Swansea Valley Business Park, Ystalafera

Flood Consequences Assessment

April 2020

Tulip Engineering Consultancy Limited 34 Culfor Road, Loughor, Swansea SA4 6TY www.tulipengineering.co.uk

Client Name: CB3 Consult Ltd. Document Reference: FCA/01 Project Number: J009

Issue Date Author Comments

01 14.04.2020 Graeme Tulip First Issue BEng CEng MICE

This report has been prepared for the sole and exclusive use of CB3 Consult Ltd from whom it was commissioned in response to their particular requirements and brief.

This report may not be relied upon by any other party.

The contracts (Rights of Third Parties) Act 1999 shall not apply to this report and the provisions of the said Act are expressly excluded from this report.

This report may not be used for any purpose other than that for which it was commissioned.

This report may not be reproduced and/or made public by any means without the prior written permission of Tulip Engineering Consultancy Ltd.

Information, views and conclusions presented in this report are based on information provided by others. That information has neither been checked nor verified by Tulip Engineering Consultancy Ltd. Tulip Engineering Consultancy Ltd accepts no liability for any inaccuracy resulting from inaccurate information provided by others.

Contents

1. Introduction ...... 2 1.1 Terms of Reference ...... 2 2. Site Description ...... 3 2.1 Location ...... 3 2.2 Watercourses ...... 4 2.3 Topography ...... 4 2.4 Soils, Geology & Hydrogeology ...... 5 2.5 History ...... 5 3. Proposed Development ...... 6 3.1 Layout ...... 6 3.2 Levels ...... 6 4. Planning Policy and Flood Risk ...... 7 4.1 Proposed Development and TAN 15 ...... 7 4.2 Justification Test ...... 7 5. Existing Flood Risk Review ...... 8 5.1 Historical Flooding ...... 8 5.2 Fluvial Flood Risk ...... 8 5.3 Surface Water Flood Risk ...... 8 5.4 Reservoir Flood Risk ...... 8 5.5 Groundwater Flood Risk ...... 8 6. Hydraulic Modelling ...... 9 6.1 Existing Hydraulic Model ...... 9 6.2 Updated Hydraulic Modelling ...... 9 7. Conclusions & Recommendations ...... 11

Appendices A. LIDAR Plan, Topographical Survey Plan B. Architectural Site Plan, 3D Image C. Flood Maps D. Hydraulic Modelling Technical Note

1 Swansea Valley Business Park, Ystalafera Project Number: J009 Document Reference: FCA/01 https://d.docs.live.net/9692ee99776ac28f/Documents/Tulip Engineering Consultancy/Jobs/J009 - Swansea Valley Ind Est FCA/Production/Data - Internal/FCA - Swansea Valley Ind Est.docx

1. Introduction

1.1 Terms of Reference Tulip Engineering Consultancy was commissioned by CB3 Consult Ltd to prepare this Flood Consequences Assessment (FCA) to support a planning application for the development of Industrial Units on brownfield land at Swansea Valley Business Park, Glan Yr Afon, Ystalyfera. Industrial development is classified as “less vulnerable” development in Technical Advice Note (TAN) 15 Development & Flood Risk (Welsh Assembly Government, 2004).

The proposed development site lies within Zone C2 of the Development Advice Map (DAM) published by Natural Resources Wales (NRW). Zone C2 is defined as areas at risk of flooding “without significant flood defence infrastructure” (Welsh Assembly Government, 2004).

The objective of this report is to undertake a study into the hydrological issues affecting the site, and establish whether and to what extent the consequences of flooding can be managed over the lifetime of the development, using the principles and tests set out in TAN 15.

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2. Site Description

2.1 Location Swansea Valley Business Park is an established industrial site which lies between Ystalyfera to the north and Godrergraig to the south. The site is directly bounded to the east by the A4067 Glanyrafon Road, with the banks of the River Tawe situated parallel to the road and approximately 70m away in the south-easterly direction.

The National Grid Reference for the site is: SN 76505 08226.

A site location plan is shown in Figure 1.

Figure 1: Site Location Ordnance Survey Data © Crown Copyright and Database Right 2020

An aerial view of the site is shown in Figure 2.

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2.2 Watercourses The Afon Tawe is a designated main river which rises in the Brecon Beacons above Llyn y Fan at 590m above sea level and flows in a generally south-westerly direction to Swansea Bay. The river drains a total catchment of some 270km2. The Tawe flows approximately 70m to the east of the proposed development.

The Afon Twrch, also a designated main river and a main tributary of the Tawe, rises in the Black Mountains and flows in a generally southerly direction to Ystalyfera where it joins the Tawe approximately 0.7km north-east of the development site. The Afon Twrch catchment is approximately 50km2 at the confluence with the Tawe.

2.3 Topography The development site sits in the relatively flat Tawe valley floor some 70m from the river. The width of the valley floor is some 0.8km at this point. The valley floor area widens markedly upstream (north) of the site, where the Twrch joins the Tawe and the two valleys merge.

A plan showing the site location, lidar ground levels, and all OS-mapped watercourses (main rivers and ordinary watercourses) in the vicinity is included in Appendix A.

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A topographical survey of the development area and adjacent industrial unit dated March 2016 is also included in Appendix A. This shows that the level of the rectangular development plateau is raised some 1m above the adjacent industrial land to the west.

The development site elevation ranges between approximately 58.0m AOD at the northern end to 59.0m AOD at the southern end. The large existing industrial unit and the industrial estate access road immediately to the west are at a lower level of approximately 56.8m AOD. The main road (A4067) to the east is at a similar level to the development site.

2.4 Soils, Geology & Hydrogeology Site soils are described as loamy in texture and freely draining according to the Cranfield University Soilscapes Viewer.

The geology at the site is described as superficial alluvial deposits (clay, silt, sand and gravel) overlying mudstone, siltstone and sandstone bedrock, according to the BGS Geology of Britain Viewer.

The aquifer designation of the sedimentary bedrock is Secondary A (capable of supporting water supplies at a local rather than strategic scale). The site is not in a groundwater Source Protection Zone area.

2.5 History The area in the vicinity of the site was historically the location of the Ystalafera Iron & Tin Plate Works. An overlay showing the site location in relation to the 1910 OS Map is shown in Figure 3.

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3. Proposed Development

3.1 Layout The proposed development consists of two industrial sheds housing seven business starter units, with associated access road and parking spaces.

The existing industrial estate access road is to be realigned to run some 7m closer to the existing adjacent industrial building, to increase the developable area of the plot.

Proposed architectural plans and elevations are included in Appendix B.

3.2 Levels Proposed carpark and building floor levels are not yet finalised, although it is anticipated that proposed ground levels will be similar to existing levels, with small localised differences due to cut/fill redistribution to flatten out the bank at the northern site boundary.

The realigned access road profile will need to be set to ensure suitable access to both the proposed site and tie in to the adjacent large existing industrial unit.

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4. Planning Policy and Flood Risk

4.1 Proposed Development and TAN 15 The development proposal is for industrial units on brownfield land in an industrial area of Ystalafera. Industrial development is classified as ‘less vulnerable’ development in TAN 15.

The Development Advice Map (DAM) is a flood map published by NRW for land use planning purposes. It is used alongside Planning Policy Wales and Technical Advice Note (TAN) 15 to direct new development in respect to flood risk. Together, they form a precautionary framework to guide planning applications.

The map is based on Natural Resource Wales' extreme flood outlines (zone C) and the British Geological Survey drift data (zone B). Zone B data was originally published 2004 and updated in 2017. Zone C data is revised quarterly by ongoing hydraulic modelling and represents areas affected by flooding in events with up to a 1 in 1000 annual chance of occurring (0.1% Annual Event Probability), but no allowance for future climate change.

The Development Advice Map in the vicinity of the proposed development is included in Appendix C. The Map shows that the development site currently lies within the blue shaded zone C2 area, defined as “areas of the floodplain without significant flood defence infrastructure”.

TAN15 provides for less vulnerable development in zone C2, subject to application of the justification test, including acceptability of consequences.

4.2 Justification Test TAN15 Section 6 states that development will be justified if it can be demonstrated that:

1. Its location in zone C is necessary to assist or be part of a local authority regeneration initiative or a local authority strategy required to sustain an existing settlement; or

2. Its location in zone C is necessary to contribute to key employment objectives supported by the local authority, and other key partners, to sustain an existing settlement or region; and

3. It concurs with the aims of Planning Policy Wales and meets the definition of previously developed land; and

4. The potential consequences of a flooding event for the particular type of development have been considered and found to be acceptable.

In this case this development is considered to meet the second and third criteria, whilst the fourth is supported by updated flood modelling undertaken specifically for this FCA, as described in Section 6 and Appendix D of this report.

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5. Existing Flood Risk Review

5.1 Historical Flooding The site has not experienced any flooding in the past according to NRW’s map of historical flood outlines.

5.2 Fluvial Flood Risk The NRW Zone 2 & 3 Map in Appendix C shows the lower part of the site in zone 3 (up to 1 in 100 annual chance of flooding) and the remaining higher part of the site in zone 2 (up to 1 in 1000 annual chance of flooding).

This map also indicates that the zone 3 area is classed as ‘area benefitting from flood defences’, although this area is not shown as green-coloured zone C1 (defended) on the DAM Map.

A additional ‘Flood Zone Plan’ is included in Appendix C, showing flood zones 2 & 3 overlaid on an map which also includes the site topographical survey, lidar ground elevation data and OS watercourses.

It is important to note that this is the fluvial flood risk as shown on the current (existing) flood maps which guide the planning process. The updated fluvial flood modelling described in Section 6 effectively supersedes this existing fluvial flood risk.

5.3 Surface Water Flood Risk The surface water flood risk map included in Appendix C shows a high risk area along the existing access road to the industrial estate, with the remainder of the development plot in very low or low risk area.

The existing access road will be reprofiled and drained as part of this development proposal. Furthermore the development site itself will be subject to sustainable drainage design/SAB approval and as such it is considered unlikely that the proposed development will increase the risk of surface water flooding or the rate and volume of surface water runoff.

5.4 Reservoir Flood Risk The development site is not at risk of flooding from reservoir failure according to NRW’s flood risk mapping.

5.5 Groundwater Flood Risk The development site is not in an area prone to groundwater flooding according to available BGS mapping, which is supported by NPT’s Local Flood Risk Management Strategy which states that there are no specific areas of groundwater flooding recorded historically in the NPT area.

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6. Hydraulic Modelling

6.1 Existing Hydraulic Model This section of the report will reassess the flood risk indicated by the DAM maps and establish whether the consequences of the risk of flooding may be considered acceptable.

The current DAM Map flood outline in the site locality is informed by the results of flood modelling undertaken in 2016 by JBA Consulting for the Ysgol Gyfun Ystalafera Flood Consequences Assessment. This model was in turn based largely on a 2013 Cwm Twrch 1D-2D model also developed by JBA Consulting on behalf of NRW.

The hydrology calculations from 2016 have now become outdated due to ongoing developments in hydrology methods, guidance and data availability. As part of this development FCA, updated hydrology and modelling has been commissioned.

6.2 Updated Hydraulic Modelling The updated modelling undertaken by JBA Consulting for this FCA encompassed updated hydrology (input flow) calculations, more realistic application of input flows and 1D model updates. Model scenarios were run using the latest TUFLOW software and current climate change (30%) allowance.

A Technical Note from JBA Consulting summarising the updated modelling exercise, is included in Appendix D of this report.

Results from the updated modelling show that the proposed development floods in neither the 1 in 100 (1%) AEP with climate change allowance, nor the 1 in 1000 (0.1%) AEP. The 0.1% AEP flood map extent is shown in Figure 4.

Flooding is shown to emanate from the right bank of the Afon Twrch some 1km upstream of the site at Ysgol Gyfun Ystalafera. The overland flood flow-path is then southerly before ponding around Varteg Road, but does not reach beyond the roundabout towards the development site.

TAN15 guidelines require a flood-free development level for fluvial flood risk of 1% (1 in 100 annual chance) probability over the lifetime of the development. The updated modelling results displayed in Figure 4 show that the proposed development would be compliant with the flood-free development level criteria (A1.14) of TAN15. Consequently it is clear that no ground level alterations would be required in order to meet this criteria.

Emergency access/egress to/from the site needs to be considered in light of the TAN15 recommendations. The map in Figure 4 indicates that the immediate site access road and mini-roundabout would be flood free during the 0.1% AEP event. The main A4067 Glan Yr Afon road roundabout is shown to suffer flooding up to a depth of 0.6m on the eastern side, which is within the “maximum permissible floodwater depth over the defined route during extreme flooding” figure of 1.0m given in A1.15 of TAN15.

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Whilst access to the A4067 during the 0.1% APE event may be hampered, the availability of the B4599 would be unaffected and would allow for safe evacuation from the site or access for emergency vehicles if required.

The ‘no flooding elsewhere’ criterion of TAN15 is considered negligible in this assessment since it has been demonstrated that the site would not flood during either the 1%CC or 0.1% AEP events.

Figure 4: Updated Model: 0.1% AEP Flood Depths

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7. Conclusions & Recommendations

• This planning application is for industrial development (classed as less vulnerable in TAN15) on brownfield land at Swansea Valley Business Park. • The requirement for this FCA is due to the proposed development site location in the flood plain (zone C2 of the current Welsh Government Development Advice Map). • However, updated flood modelling undertaken specifically for this FCA for this development, has demonstrated that the proposed development site is outside the flood plain, that is, flood-free during both the 1%CC and 0.1% AEP events. • The most up to date analysis of flood risk to the site is therefore shown to be less than that suggested by the current DAM Map, and the key TAN15 acceptability tests in relation to flood-free floor level, no flooding elsewhere and access/egress are all met by default. • The proposed development is compliant with all key aspects of TAN15 and as such it is considered that this land is suitable for industrial development in relation to planning policy and flood risk.

