United Kingdom
T +44(0) 131 221 2300 F +44(0) 131 221 2399, W www.mottmac.com
Revision Date Originator Checker Approver Description
A 21.04.2011 L. Mair D. Dray P. Phipps First Issue
B 05.05.2011 L. Mair P.Phipps For Consultation
Issue and revision record
This document has been prepared for the titled project or
named part thereof and should not be relied upon or used
for any other project without an independent check being
carried out as to its suitability and prior written authority of
Mott MacDonald being obtained. Mott MacDonald accepts no
responsibility or liability for the consequence of this document
being used for a purpose other than the purposes for which it
was commissioned. Any person using or relying on the
document for such other purpose agrees, and will by such
use or reliance be taken to confirm his agreement to indemnify
Mott MacDonald for all loss or damage resulting therefrom.
Mott MacDonald accepts no responsibility or liability for this
document to any party other than the person by whom it was
commissioned.
To the extent that this report is based on information supplied
by other parties, Mott MacDonald accepts no liability for any
loss or damage suffered by the client, whether contractual or
tortious, stemming from any conclusions based on data
supplied by parties other than Mott MacDonald and used by
Mott MacDonald in preparing this report.
260186/BNI/SNI/002/* 09 April 2011 PiMS
Dundee Coastal Study Stage 2
Chapter Title Page
Executive Summary 1
1. Introduction 2
1.1 Background _______________________________________________________________________ 2
2. Options 3
2.1 Guidelines ________________________________________________________________________ 3
2.2 Method ___________________________________________________________________________ 3
3. Dundee Coast Management Sections 4
4. Dundee Coastal Study Options 5
Appendices
Appendix A. Management Section Sketch Plan
Figures
Figure 1.1: Dundee City Frontage
Tables
Table 3.1: Management Sections
Table 4.1: Options
Content
260186/BNI/SNI/002/* 09 April 2011 PiMS
Dundee Coastal Study Stage 2
Dundee City Council (DCC) is responsible for 16.5km
of coastal frontage and has discretionary powers to
build flood defences for non-agricultural land under the
Flood Prevention (Scotland) Act 1961. Dundee City
Council has commissioned Mott MacDonald to produce
preferred outline management solutions for different
frontage sections, to submit to the Dundee City Council
City Development Committee and also obtain approval
from the Scottish Government for progression of the
schemes.
This report provides a record of the proposed short-
listed options to take forward to more detailed
consideration.
Executive Summary
260186/BNI/SNI/002/* 09 April 2011 PiMS
Dundee Coastal Study Stage 2
1.1 Background
Dundee City Council (DCC) is responsible for 16.5km of coastal
frontage and has discretionary powers to build flood defences for non-
agricultural land under the Flood Prevention (Scotland) Act 1961. The
frontage extends from Invergowrie Bay in the west to the Dighty Burn in
the east, and includes environments ranging from shingle foreshores,
industrial areas, reclaimed land and sandy recreation beaches
Figure 1.1: Dundee City Frontage
Dundee City Council is currently investigating potential flood defence
options as part of the Dundee Coastal Study Stage 2. The purpose of
the Stage 2 Study is to produce a preferred outline management
solution to present to the Scottish Government in order to obtain
approval for progression of the scheme.
As part of the process to develop preferred outline management
solutions, a short list of preferred options was developed through a
Multi Criteria Analysis (MCA) Workshop. The MCA options workshop
for the Dundee Coastal Study Stage 2 was held in Dundee City Council
Offices in Dundee and was attended by members of the Dundee City
Council and Mott MacDonald.
The preferred options that were identified during this workshop are
presented in this Draft Plan – Options Report.
1. Introduction
260186/BNI/SNI/002/* 09 April 2011 PiMS
Dundee Coastal Study Stage 2
2.1 Guidelines
Under Scottish Government1 and Defra FCDPAG
2 guidelines when
undertaking the project appraisal process all possible strategies for
coastal management should be considered. The options include
strategies ranging from minimum interference ‘do nothing’ and ‘maintain
existing’ through to high interference hard engineering structures.
All options have been initially reviewed but only those considered
appropriate for the particular site conditions, protection needs and
standards of service were to taken forward to full benefit cost analysis.
2.2 Method
A multi criteria approach was adopted to support semi-quantitatively the
suitability and cost of different options against the assets benefiting
from defence. The asset criteria such as property, infrastructure,
environment and tourism etc. were weighted in relation to their
importance within the section of the frontage under consideration.
The broad relative cost of a coastal management option was also
considered against the assets to be protected. Such a method helps to
filter out unsuitable options and provide an auditable trail for future
reference in the decision making process.
