LAND OFF MILKING LANE DARWEN
HYDRAULIC ASSESSMENT OF PROPOSED FLOOD
MITIGATION
For Barnfield Blackburn Ltd Kenyon Lomeshawe Industrial Estate Nelson Lancashire BB9 5SP JUNE 2020 Milking Lane, Darwen Hydraulic Assessment
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MILKING LANE, DARWEN
HYDRAULIC ASSESSMENT
Document Tracking Sheet
Document Reference: HYD397_MILKING.LANE_HYDRAULICASSESSMENT Revision: 3.0 Date of Issue: 25th June 2020 Report Status: FINAL
Prepared by: ______Dominic Kearney BEng (Hons), MSc, PhD Principal Hydraulic Analyst
Checked by: ______Richard Nicholas BEng (Hons) MBA GMICE MCIWEM Director
Authorised by: ______Rob Ankers BEng (Hons) MBA GMICE MCIWEM Director
Revision History: Rev.: Date: Status: Prepared by: Checked by: Issued by: 2.0 12.02.2020 ISSUE 2 DK DK DK 1.0 18.09.2019 ISSUE 1 DK DK DK 0.0 29.07.2019 DRAFT DK DK DK
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CONTENTS Document Tracking Sheet ...... iii CONTENTS ...... v Figures & Tables ...... vi Specialist Software ...... vii Abbreviations & Acronyms ...... vii
1.0 INTRODUCTION ...... 8 1.1 Commission ...... 8 1.2 Outline of Assessment ...... 8
2.0 DEVELOPMENT SITE ...... 9 2.1 Location ...... 9
3.0 HYDROLOGY ...... 10 3.1 Introduction ...... 10 3.2 Catchment Descriptors ...... 10 3.3 Flow Estimation ...... 11 3.4 Confidence Limit ...... 11
4.0 HYDRAULIC MODELLING ...... 13 4.1 Existing Scenario Model Details ...... 13 General ...... 13 Model Boundaries ...... 13 Structures ...... 15 4.2 Model Flows ...... 16 4.3 Assumptions ...... 17 4.4 Calibration ...... 17 4.5 Model Simulations ...... 18 Model Run Parameters ...... 18 Simulations ...... 18 4.6 Model Results ...... 18 Flood Zone Extents ...... 18 1% AEP event (1 in 100 year Return Period) ...... 18 0.1% AEP event (1 in 1000 year Return Period) ...... 19 Climate Change ...... 20 4.7 Model Stability ...... 20 4.6 Results Discussion ...... 22
5.0 PROPOSED SCENARIO MODEL ...... 23 5.1 Proposed Solution ...... 23 5.2 Proposed Scenario Model Runs ...... 25 Simulations ...... 25
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Flood Extent, Depth and Level ...... 25 Flow to River Darwen ...... 26 Blockage Analysis ...... 29 Sensitivity Analysis ...... 29
6.0 CONCLUSIONS ...... 34 6.1 Hydrology ...... 34 6.2 Model Sensitivity ...... 34 6.3 Flood Zones ...... 34 6.4 Climate Change and Blockage ...... 34 6.5 Proposed Flood Mitigation...... 34
BIBLIOGRAPHY & REFERENCES ...... 36 Web-based References ...... 36
APPENDIX A: LOCATION PLAN ...... APPENDIX B: SITE VISIT PHOTOGRAPHS ...... APPENDIX C: HYDROGOLICAL ANALYSIS ...... APPENDIX D: CATCHMENT AREAS PLAN ...... APPENDIX E: SURVEYED CROSS SECTIONS...... APPENDIX F: MODEL SCHEMATIC ...... APPENDIX G: FLOOD ZONE PLAN ...... APPENDIX H: PREDICTED FLOOD DEPTH AND LEVEL PLANS ...... APPENDIX I: PROPOSED SCENARIO FLOOD DEPTH AND LEVEL PLANS ...... APPENDIX J: BLOCKAGE PLANS ...... APPENDIX K: DAVY FIELD DRAIN CULVERT CCTV SURVEY ...... APPENDIX L: SITE TOPOGRAPHICAL SURVEY ...... APPENDIX M: NOTES OF LIMITATIONS ......
Figures & Tables Figure 1: Aerial photograph of site (Google Maps, 2019) ...... 9 Table 1: Key catchment descriptors ...... 10 Table 2: Statistical Method Flow Estimates ...... 11 Figure 2: Downstream stage-time boundary conditions ...... 14 Figure 3: 1D Model Schematic (Betts Hydro, 2019) ...... 15 Table 3: Full list of structures of modelled watercourses ...... 16 Table 4: Flow pro-rata according to catchment area for Davy Field Brook ...... 16 Table 5: Flow pro-rata according to catchment area for Davy Field Drain ...... 17 Table 6: Manning’s roughness coefficients for the flood plain ...... 17 Figure 4: Predicted Floodplain Plan (Betts Hydro, 2020) ...... 19 Figure 5: 1 in 100 year climate change 1D convergence, 1D mass error and cumulative mass error 21 Figure 7: Proposed Davy Field Drain proposed open channel and storage basin ...... 23 Figure 8: Typical cross section through proposed channel and flood storage basin ...... 24 Table 7: Proposed check weirs ...... 24 Figure 9: Typical check weir cross section ...... 24
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Table 8: Peak water level and depth in the proposed flood storage basin ...... 25 Figure 10: 1 in 100 year existing and proposed total flow to River Darwen ...... 27 Figure 11: 1 in 100 year plus climate change existing and proposed total flow to River Darwen 27 Figure 12: 1 in 1000 year existing and proposed total flow to River Darwen ...... 28 Figure 13: 1 in 1000 year combined culvert outfall and overspill flow existing and proposed . 28 Table 9: Structures test in blockage analysis ...... 29 Figure 5: 1 in 100 year climate change event proposed model 1D convergence, 1D mass error and 2D cumulative mass error ...... 31 Table 10: Sensitivity analysis results ...... 33
Specialist Software Flood Estimation Handbook Web Service – Determination of Catchment Descriptors and depths of rainfall. QGIS – Mapping requirements Flood Modeller (4.5) – 2019 TUFLOW Build: 2016-03-AA-iSP-w64
Abbreviations & Acronyms
AEP Annual Exceedance Probability NGR National Grid Reference CC Climate Change NPPF National Planning Policy Framework EA Environment Agency OS Ordnance Survey FEH Flood Estimation Handbook PFRA Preliminary Flood Risk Assessment FRA Flood Risk Assessment SFRA Strategic Flood Risk Assessment FZ Flood Zone TWL Top Water Level Ha Hectare PPG Planning Practice Guidance LLFA Lead Local Flood Authority LPA Local Planning Authority mAOD Metres Above Ordnance Datum ReFH Revitalised Flood Hydrograph
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1.0 INTRODUCTION
1.1 Commission 1.1.1 This Hydraulic Assessment was commissioned by the joint venture Barnfield Blackburn Ltd in support of mixed-use development on the development site off Milking Lane.
1.1.2 This assessment follows the initial Hydraulic Assessment undertaken by Betts Hydro in July 2019 which assessed the flood risk posed by the two watercourses: Davy Field Brook and Davy Field Drain which pass though the site. The result of that assessment found that Davy Field Drain posed a flood risk to the site in the 1 in 100 year event and higher.
1.1.3. The present assessment examines a potential flood risk mitigation solution to reduce the extent of flooding to the site.
1.2 Outline of Assessment 1.2.1 The baseline hydraulic model from the previous assessment has been updated following a CCTV survey of the culverted reach of Davy Field Drain. This updated model has been used as a comparison for the proposed flood mitigation model.
1.2.2 As with previous assessment Betts Hydro has the used Flood Modeller Pro and TUFLOW to construct a dynamically linked 1-D/2-D hydraulic model for the proposed flood mitigation.
1.2.3 This Hydraulic Assessment report details the modifications to the baseline model, and the creation of a proposed scenario model which tests the proposed mitigation solution. It then presents the results in the proposed scenario showing flood extents and depths in the 1% AEP (1 in 100 year) and the 0.1% AEP (1 in 1000 year) events. In order to identify future predicted flood risks due to climate change, the 1% plus CC (1 in 100 year return period with an allowance for climate change) has also been assessed.
1.2.4 A comparison has been made between the peak flow leaving the site in the existing and proposed scenarios to demonstrate that flood risk is not increased elsewhere as a result of the proposals.
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2.0 DEVELOPMENT SITE 2.1 Location 2.1.1 The proposed development site is located between Blackburn and Darwen, adjacent to the M65. The development site is accessed from Greenbank Terrace to the west of the site. The site covers a large area of land that was previously brownfield and features two existing office buildings near the entrance to Greenbank Terrace.
2.1.2 The Ordnance Survey National Grid Reference (OS NGR) for the site is 369337 (Easting), 424620 (Northing) and the nearest postcode is BB3 0SS. The site location plan is shown in Appendix A. The site red line boundary is shown Figure 1.
2.1.3 The site features two watercourses, the larger Davy Field Brook which runs to the south of the site, connecting into the River Darwen to the west and Davy Field Drain running through the centre of site in a small valley before entering a culvert in the centre of the site which conveys flows under the site and Greenbank Terrace to the River Darwen as seen in Figure 1.
Site Area EA Main River Ordinary Watercourse
Paul Rink Way
M65
Figure 1: Aerial photograph of site (Google Maps, 2019)
2.1.4 A site visit to inspect the two main watercourses was undertaken on two separate occasions in April 2019, photographs of the site, structures and watercourses can be seen in Appendix B.
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3.0 HYDROLOGY 3.1 Introduction 3.1.1 A separate full hydrological analysis has been undertaken using the FEH statistical (pooled group and single site) and the Revitalised Flood Hydrograph (ReFH) methods. The full details of this analysis are included in Appendix C.
3.2 Catchment Descriptors 3.2.1 The Flood Estimation Handbook (FEH) Web Service provides the Davy Field Brook and Davy Field Drain catchment areas and descriptors. The key catchment descriptors for the two watercourses are provided in Table 1. A composite plan showing all sub- catchment areas is shown on drawing no. HYD073/050/A in Appendix D. Catchments were cross referenced using LiDAR to confirm the catchment boundaries were correct.