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APPENDICES

A. LIDAR Plan, Topographical Survey Plan

Swansea Valley Business Park, Ystalafera Project Number: J009 Document Reference: FCA/01 https://d.docs.live.net/9692ee99776ac28f/Documents/Tulip Engineering Consultancy/Jobs/J009 - Swansea Valley Ind Est FCA/Production/Data - Internal/FCA - Swansea Valley Ind Est.docx

Afon Twrch GOROF

32 El Sub Sta

Ysgol Gymraeg Dyffryn Glowyr 35 Ynyscedwyn

36 80.2m

53 40 22

BETHEL ROAD (Sch) 19 Enterprise Park 5

38 19 COEDLAN 45 / Parc Menter

1 1 Ynyscedwyn 18

40 20 13 7 47 14 77

Tank 15 6 21

44 306 23 33 13

305

17 GOROF ROAD

12 27 73 7 300 5 311 2 COLLEGE ROW TCB

HEOL ABRAM 12 51 19 41 10 53a 59 HEOL MEURIG

28 62 65

Cwrt 71

58 SPENCER TERRACE 67 321 11 Gorof

6 329 27 1 to 7 to 1 1 Shelter

El Sub Sta 21 1 1 to 23

Track 75.3m El Sub Sta

57 6 Shelter 1a 326 20 HEOL AARON

1 201 to 207 Track Pond Erw HydrefHAFAN CLOSE 71 1 327

41 62 Hazeldene 79.6m

328

68 24 1 36

14 3 72 4 330 Ystradgynlais 33

1 New 37 Workshops

Hall Houses 4 A 4067 El Sub Sta 75.7m 7 56

CWRT Y GLOCH 1 2 1

Issues El Sub Sta 26 FB Mast (telecommunication)

Weir 23 16a TRAWSFFORDD

82.3m 1 Path (um) 1

GP 51 GP Subway Lighting Tower Club 16 65

Gors-y-garamod 6 Palleg Place 14

Wood HEOL YR YSGOL / B4599 Track 4 7 GOROF ROAD Mast CWMPHIL ROAD El Sub Sta 73.7m Maes-y-Glan Track 15

SCHOOL ROAD 13

10 1

10 Play Area

Works 62 11 23 79.2m FB 80.1m Cycle Path 74.7m 21 Works Glyn View

19 7 17 Lighting Tower Path (um) 11 75.6m Cricket Ground Glantwrch PW Saron 7 Bungalow Sports Ground Apostolic

Cwm Wanderers 20 Recreation Ground Stand 18 Church 2

(Football Ground) Works 52 1

1 61

El Sub Sta Tan-y-coed 16 Path (um) 91 94

Lighting Towers 48

ESS 13 Rose Cottage 76.2m Home Farm

Cycle Path

15 14

Ty Gwyn 10 Cottage Path (um) Pinetree Lodge 90 Dan-y- FB Coed LB 16

2 LLYS YNYSCEDWYN Brook 8 TCB Lodge 17 2 Wayside 1 Pond 5

Gurnos Gurnos

Gurnos House 28

Cott 97

Villas

4 Bowling Green

1 1 2 Cycle Path Pavilion Bowling Green 24

1 Gurnos Club 87 Y Bwthyn 38a Track Meadow Lodge HEOL GLANTAWE 18

15 6

Tennis Courts 36 Industrial Estate 85 102 Midland 99 23 7 Depot Depot Terrace Erwlas 47

101b

101a Burial Ground 105 Track Rivendell Works 100

Drain Y Cedrwydd 84 12 Path (um)

3 23

PEN-YR-GRUG Gilfach Goch 10

1 A 4068

111 Farm Issues Afon Twrch 125

108 9 110a 110b

18 Clun-gwyn 16 4 10

The Beeches 125a 10 107 1 Caringdale 159.3m CWRT Y GAMLAS

2 22

PEN-YR-ALLT 33

126a HEOL YNYSCEDWYN / YNYSCEDWYN ROAD Sunny 8 11 Bank 128 127 Wharf 74.0m Springfield 126b

Reservoir Cottage Ty-Ni 11

Track 13 (covered) 79 2 Workings (dis) 31 Neuaddllwyd

78b BRON YR ALLT Golwg 36

5 Mynydd 78a ETL Pits 5 Shelter

Alltygrûg (disused) The 77a

3 Public Recycling Facility

Cottage 8 1 Arosfa

House 8 1 27 77b Afon Tawe / River Tawe 11 TAWE PARK Burial Ground 76 4

Crymlyn

12 76b 31

12 25

Track 3

156.7m 75 Drain Four B 4599 3

El Sub Sta Seasons 13 Path (um)

2 Depot 5 Drain Ruin Level BRYN-Y-GRUG Pond El Sub Sta 173.7m (disused) Path Picnic Area

Wern Fawr 7 Pond The All Black's Arms

Playground (PH) Ysgol Maesydderwen 81.0m 16

192.5m Allt-y-grûg 2 or Maesydderwen School 8 Drain 1 1 Heap Pond

El Sub Sta 6 183.9m Levels 25 214.6m 5 (disused) (dis) Garage

42 Woodlands Business Park 19 2 Path (um) Path (um) 4 / Parc Busnes Coed Cedwyn

Issues 223.6m 68 Collects Path (um) 1

3 83.7m Superstore

17 1 2

TCB Path (um) 20 Glanyronen Track 173.6m 72.4m Cottage 1 1

Heap 44 El Sub Sta 162.3m 16 Y GILFACH LB 6 (dis) Tanks 123 El Sub Sta 121 72.1m Pont Aur 47 201.8m 48

158.0m Weir 62

119

Pandy 55 117 Moel-Llys

Lighting Towers Feeder (disused) GURNOS ROAD Glanyronen

114 115 54 ETL Track El Ps 4 7

113 3 LB 2

8 1 112

Tank Ppg Sta 15 65 52 93 ETL 91 El Ps Ystradgynlais Path (um) 55

Works 140.3m MAES-Y-COED 9 Sports Centre 57 to 60 Collects Sunnybank ESS Lighting Towers

87 5

86 Birkdale Tip 3 47 6

Coach House 48 61 Spring 101 8 100 (disused) Cycle Way 37 187.6m 85.1m

Sinks El Ps 42

197.7m Drain 84

Llys Fredrick 5 75 6 Maes-y-coed House Tennis Court PONT AUR 46 Issues 4 4 64 Golwg y Cwm 3 1 1

4 11 Jones Hen Felin 5 15 Weir The

4 67

75 16 Posts Posts PENYWERN Oaks

10 Millfield Llys-Swynol 91

9 88 121.0m 3 GG

13 GP MAES Y DDERWEN GDNS 72

73 86.6m 70.5m Play Area 71

1 The Nook

7 6 Filling Station 1 Ty Gardd

63 13

6 1 7

1 68

Recreation Ground 8 71.0m 67

Capital Bldgs 23 70 5 12

El Sub Sta Ambulance 5

Level Play Area 42 Station

Islwyn 1 24 Ty Afal Parc Gwaith Hearn Ynyngedwyn 67

(disused) 1 Chy 64 1 CLYNGWYN ROAD 11 Garage / Ynyscedwyn Ironworks Park 2 Maes y Dderwen

79 1 Twrch

Teg Fan Gardens 4

74 110.9m Bridge Garage 49 53 59 58 3 Tip 2 62 Ynys-Cedwyn

Sinks 47 67.8m 14 Gilfach-yr-haidd 2

LB 13 (disused) Glan-Twrch 7 Lodge Glyn Dderwen Shelter 1 Maes- 118.6m 56 60 1

15 GURNOS ROAD 58 14 y-coed 54

Tel Ex ALDER AVENUE

52 4 14

14 WIND ROAD 5

TAN-Y-FARTEG 4 50 59 6

Track 12 45 36 Y BERLLAN Ddolwen 16 Drift

69.0m Shelter

50 Blaenant Ho

13 35 62 3 Surgery 3 (disused) Collects 46 7 67.6m 69.5m 52 39 11 TIRBACH ROAD 1 Glannant Ho 84.5m PH 9

100.8m 2 ESS 67 Shelter 1

46 1 WILLIAM STREET

18 Erw 44 7 LON TANYWEN / TANYWERN LANE 10 1 5

31 Line of Posts Path (um) 13 66.7m 6 28 Fair 1 65 33 54

44 24

Collects HEOL TUDOR / TUDOR STREET 26

8 13

9 15 19 61

63 SM

1 2 Ty Gwyn-bâch 47 29 8 Swn GLANTAWE PARK 40

Dan-y- yr Eos

8 26 4 1

18 Ty'rwaun Maesydderwen 23 6 GLANTWRCH 27 TCB 50 Coed

7 52 Works 30 9

50 12 2 34 23 67.1m 3 CLARE ROAD / HEOL CLARE 25 Path (um) 7 4

5 CROESFFYRDD

27 19 Govt

36 13

69.9m 4

37 18

Offices 18

118.7m 15 2

Delfan 20 Yr-Hen-Bont 25 48 Pond 29

Track 16 1 33 Hall (Residential Home) GLANTAWE 13 GLANNANT TERRACE

176.7m HEOL GLANRHYD / GLANRHYD ROAD

24 Hall 15 Ystradgynlais

Clinic 17a 26 44

Llechwedd 87.2m 46 9

42 10 56 11 4 GOUGH AVENUE 40

14 15 9

27 40 15

15a 28

18 Community 20

24 Liby 38

11 67 67.6m Tynedale SWAN LANE

Drain 11 16 Maesgwyn 9 16a 13 Newlyn 11 39 8 Hospital 26 7

Issues A 4067 PARK 12

Path (um) Path 26a ALLTYGRUG ROAD / HEOL ALLTYGRUG

7 36 9 Chapel 66

74.2m 18 Brynbach 1 SAINT DAVIDS ROAD Church Shelter Milborough 11 Club Chrisgar 63 25 Issues 4 GLANTWRCH B4599

Track TWYN-YR-YSGOL Court 26

57 10a SWANFIELD / MAES ALARCH

1 to 5 to 1 18

8 91.7m 76

Cattle Grid 4 68.6m 5 Dumfries Place COMMERCIAL STREET 7 Cornerways 2 67.8m

Cartref 8

Shingle

2 20 LB

51 6

24 12a

MILBOROUGH ROAD / HEOL MILBOROUGH 84

55 43 10

RD 17 Coch

1 94 Shelter 3 82

30 3 53 4

PENTWYN 92

LB 81.9m GLANTAWE PK 1 1 38 39 14 24 94

33 49 88

43 45 47 B 4599 84

126.8m 4 3 98

82.7m 80

37 1 to 8 47 20

3 Level

El 2

41 13 4

37 2 3

100

70 13 34 12 Sub (disused)

Pipeline

5 1 79 60 Sta 31 Arnold Court

51 106

4 72 Path

43 12 18

2 FB

27 PH

65 Glan-rhyd

CLAREHEOL ROAD CLARE / 48 67.5m 116 Glan-rhyd 4 Path

119.5m 8

4 1 ESS

El Ps 2

38 5

A 4067 53

1 GLAN-YR-YSGOL 87.1m 16

5 GLANNANT TERRACE

Y Wern 6

11 7 19 9 3

Community 6 SNOW TERRACE Primary School 38 Nant-y-Mynydd The Elms

8 Centre Ruin 1 8

2 Cysgod 7 Bank 2

Track Lynsdale

1 Y YR AFON 16 Heap 31 Mynydd SAINT DAVID'S ROAD Glan-rhyd

170.1m 67.4m 16 4 Cottage (dis) 31 FFORDD Drain Ty Gwyn 1

7 Meml 1 The Poplars

Rhoscerdd Track Club 4 Path (um) Tank 19 Playing Field

1 66.2m

130.4m LB 89.1m 24 27 RHYDWEN 5 Pol 6

Brynderwyn Ysgol Bro Tawe

24 7

Sta 8

SCHOOL ROAD 8 9

(Sch) 9 Ford 2 20 25

Y GILWERN COMMERCIAL STREET / STRYD MASNACHOL

12 114.1m 6 22

4 23 167.6m WERNWOOD ROAD Shelter B 4599 28

2 20 Church

18 Cystanog

30 Track 15 12 Track Pavilion

Spreads 1 Level 91.6m 6 65.9m

25 PENYWERN ROAD Path (um) 17 14 64.8m

(disused) 2

12 5 5a Hall

Playing Fields 24

Pond 1 111.6m 3

Maes-y-wern 1

23 22

17 7

4 Wern House 18 Histon Pond Pond Penrhiwfarteg 9 Afon Tawe / River Tawe 100.9m Bungalow Path (um) 5

11 10 7 1 96.7m

20 25 13 8 Pond Swn y Nant Tank 6 Heulwen (PH) OLD WERN ROAD 9 Pant-y-gwanyd 32 81.2m 3 120.8m DARREN ROAD Glan-rhyd

29 Bridge 122.6m 19 20 ETL Level Path Path (um) Derlwyn El Sub Sta 1 30 69.0m (disused) (um) 13 Issues 118.0m Lay-by El Sub Sta 102.5m 42 94.6m FB Tank CG Wern Pond 12 PW Pond 10 Oleu 31 Car Park Wern Villas 11 2 El Sub Sta PO LB Spring 11 DEELEY ROAD 1 Sewage Works Issues Drain 7 54 36 30 Ysgol Gymraeg Ystalyfera Path Issues 56 Dismantled Railway

Surgery 1 39

Path (um) 41 38 Issues 62

2 LOWER WERN ROAD

45 21 ETL 47 Sorting 8 Farteg-fach PH Office 63.4m Park House Track GOUGH ROAD / HEOL GOUGH Path (um) 74 TCB Carreg Pentwyn Farm 46

Shingle Track 53 Ystalyfera Rugby Club 5 13 Subway 47 WERN ROAD / HEOL Y WERN PROSPECT PLACE 62.9m 15

172.7m 104.2m 36 FB 86

88 6 ESS 99.1m 7

53 Ynys-glan-Tawe Hall 5a

Collects 69 94 5

Track

1 ZOAR ROAD3 / HEOL ZOAR Drain

59 FFORDD GLANDWR ETL

Track 41 100.2m 1 CANAL TERRACE Levels Stone Pond (disused) Path (um) 1 165.5m 100 Bowling Green 1 to 35 Waterfall 62 Maes-Y-Darren WEMBLEY ROAD Tennis Courts 102 Avonsbrie Parc-y-Darren Play Area GLAN YR AFON