This approach is recommended in the Scottish Government’s Flood
Prevention Schemes: Guidance for Local Authorities guidelines, Defra
FCDPAG guidelines and was updated using recent guidance from the
Joint Defra/EA Flood and Coastal Erosion Risk Management R&D
Programme3.
_________________________
1 Flood Prevention Schemes: Guidance for Local Authorities (2005). CHAPTER 5
Economic Appraisal. Most recent files are available from the Scottish Government website: http://www.scotland.gov.uk/Publications/2005/10/0794935/49364
2 Project appraisal guidance: procedural guidance for operating authorities. Most recent
files are available from the Defra website: http://www.defra.gov.uk/Environ/Fcd/pubs/pagn/default.htm
3 Risk and Policy Analysts Ltd. (2004) Evaluating a multi-criteria analysis (MCA)
methodology for application to flood management and coastal defence appraisals Guidance for the MCA-based element of the current approach to appraisal. Outcome of the Joint Defra/EA Flood and Coastal Erosion Risk Management R&D Programme. R&D Technical Report FD2013/TR
2. Options
260186/BNI/SNI/002/* 09 April 2011 PiMS
Dundee Coastal Study Stage 2
Owing to the length of the frontage (approx. 16.5km),
compartmentalised flood cells, the variety of environments, existing
defences, and assets, the frontage was divided up into 9 management
sections.
The management sections have been presented below in Table 3.1.
Table 3.1: Management Sections
Section Length Area Existing Defence Issue
1 1,050m Landfill site Shallow gradient vegetated embankment with light rock armour and rubble protection
Erosion
2 1,565m Airport Steep armoured embankment with rock armour, rubble, concrete block, and brickwork protection.
Flooding & Erosion
3 3,185m Riverside Drive Sloped open faced masonry revetment with wave wall
Flooding
4 3,585m City Centre and Port of Dundee
Vertical pointed masonry wall Flooding
5 720m Industrial Area Sloping rock filled gabion baskets, concrete and rock rubble embankment
6 1,470m Coastal Walkway Concrete walkway backed by a masonry retaining wall
7 460m Yacht Club Shallow sloping shingle and grassed bank
Flooding & Erosion
8 2,290m Broughty Ferry Sloping masonry block/concrete wall revetment above shingle beach
Flooding
9 2,570m Beach and Dunes Dunes, sandy beaches with groynes and rubble/boulder upper banks
Flooding & Erosion
A sketch plan (MMD-260186-C-SK-000-XX-0025) detailing the
management sections has been provided as an appendix (A) to this
document.
3. Dundee Coast Management Sections
260186/BNI/SNI/002/* 09 April 2011 PiMS
Dundee Coastal Study Stage 2
The shortlist of proposed options are presented below in Table 4.1 with
respect to the 9 management sections.
Table 4.1: Options
Management Section
Long-list of management solutions
The options to be taken forward to the short-list have been shown in bold
Comments
Section 1:
Landfill Site
� Do nothing
� Do minimum/ maintain/tidy
� Rock armour revetment
� Reno mattress
� Concrete mattress
� Open stone asphalt
� Structural wall (concrete, gabion basket
etc)
� Beach recharge
The do nothing and beach recharge solutions were not deemed suitable as they did not satisfy the environmental and public health objectives for this section.
Owing to the potential contaminated land issues, this section requires a solution which will act as a barrier to protect the potentially contaminated material. The structural wall solution was deemed unsuitable as this section requires a natural looking and sustainable solution to fit with the environmental regeneration which is planned for this section of the frontage.
A structural wall would also be isolated with no “hard” structure to tie into at each end, therefore would not satisfy the strategic objective. The reno mattress, concrete mattress and open stone asphalt solution are all similar variations of generic erosion protection solutions, and therefore the suitability of each will be assessed with respect to specific site conditions.
Section 2:
Airport
� Do nothing
� Do minimum/maintain
� Earth Bund with erosion protection
� Secondary earth bund set back from
the frontage (suitability dependent on
the aviation regulations)
� Coastal protection structure
� Wave wall
� Secondary flood defence around buildings
The do nothing, do minimum/maintain and coastal protection structure solutions were deemed unsuitable as they did not satisfy the technical objective of protecting at-risk assets (i.e. the airport) from flooding as they did not involve an increase in defence height. The secondary flood defence around buildings solution was also deemed unsuitable as it assumed that the runway could be closed from time to time during flood events. This would have also impeded access to the runway from the terminal and service buildings.