Description Davy Field Brook Davy Field Drain AREA 13.43 0.835 FARL 0.947 1.0 PROPWET 0.51 0.51 BFIHOST 0.38 0.355 DPLBAR 5.08 1.27 DPSBAR 96.6 48.3 SAAR 1362 1266 SPRHOST 41.27 37.1 URBEXT1990 0.0143 0.2365 URBEXT2000 0.0186 0.4817 Table 1: Key catchment descriptors
3.2.2 Further assessment of the SPRHOST and BFIHOST to verify the data has been undertaken. A review of the BGS geological maps identifies Pennine Lower Coal Measures consisting of mudstone, siltstone, and sandstone in the wider catchment. The superficial deposits consist of Devensian till. Cranfield Soil Scapes also identifies clayey soil within the catchment and class 4 soil type. The above information corresponds with the SPRHOST (41.27) BFIHOST (0.38) indicating a catchment with low permeability.
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3.3 Flow Estimation 3.3.1 The Statistical method, ReFH and ReFH + Statistical methods provide similar results for Davy Field Brook with ReFH slightly lower than the statistical method and very much lower for Davy Field Drain. Without any measured flood or flow data the choice is subjective, but the statistical method is often preferred as it is more robust, based on measured flow data and involves fewer assumptions. EA’s ReFH guidelines suggest ReFH does not perform well on urban or permeable catchments. These are not constraints on Davy Field Brook but may be an issue on the Davy Field Drain with a high URBEXT. The hydrology study concluded that the Statistical Method was the most appropriate to use for this site which estimated the flows as shown in Table 2. The critical storm duration for the total catchment was 5.409 hours and this was used for both catchments.
FLOW ESTIMATE (m3/s) RETURN PERIOD DAVY FIELD DAVY FIELD BROOK DRAIN 1 in 20 Q20 22.33 2.72 1 in 100 Q100 33.45 3.64 1 in 1000 Q1000 59.49 5.78
Table 2: Statistical Method Flow Estimates
3.3.2 The model connects Davy Field Brook and Drain to the River Darwen model to the west. The upstream QT boundary and downstream HT boundary have been extracted from the existing EA River Darwen Model (2012), for the relevant return periods.
3.4 Confidence Limit 3.4.1 Confidence limits for flood estimates are difficult to calculate and remain a subject for research. Quantitative assessment of uncertainty often uses confidence intervals and the 95% confidence interval is the range within which we are 95% confident that the true answer lies. There are no widely available straightforward techniques for assessing confidence intervals for flood estimates (See Flood Estimation Handbook Vol 1 - 5.6) and whilst FEH provides confidence intervals for some components of flood estimates it does not suggest any techniques for combining them together and accounting for the other sources of uncertainty. The overall uncertainty is a combination of (i) the variability of QMED; (ii) the variability of the growth curve; and (iii) the covariance between QMED and the growth curve.
3.4.2 Examples of quantitative assessment for the FEH statistical method include:
Obtain confidence intervals for QMED when QMED is derived from flood peak data or catchment descriptors or using the factorial standard error associated with the Revised QMED equation. The revised 68% confidence interval for QMED is (0.70QMED, 1.43QMED) and the revised 95% interval is (0.49QMED, 2.04QMED).
Derive confidence intervals using the resampling routine in WINFAP-FEH for single-site growth curves, but for the much more widely used pooled growth curves, although this is theoretically possible and could be done if suitable software were developed, this is not available at present.
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3.4.3 It is often required to calculate confidence limits for a large scale and detailed flood studies but for a 1 or 2 day flood estimate to be used as part of a Flood Risk Assessment, this is seldom required.
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4.0 HYDRAULIC MODELLING 4.1 Existing Scenario Model Details
General 4.1.1 An unsteady state dynamically linked 1D/2D model of the watercourses and floodplain was developed using Flood Modeller Professional version 4.5 and TUFLOW Build: 2016- 03-AE-iSP-w64.
4.1.2 A topographical survey including cross sections of the watercourses have been undertaken by Powers and Tiltman Ltd in May 2019 and these were used to create the 1D channel component of the model. The cross sections from the survey are included in Appendix E. A CCTV survey of the Davy Field Drain culvert was undertaken on 28th October 2019 by NDDS Ltd. The details of this survey are provided in Appendix K.
4.1.3 Interpolated cross sections were included in between the surveyed sections to provide increased model stability. This facilitated the representation of the in-channel flood extent. The frequency of the interpolated sections increased in the meanders of the watercourses to create a more accurate output.
4.1.4 The floodplain digital terrain model was generated from LiDAR data (1m resolution flown 2017) and a 3D site-specific topographical survey completed by Survey Operations in August 2018 (Appendix L). The watercourse was modelled in the existing scenario for the 1% and 0.1% annual exceedance probability (AEP) events plus allowance for climate change. The 1D model schematic is shown in Figure 3 and the full 2D schematic is provided on Drawing No. HYD397/099/A in Appendix F.
Model Boundaries 4.1.5 The upstream boundary of the model is at OS NGR 369897, 424476 and the downstream boundary is at OS NGR 368910, 424787 downstream of the site on the River Darwen. The Environment Agency
4.1.6 According to the backwater length equation, L = 0.7 x depth/gradient, the backwater length for the River Darwen at the downstream boundary has been calculated using an average gradient of 0.015 and the typical bank full depth is 2.5m:
L = 0.7 x 2.5/0.015 = 116m.
4.1.7 The downstream boundary of the model is approximately 200m downstream of the site. A portion of the Environment Agency 2012 River Darwen model has been incorporated into the present study model. The relevant Environment Agency 2012 River Darwen model stage hydrographs from node DARW_4513 was used for the 1 in 100 year and 1 in 1000 year events, respectively. The 1 in 1000 year event was also used for the 1 in 100 year plus 35% climate change event. The downstream stage-time hydrographs are shown in Figure 2.
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Time Series: DARW_4513 - Stage: DARW_4513; 1 - 10 h. 116.6 116.55 116.5 116.45 116.4 116.35 116.3 116.25 116.2 116.15 116.1 116.05 116 115.95 115.9 115.85 115.8 115.75 115.7 115.65 115.6 115.55 115.5
Stage (m AD) (m 115.45 Stage 115.4 115.35 115.3 115.25 115.2 115.15 115.1 115.05 115 114.95 114.9 114.85 114.8 114.75 114.7 114.65 114.6 114.55 114.5 1 1.2 1.4 1.81.6 2 2.62.42.2 2.8 3 3.83.63.43.2 4 4.84.64.44.2 5 5.65.45.2 5.8 6 6.86.66.46.2 7 7.2 7.87.67.4 8 8.68.48.2 8.8 9 109.89.69.49.2 Time (h)
1% AEP Head-Time Boundary 0.11% AEP Head-Time Boundary
Figure 2: Downstream stage-time boundary conditions
4.1.8 The top of bank crest for each cross section was chosen as the highest point on either side of the watercourse whilst ensuring an adequate width of the 1D channel to maintain stability. The top of bank levels have been obtained from the topographical survey. The survey Ordnance Survey coordinates of the tops of bank have been used to define the 1D/2D boundary (HX line and ZP points) which ensures that the 2D channel width in the development area is equal to the 1D channel width.
4.1.9 A 2D HQ boundary (normal depth) has been applied on a section of the 2D domain boundary at the Bolton-Blackburn Railway Line. This to allow flow along the railway line to leave the model domain. The LiDAR data shows that the railway line continues to fall northwards away from the model boundary and flow along this route cannot re- enter the channel.
4.1.10 The upstream model boundary on Davy Field Brook just downstream of Roman Road at NGR 369899 E, 424481 N. The most upstream cross section from the original cross section survey was node DB_0000 at NGR 369582 E, 424331 N. Initial runs of the model found instabilities in the reach from the upstream boundary to the Ribble Valley railway culvert and so the model was extended upstream. Two additional cross sections (DB_0000C1 and DB_0000C2) were created by copying node DB_0000 and raising the bed levels according to the gradient calculated from the LiDAR data. This improved the model stability and allowed the flood plain storage between Roman Road and the Ribble Valley railway to be used.
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Figure 3: 1D Model Schematic (Betts Hydro, 2019)
Structures 4.1.11 There are 6 no. structures on Davy Field Brook and 4 no. structures on Davy Field Drain. These are detailed in Table 3. The potential for the structures to overtop has been incorporated into the model by use of 2D H link lines. Short crossings (typically a standard road width) have been represented by orifice or arch bridge units which is appropriate for short culverts or bridges according to the Flood Modeller software guidance. Longer culverts have been represented using conduit units.
4.1.12 The spill coefficient for in channel spills used is the default Flood Modeller Pro value of 1.2. This value was appropriate as it is conservative (i.e. will generate a higher upstream water level) and the nature of the spills as more like natural channel beds rather than engineered weirs. The spill coefficient for the overtopping of the bridge at DB_0586 is also 1.2 because it is a bridge deck and not a designed weir.
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Node Easting Northing Watercourse Location Structure Type Davy Field Railway DB_0155 369424 424384 Circular Culvert Brook Crossing Davy Field DB_0260 369293 424422 M65 Culvert Brook Davy Field Clear Span Bridge DB_0586 369105 424554 Access Bridge Brook Deck Lower Davy Field Clear Span Bridge DB_0647 369036 524544 Eccleshill Brook Deck Road Davy Field Clear Span Bridge DB_0716BUS 368989 424578 Paul Rink Way Brook Deck Near access Davy Field Clear Span Bridge Not Surveyed 369118 424546 road to south Brook Deck parcel Davy Field D/S of M65 DB_0260SPUS 369248 424461 In-channel spill Brook culvert Davy Field DB_0586SU 369105 424554 Access Bridge Bridge deck spill Brook Davy Field DB_0598SPUS 369089 424558 Unspecified In-channel spill Brook Davy Field DF_0057OUS 369377 424837 Railway line Culvert Drain Davy Field 2no. circular DF_0189 369285 424768 Milking Lane Drain culverts Davy Field DF_0250 369231 424741 Footbridge Clear Span Drain Davy Field DF_0375 369122 424683 Within Site Culvert Drain D/S of Davy Davy Field DF_0499A 368994 424671 Field Drain In-channel spill Drain outfall Table 3: Full list of structures of modelled watercourses
4.2 Model Flows 4.2.1 The peak flows at the downstream end of Davy Field Brook and Davy Field Drain were estimated using the FEH Statistical Method as detailed in Chapter 3 and Appendix C. The flow on each watercourse was proportioned pro-rata according to catchment area at the inflow location.