65 106 2a

108 Pavilion 61.2m 1a Shelter Aber-twrch

161.2m 87

2 2

1 66 47 Afon Twrch

3 El Ps

2 Vicarage 120 12

10 118 13 97 Pant-y- ETL WOODMANS TERRACE 8 72 60.6m

gwanyd Row 1

9 Play Area 103 7

11 9 4 7 16 13 10

14 5 109

6 15 24 62.2m Issues 16 17

Level 14 Pond 4 El Ps

(disused) 105.2m 1 Track 5 6 99

1a 17 Track Heap 6

97 El Sub Sta 108 Outfall Drain (dis) 27 Afon Tawe / River Tawe

THE GARDENS MINYFFORDD Path 4 Shelter 5 8 Golwg 12

4 18 Weir Y Shingle

7 60 Darren WADE AVENUE

60.9m YNYSYDARREN ROAD / HEOL YNYSYDARREN Shingle 54 Issues 139.4m 26

Meadow Vale

56 1

Penlan-Fâch 63 17 Path (um) PH Issues 10 87 11

Ystalyfera 98 Caeralem

15 14

Drain 29 23 31 FB

Issues Path 13 Track 20 ETL VINE ROW 33

35 Track 36

64 Spreads

24 24

28 37 Ford Play Area 21

27 28 32 75 Track

26 27

33 58.7m Path (um)

25 17 37 68

26 Ford

25 GLAN YR AFON Spring Spring 84

41 38 Weir

24 El Sub Sta Spring FFORDD EMLYN

112.2m 40 Levels Ford Tir Garw Path 32 12 33 El Sub Sta (disused)

20 65 44 48 Spring Path (um)

Path 69 34 Pond 49 Heap (dis)

Spring Issues Heap (dis) 7

Pond Track Spreads

49 Path (um) 1

Pond 51 Farteg-uchaf 53 Shelter

73 LB Track

50 41

44 El Sub Sta 39 36 37 Issues

70 Tank Shingle

Drain

65 Path (um) VARTEG ROAD PO 56 TCB 27 Ynyscu House

67 110.1m 13

Spring Pen-y-graig 48

15 1 42 42

130.4m 43 Pond 28

14 56.6m Track

14 Weirs Level Spreads

2 97 51 (disused) Level Oak Villas Shelters 59.9m (disused) 52 Shingle Spring 53 Path (um)

Green Croft 1 to 4 Track 4 to 1 54 Track Varteg 7 House Ty'r-graig 13 1 59 13 18 Track Heap (dis) Dan-y-Coed 12 25 MINYRAFON GRAIGYMERCHED 27 Track 28 26

2 Spring 81

Cwar 132.2m Filling Station 1 24 59.7m Track Path (um) 109.0m Pen-y-graig Sunnyville B 4599 59.8m (disused) Path (um) GLAN YR AFON

60.6m

87 86 88 8

Track 125.1m 93

Path (um) Quarries CYFYNG ROAD Swansea Valley Business Park Rev Date Path (um) Office 100 Ruin Row (disused)

102 Track 11 Track

105 Waterfall

Track

107 Drain 111

111a Afon Tawe / River Tawe 102.3m FB Pond

6 113

ETL

115 116 108.7m Graig Arw GLAN YR AFON

Glan-yr-afon Collects Car Park 2 Level Spring (disused) Twyneglur 59.0m LB Shingle Cwar Pen-y- FB Farteg-isaf 100.6m Path (um) Graig-arw Issues 1 (disused) 126

3 128 Ynisgeinon House 29 Drain 5 28 Spring Track 9 Workings (dis) Pond

11 23

Danygraig 22

ETL Track ETL TCB Ynisgeinon Farm

Shelter Track CLEES LANE 18 Track

Shelter 101.5m 4 Issues 19 3

Post

1 Craig 19

21 2

Arw 20 Pond Track 25

Pantteg 28 30

Track

Issues

62.2m Heap A 4067 Track (dis) tulip Lower tulip 99.8m Pantteg 38 Pond 1 engineering consultancy El Ps Drain Heap (dis)

Spring The Willows 20

Level Pantteg Hall Capel (disused) Fountain Hall Spreads Cwar Club Pen-y-graig-arw West Y Darren Shaft 34 Culfor Road, Loughor, Swansea SA4 6TY (disused) Danygoeden Widdon (dis)

Pantteg 8 Heap

Tarren y Gigfran (dis) 49 Issues

94.9m 50 64.9m tel: 01792 893407 mob: 07843 491524 Issues Track El Ps Woodlands

Issues Track Issues 7

Track 56 Sluice e: [email protected]

Briardale 5b Weir

65.6m

60 5a Issues El Ps w: www.tulipengineering.co.uk

Pantteg 63 Sinks STRYD NEWYDD / NEW STREET Sinks 2 Issues

Shelter GLAN YR AFON ETL 1

Darren Fach

68.5m ETL 1 Track

21 1

Path (um) 4 74

15 LLYS GRAIG ARW Mast Mast (TV) 12 Mine

HEOL EGLWYS / CHURCH ROAD 66.5m (disused) 47 74.8m Track 8 Shelter Drain 52.2m

6 51

Issues El Ps 7 1

LB PANT Y8a FFYNNON TERRACE / TERAS PANT Y FFYNNON Ford 78.7m

Playing Field Earthworks 8

Waterfalls 82.6m Sinks Issues Mast Crynant Forest Cemetery Track Client:

Track Issues El CB3 CONSULT LTD Sub Sta Sinks Track Pond

Mast Issues

Sinks 13 Hall

Path Mynydd Allt-y-grug Sinks El Ps Waterfall Sheepfold Spring 52.7m 1e (disused) Issues 1f Pond 86.0m 1g 1h FB 1a 1b 1c

Sinks The 1d Workings (dis) 34

23 Bungalow Sinks Workings (dis)

GRAIG ROAD 24 Levels 40 Recreation Ground

(disused) Issues 41 2 Sheepfold Sinks 17 Shelters TCB

18 (disused) Play Area 10

HODGSON'S ROAD FB Path (um) A 4067 Project: Issues 12 15 Collects

5 SWANSEA VALLEY OWEN'S LANE LB 7 PANTYFFYNNON 82.9m Farteg Hill Llygad y Ffynnon Chemical Row SubEl Sta Spring

22 Ford 17 Issues Track 41 Drain 30 El Ps

39 Issues ETL

Graig Arw Sinks FBs 26 IND. EST. FCA

34 29 Waterfall Issues

51.2m 24 8

LLYS YNYSGEINON 29 48

27 7 Path (um)

46 39 23

PANTYFFYNNON 44

18 2 48 1 Drain

19 21

FFORDD Y GLOWYR 38 Lock River Tawe

17 Drg Title: / Afon Tawe (disused) 12

51 LIDAR PLAN Track 20 11 60 11 Spreads 13

14 2 57

88.7m 28 Issues

59 344.5m

14 Shelter 19 24

Issues 22 Spring 10 5

ETL Drain 15 FFORDD DANYGRAIG

16 3

Sinks Lock 16

Spring (disused) 1 14 LLYS RHAEADR Ford Issues Track 1 1 7

Track

6 Spring

2 3 198

GOLWG Y MYNYDD 2 12 Waterfall

1 LLYS YR AFON Drain Levels 4

Shelter 4 3

1 Crynant Forest

88.3m 11

205 Collects 4 20 CRIMEA COURT Quarries Springs

17 2 Path (um) (disused) 206

Issues 20 8 Issues

16 20 335.4m

25 26 14 207

1 Mine Mine 4 9 27 2

(disused) 22 1 5 Graig y 8

210 Darren

95 11 Sinks Date: Status: Scale: Issues

GRAIG NEWYDD 5 1 Ford Drain 212 3

17 213

97 7 216

1 Path (um) Issues 19 10 GRAIG Y DARREN

Drain 28 87.2m 12 2

2 Collects 1:10,000 33 214 20 8 18 Collects 16 Level Cilbrwyn 14 (disused) Drain El Issues 09.04.2020 PLANNING

21 Sub Ford 17

Drain to

Sta 31 219 11

Track 33

101 28 CARREG YR AFON 23

7 Drain to LLYS CAMBRIAN Levels

102

GRAIG ROAD 39 13 Path (um)

21 Outfall Issues (disused)

88 41 Pen-y-graig

6 Issues 3

8 Level 12

1 Ford 15

71 82 35 Sinks 88.1m (disused) Patagonia Farm 104 Drain 74

Track

64 19 43 Track Drain Size:

Drain 41 Ford

52 23 Level Level Ruin Track

(disused) (disused)

44 80 64

62 1

14 72 2 LLYS HARRY

Path (um)

25 Rev. 27 Drg No.

2 11

49 57

1 - A3

108 Lock Drain J009/001 37 41 Ford

(disused) Issues 55

12 Collects ETL 335.3m Track GRAIG Y FFOREST Daren Oliver Civil Eng Services Ltd

THE TOTAL ON-SITE ENGINEERING SOLUTION 1 Heol Yr Ysbyty, Castle View, Caerphilly CF83 1TA Mobile- 07919 326969 Office- 02920 886120 Email- [email protected] www.darenoliversurveying.com Contract Mr Paul James Swansea Valley Business Park Glanyrafon Roundabout Ystalyfera SA9 2EE Topographical Survey

Drawing Number 10007/001/CD/DLO

Scale 1/250 @ A0

Date 24/03/2016

Drawn by DLO

B. Architectural Site Plan, 3D Image

56.96 56.98 SV G 56.86 57.39 56.75 56.82 56.78 56.80 57 56.83 56.79 56.88 56.78

56.79

58.34 GALVANISED STEEL 56.83 56.78 FENCE 56.81 57.04 56.92

57 56.90 56.95

56.75 58 SUB-BASE 56.85 56.95 56.89 56.79 56.81 57 57

56.90 57

56.80 56.78 57

56.79

57.89 56.91 56.85

56.82 56.90 58 56.82 56.86 56.84

58.21

56.79

56.78 56.84 56.77

58 56.84 56.76

56.82 56.84

BT 56.91 56.89

58 56.78 56.94 56.92 56.88 G 56.80 56.89 56.88

56.91 G 56.79 MH 56.77 CL

57 56.88 56.86 56.75 56.80 56.8156.80 56.80 56.80 56.81 56.83 56.82 56.81 56.7756.83 57.84 56.80 57.50 56.79 GPS1 G 56.81 56.84 56.80 56.88 56.79 56.76 56.77 E 276467.129

57 Z 57.76 56.819 56.83 56.82

D2 E N276515.090 56.79 Z208267.110 56.922

56.87 56.80 56.81 56.75 56.86 56.86 56.80

58.07

58 56.94 56.88

56.97 57 GRASS

58.13 57.02 57 56.99 56.96 57 56.90

58.20 57

56.97 57.03 57 58 57.23 57.37

57.35

57 57 57 57

57 58.44 57

57.04 57.01

57.89 58.16

58 57.13

57.94 58

58 57.17 57.18

58.77 57.29

57.54

FENCE GALVANISED STEEL GALVANISED TARMAC

57.50 57.36

57.47

GALVANISED STEEL CL FENCE 58.71 58.42 58.00 57.52 58.39

58.43 57.44 58

57.56

58.98

57.56 57.59

58.01 RE-LANDSCAPED Eaves Level 57.61 62.70 AREA 58.41 58.61 58.65 58.46 58.64 58.44 57.52 58.88

57.59 57.59 59

57.68 59.03 59

59 57.73

58 FENCE

57.70

59 59

57.84 Ridge Level 64.86 58.87

58.73 57.71 58.80 58.52 58.74 58.59 58.55

59.08

58 59

SV 59

SV 57.67 MH

59.12 59

D4 59 59

57.68 59

57.68

59.15 59.16 59 59.09 57.71

58.97 59 59.24 BT 58.78 59.21 58.75

58.67

59 57.81

59.14 59 58 59.11 58.35 59.06 59.09

59.02 57.76

59 59 RS 59.09

59 59 BT 58.99 59 59 59.0159 58.04

59 59 59 59 58.99

58.96 59 59 LP

59.24 59 58.91 58 A4067 SLB 58.96 G 57.89 59.16 SLB 58.89 58.86 57.83 58.78 58.84

RS LP

58.19

59.04 59 58.69 58 59.12 58.80 58.65 G RS 58.02 59 59.00 RS 58.14

59 58.69 59.07 59 58.52 E 58.16

59.15 58.63 G N276552.026 59 Z208231.154 58.51 59 59.02 59 D3 59.03 58.530 58.45 58.36 59.06 58.52 58.21 59.00 58.97 LP 58.40 59.07 RS

58.95 58.96 58.45 58.39 58.98 58.25 58.97 58.91 58.87 58.31

58.91 A4067 58.98 59

58.86 A4067 58.15 59.00 58.65 58.80

58.73 58.52

58.62 G 58.36 58.59

58.51 58.16

58.39

C. Flood Maps

Map Title

Map Perygl Llifogydd / Flood Risk Map

Allwedd / Map Key Zone C1 Zone C2 Zone B Zone A

Graddfa / Scale 1: 5,001

Dyddiad / Date 12/04/2020

Ceir rhestr lawn o delerau ac amondau yn https://naturalresources.wales/rhybuddsafonol neu drwy gysylltu ag 0.3 0 0.13 0.3 [email protected]. A full list of terms and condiitions is available from the https://naturalresources.wales/StandardNotice or by contacting [email protected] © Crown copyright and British_National_Grid Kilometers database rights 2017 Ordnance Survey 100019741. Geological Mapping: British Geological Survey ©NERC. Centre for Ecology & Hydrology © NERC (CEH). Defra and Met Office © Crown copyright. © Cranfield University. © James Hutton Institute. Land & Property Services © Crown copyright and database right. Map Title

Map Perygl Llifogydd / Flood Risk Map

Allwedd / Map Key Main Rivers Flood Defences Areas Benefiting from Flood Defences Flood Storage Areas Floodmap Flood Zone 3 Floodmap Flood Zone 2

Graddfa / Scale 1: 5,001

Dyddiad / Date 12/04/2020

32 El Sub Sta

Ysgol Gymraeg Dyffryn Glowyr 35 Ynyscedwyn

36 80.2m

53 40 22

BETHEL ROAD (Sch) 19 Enterprise Park 5

38 19 COEDLAN 45 / Parc Menter

1 1 Ynyscedwyn

40 20 13 7 47 14 77

Tank 15 6 21

44 306

23 33 13

305

17 GOROF ROAD

12 27 73 7 5 300 311 2 COLLEGE ROW TCB

HEOL ABRAM 12 51 19 41 10 53a

59 HEOL MEURIG

28 62 65

Cwrt 71 58 SPENCER TERRACE 67 321

11 Gorof

6 329 27 1 to 7 to 1 1 Shelter

El Sub Sta 21 1 1 to 23

Track 75.3m El Sub Sta

57 6 Shelter 1a 326 20 HEOL AARON

1 201 to 207 Track Pond Erw HydrefHAFAN CLOSE 327 71 1

62 Hazeldene 79.6m 68 328

24 1 36

14 3 72 4 330 Ystradgynlais 33

1 New Workshops 37 4 A 4067

Hall Houses El Sub Sta 75.7m 7 56

CWRT Y GLOCH 1 2 1

Issues El Sub Sta 26 FB Mast (telecommunication)