Section 3:
Riverside Drive
� Do nothing
� Do minimum/maintain/monitor
� Improve (fill in gaps etc)
� Raise current level of defence
� Raise land at defence and wall level
� Secondary bund around playing field
� Replace wall
� Temporary demountable flood barriers
It has been identified that an increase in the defence level is required to fulfil the technical objective of defending the frontage and assets from flooding over the 100 year study life. Owing that do nothing, do minimum/maintain/ monitor and improve do not involve an increase in the defence level, these are considered unsuitable solutions. The secondary bund around the playing field was deemed unsuitable as it could not be implemented along the full Riverside Drive frontage section. There was discussion of dividing Section 3 in two parts to allow for this and will be assessed in due course. The replace wall solution was deemed unsuitable due to its upfront capital cost with no added benefit.
4. Dundee Coastal Study Options
260186/BNI/SNI/002/* 09 April 2011 PiMS
Dundee Coastal Study Stage 2
Management Section
Long-list of management solutions
The options to be taken forward to the short-list have been shown in bold
Comments
Section 4:
City Centre and Port of Dundee
� Do nothing
� Do minimum/maintain
� Flood wall
� Land raising
� Demountable flood barrier
� Reconstruct wall (pile etc)
� Individual flood protection for buildings
� Rock armour revetment w/ crest structure
For this frontage section, only 2 solutions fulfilled the objectives. Do nothing and do minimum/maintain were discounted as they do not involve increasing the existing defence level. There is the potential for this section to be further divided into the “operating port” and “non-operating port” frontages. This could then mean that the do minimum solution could be considered for the “operating port” area. Land raising was not considered feasible due the large area involved. The reconstruct wall option was considered not feasible owing to the upfront capital cost and considering the high residual life of the existing wall. Individual flood protection around buildings was deemed unsuitable as it did not protect infrastructure or the public’s safety. The rock armour revetment was deemed unsuitable because of the still functioning Port of Dundee facility.
Section 5:
Industrial Area
� Do nothing
� Do minimum/maintain
Due to the existing relatively high defence levels and the minimal landward assets, it was decided that the most suitable solution for these areas would be do nothing and do minimum.
Section 6:
Coastal Walk
� Do nothing
� Monitor/maintain
This section has been recently upgraded and defence level is sufficient to defend the frontage, critical infrastructure and assets from flooding and coastal erosion. Therefore the only 2 solutions considered are the do nothing and the monitor/maintain options.
Section 7:
Yacht club
� Do nothing
� Do minimum/maintain
� Recharge
� Sediment retention structures
� Edge structure
� Land raising (on frontage or at rail line)
� Fill in gaps in landward flood wall
There is currently no erosion protection in place along this frontage. If left unprotected, there is potential for the coastal footpath to be lost and put pressure on the railway line. It is for this reason that the do nothing solution was deemed unsuitable. The land raising solution was also deemed unsuitable due to the minimal property requiring protection. Although a short list of 5 options has been highlighted, a combination of solutions must be implemented to fulfil the objectives. For example, Do minimum and maintain should be coupled with fill in gaps, as the do nothing does not afford any flood protection. Likewise, sediment retention structures and recharge.
Section 8:
Broughty Ferry
� Do nothing
� Do minimum/maintain
� Flood wall
� Shingle recharge
� Beach management
� Temporary demountable flood barriers
� Mechanical street barriers
The key requirement for a management solution along this section of the frontage is to provide flood defence for the properties in Broughty Ferry. To achieve this requirement, a solution must involve an increase in the current defence level. Therefore, the do nothing, do minimum/maintain, shingle recharge and beach management solutions were all deemed unsuitable.
260186/BNI/SNI/002/* 09 April 2011 PiMS
Dundee Coastal Study Stage 2
Management Section
Long-list of management solutions
The options to be taken forward to the short-list have been shown in bold
Comments
Section 9:
Beach and Dunes
� Do nothing
� Do minimum/maintain
� Manage dunes
� Sediment retention structure (e.g.
groynes) & recharge
� Offshore breakwaters
� Hard rock revetment structures
Both beach erosion and dune degradation affect this section of the frontage, therefore the do nothing solution did not fulfil the objectives. If compromised the dune systems would afford no benefit with respect to flood defence. The offshore breakwater solution was deemed unsuitable as it would not increase the flood deference level and would prove costly. Hard revetment structures were considered out of keeping with the environmental and amenity objectives and were therefore discounted as solutions. Hard revetment rock structures are currently in use at the far eastern extents of the frontage, and appear to be fulfilling their coastal protection requirements. Therefore, it may be sensible to divide this management section further.
Source: MCA Workshop Spreadsheets
260186/BNI/SNI/002/* 09 April 2011 PiMS
Dundee Coastal Study Stage 2
Appendix A. Management Section Sketch Plan
Appendices
260186/BNI/SNI/002/* 09 April 2011 PiMS
Dundee Coastal Study Stage 2
Appendix A. Management Section Sketch Plan
3 260186/BNI/SNI/002/* 09 April 2011 PiMS
Dundee Coastal Study Stage 2
<Insert content here>