4.2.2 The relative catchment areas and the proportioned flow at the flow input points for Davy Field Brook are shown in Table 4 and likewise for Davy Field Drain in Table 5. The catchment area at the upstream boundary of the model was used to proportion the upstream boundary flow and the remaining flow was added as lateral inflow.
1 in 100 year plus Davy Field Area 1 in 100 year flow 1 in 1000 year Proportion climate change flow Brook (km2) (m3/s) flow (m3/s) (m3/s) Upstream 12.290 0.915 30.611 41.324 54.440 Lateral 1.140 0.085 2.839 3.833 5.050 Total 13.430 1.000 33.450 45.158 59.490 Table 4: Flow pro-rata according to catchment area for Davy Field Brook
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1 in 100 year plus Davy Field Area 1 in 100 year flow 1 in 1000 year Proportion climate change flow Drain (km2) (m3/s) flow (m3/s) (m3/s) Upstream 0.610 0.735 2.675 3.611 4.248 Lateral 0.220 0.265 0.965 1.303 1.532 Total 0.830 1.000 3.640 4.914 5.780 Table 5: Flow pro-rata according to catchment area for Davy Field Drain
4.3 Assumptions 4.2.1 A roughness Manning’s n values have been chosen for the watercourses’ channels based on observations and site photographs. There was some variation observed in channel roughness, however a value of 0.035 was used for majority of the sections, some of the channel of Davy Field Brook is within a narrow concrete channel near to the M65 and as result had a lower Manning’s value. The flood plain roughness values used are shown in Table 6, based on the OS Mastermap descriptions.
OS Mastermap Description Manning’s roughness coefficient General Surface 0.033 Natural Environment 0.060 Inland Water 0.030 Building 1.000 Landform 0.035 Railway 0.040 Roadside 0.030 Road or Track 0.014 Path 0.016 General Surface, Structure 0.050 Landform, Road or Track 0.035 Structure (Pylon) 0.020 Non-coniferous tree 0.070 Table 6: Manning’s roughness coefficients for the flood plain
4.4 Calibration 4.4.1 The Environment Agency 2012 River Darwen model was hydrologically and hydraulically calibrated using the Ewood Gauging Station (grid reference SD677262). Flow and stage from three events (31st January 1995, 14thJune 2002, and 21st January 2008) were used to calibrate flow and level in the River Darwen model.
4.4.2 Calibrated upstream River Darwen boundary flow and downstream boundary stage have been used in the present study model which provides confidence in the downstream boundary. No gauging stations are present on Davy Field Brook or Davy Field Drain and so direct calibration of those watercourses was not possible.
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4.5 Model Simulations
Model Run Parameters 4.5.1 The default 1D Flood Modeller run parameters were used, with the following exceptions:
dflood = 15 maxitr = 7
4.5.2 The dflood parameter was increased due to high water depths at the upstream culvert inlet. The maxitr parameter was set to 7 because prime numbers are recommended for this parameter. The dflood value of 15 was used to allow the simulation to run in 1D only as part of the model development.
Simulations 4.5.3 The following simulations were undertaken:
1% AEP (1 in 100 year) 1% AEP plus 35% climate change 0.1% AEP (1 in 1000 year)
4.5.4 As the impacts of climate change are already being witnessed throughout the globe and locally in the UK there is a requirement to consider the increased risk as a result of climate change. Based on the Environment Agency guidelines (2016) for the North West region an allowance of 35% has been used to determine predicted increases in storm intensity and how this will impact the site.
4.6 Model Results
Flood Zone Extents 4.6.1 In order to draw comparison against the published EA flood map for planning, a plan showing the predicted flood extents in the 1% AEP event (1 in 100 year event) and 0.1% AEP (1 in 1000 year event), delineating Flood Zone 3 and Flood Zone 2 respectively has been produced as shown on Drawing No. HYD397/100/C in Appendix G and illustrated in Figure 4.
4.6.2 In the predicted 1% AEP (delineating Flood Zone 3) and 0.1% AEP (delineating Flood Zone 2) events, flooding mainly occurs to the west of the site, adjacent to Greenbank Terrace. Davy Field Brook to the south of the site is predicted largely remain in-channel. The predicted flooding on the site during the 1% AEP and 0.1% AEP is due to overtopping of the culvert which conveys Davy Field Drain to the River Darwen through the site. As Davy Field Drain has a small catchment there is only a limited difference between the 100 year and 1000 year flows, however depths do increase between the two events.
1% AEP event (1 in 100 year Return Period) 4.6.3 A Flood depth plan has been produced for the 1% AEP event seen on drawing no. HYD397/103/E in Appendix H. Flood depth within the site boundary range between approximately 0.011m and 0.269m. Most of the flooding is associated with the
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overtopping of the Davy Field Drain culvert. There is a small amount of flooding from Davy Field Brook.
4.6.4 Flood level in the 1%AEP event is shown on drawing no. HYD397/104/E in Appendix H. The peak flood level on site ranges between approximately 121.469mAOD and 123.399mAOD.
Figure 4: Predicted Floodplain Plan (Betts Hydro, 2020)
0.1% AEP event (1 in 1000 year Return Period) 4.6.5 A flood depth has been produced for the 0.1% AEP event on drawing no. HYD397/109/C in Appendix H. The predicted extent in this event is the greatest out of those modelled. Similarly, to the 1%AEP event, the culvert conveying Davy Field Drain through the western area of site is exceeded and flows run overland to the west, ultimately connecting into the River Darwen. Some flooding also comes from Davy Field Brook, flowing northwards towards the centre of the centre and merging with the flooding from Davy Field Drain. Depths onsite range from approximately 0.024m to 0.738m.
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4.6.6 Flood level in the 0.1%AEP event is shown on drawing no. HYD397/110/C in Appendix H. Peak level on the site ranges between approximately 121.483mAOD to 123.474mAOD.
Climate Change 4.6.7 The 1% AEP event plus climate change scenario was simulated with an additional 35% to allow for future climate change. The flood depth map for this scenario is shown in Drawing No. HYD397/106/E in Appendix H. The predicted flood extent is similar to that observed in the 1% AEP and 0.1% AEP events. The majority of the flooding occurs in the western area due to exceedance of the culvert entrance as seen in the other events. Flood levels range from approximately 0.019m up to 0.589m.
4.6.8 The peak water level in the 1 in 100 year plus climate change event is shown on drawing no. HYD397/107/E in Appendix H. The peak water level on the site ranges between approximately 121.483mAOD in the north of the site to 123.473mAOD and the Davy Field Drain culvert.
4.7 Model Stability 4.5.1 The models both run stably in both 1D and 2D. Figure 5 shows the existing 1D model convergence and inflow and outflow for the 1 in 100 year climate change event. Model convergence is within the default tolerance for the vast majority of the simulation with only two brief spikes of non-convergence. The 1D mass error is roughly between 0 and -2% and the TUFLOW cumulative mass error is between +/-1% for the majority of the simulation.
4.5.2 Flood Modeller Pro guidance on 1D mass error does not specify a limit but states that a mass error approach 10% is worthy of further investigation. As such, a 1D mass error of between 0 and -2% is acceptable. A 2D mass error of between -1% and +1% is acceptable in TUFLOW modelling guidance. The dV value is consistent with no large values or jumps.
4.5.3 A number of warnings were report in the TUFLOW log files. The explanations for these warnings are:
WARNING 2218 - Manning's n value of 1. for Material 10062 is unusually low or high. The value of 1 is used to represent buildings.
WARNING 2218 - Manning's n value of 0.9 for Material 506 is unusually low or high. This value was used as a stability patch
WARNING 2073 - Object ignored. Only Points, Lines, Polylines & Region Centers used. Null shape. Null objects were identified and ignored. Investitigation of the relevant shp file however found no null objects.
XY: WARNING 1317 - WLL does not cross (2 point WLL only) or snap to 1D channel. Warning regarding the representation of the 1D graphical output.
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Figure 5: 1 in 100 year climate change 1D convergence, 1D mass error and cumulative mass error
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4.6 Results Discussion 4.6.1 As seen in the results for the existing scenario, for all modelled results, predicted flows from Davy Field Brook impact the southern portion of the site, with flows remaining in channel for the 1% AEP event. Some flooding from Davy Field Brook occurs in the 1 in 100 year (1%AEP) climate change and the 1 in 1000 year (0.1%AEP) events. The majority of the flooding, however, is associated with Davy Field Drain and the overtopping of the culvert.
4.6.2 In all of the modelled events flow from Davy Field Drain is shown to exceed the capacity of the culvert entrance located within the centre of the site. The result of this is a shallow overland flow path where flood depth is mostly less than 70mm. This flow path ultimately connects into the River Darwen to the west of the site over Greenbank Terrace. A photo of the culvert inlet is located in Appendix B and the area of the culvert inlet is measured at 0.78m².
4.6.3 The Davy Field Drain culvert is prone to blockage and so it is intended as part of the proposed development to remove this culvert and reinstate an open channel. This open channel will remove the flood risk from the site and improve the ecology of the watercourse.
Calibration 4.6.4 No gauge is available for Davy Field Brook or Davy Field Drain which is typical for small watercourses such as these. The River Darwen model, from which flow and stage hydrographs were obtained was calibrated for hydrologically and hydraulically using gauged data, the nearest of which being at Ewood.
4.6.5 It was not possible to find any anecdotal evidence of flooding on the site. In absence of such information a robust sensitivity analysis, assessing Manning’s roughness, structure coefficients, flow and downstream boundary condition has been undertaken. Blockage analysis of key structures has been undertaken.
4.6.6 The flood extent outputs look reasonable according to the topography and structures present. It would be expected that the Davy Field Drain culvert overtops given its size relative to the flow.
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5.0 PROPOSED SCENARIO MODEL
5.1 Proposed Solution 5.1.1 Barnfield Blackburn Ltd commissioned Betts Hydro to produce a flood mitigation solution that would allow the site to be developed. Betts proposed a flood mitigation solution comprising of the de-culverting of Davy Field Drain and reinstating an open channel as far as Greenbank Terrace. In addition, a storage basin is proposed which will store flood water up to and including the 1 in 100 year event include 35% climate change. A series of 4no. check weirs are proposed on Davy Field Drain upstream of the storage basin. A general arrangement of the proposed new channel and storage basin is shown in Figure 7.