Weir 23 16a TRAWSFFORDD

82.3m 1 Path (um) 1

GP 51 GP Subway Lighting Tower Club 16 65

Gors-y-garamod Palleg Place 6 14

Wood HEOL YR YSGOL / B4599 Track 4 7 GOROF ROAD Mast CWMPHIL ROAD El Sub Sta 73.7m Maes-y-Glan Track 15

SCHOOL ROAD 13

10 1

10 Play Area

Works 62 11 23 79.2m FB 80.1m Cycle Path 74.7m 21 Glyn View Works 19

7 17

Path (um) 11 75.6m Cricket Ground Lighting Tower Glantwrch

Saron 7 Bungalow PW Sports Ground Apostolic

Cwm Wanderers 20 Recreation Ground Stand 18 Church 2

(Football Ground) Works 52 1 1 61

El Sub Sta Tan-y-coed 16 Path (um) 91 94

Lighting Towers 48

ESS 13 Rose Cottage 76.2m Home Farm

Cycle Path

15 14

Ty Gwyn 10 Cottage Path (um) Pinetree Lodge 90 Dan-y- FB Coed LB 16

2 LLYS YNYSCEDWYN Brook 8 TCB Lodge 17 2 Wayside 1 Pond 5

Gurnos Gurnos

Gurnos House 28

Cott 97

Villas

4 Bowling Green

1 1 2 Cycle Path Pavilion Bowling Green 24

1 Gurnos Club

87 Y Bwthyn 38a Track Meadow Lodge HEOL GLANTAWE

18 15 6

Tennis Courts 36

Industrial Estate 85

102

Midland 99 23 7 Depot Depot Terrace Erwlas 47

101b

101a Burial Ground 105 Track Rivendell Y Cedrwydd Works 100

Drain 84 12 Path (um)

3 23

PEN-YR-GRUG Gilfach Goch 10

A 4068 1

111 Farm Issues Afon Twrch 125

108 110a

9 110b

18 Clun-gwyn 16 4 10

The Beeches 125a 10 107 1 Caringdale 159.3m CWRT Y GAMLAS

2 22 33 PEN-YR-ALLT 126a HEOL YNYSCEDWYN / YNYSCEDWYN ROAD Sunny

8 11 Bank 128 127 74.0m 126b Wharf Springfield

Reservoir Cottage Ty-Ni 11

Track 13 (covered) 79

2 Workings (dis) 31 Neuaddllwyd BRON YR ALLT Golwg 36 78b

5 Mynydd 78a ETL Pits 5 Shelter 77a

Alltygrûg (disused) The

3 Public Recycling Facility

Cottage 1 Arosfa

8 27

House 8 1 77b

Afon Tawe / River Tawe 11 TAWE PARK Burial Ground 76 4

Crymlyn

12 76b 31 25 12 Track

156.7m 3 75 3

Drain Four B 4599 El Sub Sta Seasons 13 Path (um) Depot 2

Drain Ruin Level 5 BRYN-Y-GRUG El Sub Sta 173.7m Pond (disused) Path Picnic Area

Wern Fawr 7 Pond The All Black's Arms

Playground (PH) Ysgol Maesydderwen 81.0m 16

192.5m Allt-y-grûg 2 or Maesydderwen School 8 Drain 1 1 Heap Pond

El Sub Sta 6 183.9m Levels 25 214.6m 5 (disused) (dis) Garage

2 Woodlands Business Park 19 Path (um) Path (um) 4 / Parc Busnes Coed Cedwyn

Issues 223.6m 68 Path (um) 1

Collects 3 83.7m Superstore

17 1

TCB Path (um) 20 Glanyronen Track 173.6m 72.4m Cottage 1 1

Heap 44 El Sub Sta 162.3m 16 Y GILFACH LB 6 (dis) Tanks 123 El Sub Sta 121 72.1m Pont Aur 47 201.8m 48

158.0m Weir 62

119

Pandy 55 117 Moel-Llys

Lighting Towers Feeder (disused) GURNOS ROAD Glanyronen

114 115 54 ETL Track El Ps 4 7

113 3 LB 2

8 1 112

15 65 Tank Ppg Sta 52 93 ETL 91 Ystradgynlais El Ps 55

Path (um) 56

Works 140.3m MAES-Y-COED 9 Sports Centre 57 to 60 Collects Sunnybank ESS Lighting Towers

87 5

10 86 Birkdale

Tip 3

47 6

Coach House 48 61 Spring 101 8 100 (disused) Cycle Way 37 187.6m 85.1m

Sinks El Ps 42

197.7m Drain 84

Llys Fredrick 5 75 6 Maes-y-coed House Tennis Court PONT AUR 46

Issues 4 4 64 Golwg y Cwm 3

1 1 11 4 Jones Hen Felin 5 15 Weir The

4 67

75 16 Posts Posts PENYWERN Oaks

10 Millfield Llys-Swynol 91

88 121.0m 13 3 MAES Y DDERWEN GDNS GG

GP 71

72 73 70.5m Play Area

86.6m 1

The Nook

2 7 6 Filling Station 1 Ty Gardd

63 13

7 6 1

1 68 8 71.0m Recreation Ground 67

Capital Bldgs 23 70 5

12 El Sub Sta Ambulance 5

Level Play Area 42 Station

Islwyn 1 24 Ty Afal Parc Gwaith Hearn Ynyngedwyn

(disused) 67 1 Chy 64 1 11 / Ynyscedwyn Ironworks Park CLYNGWYN ROAD Garage 2 Maes y Dderwen 79 1 Twrch Teg Fan Gardens

74 110.9m Bridge Garage 4 53 58 3 49 59 2 62 Tip Ynys-Cedwyn

Sinks 47 67.8m

Gilfach-yr-haidd 2 LB 14 (disused) Glan-Twrch 13 Glyn Dderwen 7 Lodge Shelter 1 Maes- 118.6m 56 60 1

15 58 GURNOS ROAD 14 y-coed 54

Tel Ex ALDER AVENUE

52 4

14 WIND ROAD 5

TAN-Y-FARTEG

50 59 45 Ddolwen

Track 12 36 Y BERLLAN 6 16 Drift

69.0m Shelter

50 Blaenant Ho

13 35 62 3 Surgery 3 (disused) Collects 46 7 67.6m 69.5m 52 39 1 Glannant Ho

11 84.5m TIRBACH ROAD PH 9 100.8m 2 ESS 67 Shelter 1

46 1 WILLIAM STREET

44 7 Erw 18 LON TANYWEN / TANYWERN LANE

10 5

1 31 Path (um) 13 66.7m Line of Posts 28 Fair 1 6 65 33 54

44 24

Collects HEOL TUDOR / TUDOR STREET 26

8 13 9

15 61 63 SM 19

1 2 Ty Gwyn-bâch 47 29 8 Swn GLANTAWE PARK 40

Dan-y- yr Eos 26 4

1 23

18 Ty'rwaun Maesydderwen 6 GLANTWRCH 27 TCB 50 Coed

7 52 Works 30 9 50 12 23 2 3 34 67.1m CLARE ROAD / HEOL CLARE Path (um) 25 4

5 7 CROESFFYRDD

27 19 Govt

3 24

36 13

69.9m 4

37 18

Offices 18

118.7m 15 2

26 Delfan 20 Yr-Hen-Bont 25 48 Pond 29

Track 16 1 33 Hall (Residential Home) GLANTAWE 13 GLANNANT TERRACE

176.7m 24 HEOL GLANRHYD / GLANRHYD ROAD Hall 15 Ystradgynlais

17a 26 Clinic 44

Llechwedd 24 87.2m 9 46

42 10 56 11 4 GOUGH AVENUE 40

14 15 9

27 40

15a 15

28 18 Community 20 24 38

11 Liby 67 67.6m Tynedale SWAN LANE

Drain 11 16

Maesgwyn 9 16a 13 11 Newlyn 39 8 Hospital 26 7

Issues A 4067 PARK

22 12

Path (um) 26a ALLTYGRUG ROAD / HEOL ALLTYGRUG

7 36 9 Chapel 66

74.2m 18 Brynbach 1 SAINT DAVIDS ROAD Church Shelter Milborough 11 Club Chrisgar 63 25 Issues GLANTWRCH B4599

Track TWYN-YR-YSGOL 4 Court 26

57 10a SWANFIELD / MAES ALARCH

1 to 5 to 1 18

91.7m 76

Cattle Grid 4 68.6m 5 Dumfries Place

COMMERCIAL STREET 7 Cornerways 2 67.8m

Cartref 8

Shingle

2 20 LB

51 6

MILBOROUGH ROAD / HEOL MILBOROUGH 12a

55 43 10

RD 17 Coch

1 94 Shelter 3

30 3 53 4

PENTWYN 92

LB 81.9m GLANTAWE PK 1 1 38 39 14 24 94 49 88

33 43 45 47 B 4599 84

126.8m 4

3 80

37 1 to 8 82.7m 98

47 20

3 Level

El 2

41 13 4

37 2 3

100

12 13 34 Sub (disused)

Pipeline

5 1 79 31 Arnold Court60 Sta

51 106

4 72 Path

43 12 18

2 FB

27 PH

65 Glan-rhyd

CLAREHEOL ROAD CLARE / 48 67.5m 116 Glan-rhyd 4 Path

119.5m 8

4 1 ESS

El Ps 2 38 5 A 4067 53

GLAN-YR-YSGOL 1 87.1m 16

Y Wern 6 5 GLANNANT TERRACE

11 7 19 9 3

Community 6 SNOW TERRACE

Primary School 38 Ruin Nant-y-Mynydd The Elms

8 Centre

1 8

2 Cysgod 7 2 Bank

Track Lynsdale 1 Y YR AFON 16 Heap 31 Mynydd SAINT DAVID'S ROAD Glan-rhyd

170.1m 67.4m 16 (dis) 4 31 FFORDD Cottage Drain Ty Gwyn 1 7 Meml

The Poplars 1

Rhoscerdd Track Club 4 Path (um) Tank 19 Playing Field

1 66.2m 130.4m LB 89.1m 24 27 RHYDWEN 5

Brynderwyn Pol Ysgol Bro Tawe 6

7 24

Sta 8

SCHOOL ROAD 8 9

(Sch) 9 Ford 2 20 25

Y GILWERN COMMERCIAL STREET / STRYD MASNACHOL

12 114.1m 6 22

4 23

Shelter B 4599 167.6m WERNWOOD ROAD 28

2 20 Church

18 Cystanog 30

Track 15 12 Track Pavilion 1

Spreads Level 91.6m 6 65.9m

Path (um) 25 PENYWERN ROAD

17 14 64.8m

(disused) 12 2 5 5a Hall

Playing Fields 24

Pond 1 111.6m 3 1 Maes-y-wern

23 22

7 18 Pond

4 Wern House Histon Pond Penrhiwfarteg 9 Afon Tawe / River Tawe 100.9m Bungalow

Path (um) 5

11 10

7 1 96.7m 13 8 Swn y Nant 20 25 Pond Tank 6 Heulwen (PH) OLD WERN ROAD 9 Pant-y-gwanyd 32 81.2m 3 120.8m DARREN ROAD Glan-rhyd

29 Bridge 19 122.6m

Level Path Path (um) 20 ETL Derlwyn El Sub Sta 1 (um) 30 69.0m 13 Issues (disused) 118.0m Lay-by El Sub Sta 102.5m 42 94.6m FB Tank Wern

Pond CG 12 Pond 10 PW Oleu 31 Car Park Wern Villas 11 2 El Sub Sta PO LB Spring 11 DEELEY ROAD 1 Sewage Works Issues Drain 7 54 36 30 Ysgol Gymraeg Ystalyfera Path Issues 56 Dismantled Railway

Surgery 1 39

Path (um) 41 38 Issues 62

2 LOWER WERN ROAD

45 21 ETL 47 Sorting 8 Farteg-fach PH Office 63.4m Park House Track GOUGH ROAD / HEOL GOUGH Path (um) 74 TCB Carreg Pentwyn Farm 46

Shingle Track 53 13 Subway Ystalyfera Rugby Club 47 5 WERN ROAD / HEOL Y WERN PROSPECT PLACE 62.9m 15

172.7m 104.2m 86 36 FB

88 6 ESS 99.1m 7

53 Ynys-glan-Tawe

Hall 5a

Collects 69 94 5

Track

1 ZOAR ROAD3 / HEOL ZOAR Drain

59 FFORDD GLANDWR ETL

Track 41 100.2m 1 CANAL TERRACE Levels Stone Pond (disused) Path (um) 165.5m 1 100 Bowling Green 1 to 35 Waterfall 62 Maes-Y-Darren WEMBLEY ROAD Tennis Courts 102 Avonsbrie Parc-y-Darren Play Area GLAN YR AFON

65 106 2a

108 Pavilion 61.2m 1a Shelter Aber-twrch

161.2m 87

2 2

1 66 47 Afon Twrch

3 El Ps

2 Vicarage 120 12

10 118 13 97 Pant-y- ETL WOODMANS TERRACE 8 72 60.6m

gwanyd Row 1

9 Play Area 103

7 9 11 4

16 7 13 10

14 5

109 24 15 6 62.2m Issues 16 17

Level 14 Pond

4 1 El Ps (disused) 105.2m

Track 5

99 1a 6 17

Track Heap 6

97 El Sub Sta 108 Outfall Drain (dis) 27 Afon Tawe / River Tawe THE GARDENS MINYFFORDD 4 Path 5 Shelter 12 8 Golwg

20 18 Weir

Y 4 Shingle

7 60 Darren WADE AVENUE

60.9m YNYSYDARREN ROAD / HEOL YNYSYDARREN Shingle

139.4m 54 Issues 26

Meadow Vale

1 Penlan-Fâch 63 17 Path (um) PH Issues 10 11 87

Ystalyfera 98 Caeralem

15 14

Drain 29 31 FB 23

Issues Path 13 Track 20

VINE ROW 33 ETL

35 Track

36 64 Spreads

24 24

28 28

37 Play Area Ford

27 32 28 75 Track

33 58.7m Path (um)

17 37 68

26 Ford

25 GLAN YR AFON Spring Spring 84

41 38 Weir Spring 24 FFORDD EMLYN El Sub Sta

112.2m 40 Levels Ford Path Tir Garw 32 33 12 El Sub Sta (disused)

20 65 44 48 Spring Path (um)

Path 69 Pond 34 Heap (dis)

Spring Issues 49 Heap (dis) 7

Pond Track Spreads

49 Path (um) 1

Pond 51 Farteg-uchaf 53 Shelter

73 LB Track

50 41

44 El Sub Sta 39 36 37 Issues

70 Tank Shingle

Drain

65 Path (um) PO 56 TCB 27 VARTEG ROAD Ynyscu House

67 110.1m 13

Spring Pen-y-graig 48

15 1 42 42

43 Pond 130.4m 28

14 56.6m Track

14 Weirs Level Spreads

50 2

97 51 (disused) Level Oak Villas Shelters 59.9m (disused) 52 Shingle Spring 53 Path (um)

Green Croft 1 to 4 Track 4 to 1 54 Track Varteg 7 House Ty'r-graig 13 1 59 13 18 Track Heap (dis) Dan-y-Coed 12 MINYRAFON GRAIGYMERCHED 27 25 Track 28 26

2 Spring 81

1 Cwar Filling Station 24 59.7m Track Path (um) 132.2m 109.0m Pen-y-graig Sunnyville B 4599 59.8m (disused) Path (um) GLAN YR AFON

60.6m 86

87 88 8 57.02 Track 56.93

93 57.33 125.1m 57 57

57.25 57 57.73 57 57.36 57 TARMAC

Path (um) 57.00 57.31 57 57.61 57.31 56.82 57 56.88 57 57.10 CYFYNG ROAD Swansea Valley Business Park Rev Date

Path (um) Office 57 56.92 100 57.03 56.72 Ruin Row 56.90 57

102 56.95 56.86 57 56.88 Track 57

11 56.86 57.63 8

105 MH 57.02 CL 56.93 57 56.95 56.92 56.82 56.79

56.81 57.05

107 57 57 57 57.02 56.87 57 57 56.91 57.15

57.28 57.62 57

111 56.87 57.42

57 57

111a 57 56.84 Afon Tawe / River Tawe 57 102.3m GRASS

FB Pond 56.98 56.96 56.97 57 6 57.05 56.84 57.60 56.88 TARMAC

113 56.86 57.09

56.87 57 56.95 SV ETL 57 56.84 57 GRASS

115 56.86 56.92

57 116 56.85 56.87 CONCRETE 57 56.84 57.00 57.09

108.7m 56.75 57.00 57.28 56.81 57.20 PAD 57 57.03 56.90 57.54 TP 56.98 57.27

Graig Arw GLAN YR AFON 57 57.08 O/H Ridge Level Glan-yr-afon 56.81 64.38 57 Car Park 56.95 56.87 2 56.81 57.37 57 57.39 56.86 57 Eaves Level Level 57 57.03 57.02 56.88 62.13 (disused) 56.93 56.89 56.81 Twyneglur 59.0m 56.84

56.80 LB Shingle 57 56.85 57 57.44 MH 57.06 57.41 MH FB CL Cwar Pen-y- 100.6m CL 56.86

Path (um) 56.95 57.00 56.80 57 Graig-arw 57

1 57.01 56.89 O/H 126

57.07

57.55 (disused) 56.84

57 57

3 128 Ynisgeinon House

29 Drain 5 56.86 GRASS 57.25 28 57 56.83 57.04 Track

9 56.88 57.04 D2E 57 57.50

56.89 G 57 57 56.92 57 276515.090 57 N 11 23 56.90 208267.110 56.92 Z

Danygraig 22 56.8156.86 56.922 57 56.83 56.90 56.77

56.79

ETL TCB 56.81 57 Ynisgeinon Farm INDUSTRIAL 56.89 TARMAC 57.56 57.17 Shelter MH 56.77

Track CL CLEES LANE 18 BUILDING 56.82

Shelter 101.5m 4 56.88 56.75 57.13 19 56.83 3

Post 56.80 56.79 56.82 56.82 56.77

57 1

Craig 19 56.85 GALVANISED STEEL 57.36

21 Swansea Valley Business Park 57.56 Eaves Level 2 56.75 FENCE 56.75

20 Pond 62.70 Arw 56.76 56.76 56.82 Track 25 Office

Pantteg 28 30

56.85 56.87 56.80 57 57.29

56.90 Issues 56.78 56.79 56.79 56.88 Row 62.2m

MH 56.75 57 57.59

Heap CL 57 A 4067 57.23 (dis) 56.83 56.79 57.01 56.80 tulip Lower G 56.85 tulip Pantteg 57.44 99.8m 56.84 56.80 38 57.18

Pond 56.80 57.61 1 57.37 56.91 engineering consultancy Drain El Ps

57.02 56.88 56.94

Spring The Willows 56.89 56.89 G 56.79

57 20

57.50 Floor Level 57.54 57.47 57.52 57.02 Level 56.89 11 57.09 Pantteg Hall Capel (disused) 56.84 56.79 GALVANISED STEEL

Fountain Hall FENCE 57.59 Spreads Cwar 56.78 Club G 57.94 57.56 56.93 56.86 Pen-y-graig-arw 56.89 57.59 56.92 57.52

West 56.86 56.85 56.80 Ridge Level

56.92 56.91 CONCRETE 58 34 Culfor Road, Loughor, Swansea SA4 6TY

(disused) 64.86

Danygoeden MH 56.87 56.79 58 57.68 CL

57.59 Pantteg 8

Heap 56.86 57.73 57.70 58 58.00

Tarren y Gigfran (dis) 56.86 58

57.04 56.87 57 57.71

57.02 Floor Level 56.80 57.67 49 56.84 58.19 56.93 57.08 56.82 57.68 58.16

57 MH 57.71 58

94.9m 50 64.9m 56.81 CL 57.68 tel: 01792 893407 mob: 07843 491524 56.86 Track 56.89 57.03 57.81 57.76 56.98 57 56.85 56.96 58.01

Woodlands 56.88 RS 58.25

56.84 56.96 56.81 58 57.83 MH 57

57 CL

57.01 58.02 58.21

18 Issues 56.92 58

56.93 57 7 57.57 56.79 56.81 56.92 57 57.00 56.86 56.94 57.84 58.40 57.00 57 GALVANISED STEEL

FENCE LP 58.15

58 58.14

56 Sluice 57 58.16 e: [email protected]

SV 57.89 56.84 58 57.02 58.36

Briardale 56.76 56.74 58.39 5b Weir CONCRETE 56.98

65.6m 56.91 56.81 58.16

60 56.89

5a 56.91 56.75 56.99 58 58.45

G 56.80 56.91 56.94

57 58.36

56.82 El Ps 58 Issues 58

Ridge Level 58 w: www.tulipengineering.co.uk

64.39 56.97 63 56.91 58.16

Pantteg 56.90 56.91 56.86 58.04 STRYD NEWYDD / NEW STREET 56.75 57 Sinks 56.95 58.51 Sinks 2 57.03 57.35 58.33

MH 56.87 56.83 G

Shelter GLAN YR AFON 56.79 CL 58 1 56.86 57.02 56.78 56.89 56.90 58.31

Darren Fach 56.90 57 68.5m 56.77 BT 56.88 58.33 58.36

56.95 56.97 57.89 1 58.32

21 G 56.93 G 58

1 E D3 4 56.79 56.81

Path (um) 56.83 57.00 276552.026

57.00 74 N

15 LLYS GRAIG ARW G 56.95 57 208231.154 56.79 57 E 57 58.43 58.52 Z

276422.660 Floor Level Eaves Level 57 57.01 58.530 12 Mine N 56.90 MH A4067 56.78 57.06 56.95 CL 56.78 61.97

(disused) 208229.562 58 HEOL EGLWYS / CHURCH ROAD 66.5m D5 Z 56.98 58.35

47 56.785 56.89 MH 56.90 74.8m Track CL 57

57.06 58.41 8 Shelter 57 56.92 58.45 58.39 Drain 56.78 56.80 52.2m 56.91 6 RS

56.87 56.80 SV 58.52 51 56.87 56.93 56.78 MH 58.65

Issues El Ps CL 57

SUB-BASE 56.82 56.88 7 57.81

1 58.52 58

LB PANT Y8a FFYNNON TERRACE / TERAS PANT Y FFYNNON Ford 56.95

78.7m 56.83

57 57 56.77 Playing Field 58 58.39

8 56.93 MH CL 58.51 56.87 56.95 Waterfalls 58.02 56.91 56.91 82.6m 56.79 G 58.69 Sinks 56.76 56.91 G 58.52 Issues 56.86

56.80 56.93 58 58.52

Track Cemetery 58 56.88 56.76 56.83 SLB

56.78 58.44 57 57 Client: 56.86 58.65

58.35 56.94 57.01 Issues 58 56.79 MH El CL 56.79 MH 56.82 56.76 56.94 LP 56.77 CB3 CONSULT LTD Sub Sta CL

Sinks Track Pond 56.88 57.89

58 58.11 56.84 G 56.90 57 57.25 56.90 56.93 58.59

FENCE 57 56.81 58.55

Issues 58 RS RS

56.85 RE-LANDSCAPED G

57 56.79 56.88 58.42

58 AREA 58.78 13 56.79 Sinks 56.86 56.88

58.47 57 58.63

Hall 56.80

58 56.79 58.67 58 56.83 SLB TARMAC 56.88 56.81 56.80

Path G Sinks 58.09 57 Mynydd Allt-y-grug El Ps 56.82 56.91

Waterfall 56.80 56.80 57 56.84 58.46 58.62 Spring 52.7m 58.43 Issues 1e 86.0m 1f Pond 56.79 56.80 56.90 1g 56.83 56.78 57.46 1h G

FB 1a 58 58.05 58.86

1b 56.87 1c 57

Sinks The 1d 58.00 57 58.69

56.78 58.54 58.59 34

23 Bungalow Sinks

56.87 MH 24 GRAIG ROAD 56.78 CL

56.80

Levels 40 Recreation Ground 56.84 58.71 58.45 57 GALVANISED STEEL

(disused) Issues FENCE

41 58 Sheepfold 56.88 MH 57

Sinks 17 Shelters TCB 2 18 CL 56.87 (disused) 58.73 58.06 56.84 56.93 58.75

Play Area 56.77 10

58.91

SUB-BASE 58.87 58 HODGSON'S ROAD 57 FB 57.37 Path (um) A 4067 56.92 56.77 58.61 Project: G 56.91 56.78 G

12 58.41 58.06 56.81 58.04

15 58

Collects 57

5 57 E 58.80 SWANSEA VALLEY

OWEN'S LANE LB 7 N276467.129 58.54

82.9m PANTYFFYNNON 56.77 58.74 57 GPS1 Z208199.071 LP Chemical Row 58.80

Llygad y Ffynnon 56.819 56.78 58

57.89 58

SubEl Sta 56.92 22 Ford 57

17 56.80 58.78

58.99 Issues 58 56.89

56.79 A4067 58.34 57 57.51 41 Drain El Ps 30 G 39 58.97 Issues

ETL 57 58.65

58 56.78 58.02

Graig Arw Sinks 57.50 56.89

FBs 59

26 58.21 56.92 IND. EST. FCA 57

57 56.79 RS 29 58.84 58.86

57 57.40 59 Waterfall 59 58.49

Issues 58 59.01

24 58.73

8 51.2m 57.28 59

57.41

LLYS YNYSGEINON 29 57.84 59 7

27 48 Path (um) 58.97

46 57.76

39 23

44 57.78

PANTYFFYNNON 59 59 18

2 58

59 59 59.02

48 1

58.25 59 Drain 58 58.91

58.07 59.09 58.13

19 21 58.64 38 58.89 Lock FFORDD Y GLOWYR River Tawe 58.20 59

17 Drg Title:

/ Afon Tawe

59 RS (disused) 12 SV 59

58.65 G 59 GLAN YR AFON SV

51 58.44 58.80 59 FLOOD ZONE 20 Track 59 11 60

11 59 58.96 13

14 2 59.09

57 28 59.09

88.7m BT 58.91 59 58.77

14 Shelter 19 24

12 Issues 22

GALVANISED STEEL BT 59

10 5 FENCE 59

59.11 Drain 15 FFORDD DANYGRAIG Glan-yr-afon

16 3 58.88 59.00

Sinks Lock 16 1

Spring (disused) 59 59

14 59 PLAN 58.98 LLYS RHAEADR Ford 59 58.96 Issues Track 58.87 1 58.96 1 7

58.98 58.97

6 Spring

2 59 58.98

3 59.16 59

198

GOLWG Y MYNYDD 59 12 Waterfall 59.03

1 Car Park LLYS YR AFON 59 59.14 Drain

4 59

Levels 59 59 59.00

Shelter 59 4 3 FENCE 1

88.3m 11

205

12 E Collects 4 276500.415 20 CRIMEA COURT N

Quarries 59 59.04 2 59.08

17 Path (um) D4 208167.867 206 Z 58.95

(disused) A4067

Issues 20 8 59 20 59.171

16 58.99

59 14 59

25 26 207

1 Mine Mine 4 9 59.21 27 2 59.15

(disused) 22

1 5 59 Graig y 8

210 Darren MH CL

95 11 Sinks Issues 59.12 Date: Status: Scale:

GRAIG NEWYDD 5 1 Ford 59 212 3 Drain

213 59.00

97 7 216

1 Path (um) 59.16 19 59.02 10 GRAIG Y DARREN 87.2m Drain 28 12 2 59.24

2 1:10,000 33 214 20 8 18 Collects 16 Level Cilbrwyn 14 (disused) Drain 59.06 El 09.04.2020 PLANNING

22 59.0m

21 Sub

17 59.03

Drain to

Sta 31 219 11 Track 101 33

28 CARREG YR AFON 59.24

23 59.07

7 Drain to LLYS CAMBRIAN 102

59.07

GRAIG ROAD 39 13 Path (um)

21 Outfall Issues

88 41 Pen-y-graig G 59.06

12 Level

1 Ford 59.12

15 71 82 35 Sinks (disused)

Patagonia Farm 88.1m 59.15

104 Drain 74

19 64 43 Track Drain Size:

Drain 41 Ford 23 Level Ruin 52 Level (disused) (disused)

44 80 64 62 1 Shingle 14 72 2 LLYS HARRY

Path (um)

25 27 Drg No. Rev.