5.2.2 The de-culverting of Davy Field Drain provides the following benefits:
Improved ecology of the watercourse; Extra flood storage provided by the proposed open channel; Elimination of flooding on the site and to Greenbank Terrace in events up to and including the 1 in 1000 year event; A reduction in total flow from Davy Field Drain entering the River Darwen.
5.2.3 The flood storage basin will provide the following benefits:
Remove flooding to the site up to the 1 in 100 year plus 35% climate change event; Remove flooding to Greenbank Terrace up to the 1 in 100 year plus climate change event.
Check weirs Proposed storage basin 1
Base level = 120mAOD
Base level = 119mAOD 2 3 4 Reinstated watercourse
Figure 7: Proposed Davy Field Drain proposed open channel and storage basin
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5.2.3 A typical cross section through the proposed channel and storage basin, with indicative top water levels, is shown in Figure 8 (not to scale).
Open channel Storage basin
1 in 100yr CC
1 in 100yr
1 in 20yr
Figure 8: Typical cross section through proposed channel and flood storage basin
5.2.4 The 4no. check weirs are proposed to be a maximum of 1.5m above the existing bed level. Each weir will comprise a pipe allowing low flow through. Pipe proposed pipe diameters proposed are shown in Table 7. A sketch of a proposed check weir is shown in Figure 9.
Weir no. Model node Pipe diameter (mm) 1 DF_0294 375 2 DF_0340 375 3 DF_0358 375 4 DF_0375 525 Table 7: Proposed check weirs
Weir crest
1.5m Pipe
Figure 9: Typical check weir cross section
5.2.5 The Storage Area was modelling in the 2D domain for the 1 in 100 year and 1 in 100 year plus climate change simulations. In the 1 in 1000 year simulation, the storage area was modelling in the 1D domain which gave more reliable results.
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5.2 Proposed Scenario Model Runs
Simulations 5.2.1 The following simulations were undertaken:
1% AEP (1 in 100 year) 1% AEP plus 35% climate change 0.1% AEP (1 in 1000 year) 1% AEP sensitivity tests (roughness, flow, loss coefficients, downstream boundary) 1% AEP plus climate change blockage analyses (4 no. structures)
Flood Extent, Depth and Level 5.2.2 The flood depths and levels for the proposed scenario are provided in Appendix I. The flood depth for the 1 in 100 year event is shown on drawing no. HYD397/403/C. The 1 in 100 year event in Davy Field Drain is contained with the proposed open channel and no flooding occurs on Greenbank Terrace from Davy Field Brook. Some flooding does occur from Davy Field Brook with flood depths between approximately 0.019m and 0.242m. The flood levels are shown on drawing no. HYD397/404/C and range between approximately 121.482mAOD and 121.666mAOD.
5.2.3 Proposed flood depth in the 1 in 100 year plus climate change event is shown on drawing no. HYD397/405/C in Appendix I. The flood extent on Davy Field Drain for this event is contained wholly with the proposed channel and flood storage basin. Flooding on Greenbank Terrace does not occur from Davy Field Drain but it does occur from Davy Field Brook. The overall extent of flooding on Greenbank Terrace and the site is considerably reduced. The peak depth in the proposed storage area is 1.604m. The peak flood level for the proposed scenario 1 in 100 year climate change event is shown on drawing no. HYD397/406/C. It can be seen that peak flood levels on the River Darwen flood plain are reduced in the proposed scenario.
5.2.4 Drawing no. HYD397/405/B in Appendix I shows flood depth in the extreme 1 in 1000 year event. The flood storage basin is exceeded in this event, but flood extent to Greenbank Terrace and the site is reduced significantly. Peak flood levels on the River Darwen flood plain are also reduced in the proposed scenario. Peak top water levels in the proposed flood storage basin for the 1 in 100 year, 1 in 100 year plus climate change and 1 in 1000 year events are shown in Table 8.
Event Peak water level (mAOD) Peak depth (m) 1 in 100 year No flood No flood 1 in 100 year plus climate 120.604 1.604 change 1 in 1000 year 121.264 2.264 Table 8: Peak water level and depth in the proposed flood storage basin
5.2.5 In the 1 in 1000 year event, the proposed storage was modelled as a 1D reservoir unit with spill units from the main channel as better performance was observed for this event using this configuration. By way of a check, the 1 in 100 year climate change event was also run with the storage in 1D. This simulation predicted a peak storage
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level 120.650mAOD which is just 46mm higher than the level of 120.604 predicted in the 2D storage model. In terms of a percentage of the maximum predicted depth in the storage, this represents less than 3% and so we can have confidence in the validity of both model configurations.
Flow to River Darwen 5.2.6 The total flow to the River Darwen has been reduced by the proposed open channel and flood storage basin. Due to the incorporation of the open channel and flood storage basin, overland flow from the site across Greenbank Terrace has been removed. This has also resulted in a small increase in flow entering the Darwen via the Greenbank Terrace culvert. A comparison between the total flow entering the Darwen in the existing and proposed scenarios has been undertaken by combining the flow entering via the culvert and flow entering over land.
5.2.7 In the 1 in 100 year event, all over land flow from Davy Field Drain has been removed and flow only enters the River Darwen via the Greenbank Terrace culvert. In the existing scenario, flow enters the Darwen via both the culvert and via overland flow. The existing scenario culvert flow and overland flow has been combined to provide the total flow. A comparison between proposed and existing flow to the Darwen in the 1 in 100 year event is shown in Figure 10. It can be seen that, in the proposed scenario, flow to the Darwen peaks at around 3.6m3/s. In the existing scenario, the combine culvert and overland flow to the Darwen has a peak of over 4.1m3/s.
5.2.8 A similar comparison was undertaken for the 1 in 100 year event plus 35% climate change. In this event, as in the 1 in 100 year event, all overland flow to the River Darwen has been removed in the proposed scenario. Figure 11 shows the comparison between the proposed culvert flow and the total existing scenario flow. The peak proposed flow to the River Darwen lower than the peak existing flow.
5.2.9 In the 1 in 1000 year event, overland flow to the River Darwen occurs in both the existing and proposed scenario. In the proposed scenario, however, the extent of flooding across Greenbank Terrace is reduced. A comparison of total flow in the existing and proposed scenarios in the 1 in 1000 year event is shown in Figure 12. There is an initial peak in the existing flow at around 3.5 hours that is higher (approximately 5.9m3/s) than the proposed flow (approximately 3.9m3/s) followed by a second peak at approximately 5.5hours where the proposed (approximately 6.2m3/s) is greater than the existing (approximately 5.2m3/s).
5.2.10 For a clearer picture of the pre and post development flow off-site, the culvert outfall flow combined with the proposed storage overflow or existing culvert overtopping flow were compared in the pre and post development scenarios. This analysis is shown in Figure 13.It can be seen that the peak combination of Davy Field Drain outfall flow and overflow from the proposed storage area (approximately 4.2m3/s) is lower than the peak combined flow of the existing Davy Field Drain outfall and the Davy Field Drain culvert overtopping (approximately 5.1m3/s)
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4.5
4
3.5
3
2.5
2
Flow (cumecs) 1.5
1
0.5
0
024681012
Time (hours)
Total Proposed Total Existing
Figure 10: 1 in 100 year existing and proposed total flow to River Darwen
6
5
4
3
Flow (cumecs) 2
1
0
024681012
Time (hours)
Total Proposed Total Existing
Figure 11: 1 in 100 year plus climate change existing and proposed total flow to River Darwen
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Figure 11: 1 in 1000 year existing and proposed total flow to River Darwen
6
5
4
3
2
1
0 024681012 Existing Culvert + Overspill Proposed culvert + overspill Figure 13: 1 in 1000 year combined culvert outfall and overspill flow existing and proposed
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Blockage Analysis 5.2.9 Blockage analysis was undertaken on 3 key bridge crossings on Davy Field Drain and Davy Field Brook as seen in Table 9. The Environment Agency’s requirements for the blockage analyses were 50% blockage for bridges with openings of greater than 1m² in area and 90% blockage for those with openings of 1m² in area or less. Blockages were run in the 1% AEP event plus CC.
Node Watercourse Opening Area Blockage (%) DB_0586 Davy Field Brook >1m² 50 DB_0647 Davy Field Brook >1m² 50 DF_0716 Davy Field Brook >1m² 50 Table 9: Structures test in blockage analysis
5.2.10 A blockage of 50% was simulated at the bridge on Davy Field Brook at node: DB_0586. The flood depth plan, shown in Drawing no. HYD397/209/A and Appendix J shows the flood extent extends further north into the site when compared to the unblocked 1% AEP event plus climate change event. Depths onsite range from less than 0.25m to >0.50m. The peak level for this blockage scenario is shown in Drawing no. HYD397/210/A to be 122.198mAOD.
5.2.11 Lower Eccleston Road bridge to the south-west of the site on Davy Field Brook (node: DB_0647) was simulated with a 50% blockage. The flood depth plan, shown in Drawing no. HYD397/203/E in Appendix J shows that due to the blockage, flows overspill the bridge and flow north over the roundabout onto Greenbank Terrace. On the site predicted flood depth and extent shows a slight increase when compared to the unblocked scenario. Peak water level on the site is shown to be 122.057mAOD on Drawing no. HYD397/204/E in Appendix I.
5.2.12 A 50% blockage was simulated at Paul Rink Way bridge at node DB_0716. The flood depth plans are shown in drawing no. HYD397/205/E in Appendix J. In this blockage scenario, the flood extent is similar to that of a blockage at DB_0647 with flooding predicted to affect the roundabout adjacent to the site. The predicted flood depths range between approximately 0.020m to >0.50m. A peak water level of 121.944mAOD is shown on Drawing no. HYD397/206/E in Appendix J.
5.2.13 Blockage at the Davy Field Drain culvert (node DF_0375) was not tested as it is intended that this culvert be removed as part of the flood mitigation strategy.
Sensitivity Analysis 5.2.14 The sensitivity of certain model parameters has been tested in the 1 in 100 year plus climate change event. Although it would be optimal to test Manning’s roughness by - 20% as well as +20%, there was difficulty running the model with such low Manning’s roughness and so -10% was used instead. The full list of parameters tested was:
Manning’s roughness (n) in the channel and flood plain +20% and -10% Flow (Q) +20% Structure coefficients +/-20% Downstream boundary condition +0.5m
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5.2.15 The results of the sensitivity analysis are shown in Table 10. The results of the sensitivity test show when Manning’s roughness is increased by 20% in the channel and flood plain, the peak water level changed by a mean value of +0.026m. The peak increase was 0.283m at cross section DF_0499SPDS at the confluence with the River Darwen. Reducing Manning’s roughness by 10% in the channel resulted in a mean change in peak water level of -0.003m and a peak increase of 0.290m.