2 11

49 57

1 - A3

108 Lock J009/002

41 Ford Issues (disused) 55

ETL 12

Track GRAIG Y FFOREST Path (um) Map Title

Map Perygl Llifogydd / Flood Risk Map

Allwedd / Map Key High Surface Water Flood Risk - Extent Medium Surface Water Flood Risk - Extent Low Surface Water Flood Risk - Extent

Graddfa / Scale 1: 5,001

Dyddiad / Date 12/04/2020

D. Hydraulic Modelling Technical Note

TECHNICAL NOTE JBA Project Code 2019s0932 Contract Swansea Valley Modelling Client CB3 Consult Ltd Day, Date and Time 4th September 2019 Author Adam Sinclair Reviewer Amy Evans Subject Hydraulic modelling report

1 Introduction

1.1 Terms of reference JBA Consulting have been commissioned by P & C James to undertake hydraulic modelling of the Afon Twrch and Afon Tawe to support a proposed new development at Swansea Valley Business Park in Glanyafon, Ystalyfera in West Wales. The hydraulic modelling required the updating the existing modelling in the study area as well as updating the hydrological estimates applied to this model.

1.2 Study area The proposed development site is located on Glan Yr Avon road in Glanyafon. The Afon Tawe flows approximately 50m to the south-east of the proposed development from north to south. The Afon Twrch is located approximately 685m to the north-east of the proposed development. The Ordnance Survey (OS) National Grid Reference for the site is SN 76966 09006.

1.3 Proposed development and planning policy The proposed development is for industrial units on brownfield land. Industrial development is classified in Technical Advice Note (TAN) 15 as 'less vulnerable' development (Welsh Assembly Government, 2004). The proposed development site is currently within Natural Resources Wales (NRW)Development Advice Map (DAM) Zone C2, defined as areas at risk of flooding 'without significant flood defence infrastructure' (Welsh Assembly Government, 2004). The NRW Flood Map is informed by the results of the 2016 Ysgol Gyfun Ystalyfera Flood Consequence Assessment (FCA) 1D-2D model. This model was developed by JBA Consulting as part of an FCA for a school building at the Ysgol Gyfun Ystalyfera Primary School. The 2016 model is largely based on a 2013 Cwm Twrch 1D-2D Flood Hazard Modelling model, also developed by JBA Consulting on behalf of Natural Resources Wales (NRW). The main changes undertaken in 2016, were to include the latest LIDAR, update the representation of the footbridge between Glan Yr Avon and Glanwrch as well as to update the hydrological inflow for the Afon Twrch. NRW’s DAM showing of the proposed development location is shown in Figure 1-1.

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Afon Twrch

Afon Tawe

Figure 1-1: NRW’s DAM showing the proposed development site location (proposed development site in red)

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2 Flood risk assessment

2.1 Hydraulic model The 2016 Ysgol Gyfun Ystalyfera Flood Consequence Assessment 1D-2D model was updated to assess the flood risk at the Swansea Valley Business Park site.

2.2 Hydrology The hydrology calculated in 2016 is now outdated due to developments in hydrology methods, guidance and data availability. Therefore, new hydrological inflows were generated for both the Afon Tawe and Afon Twrch. The updated flows have been developed using the Flood Estimation Handbook (FEH) Statistical method as QMED was has been improved by using local donors. Full details of the method used to generate the peak flows can be found in the flood estimation report, in Appendix A. Peak flows derived for this study are provided in Table 2-1. Table 2-1: Estimated peak flows

Flood peak (m3/s) for the following AEP (%) events Site code 50 1 0.1 TWR_01 66 157 248.8 TAW_01 169 369 576.8 TAW_02 115 252 393.3

The updated hydrology was incorporated within the model as shown in Figure 2-1. Within the 2016 modelling, the intervening area hydrograph between Taw_01 and Taw_02 was applied as two point inflows. This method has been updated so that the inflow is spread equally across all model nodes on the Afon Tawe. This method has been selected as an inspection of aerial imagery, mapping and LIDAR data shows that there are a large number of small drains on the left bank of the Afon Tawe that drain into the channel throughout the reach represented in the model.

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Figure 2-1: Inflows applied to updated model

2.3 1D model updates The following updates have been made to the 2016 model to ensure that it is in line with current modelling best practice: • All bridge 'B' channel types have been changed to the newer 'BB' channel type, which automatically calculates losses. Form Loss Values for these structures have been updated to 0.001, unless piers are present at the structures. • All weir 'W' channel types have been changed to the newer 'WW' channel type. Each structure has been reviewed and an appropriate Cd value selected.

2.4 TUFLOW version The updated model was simulated with the new hydrology using TUFLOW version 2018-03-AE-iSP-w64.

2.5 Model Scenarios Simulations were completed for the 1% Annual Exceedance Probability (AEP) event with an allowance for climate change (plus 30% (Welsh Government, 2016) and 0.1% AEP event. The modelling files are shown in Table 2-2.

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Table 2-2 Hydraulic modelling files

Run TWRC_077_Q0100CC_8.5hr Reference TWRC_077_Q1000_8.5hr

Purpose of The purpose of this model scenario was to understand the Runs: baseline flood risk to the proposed development. ISIS/TUFLOW file File names: and Version: TWRC_077_~e1~_8.5hr.tcf TAWE_007.tbc TWRC_003_A.tbc TWRC_077.ecf Materials_NWPT.tmf

bc_dbase_CWMTWRCH_076.csv CWMTWRCH_076.trd TAWE_076.tgc TWRC_008.tgc Model Timesteps: 1D model timestep: 1s 2D model timestep: 2s

Run Time: Model run time: 20 hours Maximum simulation time: 1:01 hours

Return period(s): 1% AEP with an allowance for climate change (+30%). 0.1% AEP.

Run Multi-domain model. Settings: Defended model.

Comments on Negative depth warnings: 0 results: Maximum cumulative ME: 0.50%

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3 Modelling Results

3.1 Mapped Results

3.1.1 Updated 1% AEP plus Climate Change (30%) Results from the updated modelling show that the proposed development site does not flood during the 1% AEP plus climate change event. The maximum depths for this modelled event are shown in Figure 3-1.

Figure 3-1: 1% AEP plus climate change maximum flood depth

3.1.2 Baseline 0.1% AEP event Results from the updated modelling show that proposed development site does not flood during the 0.1% AEWP event. Out of bank flooding occurs on the right bank of the Afon Twrch at Ysgol Gyfun Ystalyfera, which flows south before ponding around Varteg Road, approximately 160m to the east of the proposed development. The maximum depths for this modelled event are shown in Figure 3-2.

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Out of bank flooding on the right bank of the Afon Twrch

Ponding at Varteg Road

Figure 3-2: Baseline 0.1% AEP event maximum flood depth

3.2 Model performance • The model ran stably for all events. The model simulation time was approximately 1 hour. • Peak mass error was 0.50% which occurred during the 0.1% AEP event. This is within the acceptable limit of +/-1%. • No negative depths occurred in either the 1D or 2D domain for any of the model simulations undertaken as part of this study. • A total of 36 check and warning messages were generated during the simulation. None of them are messages that didn't occur during the original modelling.

3.3 Modelling assumptions and limitations • No further updates have been made to the 2016 model, other than those detailed in Section 2. • The hydraulic modelling does not represent flooding from; surface water, groundwater or sewers.

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4 Conclusions and recommendations • JBA Consulting were commissioned by P & C James to undertake hydraulic modelling to inform an FCA for a proposed development site at Swansea Valley Business Park, Ystalyfera. • The Ysgol Gyfun Ystalyfera FCA model, developed in 2016 by JBA Consulting was updated as part of this study. The 1D structure model representation and inflow hydrology was updated to comply with the latest methods and guidance. • The updated model was simulated using the latest software version to generate flood risk mapping for the 1% AEP event with an allowance for climate change and the 0.1% AEP events. • Results from the updated modelling show that the proposed development floods in neither the 1% AEP plus climate change event nor the 0.1% AEP event.

5 Bibliography Welsh Assembly Government. (2004). Technical Advice Note 15: Development and Flood Risk. Welsh Government. (2016). Flood Consequence Assessments: Climate change allowances.

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Appendix A: FEH calculation record

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Flood estimation report: Afon Twrch & Afon Tawe, Swansea

Introduction

This report template is based on a supporting document to the Environment Agency’s flood estimation guidelines. It provides a record of the hydrological context, the method statement, the calculations and decisions made during flood estimation and the results. Contents

1 Method statement 3 2 Locations where flood estimates required 8 3 Statistical method 10 4 Revitalised flood hydrograph 2 (ReFH2) method 14 5 Discussion and summary of results 16 6 Annex 19

Approval

Name and qualifications Date Method statement prepared Kate Drewett BSc MSc 02/08/2019 by: Method statement reviewed Jenni Essex BSc MSc PhD CEnv 12/08/2019 by: MCIWEM C.WEM Calculations prepared by: Kate Drewett BSc MSc 02/08/2019

Calculations reviewed by: Jenni Essex BSc MSc PhD CEnv 12/08/2019 MCIWEM C.WEM

Revision History

Revision Date issued Amendments Issued to reference V1.0 14/08/2019 - CB3 Consult Ltd

AAA-JBAU-XX-00-RP-HO-0001-S0-P01-FEH_Calculation_Record 1

Abbreviations

AEP ...... Annual Exceedance Probability AM ...... Annual Maximum AREA ...... Catchment area (km2) BFI ...... Base Flow Index BFIHOST ...... Base Flow Index derived using the HOST soil classification CFMP ...... Catchment Flood Management Plan CPRE ...... Council for the Protection of Rural England FARL ...... FEH index of flood attenuation due to reservoirs and lakes FEH ...... Flood Estimation Handbook FSR ...... Flood Studies Report HOST ...... Hydrology of Soil Types NRA ...... Natural Resources Wales NRFA ...... National River Flow Archive OS ...... Ordnance Survey POT ...... Peaks Over a Threshold QMED ...... Median Annual Flood (with return period 2 years) ReFH...... Revitalised Flood Hydrograph method SAAR ...... Standard Average Annual Rainfall (mm) SPR ...... Standard percentage runoff SPRHOST ...... Standard percentage runoff derived using the HOST soil classification Tp(0) ...... Time to peak of the instantaneous unit hydrograph URBAN ...... Flood Studies Report index of fractional urban extent URBEXT1990 ...... FEH index of fractional urban extent URBEXT2000 ...... Revised index of urban extent, measured differently from URBEXT1990 WINFAP-FEH ...... Windows Frequency Analysis Package – used for FEH statistical method

AAA-JBAU-XX-00-RP-HO-0001-S0-P01-FEH_Calculation_Record 2

1 Method statement

1.1 Requirements for flood estimates

Overview The purpose of the study is to update an existing 1D-2D model of the Afon Tawe and Afon Twrch at Ystalyfera, South Wales, determine the flood risk for a development site at Swansea Valley Business Park (approximate NGR 276499, 208214). This requires a new hydrological assessment for the location of interest to ensure that the most appropriate flood flow estimates are used in the model, using the latest methods, data and software. Design peak flow estimates and hydrographs are required for the purposes of the hydraulic modelling and will be generated for a range of annual exceedance probability (AEP) events. However, for the purposes of this study, only the 1% and 0.1% AEP events are required to be modelled. The effects of climate change will be accounted for using the latest guidance1. An uplift of 30% will be made to the 1% AEP flow estimates, based on the location of the catchment within the Western Wales district. Project scope The study is being undertaken for a small development application; the project scope reflects this purpose. There is a limited amount of time available for the hydrological assessment, which constrains the complexity to a routine assessment: • Brief Internet search only for information on historical flooding. • No rating reviews or flood event analysis for local gauges. • No consideration of fluvial-fluvial joint probability of flooding from the Afon Tawe and Afon Twrch. • Previous hydrological analysis will be assessed to identify if this can be made use of within the current study.

1 Welsh Government (2016) CL-03-16 Guidance for Flood Consequence Assessments – Climate Change Allowances. Available at: https://gweddill.gov.wales/docs/desh/publications/160831guidance-for-flood-consequence-assessments-climate-change- allowances-en.pdf AAA-JBAU-XX-00-RP-HO-0001-S0-P01-FEH_Calculation_Record 3

1.2 The catchment

Afon Tawe

Afon Twrch

Figure 1-1 Catchment overview & location of flow estimation points

Figure 1-2 Site location

AAA-JBAU-XX-00-RP-HO-0001-S0-P01-FEH_Calculation_Record 4

Description The Afon Tawe rises in the Brecon Beacons near Moel Feity. It flows in a south- westerly direction to Swansea, where it discharges into the Bristol Channel. The topography is steep throughout the catchment. The main tributaries are the River Twrch which joins the Tawe at Ystalyfera, the Cwm Du at Ynsmeudwy, the Upper Clydach River at Pontardawe and Cwm Clydach joins the Tawe downstream at Clydach. The Afon Tawe has a catchment area of approximately 924m2 just upstream of the confluence with the Twrch. The Afon Twrch rises in the Black Mountains near Llyn y Fan Fach and flows in a southerly direction to the Afon Tawe at Ystalyfera. The main tributaries are the Nant Gyws and the Afon Llynfell. The Afon Twrch catchment is approximately 50km2 at the confluence with the Tawe.

Both catchments are essentially rural with most urbanisation concentrated in the lower catchment and along the watercourses. The main settlements within the Twrch catchment are Cwmllynfell, Cwm-twrch Uchaf, Cwm-twrch Isaf and Gurnos before the Twrch joins the Tawe at Ystalyfera. There are former opencast mine workings in the lower catchment and some forested areas. The British Geological Survey website2 1:50,000 scale mapping shows the catchment to be underlain by the following: • Upper catchment: o Upper and Lower Devonian Rocks (undifferentiated) – sandstone and conglomerate, interbedded o Dinantian Rocks (undifferentiated) – limestone with subordinate sandstone and argillaceous rocks, with some superficial deposits of till o Millstone Grit Group – mudstone, siltstone and sandstone, with some superficial deposits of till • Lower catchment: o Pennine and South Wales Lower and Middle Coal Measures Formations – mudstone, siltstone, sandstone, coal, ironstone and ferricrete, with some superficial deposits of till o South Wales Upper Coal Measures Formation – mudstone, siltstone, sandstone, coal, ironstone and ferricrete. Soils in the upper catchment are mostly described as slowly permeable, wet, very acid upland soils. Downstream of Ystradgynlais, soils are more mixed including some areas of freely draining acid loamy soils3. The catchment response to rainfall is likely to be rapid due to the steep topography and reasonably impermeable geology and soils. The historical mining operations may have changed the natural runoff response of the catchment. It is difficult to determine the exact consequences of this, certainly not without a detailed investigation of available data; this assessment is not within the scope of the study.

1.3 Source of flood peak data

Source NRFA peak flows dataset, Version 7, released October 2018. This contains data up to water year 2016-17.

2 http://mapapps.bgs.ac.uk/geologyofbritain/home.html 3 http://landis.org.uk/sooilscapes/index.cfm AAA-JBAU-XX-00-RP-HO-0001-S0-P01-FEH_Calculation_Record 5

1.4 Gauging stations (flow or level)

Water- Station NRFA Catchment Type Start of record and course name number area (km²) (rated / end if station closed ultrasonic / level…) Twrch Gurnos Unknown 49.9 Level N/A

1.5 Other data available and how it has been obtained Type of data Data Data Source of Details relevant available data to this ? study? Check flow gaugings No N/A N/A N/A

Historic flood data Yes Yes Various An internet search found reports of landslips and surface water flooding in 2012 and 2016. A flood investigation report4 revealed surface water and river flooding on 3rd September 2016 caused internal flooding to a number of properties on Gough Road in Ystalyfera. Flow or river level data No N/A N/A N/A for events Rainfall data for No N/A N/A N/A events Potential evaporation No N/A N/A N/A data Results from previous Yes Yes JBA JBA Consulting. April 2013. studies Consulting Cwm Twrch 1D-2D Flood Hazard Modelling. JBA Consulting. November 2016. Ysgol Gyfun Ystalyfera FCA. Other data or No N/A N/A N/A information

1.6 Hydrological understanding of catchment Conceptual model The main site of interest is the proposed development site on the right bank of the River Tawe, downstream of the confluence of the Twrch and Tawe. Peak flows in the Afon Twrch and Tawe exceeding the channel capacity is the most likely cause of flooding to the site. There is a road bridge and footbridge across the Afon Tawe adjacent to the site; these do not

4 Neath Port Talbot Council, 2017. Investigation Report into Flooding Incident of 3rd September 2016 Gough Road, Ystalyfera. AAA-JBAU-XX-00-RP-HO-0001-S0-P01-FEH_Calculation_Record 6

appear to be a significant constriction to flow. Unusual catchment There are former opencast mine workings within the catchments. It is features not known how these will affect runoff response from the catchment and they have not been specifically considered within this assessment (not within scope).

1.7 Initial choice of approach Is FEH appropriate? Yes Initial choice of method(s) Both FEH Statistical and ReFH2 methods are suitable for flood and reasons flow estimation for the Afon Twrch and Tawe catchments. The How will hydrograph shapes catchments are not large, permeable or urbanised. be derived if needed? The FEH Statistical and ReFH2 methods will both be applied, Will the catchment be split and the results compared as there no clear reason to prefer into sub-catchments? If so, one method over the other at this stage. how? Hydrograph shapes will be derived using the ReFH2 model. If the FEH Statistical method generates the preferred design peak flow estimates, the ReFH2 hydrographs will be fitted to the Statistical peaks. Intervening area catchment descriptors will be derived for the area between lumped catchment flow estimation points. Lateral inflows will be applied to the model across this reach, if required. Software to be used (with FEH Web Service5/ WINFAP v3.0.0036 / ReFH2.2 version numbers)

5 CEH 2015. The Flood Estimation Handbook (FEH) Online Service, Centre for Ecology & Hydrology, Wallingford, Oxon, UK. 6 WINFAP-FEH v3 © Wallingford HydroSolutions Limited and NERC (CEH) 2009. AAA-JBAU-XX-00-RP-HO-0001-S0-P01-FEH_Calculation_Record 7

2 Locations where flood estimates required

The table below lists the locations of subject sites. The site codes listed below are used in all subsequent tables to save space.

2.1 Summary of subject sites Site Type of Watercourse Name or Easting Northing AREA Revised code estimate description on FEH AREA if L: lumped of site CD- altered catchment ROM S: Sub- (km2) catchment TWR_01 L Afon Twrch Afon Twrch 277100 208450 50.7 - catchment at confluence with Afon Tawe TAW_01 L Afon Tawe Afon Tawe at 275450 206550 150.6 - Godre’r- graig (downstream model extent) TAW_02 L Afon Tawe Afon Tawe 278350 209000 91.8 - upstream of Glan-rhyd Bridge (upstream model extent) TAW_01 S Afon Tawe Intervening - - - 8.1 _IA area between TAW_02, TWR_01 and TAW_01 Note: Lumped catchments (L) are complete catchments draining to points at which design flows are required. Sub-catchments (S) are catchments or intervening areas that are being used as inputs to a semi-distributed model of the river system. There is no need to report any design flows for sub-catchments, as they are not relevant: the relevant result is the hydrograph that the sub-catchment is expected to contribute to a design flood event at a point further downstream in the river system. This will be recorded within the hydraulic model output files. However, catchment descriptors and ReFH model parameters should be recorded for sub-catchments so that the results can be reproduced. The schematic diagram illustrates the distinction between lumped and sub-catchment estimates.

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2.2 Important catchment descriptors at each subject site (incorporating any changes made)

Red text indicates changes made to FEH catchment descriptors. URBEXT2000 has been updated to the current year (2019).

Site DPLBAR DPSBAR SAAR URBEXT FARL PROPWET BFIHOST FPEXT code (km) (m/km) (mm) 20007 TWR_01 0.995 0.62 0.377 10.14 124.1 1987 0.016 0.035 TAW_01 0.994 0.62 0.373 14.84 141.6 2024 0.018 0.042 TAW_02 0.993 0.62 0.358 12.59 146.8 2071 0.014 0.039 TAW_01 - 0.62 0.518 3.15 192.1 1724 0.076 - _IA

2.3 Checking catchment descriptors Record how catchment The catchment boundaries exported from the FEH Web Service were boundary was checked compared to Ordnance Survey (OS) contour mapping8, spot and describe any heights9 and 2m LiDAR data. The catchment boundaries from the changes FEH Web Service appear reasonable and correlate with the mapping for the upstream catchment to the study site. Some minor discrepancies were found between the FEH catchment boundaries and the contours, spot heights and watercourse lines. One noted difference was with the TWR_01 catchment boundary in the south-western corner. It was decided to retain the FEH catchment area which is the larger value and will therefore be more conservative, as done in the 2016 study. Record how other A qualitative check of the FEH Web Service BFIHOST values was catchment descriptors undertaken by comparing it to the geology and soils detailed in were checked and Section Error! Reference source not found.. The BFIHOST value describe any changes. is consistent with the geology and soils shown to underlie the catchments. The FARL values for all flow estimation points are supported by OS mapping which shows only small online ponds on the rivers.

A qualitative check of the URBEXT2000 values were made by comparing the FEH Web service values to current OS mapping. The value is as would be expected for an essentially rural catchment with a small amount of urbanisation in the lower extent. No changes were made except to update URBEXT2000 to the current year (2019).

Source of URBEXT URBEXT2000 Method for updating of CPRE formula from 2006 CEH report on URBEXT2000 URBEXT

7 URBEXT 2000 updated to 2019 8 OS Open Data. Terrain50_Contours 9 OS Open Data. Terrain50_SpotHeights AAA-JBAU-XX-00-RP-HO-0001-S0-P01-FEH_Calculation_Record 9

3 Statistical method

3.1 Overview of estimation of QMED at each subject site Data transfer NRFA Distance Moderated If more Initial numbers between QMED than one QMED Urban for centroids adjustment donor Final adjust- rural donor dij (km) factor, Site QMED (m3/s) sites (A/B)a ment code estimate factor (from used (m3/s) catchment (see (UAF)

descriptors) Final method 3.3)

Weight

adjustment Weighted ave.Weighted TWR_01 58 DT 58008 9.54 1.07 0.5 1.12 1.116 65.7 59001 3.45 1.18 0.5 TAW_01 150 DT 58008 8.76 1.08 0.5 1.11 1.108 168.9 59001 4.61 1.16 0.5 TAW_02 104 DT 58008 9.72 1.07 0.5 1.10 1.098 115.2 59001 6.85 1.14 0.5 Are the values of QMED spatially consistent? Yes, TAW_01 is the most downstream and has the greatest QMED. The sum of the upstream flows is greater than the downstream flow, which is as would be expected. Method used for urban adjustment for subject and WINFAP v410 donor sites Parameters used for WINFAP v4 urban adjustment if applicable Impervious fraction for Percentage runoff for Method for calculating fractional urban built-up areas, IF impervious surfaces, cover, URBAN PRimp 0.3 70% From updated URBEXT2000 Notes Methods: AM – Annual maxima; POT – Peaks over threshold; DT – Data transfer (with urban adjustment); CD – Catchment descriptors alone (with urban adjustment); BCW – Catchment descriptors and bankfull channel width (add details); LF – Low flow statistics (add details). The QMED adjustment factor A/B for each donor site is given in Table 3.2. This is moderated using the power term, a, which is a function of the distance between the centroids of the subject catchment and the donor catchment. The final a estimate of QMED is: (A/B) x QMEDinitial x UAF Important note on urban adjustment The method used to adjust QMED for urbanisation published in Kjeldsen (2010)11 in which PRUAF is calculated from BFIHOST is not correctly applied in WINFAP-FEH v3.0.003. Significant differences occur only on urban catchments that are highly permeable.

10 Wallingford HydroSolutions (2016). WINFAP 4 Urban adjustment procedures. 11 Kjeldsen, T. R. (2010). Modelling the impact of urbanization on flood frequency relationships in the UK. Hydrol. Res. 41. 391-405.

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3.2 Search for donor sites for QMED (if applicable) Comment Hydrology estimations were carried out in 2016 by JBA for the Afon Twrch. The on potential two donor sites used in the 2016 study have been retained for the current study. donor sites Potential donor sites were investigated using the function within WINFAP coupled with the National River Flow Archive (NRFA) website to search for nearby gauges. Their catchment descriptor derived QMED value was compared with their observed QMED value to determine the magnitude of the adjustment factor. Six stations were considered in detail as donors for the TAW_01 and TAW_02 catchments: • 58002 – Neath at Resolven • 58006 – Mellte at Pontneddfechan • 58008 – Dulais at Cilfrew • 59001 – Tawe at Ynystanglws • 59002 – Loughor at Tir-y-dail • 60009 – Sawdde at Felin-y-cwm 60009 and 59002 were rejected as the SAAR value was significantly lower than the study catchments and they had the highest QMED adjustment factors. 59001 is on the Afon Tawe but located several kilometres downstream of the study site; catchment centroids for the study catchments are the closest to this gauge. It also has similar FARL (0.996) and BFIHOST (0.407) values, however the SAAR value (1890mm) is lower than the study catchments. 58008 has similar FARL (0.999), BFIHOST (0.377) and URBEXT (0.0181) values, but also has a lower SAAR value (1806mm) than the study catchments. 58002 and 58006 have the most similar SAAR values to the study catchments, however they have lower FARL values (0.983 and 0.975 respectively), indicating a greater attenuation to lakes and reservoirs. 58008 and 58006 have the lowest QMED adjustment factors. 58008 and 59001 are the two closest gauges to TAW_01. 58002 and 59001 are the two closest gauges to TAW_02. It was decided than an equal weighting of 59001 and 58008 was most appropriate for both TAW_01 and TAW_02 catchments to adjust QMED. This is consistent with the approach used for TWR_01.

3.3 Donor sites chosen and QMED adjustment factors NRFA Reasons for choosing Method Adjust- QMED QMED Adjust no. (AM or ment for from from -ment POT) climatic flow catchment ratio variation data descriptor (A/B) ? (A) s (B) 58008 See Section 3.2 AM No 56.5 46.9 1.20 59001 See Section 3.2 AM No 253 185 1.37

3.4 Derivation of pooling groups In order to avoid discontinuities in flow estimates along watercourses it is useful to use as few pooling groups as possible and to identify if one pooling group can be used to represent several flow estimation points. Default pooling groups were generated for the three locations

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and compared. All three pooling groups had quite different station composition and it was decided to use a separate pooling group for each location in this case. Name Site code Subject Changes made to default pooling Weighted of from site group, with reasons average L- group whose treated as moments descriptor gauged? s group was derived TWR_01 TWR_01 No No changes made L-CV = 0.187 L-Skew = 0.196 TAW_01 TAW_01 No No changes made L-CV = 0.169 L-Skew = 0.174 TAW_02 TAW_02 No No changes made L-CV = 0.172 L-Skew = 0.168 Note: Pooling groups were derived using the procedures from Science Report SC050050 (2008).

3.5 Derivation of flood growth curves at subject sites Site Metho If P, ESS Distribution Note any Parameters of Growth code d or J, used and urban distribution factor for name of reason for adjustment 100-year pooling choice or return group permeable period (Error! adjustment Reference source not found.) TWR_ P TWR_01 GL – Location: 1.000 2.38 01 distribution that v3 urban Scale: 0.184 provides best adjustment Shape: -0.199 fit. applied TAW_ P TAW_01 GL – Permeable Location: 1.000 2.18 01 distribution that adjustment Scale: 0.167 provides best not applied Shape: -0.177 fit. as most sites in the TAW_ P TAW_02 GL – Location: 1.000 2.19 pooling 02 distribution that Scale: 0.171 group have provides best SPRHOST Shape: -0.170 fit. >20% Notes Methods: SS – Single site; P – Pooled; ESS – Enhanced single site; J – Joint analysis A pooling group (or ESS analysis) derived at one gauge can be applied to estimate growth curves at a number of ungauged sites. Each site may have a different urban adjustment, and therefore different growth curve parameters. Urban adjustments are all carried out using the method of Kjeldsen (2010). Growth curves were derived using the procedures from Science Report SC050050 (2008).