5.2.16 With an increase of 20% in flow, there was a peak increase in peak water level of 1.206m at node DB_0000 upstream of the railway culvert on Davy Field Brook. The mean increase was 0.184m.
5.2.17 The sensitivity to structure orifice and weir coefficients was tested by increasing and decreasing the weir and orifice flow coefficients at by 20%. An increase in structure coefficients led to a maximum increase in peak water level of 0.08m at nodes DF_0499A and DF_0499B on Davy Field Drain. The mean difference was -0.006m. A reduction in structure coefficients led a maximum increase in peak water level of 0.151m at node DB_0585 upstream of Lower Eccleshill Road. The mean change was 0.005m.
5.2.18 The effect of raising the level of the downstream stage-time hydrograph by 0.5m was to cause a peak increase in water level by 0.220m at node DF_0499SPDS on Davy Field Drain at the confluence with the River Darwen. The mean change was +0.006m and there was no significant effect on water levels within the development site.
5.2.19 The sensitivity analysis has shown that there is some high sensitivity to certain parameters, for example flow. The largest impact to peak water level, however, occurs upstream of the site and the impact on water levels within the site is much lower. The sensitivity of peak water level to the model parameters will be considered when setting the freeboard for slab levels.
5.2.20 Figure 5 shows the 1D model convergence, inflow, and outflow, and 1D and 2D mass error for the 1 in 100 year event plus climate change for the proposed scenario model. Convergence of the 1D model is good and within tolerance. The 1D mass error is between 0 and -2% for most of the simulation. Apart from the initial 2 hours, the 2D cumulative mass error is mostly within +/-1%.
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Figure 5: 1 in 100 year climate change event proposed model 1D convergence, 1D mass error and 2D cumulative mass error
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Structure Downstream Manning’s Manning’s Structure 1 in 100 coeff. boundary Flow+20% n+20% n-10% coeff. - Node CC level Difference Difference +20% Difference Difference level +0.5m Difference level Difference level level 20% level (mAOD) level level (mAOD) (mAOD) (mAOD) (mAOD) (mAOD) (mAOD) DF_000A 140.796 140.835 0.039 140.781 -0.015 140.793 -0.003 140.801 0.005 140.796 0.000 140.853 0.057 DF_0057 140.662 140.689 0.027 140.674 0.012 140.645 -0.017 140.689 0.027 140.661 -0.001 140.718 0.056 DF_0073 137.243 137.285 0.042 137.197 -0.046 137.250 0.007 137.203 -0.040 137.228 -0.015 137.257 0.014 DF_0098 135.141 135.192 0.051 135.123 -0.018 135.147 0.006 135.137 -0.004 135.140 -0.001 135.175 0.034 DF_0116 134.355 134.408 0.053 134.335 -0.020 134.363 0.008 134.348 -0.007 134.354 -0.001 134.395 0.040 DF_0156 133.678 133.692 0.014 133.674 -0.004 133.668 -0.010 133.692 0.014 133.678 0.000 133.706 0.028 DF_0189 133.679 133.691 0.012 133.676 -0.003 133.668 -0.011 133.693 0.014 133.680 0.001 133.708 0.029 DF_0209 130.072 130.139 0.067 130.051 -0.021 130.057 -0.015 130.095 0.023 130.070 -0.002 130.226 0.154 DF_0250 128.467 128.522 0.055 128.444 -0.023 128.473 0.006 128.464 -0.003 128.468 0.001 128.505 0.038 DF_0251 128.467 128.522 0.055 128.444 -0.023 128.473 0.006 128.464 -0.003 128.468 0.001 128.505 0.038 DF_0294 126.907 126.916 0.009 126.905 -0.002 126.906 -0.001 126.905 -0.002 126.906 -0.001 126.936 0.029 DF_0340 125.076 125.08 0.004 125.08 0.004 125.081 0.005 125.069 -0.007 125.078 0.002 125.135 0.059 DF_0375 123.791 123.794 0.003 123.794 0.003 123.786 -0.005 123.791 0.000 123.791 0.000 123.840 0.049 DF_0499A 118.817 118.82 0.003 118.816 -0.001 118.897 0.080 118.810 -0.007 118.817 0.000 118.938 0.121 DF_0499B 118.806 118.806 0.000 118.807 0.001 118.886 0.080 118.801 -0.005 118.807 0.001 118.926 0.120 DF_0499SPUS 118.806 118.806 0.000 118.807 0.001 118.886 0.080 118.801 -0.005 118.807 0.001 118.926 0.120 DF_0499SPDS 117.631 117.914 0.283 117.418 -0.213 117.599 -0.032 117.665 0.034 117.851 0.220 117.991 0.360 DB_0000 133.475 133.235 -0.240 133.765 0.290 133.474 -0.001 133.475 0.000 133.475 0.000 134.681 1.206 DB_0059 133.468 133.222 -0.246 133.659 0.191 133.468 0.000 133.468 0.000 133.468 0.000 134.213 0.745 DB_0114U 133.461 133.209 -0.252 133.65 0.189 133.461 0.000 133.461 0.000 133.461 0.000 134.195 0.734 DB_0114 133.254 132.952 -0.302 133.509 0.255 133.253 -0.001 133.254 0.000 133.253 -0.001 134.084 0.830 DB_0124 133.129 132.743 -0.386 133.362 0.233 133.129 0.000 133.129 0.000 133.129 0.000 133.836 0.707 DB_0155 129.135 129.417 0.282 128.998 -0.137 129.135 0.000 129.135 0.000 129.135 0.000 129.306 0.171 DB_0216 127.812 127.81 -0.002 127.795 -0.017 127.813 0.001 127.773 -0.039 127.814 0.002 127.828 0.016
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Structure Downstream Manning’s Manning’s Structure 1 in 100 coeff. boundary Flow+20% n+20% n-10% coeff. - Node CC level Difference Difference +20% Difference Difference level +0.5m Difference level Difference level level 20% level (mAOD) level level (mAOD) (mAOD) (mAOD) (mAOD) (mAOD) (mAOD) DB_0247 127.806 127.792 -0.014 127.802 -0.004 127.808 0.002 127.774 -0.032 127.809 0.003 127.820 0.014 DB_0260 140.796 140.835 0.039 140.781 -0.015 140.793 -0.003 140.801 0.005 140.796 0.000 140.853 0.057 DB_0484 122.220 122.318 0.098 122.167 -0.053 122.231 0.011 122.268 0.048 122.220 0.000 122.294 0.074 DB_0507 122.209 122.295 0.086 122.158 -0.051 122.238 0.029 122.313 0.104 122.210 0.001 122.270 0.061 DB_0540 122.244 122.311 0.067 122.208 -0.036 122.266 0.022 122.333 0.089 122.243 -0.001 122.294 0.050 DB_0550 122.256 122.311 0.055 122.226 -0.030 122.279 0.023 122.341 0.085 122.256 0.000 122.312 0.056 DB_0585 122.254 122.299 0.045 122.224 -0.030 122.293 0.039 122.405 0.151 122.254 0.000 122.346 0.092 DB_0586 121.933 121.979 0.046 121.909 -0.024 121.939 0.006 121.951 0.018 121.933 0.000 122.016 0.083 DB_0598 121.914 121.928 0.014 121.904 -0.010 121.902 -0.012 121.856 -0.058 121.914 0.000 121.981 0.067 DB_0600 121.418 121.605 0.187 121.325 -0.093 121.400 -0.018 121.329 -0.089 121.417 -0.001 121.579 0.161 DB_0617 121.224 121.408 0.184 121.136 -0.088 121.213 -0.011 121.172 -0.052 121.225 0.001 121.333 0.109 TDB_0247 120.995 121.131 0.136 120.925 -0.070 120.989 -0.006 120.964 -0.031 120.997 0.002 121.115 0.120 DB_0657 120.831 120.988 0.157 120.755 -0.076 120.831 0.000 120.828 -0.003 120.834 0.003 120.931 0.100 DB_0681 120.589 120.801 0.212 120.468 -0.121 120.586 -0.003 120.572 -0.017 120.594 0.005 120.704 0.115 DB_0716 120.056 120.206 0.150 119.988 -0.068 120.040 -0.016 120.028 -0.028 120.050 -0.006 120.187 0.131 DB_0813 119.972 119.997 0.025 119.965 -0.007 119.963 -0.009 119.973 0.001 119.982 0.010 120.159 0.187 Max 0.283 0.290 0.080 0.151 0.220 1.206 Mean 0.026 -0.003 0.006 0.005 0.006 0.184
Table 10: Sensitivity analysis results
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6.0 CONCLUSIONS
6.1 Hydrology 6.1.1 A separate hydrological assessment was undertaken using the FEH Statistical single site and pooled group analyses and the Revitalised Flood Hydrograph (ReFH) method. Peak flows for the 1 in 100 year (1% AEP) and 1 in 1000 year (0.1% AEP) from the statistical analysis were chosen for the hydraulic modelling.
6.2 Model Sensitivity 6.2.1 The model was tested for its sensitivity to the parameters of Manning’s roughness, flow, structure coefficients and boundary conditions. The model was sensitive to an increase in flow at a point outside the development site, but within the site there was not any significant sensitivity (within +/- 200mm).
6.3 Flood Zones 6.3.1 The predicted 1% AEP event (delineating Flood Zone 3) and 0.1% AEP event (delineating Flood Zone 2) differs from the EA’s published Flood Map for Planning. Betterment is seen in relation to Davy Field Brook to the south of the of the site, however as Davy Field Drain has now been modelled some predicted flows in both the 1% AEP event and 0.1% AEP event are seen to impact the western area of the site, the majority of the site is flood free.
6.3.2 Flooding within the site consists of shallow flow paths caused by the entrance to the culvert conveying Davy Field Drain being under capacity. It is possible alleviation works to the culvert entrance could reduce the existing flood risk onsite.
6.4 Climate Change and Blockage 6.4.1 When a climate change factor of 50% is considered for Davy Field Brook and Davy Field Drain, the flood extent on site is not significantly different to that observed in the 1% AEP and 0.1% AEP events. Flood levels on site range between 121.5mAOD and 123mAOD.
6.4.2 Blockage simulations of the key bridge structures and culverts show some minimal increases in flood extent and level. The most significant blockage is that occurring at the bridge crossing carrying Lower Eccleshill Road, as this results in increased flooding on Greenbank Terrace and the western boundary of the site.
6.5 Proposed Flood Mitigation 6.5.1 It is proposed that the culverted reach Davy Field Drain be reinstated as an open channel as far as the Greenbank Terrace culvert and an adjacent flood storage basin be constructed. The flood basin has been designed to contain the 1 in 100 year event plus 35% climate change.
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6.5.2 The proposed scenario consisting of the proposed open channel and flood storage basin has been modelled in the 1%, 1% plus 35% climate change and 0.1% AEP scenarios.
6.5.3 The modelling has shown that the proposed channel contains the 1% AEP event within its banks. The flood storage basin is able to contain the 1% AEP event plus 35% climate change. Although the 0.1% AEP event exceeds the capacity of the storage basin, overall flood extent on Greenbank Terrace is reduced.
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BIBLIOGRAPHY & REFERENCES
National Planning Policy Framework, CLG (2012). Planning Practice Guidance, CLG (2014) Tuflow Manual, BMT (2018)
Web-based References Bingmaps – www.bing.com/Maps/ British Geological Society – www.bgs.ac.uk Google Maps – www.google.com/maps FEH Web Service – www.fehweb.ceh.ac.uk Flood Map for Planning - flood-map-for-planning.service.gov.uk Soilscapes – www.landis.org.uk/soilscapes/
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APPENDIX A: LOCATION PLAN
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HYD397_MILKING.LANE.DARWEN_HYDRAULICASSESSMENT LOCATION PLAN Land off Lower Eccleshill Road
OS X (Eastings) 369337 OS Y (Northings) 424620 Nearest Post Code BB3 0SS Lat (WGS84) N53:43:02 (53.717085) Long (WGS84) W2:27:58 (-2.466104) Lat,Long 53.717085,-2.466104 Nat Grid SD693246 / SD6933724620
Milking Lane, Darwen Hydraulic Assessment
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APPENDIX B: SITE VISIT PHOTOGRAPHS
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Milking Lane, Darwen Hydraulic Assessment
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APPENDIX C: HYDROGOLICAL ANALYSIS
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HYD397_MILKING.LANE.DARWEN_HYDRAULICASSESSMENT
Flood Hydrology
River Darwen Tributaries, Greenbank Terrace, Lower Darwen, Lancashire
June 2019
Dr Paul Garrad Consultant Hydrologist 66 Charlock Way Guildford Surrey GU1 1XZ Flood Hydrology River Darwen Tributaries at Lower Darwen, Lancashire
Flood Hydrology River Darwen Tributaries, Greenbank Terrace, Lower Darwen, Lancashire
Contents
1 INTRODUCTION ...... 1
1.1 SITE LOCATION ...... 1 1.2 METHODOLOGY ...... 1 2 FLOOD FLOW ESTIMATION ...... 2
2.1 FEH STATISTICAL METHOD ...... 2 2.1.1 Catchment Descriptors ...... 2 2.1.2 FEH Index Flood (QMED) ...... 4 2.1.3 Flood Frequency Curve ...... 5 2.2 REVITALISED FLOOD HYDROGRAPH METHOD (REFH) ...... 9 2.3 REFH2 ...... ERROR! BOOKMARK NOT DEFINED. 3 DISCUSSION ...... 11
3.1 EXTENSION AND COMPARISON OF FLOOD ESTIMATES ...... 11 3.2 COMPARISON OF FLOOD GROWTH CURVE ...... 12 3.3 HYBRID METHOD ...... 13 3.4 CLIMATE CHANGE ...... 13
i Flood Flows - Darwen Tribs - 14/06/19
Flood Hydrology River Darwen Tributaries at Lower Darwen, Lancashire
1 INTRODUCTION
1.1 Site Location
As part of a Flood Study for a site near Greenbank Terrace in Lower Darwen, Lancashire flood levels are to be derived for two tributaries of the River Darwen using a hydraulic river model. As part of this study flood flows are required at two locations (Figure 1.1) at Greenbank Terrace referred to as Davy Field Brook to the south and Davy Field Drain to the north.
Figure 1.1 Flow Estimate Site Locations
This requires estimates of peak flood flows for the 20 year, 100 year and 1000 year return period events with the addition of an appropriate allowance for climate change. The derivation of flood flows at these two locations is considered in this report.
1.2 Methodology
Flood flows are provided for a range of return periods using methods detailed in the Flood Estimation Handbook (FEH)1 and the EA’s FEH Guidelines2. Flow estimates for extreme events may be quite uncertain hence the approach is to use and compare the FEH Revised Statistical Pooling Group approach and the Revitalised Flood Hydrograph Method (ReFH). These are considered in Section 2 of this report with extension to the 1000 year return period, a comparison of flood estimates and the addition of an appropriate allowance for climate change considered in Section 3.
1 The Flood Estimation Handbook, Centre for Ecology & Hydrology, 1999. 2 Environment Agency’s Flood Estimation Guidelines, Technical guidance 197_08, January 2015 1 Flood Flows - Darwen Tribs - 14/06/19
Flood Hydrology River Darwen Tributaries at Lower Darwen, Lancashire
2 FLOOD FLOW ESTIMATION
2.1 FEH Statistical Method
As the site of interest is ungauged as a first approach it is convenient and appropriate to use the FEH Statistical method which is based on FEH Catchment Descriptors (CDs).
2.1.1 Catchment Descriptors
The FEH on-line has been used to provide the catchment delineation at the two locations (Figure 2.1). This confirms that both catchment have a simple structure with a few lakes or reservoirs and that a simple flood hydrograph response may be expected.
Figure 2.1 FEH Catchment Delineation
A comparison of the FEH catchment boundary with OS maps showed the FEH defined areas are reasonable and a manual adjustment of the FEH defined catchment area is not required.
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Flood Hydrology River Darwen Tributaries at Lower Darwen, Lancashire
Figure 2.2 OS Map
The FEH catchment descriptors (Table 2.1) show the southern Davy Field Brook catchment is small (13.43km2) and rural (URBEXT1990 = 0.0143), with some lakes or ponds (FARL = 0.947) and a high percentage runoff (SPRHOST = 41.27%). The northern Davy Field Drain catchment is smaller (0.835km2) and urban (URBEXT1990 = 0.2365), with no lakes or ponds (FARL = 1.0) and also has a high percentage runoff (SPRHOST = 37.1%). These suggest no obvious reasons for not using the FEH methods for flood flow estimation but the high level of urbanisation of Davy Field Drain is of note. A a full definition of these FEH parameters is given in FEH Volume 5.
Table 2.1 FEH Catchment Descriptors
Parameter Davy Field Brook Davy Field Drain Grid Ref SD 69000 24550 SD 69050 24700 Centroid Grid Ref SD 71804 23078 SD 70025 25223 AREA 13.43 0.835 FARL 0.947 1 PROPWET 0.51 0.51 BFIHOST 0.38 0.355 DPLBAR 5.08 1.27 DPSBAR 96.6 48.3 FPEXT 0.0266 0.0299 SAAR 1362 1266 SPRHOST 41.27 37.1 URBEXT1990 0.0143 0.2365 URBEXT2000 0.0186 0.4817
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Flood Hydrology River Darwen Tributaries at Lower Darwen, Lancashire
2.1.2 FEH Index Flood (QMED)
The FEH catchment descriptors defined above are used to derive QMED, the median annual flood (Table 2.2), using the Revised Stats Method QMED equation3. This is based on URBEXT2000 updated to 2019 and the urban adjustment factor (UAF) using Kjedsen’s updated method based on BFIHOST (Table 2.2). For the Brook catchment the rural and urban QMED values are similar but QMED-Urban is far higher for the Drain catchment.
Table 2.2 QMED from Catchment Descriptors
Site URBEXT URBEXT URBEXT UAF QMED QMED 1990 2000 2019 RURAL(m3/s) URBAN(m3/s) Brook 0.0143 0.0186 0.0193 1.019 10.18 10.37 Drain 0.2365 0.4817 0.5004 1.512 1.10 1.66
The QMED-CDs at an ungauged site are then adjusted using the ratio between QMED-CD and QMED-Flow data at a nearby local donor gauging station. The EA do not operate any flow or water level recorders on these two small watercourses and the nearest EA river flow gauge is on the River Darwen at Ewood (Table 2.3).
Table 2.3 EA Gauging Stations near Darwen
CEH Ref Watercourse Location Start Date End Date No QMED ? Pooling ? Years 71013 Darwen Ewood 03-Sep-74 17-Mar-17 44 Yes Yes
The National River Flow Archive and HiFlows database (version 7) indicates this is an open channel velocity area station which opened in 1973 with a vertical concrete wall on the left bank and a high natural bank on the right. A fixed stone bed downstream provides the control and no bypassing occurs. Multiple ratings have been applied across the period of record derived from gaugings with a model derived rating for extreme flows. The site is suitable for QMED and pooling as although gaugings do not extend beyond QMED the site is fully contained within the channel and there are no significant hydraulic changes above the maximum gauged flow. The timescale of this study does not allow for a detailed analysis of the high flow ratings but as the flow data is considered suitable for QMED these flow data are used in the flood estimation process described below.
In selecting a suitable donor gauging station FEH also provides hydrological similarity criteria as follows;
• AREA – a factor of 4 or 5 • FARL – a difference of 0.05. • BFIHOST – a difference of 0.18 • SAAR – a factor of 1.25 • SPRHOST – difference of 15
3 Improving the FEH statistical procedures for flood frequency estimation. CEH Science Report SC050050, July 2008 4 Flood Flows - Darwen Tribs - 14/06/19
Flood Hydrology River Darwen Tributaries at Lower Darwen, Lancashire
A comparison of the catchment descriptors at this potential donor station and at the two sites of interest (Table 2.4) suggests the gauge is outside the bounds of hydrological similarity in terms of catchment Area and FARL for the Drain but not the Brook catchment.
Table 2.4 Catchment Descriptors at Flow Estimate Site and Donor Gauging Stations
Site ID AREA FARL BFIHOST SAAR SPRHOST URBEXT90 71013 39.05 0.938 0.424 1340 36.71 0.0935 Brook 13.43 0.947 0.380 1362 41.27 0.0143 Drain 0.835 1.0 0.355 1266 37.10 0.2365
However, in the absence of any other stations the Ewood gauge is considered as a donor site principally as a check. A comparison suggests QMED from CDs under estimates that from flow data at Ewood and that a factor of 1.115 should be applied (Table 2.5) to the CD estimates at ungauged sites in the local area.