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3.6 Flood estimates from the statistical method Site Flood peak (m3/s) for the following AEP (%) events code 50 20 10 5 3.33 2 1.33 1 0.5 0.2 0.1 TWR_01 66 85 99 114 124 137 148 157 179 214 245 TAW_01 169 213 245 278 299 327 351 369 416 488 550 TAW_02 115 146 168 190 205 224 240 252 284 332 374

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4 Revitalised flood hydrograph 2 (ReFH2) method

4.1 Catchment sub-divisions for ReFH2 model Site code Area (km2) Rural or un- Paved Only relevant if significant transfers of water developed via sewers crossing catchment boundaries… Paved with Paved outside sewers draining topographic out of catchment with topographic sewers draining into catchment catchment TWR_01 49.44 1.27 N/A N/A TAW_01 146.38 4.25 N/A N/A TAW_02 89.79 2.01 N/A N/A Sources of Sewer capacity information (return period / rainfall N/A intensity / flow rate) N/A for creating and source of sub-divisions information

4.2 Parameters for ReFH2 model

Site Method Tprural Tpurban Cmax PRimp BL BR code (hours) (hours) (mm) % runoff for (hours) impermeable surfaces TWR_01 CD 2.70 1.35 261.46 70 35.45 1.12 TAW_01 CD 3.21 1.61 258.75 70 38.28 1.11 TAW_02 CD 2.89 1.45 248.87 70 36.02 1.06 Brief description of any flood event analysis carried out N/A Methods: OPT: Optimisation, BR: Baseflow recession fitting, CD: Catchment descriptors, DT: Data transfer (give details)

4.3 Design events for ReFH2 method Site Season Storm Storm Source of design rainfall statistics code of duration area for (FEH99 or FEH13) design (hours) ARF event (if not catchment area) TWR_01 Winter 8.5 - FEH13 TAW_01 Winter 9.5 - FEH13 TAW_02 Winter 8.5 - FEH13 Are the storm durations likely to Yes, all inflow hydrographs will use a 9.5 hour storm be changed in the next stage of duration and an areal reduction factor based on the the study, e.g. by optimisation TAW_01 location. This is the flow estimation point closest within a hydraulic model? to the site of interest (development site).

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4.4 Flood estimates from the ReFH2 method Site Flood peak (m3/s) for the following AEP (%) events code 50 20 10 5 3.33 2 1.33 1 0.5 0.2 0.1 TWR_01 58 74 85 96 103 112 120 125 142 170 199 TAW_01 160 204 235 265 284 309 330 346 389 465 541 TAW_02 111 143 165 187 201 219 234 245 276 329 382

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5 Discussion and summary of results

5.1 Comparison of results from different methods This table compares peak flows from various methods with those from the FEH Statistical method at example sites for two key return periods. Blank cells indicate that results for a particular site were not calculated using that method. Ratio of peak flow to FEH Statistical peak Site 50% AEP 1% AEP code ReFH2/FEH ReFH2/FEH TWR_01 0.89 0.80 TAW_01 0.95 0.94 TAW_02 0.97 0.97

5.2 Final choice of method Choice of method and The comparison of 50% and 1% AEP flows in Section 5.1 shows that reasons the ReFH2 peak flow estimates are lower than the FEH Statistical flows. The difference is larger for the Afon Twrch, with the 1% AEP event estimate from ReFH2 method being 20% lower than that from the FEH Statistical method. For the Afon Tawe the difference is only 3%-6%. FEH Statistical is the preferred method for generating the design peak flow estimates for the study catchment as QMED has been improved using local donors. ReFH2 is based on catchment descriptors only. It is recommended that the FEH Statistical method peak flow estimates are taken forward but with the ratio from ReFH2 applied to events above 1% AEP, as recommended in NRW guidance12. How will the flows be TWR_01 will be input as a point inflow to the top of the Afon Twrch applied to a hydraulic watercourse model extent in the hydraulic model. TAW_02 will be model? input as a point inflow to the top of the Afon Tawe watercourse model extent in the hydraulic model. TAW_01A will be distributed along the Afon Tawe, between TAW_02 and TAW_01. Modelled flows will be checked against the target flows at TAW_01 and adjustments made to the intervening area hydrographs, if required.

5.3 Assumptions, limitations and uncertainty List the main The main assumptions are: assumptions made • The FEH Web Service catchment boundary definition is (specific to this reasonable, although there are some inaccuracies when study) compared to contour data and watercourse lines. • Stations 58008 and 59001 are the most representative local donors with similar catchment descriptors and characteristics to the three study catchments and hence a similar flood response. • The pooling groups used to define the growth curve for the FEH Statistical method is representative of the catchments. • The ReFH2 model generates a representative hydrograph shape for the watercourses.

12 Natural Resources Wales. December 2017. GN008. Flood estimation: technical guidance. AAA-JBAU-XX-00-RP-HO-0001-S0-P01-FEH_Calculation_Record 16

Discuss any particular The main limitations are: limitations • There is no reported flood history for the development site against which the design peak flow estimates can be verified. • There is no flow gauge on the Afon Twrch which can be used as a donor. Give what A UK average measure of uncertainty for the FEH Statistical method information you can is presented in a technical report13 generated by a R&D project into on uncertainty in the FEH, local data and uncertainty (Environment Agency funded results, consortium of JBA, CEH and others). The 95% confidence limits for a 1% AEP flood estimate for a rural catchment (URBEXT2000 < 0.03) are 0.47-2.12 times the best estimate with a donor adjustment of QMED (one donor). Note: Confidence limits are provided for no donor, one donor and six donors; values are not provided for two donors. It is not possible to directly quantify the uncertainty for the ReFH2 method. Comment on the The design peak flow estimates and hydrographs were derived for the suitability of the purposes of this modelling study. If peak flow estimates and results for future hydrographs are required for a different purpose it is recommended studies, that, at minimum, a review of the results is carried out.

5.4 Checks Are the results Yes, flow estimates increase downstream. The sum of flows at consistent, for TWR_01 and TAW_02 are larger than the flow at TAW_01, as would example at be expected (peak flows from the Twrch and Tawe are unlikely to confluences? coincide). What do the results There are no gauges within the study area to compare flow estimates imply regarding the to. return periods of floods during the period of record? What is the range of The 1% AEP growth factor for the methods is: 100-year growth • FEH Statistical: 2.18 - 2.38 factors? Is this • ReFH2: 2.15 - 2.20 realistic? The typical range is 2.1-4.0 therefore both methods are at the lower extent of, but within, the range. This is consistent with the 2016 study. If 1000-year flows The 0.1% / 1% AEP event ratio for the methods is: have been derived, • FEH Statistical: 1.48 - 1.57 what is the range of • ReFH2: 1.56 – 1.59 ratios for 1000-year

flow over 100-year flow? How do the results JBA Consulting undertook flood modelling studies in 2013 and 2016, compare with those one of the flow estimation points is at the same location as used for of other studies? this study (TWR_01) – the Afon Twrch just upstream of the confluence Explain any with the Afon Tawe. The flow estimates for all three studies can differences and therefore be directly compared. The estimates for the 50%, 1% and conclude which 0.1% AEP events are provided in the table below. results should be Study Flow (m3/s) for the following AEP (%) events preferred.

13 Environment Agency, 2017. Using local data to reduce uncertainty in flood frequency estimation. AAA-JBAU-XX-00-RP-HO-0001-S0-P01-FEH_Calculation_Record 17

50 1 0.1 2013 66 152 297 2016 68 146 231 2019 68 157 249

There is limited information regarding the approach undertaken for the 2013 study. However, the main difference for the 2013 study to the 2016 and current study is that QMED was adjusted using the Gurnos gauging station and the adjustment was applied directly without the distance weighting. The Gurnos gauge was not used for this study or in 2016 as it has been level-only since 2003. Also a storm duration of 6.5hr was used for the 2013 study. The 2019 50% AEP event flow estimate is ~2% lower than the 2016 study. The 2019 1% and 0.1% AEP event flow estimates are ~7% larger than the 2016 study. The 2016 study FEH Statistical flow estimates are based on QMED adjusted using the same donors as this study (58008 and 59001). A storm duration of 8.5hr was also used in the 2016 study to generate ReFH2 peak flow estimates. However, a slightly different pooling group was used in the 2019 study compared to the 2016 study which may explain some differences in flow estimates. The latest peak flow data (NRFA v7) has been used in the pooling group analysis for this 2019 study. This contains an additional two years of data (for gauging stations in England, Wales & Northern Ireland) compared to the dataset used in the 2016 study. Therefore the 2019 results should be preferred as these use the latest methods, data and guidance. Are the results There is no information on reported flooding of the study site to make compatible with the this assessment. longer-term flood history? Describe any other Following the initial model run, the flows will be sense-checked to checks on the results ensure that the flow inputs result in realistic outputs. Modelled flows at TAW_01 will be checked against target flows for this location and adjustments made to the intervening area hydrographs, if required.

5.5 Final results These estimates have been generated using the FEH Statistical method with QMED adjusted using an equal weighting of Stations 59001 and 58008 for TWR_01, TAW_01 & TAW_02. The ReFH2 ratio has been applied to events above the 1% AEP event. Site Flood peak (m3/s) for the following AEP (%) events code 50 20 10 5 3.33 2 1.33 1 0.5 0.2 0.1 TWR_01 66 85 99 114 124 137 148 157 177 212 249 TAW_01 169 213 245 278 299 327 351 369 415 495 577 TAW_02 115 146 168 190 205 224 240 252 284 338 393

If flood hydrographs are needed for the next stage of Hydrographs.xlsx the study, where are they provided?

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6 Annex TWR_01 Pooling Group Years QMED L- Station Distance of data AM L-CV SKEW Discordancy 46007 (West Dart @ Dunnabridge) 0.188 36 70.1 0.177 0.162 0.073 58006 (Mellte @ Pontneddfechan) 0.38 46 86.9 0.170 0.097 1.755 47014 (Walkham @ Horrabridge) 0.411 44 39.6 0.221 0.235 0.679 21030 (Megget Water @ Henderland) 0.464 13 77.7 0.216 0.074 2.352 84020 (Glazert Water @ Milton of Campsie) 0.507 37 54.2 0.132 0.075 1.497 21017 (Ettrick Water @ Brockhoperig) 0.524 41 60.4 0.203 0.276 0.278 55004 (Irfon @ Abernant) 0.534 45 56.5 0.159 0.255 1.560 73009 (Sprint @ Sprint Mill) 0.607 48 42.1 0.180 0.199 0.044 73017 (Kent @ Bowston) 0.624 18 63.2 0.226 0.403 1.206 73011 (Mint @ Mint Bridge) 0.625 48 54.8 0.215 0.303 0.394 76014 (Eden @ Kirkby Stephen) 0.673 46 86.8 0.170 -0.026 1.488 48001 (Fowey @ Trekeivesteps) 0.693 48 17.5 0.22 0.276 0.409 74001 (Duddon @ Duddon Hall) 0.783 50 120.913 0.152 0.244 1.265

Total 520 Weighted means 0.187 0.196

TAW_01 Pooling Group Years of QMED L- Station Distance data AM L-CV SKEW Discordancy 58002 (Neath @ Resolven) 0.345 39 220.0 0.149 0.233 0.733 79004 (Scar Water @ Capenoch) 0.441 43 132.9 0.087 0.070 1.998 72015 (Lune @ Lunes Bridge) 0.447 38 202.1 0.145 0.150 0.519 55026 (Wye @ Ddol Farm) 0.448 48 115.2 0.174 0.125 0.592 73012 (Kent @ Victoria Bridge) 0.505 39 141.8 0.209 0.286 0.760 56006 (Usk @ Trallong) 0.506 44 163.6 0.193 0.148 1.204 60006 (Gwili @ Glangwili) 0.507 49 78.5 0.159 0.167 0.300 75009 (Greta @ Low Briery) 0.544 45 110.9 0.234 0.273 0.985 4005 (Meig @ Glenmeanie) 0.569 21 111.3 0.179 0.244 1.093 16003 (Ruchill Water @ Cultybraggan) 0.581 45 148.1 0.145 0.058 1.157 59001 (Tawe @ Ynystanglws) 0.598 43 253.1 0.123 0.248 1.554 81003 (Luce @ Airyhemming) 0.630 40 164.2 0.166 0.091 0.551 76004 (Lowther @ Eamont Bridge) 0.638 55 110.385 0.244 0.19 1.554

Total 549 Weighted means 0.169 0.174

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TAW_02 Pooling Group Years of QMED L- Station Distance data AM L-CV SKEW Discordancy 74001 (Duddon @ Duddon Hall) 0.223 50 120.9 0.152 0.244 1.063 16003 (Ruchill Water @ Cultybraggan) 0.232 45 148.1 0.145 0.058 0.461 58012 (Afan @ Marcroft Weir) 0.254 37 94.9 0.159 0.093 1.264 55004 (Irfon @ Abernant) 0.41 45 56.5 0.159 0.255 0.900 47024 (Tavy @ Tavistock Abbey Bridge) 0.43 23 81.8 0.206 0.139 1.390 58006 (Mellte @ Pontneddfechan) 0.508 46 86.9 0.170 0.097 1.366 96004 (Strathmore @ Allnabad) 0.514 19 198.5 0.183 0.234 0.474 73017 (Kent @ Bowston) 0.54 18 63.2 0.226 0.403 1.943 46008 (Avon @ Loddiswell) 0.585 37 63.1 0.171 0.069 1.708 4005 (Meig @ Glenmeanie) 0.636 21 111.3 0.179 0.244 0.202 60006 (Gwili @ Glangwili) 0.708 49 78.5 0.159 0.167 0.148 47020 (Inny @ Bealsmill) 0.727 33 35.0 0.198 0.135 0.998 73011 (Mint @ Mint Bridge) 0.728 48 54.835 0.215 0.303 0.734 78004 (Kinnel Water @ Redhall) 0.747 40 78.224 0.118 0.011 1.35

Total 511 Weighted means 0.172 0.168

AAA-JBAU-XX-00-RP-HO-0001-S0-P01-FEH_Calculation_Record 20

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