Table 2.5 QMED at Donor Gauging Stations
Ref QMED-CDs QMED-CDs QMED-AMAX Ratio Rural Urban 71013 21.406 24.995 27.87 1.115
The Revised Stats method then requires that this donor ratio is further adjusted based on the distance between the catchment centroids and this requires a revised adjustment of 1.074 for the Brook and 1.068 to the Drain catchment (Table 2.6).
Table 2.6 QMED Ratio at Donor Gauging Stations
Ref Centroid Centroid Distance Ratio Revised Easting Northing (km) Ratio 71013 369919 422786 Brook 371804 423078 1.91 1.115 1.074 Drain 370025 425223 2.44 1.115 1.068
This donor adjusted catchment descriptors estimate of QMED is adopted as a conservative estimate to give the final QMED of 11.14m3/s for the Brook catchment and 1.78m3/s the Drain (Table 2.7).
Table 2.7 Adopted and Adjusted QMED from Catchment Descriptors
Location QMED RURAL QMED URBAN QMED Adopted QMED (m3/s) (m3/s) Adjustment Ratio (m3/s) Brook 10.16 10.37 1.074 11.14 Drain 1.10 1.66 1.068 1.78
2.1.3 Flood Frequency Curve
The calculation of a flood frequency curve and peak flows for a range of return periods requires the construction of a pooling group and the fitting of an extreme value distribution to the annual maximum flow data from hydrologically similar sites (pooling group) using WINFAP4.
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Flood Hydrology River Darwen Tributaries at Lower Darwen, Lancashire
Due to the differences in the catchment descriptors at the two points of interest a pooled group is constructed for each site separately.
(i) Davey Field Brook
The initial pooling group contains 15 stations with 526 station years of record and one station was removed for having less than the required 8 years of data (49005, Bollingey Stream at Bollingey) leaving 14 stations with 519 station years of record. Examination of the pooling group indicates it is acceptably homogeneous and a review is not required (H2 = 0.719). The pooling group was therefore accepted. However a review of the pooling group suggests station 49006 (Camel at Camelford) has a short 11 years of record with a flat growth curve which may not be fully representative of flood conditions hence this station was removed.
The revised group then has with 13 stations and 508 years of record and examination indicates is possibly heterogeneous and a review considered optional (H2 = 0.206). There was no obvious or valid reason to remove any of the other component stations. Some discordancy often arises as several of the component stations (Table 2.8) have relatively steep growth curve (Figure 2.3) and some very flat but there was no justification for removing any sites from the group.
Table 2.8 Component Stations of Davy Field Brook Pooling Group
Station Dist Yrs QMED L-CV L- Discord data AMAX SKEW 47022 (Tory Brook @ Newnham Park) 0.075 24 6.651 0.265 0.138 1.677 25011 (Langdon Beck @ Langdon) 0.401 28 15.878 0.238 0.318 0.810 206006 (Annalong @ Recorder) 0.491 48 15.330 0.189 0.052 2.601 25003 (Trout Beck @ Moor House) 0.776 44 15.142 0.168 0.294 0.579 71003 (Croasdale Beck @ Croasdale Flume) 0.780 37 10.900 0.212 0.323 0.320 27032 (Hebden Beck @ Hebden) 0.782 51 4.052 0.204 0.247 0.455 48009 (st Neot @ Craigshill Wood) 0.808 12 8.469 0.245 0.373 0.457 28033 (Dove @ Hollinsclough) 0.839 38 4.225 0.234 0.405 0.960 27010 (Hodge Beck @ Bransdale Weir) 0.866 41 9.420 0.224 0.293 0.111 44008 (South Winterbourne @ W’bourne St) 0.880 38 0.434 0.417 0.336 3.212 49003 (de Lank @ de Lank) 0.913 51 14.324 0.225 0.206 0.322 48004 (Warleggan @ Trengoffe) 0.916 48 9.983 0.258 0.257 0.384 25012 (Harwood Beck @ Harwood) 0.953 48 32.945 0.191 0.234 1.112
WINFAP4 is often found to provide discordant pooling groups and this arises because it uses the FEH parameters FARL and FPEXT to generate a pooling group, which are measures of flood storage and attenuation, whereas the original WINFAP was based on the soil or geology as reflected in BFIHOST. It is considered that WINFAP4 will always provide a more discordant pooling group as the shape of the growth curves of the component stations is more likely to be a function of the geology. However, the EA FEH Guidelines require the use of WINFAP4 and this is method is therefore adopted in this report.
6 Flood Flows - Darwen Tribs - 14/06/19
Flood Hydrology River Darwen Tributaries at Lower Darwen, Lancashire
Figure 2.3 WINFAP Component Stations at Davy Field Brook
Two extreme value distributions are often used on the pooled group data (i) the Generalised Logistic (GL), and (ii) the General Extreme Value (GEV) distribution both fitted to annual maximum data by the method of L-Moments. In this case WINFAP4 indicates that the GL provides the best fit and is used to provide the estimated flood flows (Table 2.9) with a 100 year flow of 33.45m3/s.
Table 2.9 Estimated Flood Flows at Davy Field Brook – Stats Method
Site Return Period (Years) 2 5 10 20 50 100 Brook 11.14 15.38 18.65 22.33 28.14 33.45
(ii) Davey Field Drain
The same approach is used for Davy Field Drain. The initial pooling group contains 15 stations with 502 station years of record and no stations were removed for having less than the required 8 years of data. Examination of the pooling group indicates it is heterogeneous and a review considered desirable (H2 = 2.102). A review of the pooling group suggests one station (49006, Camel at Camelford) is a short record of 11 years which has a flat growth curve which may not be fully representative of flood conditions hence this station was removed. One station was then added to the group (26802, Gypsey Race at Kirby Grindalythe) to make the 5T requirement of FEH to provide a minimum of 500 station years of record:
The revised group then has with 15 stations and 509 years of record and examination indicates is possibly heterogeneous and a review considered optional (H2 = 1.482). There was no obvious or valid reason to remove any of the other component stations. This discordancy arises as several of the component stations (Table 2.10) have relatively steep growth curve (Figure 2.4) and some very flat but there was no justification for removing any sites from the group.
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Flood Hydrology River Darwen Tributaries at Lower Darwen, Lancashire
Table 2.10 Component Stations of Pooling Group at Davy Field Drain
Station Distance Yrs QMED L-CV L-SKEW Discord data AMAX 76011 (Coal Burn @ Coalburn) 1.090 40 1.840 0.166 0.310 0.431 45816 (Haddeo @ Upton) 2.942 24 3.489 0.306 0.387 0.945 28033 (Dove @ Hollinsclough) 3.156 38 4.225 0.234 0.405 0.625 91802 (Allt Leachdach @ Intake) 3.188 34 6.350 0.153 0.257 0.762 27051 (Crimple @ Burn Bridge) 3.280 45 4.564 0.221 0.144 0.541 92002 (Allt Coire Nan Con @ Polloch) 3.447 16 13.540 0.101 0.337 1.507 54022 (Severn @ Plynlimon Flume) 3.533 38 14.988 0.156 0.171 1.038 71003 (Croasdale Beck @ Croasdale Flume) 3.649 37 10.900 0.212 0.323 0.156 25003 (Trout Beck @ Moor House) 3.738 44 15.142 0.168 0.294 0.323 25011 (Langdon Beck @ Langdon) 3.829 28 15.878 0.238 0.318 1.066 47022 (Tory Brook @ Newnham Park) 3.905 24 6.651 0.265 0.138 0.974 206006 (Annalong @ Recorder) 4.026 48 15.330 0.189 0.052 2.517 27073 (Brompton Beck @ Snainton Ings) 4.071 36 0.816 0.203 0.060 1.475 25019 (Leven @ Easby) 4.126 39 5.677 0.340 0.377 1.703 26802 (Gypsey Race @ Kirby Grindalythe) 4.229 18 0.108 0.316 0.217 0.939
Figure 2.4 WINFAP Component Stations – Davy Field Drain
WINFAP4 is often found to provide discordant pooling groups but the EA FEH Guidelines require the use of WINFAP4 and this is method is therefore adopted in this report. Two extreme value distributions are often used on the pooled group data (i) the Generalised Logistic (GL), and (ii) the General Extreme Value (GEV) distribution both fitted to annual maximum data by the method of L-Moments. In this case WINFAP4 indicates that the GL provides the best fit and is used to provide the estimated flood flows (Table 2.11) with a 100 year flow of 3.64m3/s.
Table 2.11 Estimated Flood Flows at Davy Field Drain – Stats Method
Site Return Period (Years) 2 5 10 20 50 100 Drain 1.78 2.14 2.41 2.72 3.20 3.64
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Flood Hydrology River Darwen Tributaries at Lower Darwen, Lancashire
2.2 Revitalised Flood Hydrograph Method (ReFH)
An alternative approach to flood estimation is to use flood hydrograph methods. The original FSR/FEH rainfall runoff method (RR) underwent significant modification in 2006 taking advantage of new data and more advanced hydrological modelling techniques since the original method was developed. The improved or Revitalised Flood Hydrograph method (ReFH) retains the overall structure of the earlier FSR/FEH RR approach but with various improvements and hence ReFH is now preferred to RR. ReFH is therefore used to derive peak flows for the specified design events based on the time to peak (Tp) and critical storm duration (Table 2.12) adjusted to be an odd multiple of the selected time step.
Table 2.12 ReFH Parameters and Critical Storm Duration
Site Tp Cmax BL BR Duration Time Step Critical (hrs) (hrs) Dur (hrs) Brook 2.28 279.7 31.1 1.035 5.39 0.25 5.25 Drain 0.59 262.2 12.4 0.962 1.34 0.1 1.30
The ReFH flows (Table 2.13) are similar to the Stats Method with a QMED of 10.41 m3/s and a 100 year flow of 29.03 m3/s for the Brook and slight more dissimilar for the Drain with a QMED of 0.64 m3/s and a 100 year flow of 2.12 m3/s.
Table 2.13 ReFH Flood Estimates (m3/s)
Location Return Period (Years) 2 5 10 20 50 100 Brook 10.41 13.95 16.78 19.79 24.58 29.03 Drain 0.64 0.92 1.15 1.35 1.71 2.12
The ReFH hydrographs show the typical asymmetrical runoff profiles due to the use of a kinked unit hydrograph (Figure 2.5).
Figure 2.5 ReFH Hydrographs
Brook 35.0
30.0 100 yr 50 yr 25.0 20 yr 10 yr 5 yr 20.0 2 yr
15.0
10.0
5.0
0.0 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0
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Flood Hydrology River Darwen Tributaries at Lower Darwen, Lancashire
Drain 2.5
2.0 100 yr 50 yr 20 yr 10 yr 1.5 5 yr 2 yr
1.0
0.5
0.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
The EA’s FEH Guidelines suggest that ReFH does not perform well on urban or permeable catchments but these are not constraints on the Brook catchment but may be an issue on the Drain as URBEXT is very high.
The more recent and updated ReFH2 includes revised equations, parameters and urban extent values and the EA suggest that ReFH and ReFH2 are both used until the implications of the ReFH2 changes are understood, which implies the peak flows from ReFH2 would not be used as its results are not yet accepted. The ReFH2 Technical Guidance Document shows the Stats method provides better estimates of peak flows than ReFH1 and ReFH2 when compared to measured QMED flows in terms of standard error and bias and hence the Stats method is preferred. The only advantage of using ReFH or ReFH2 is to provide the hydrograph shape for flood routing if using the hybrid method.
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Flood Hydrology River Darwen Tributaries at Lower Darwen, Lancashire
3 DISCUSSION
3.1 Extension and Comparison of Flood Estimates
The Statistical method was originally recommended for return periods up to 200 year event and ReFH is not calibrated beyond 150 years and technically these two methods are not suitable for extrapolating to the 1000 year event. The Environment Agency's Flood Estimation Guidelines2 provide suggestions for calculating extreme floods up to the 1000 year event:
• Using a larger 200 year pooling group in the Statistical method as an intermediate between the more usual 100 year group and the potentially less homogeneous 1000 year although more recently a simple extension of the 100 year has been proposed. • Use of ReFH although this relies on extending the method beyond the data set. • Using the ReFH growth factors for the 200 and 1000 year event against the ReFH 100 year which are then applied to the Stats method 100 year peak flow.
These three methods of extension provide similar results for the Brook with ReFH slightly lower than the Stats method and very much lower for the Drain (Figure 3.1) but there is no justification for preferring any of these methods
Figure 3.1 Comparison of Flood Frequency Curves
Brook 70 Stat 60 Stat+ReFH 50 ReFH
40
30 Flow Flow (m3/s) 20
10
0 0 1 2 3 4 5 6 7 8 Logistic Reduced Variate
Drain 10 9 Stat 8 Stat+ReFH 7 ReFH 6 5 4 Flow (m3/s) Flow 3 2 1 0 0 1 2 3 4 5 6 7 8 Logistic Reduced Variate
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Flood Hydrology River Darwen Tributaries at Lower Darwen, Lancashire
Without any measured flood or flow data the choice subjective but the Stats method is often preferred as it is more robust, based on measured flow data and involves fewer assumptions. The extension of the Stats method gives a 1000 year peak flow of 59.49 m3/s for the Brook and 5.78 m3/s for the Drain (Table 3.1).
Table 3.1 Extension of Flood Flows
Site Method Return Period (Years) 2 5 10 20 50 100 200 1000 Brook Stat 11.14 15.38 18.65 22.33 28.14 33.45 39.76 59.49 ReFH 10.41 13.95 16.78 19.79 24.58 29.03 34.84 55.36 Stat+ReFH 11.14 15.38 18.65 22.33 28.14 33.45 40.14 63.79 Drain Stat 1.78 2.14 2.41 2.72 3.20 3.64 4.16 5.78 ReFH 0.64 0.92 1.15 1.35 1.71 2.12 2.66 5.08 Stat+ReFH 1.78 2.14 2.41 2.72 3.20 3.64 4.57 8.72
3.2 Comparison of Flood Growth Curve
The flood growth curves show ReFH has a slightly steeper growth curve than the Stats method at extreme flood levels and for the Drain (Figure 3.2) but are otherwise similar at lower return periods. The curves for the Brook are very similar (Table 3.2).
Figure 3.2 Comparison of Flood Growth Curves
Brook 7.0 Stat+ReFH 6.0 Stat
5.0 ReFH
4.0
3.0 Q/QMED
2.0
1.0
0.0 0 1 2 3 4 5 6 7 8 Logistic Reduced Variate
Drain 9.0
8.0 Stat+ReFH Stat 7.0 ReFH 6.0
5.0
4.0 Q/QMED 3.0
2.0
1.0
0.0 0 1 2 3 4 5 6 7 8 Logistic Reduced Variate
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Flood Hydrology River Darwen Tributaries at Lower Darwen, Lancashire
Table 3.2 Comparison of Flood Growth Curves
Site Method 2 5 10 20 50 100 200 1000 Brook Stat 1.00 1.38 1.67 2.00 2.53 3.00 3.57 5.34 ReFH 1.00 1.34 1.61 1.90 2.36 2.79 3.35 5.32 Stat+ReFH 1.00 1.38 1.67 2.00 2.53 3.00 3.60 5.73 Drain Stat 1.00 1.20 1.35 1.53 1.80 2.04 2.34 3.25 ReFH 1.00 1.44 1.80 2.11 2.67 3.31 4.16 7.94 Stat+ReFH 1.00 1.20 1.35 1.53 1.80 2.04 2.57 4.90
The EA’s FEH Guidelines emphasise that historical flood data can be particularly valuable as a guide to confirming extreme flood events and can be used to confirm which of the extreme flood flow estimation methods are the more realistic but no such data are available on these two catchments. The statistical method estimate of QMED is normally preferred as this is based on QMED confirmed or adjusted using local flow data and as the pooling group is also based on recorded flow data. The estimates from the selected methods for the Brook are all reasonably similar and for the Drain as the catchment is urbanised ReFH can be discounted. The Stats method estimates are therefore preferred for both catchments.
3.3 Hybrid Method
To incorporate these flood flows and to generate flood hydrographs in ISIS or Flood Mapper requires the use of the ReFH boundary unit and importing the FEH catchment descriptors CSV file. Under Options the peak flood flow of the generated ReFH hydrograph can be forced to fit the peak flow given by the Stats method, referred to as the hybrid method. As the flows are reasonably similar the ReFH method could be used without any adjustments.
3.4 Climate Change
A suitable allowance for increased river flow due to climate change should then be considered based on the EA’s February 2016 guidance (Table 3.3).
Table 3.3 Peak River Flow Climate Change Allowances for North West Region
Allowance The ‘2020s’ The ‘2050s’ The ‘2080s’ category (2015 to 2039) (2040 to 2069) (2070 to 2115) Upper end 20% 35% 70% Higher central 20% 30% 35% Central 15% 25% 30%
The adopted allowance should therefore depend on the type of development proposed, which dictates the allowance category, its design life and the relevant flood zone.
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Milking Lane, Darwen Hydraulic Assessment
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HYD397_MILKING.LANE.DARWEN_HYDRAULICASSESSMENT Milking Lane, Darwen Hydraulic Assessment
APPENDIX D: CATCHMENT AREAS PLAN
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HYD397_MILKING.LANE.DARWEN_HYDRAULICASSESSMENT
Milking Lane, Darwen Hydraulic Assessment
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APPENDIX E: SURVEYED CROSS SECTIONS
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Grid and Level related to OS 12 using active GPS data network OSGB36
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Amendments Date Surveyor Description of work 10 9
UN AB F LE O T R O TH O E BT 2 A SE IN C IN TI F ON OR S M IN AT T IO HI N S AR EA
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Meridian House 58/60 Hillside Road, Frodsham, Cheshire WA6 6AG Tel: 01928 734473 Fax: 01928 735573 Email: [email protected] www.powerstiltman.co.uk
1 Davy Field Brook Darwen Section Locations
Client : Betts Associates
Surveyed By : PD/JL Date : 06/06/19 Scale
Drawn By : PD/JL Drawing No : 8297/01 1:500
Checked By : PD/JL Amendment : Section 3 Chainage : 155.0 (a) Section 4 Chainage : 216.0 (a)
Pipe: Section 6 3600Ø Chainage : 260.0 (a)
Section 5 Section 1 Section 2 Chainage : 247.5 (a) Chainage : 0.0 (a) Chainage : 59.0 (a) Pipe: 3600Ø
WL: 128.40m WL: 128.30m
Vt Scale 1:100 Vt Scale 1:100 Vt Scale 1:100 Hz Scale 1:100 Hz Scale 1:100 Hz Scale 1:100
Datum 126.00m Datum 126.00m Datum 123.00m WL: 125.21 Vt Scale 1:100 Vt Scale 1:100 Unable to obtain invert level Vt Scale 1:100 Chainage Chainage Chainage Hz Scale 1:100 Hz Scale 1:100 Hz Scale 1:100 0.000 2.193 2.521 4.635 5.149 6.815 7.016 8.090 0.000 0.264 0.608 0.620 1.005 1.829 1.876 3.700 3.745
0.000 1.825 2.061 3.638 4.126 4.713 5.877 6.411 7.611 9.086 Datum 124.00m Datum 124.00m Datum 122.00m
Level : Points Level : Points Level : Points Chainage Chainage Chainage 0.000 0.543 0.592 0.873 0.893 1.003 1.371 2.181 2.730 3.261 4.216 4.376 4.512 4.586 4.599 4.626 4.864 4.964 0.000 1.446 2.669 3.331 3.531 3.554 5.232 6.729 0.000 0.467 0.492 0.997 4.680 4.990 5.074 5.723
Easting Easting Easting Level : Points Level : Points Level : Points
Northing Northing Northing Easting Easting Easting 424370.64 369539.31 128.874 424371.87424372.05 369541.13 369541.40 128.950 127.894 424373.23424373.52 369543.16 369543.58 128.069 128.302 424374.45424374.56 369544.97 369545.13424375.16 128.240 128.952 369546.02 129.005 424380.32424380.58424380.93 369450.70424380.94424381.32 369450.70 369450.69 133.223 369450.69424382.15 369450.68 132.968 424382.19 133.544 131.880 369450.66 131.123 369450.65 127.400 133.548 424384.02424384.06 369450.61 369450.61 131.131 133.364 424325.97 369577.48 129.058 424327.55424327.75 369578.40 369578.52 128.737 424329.12 128.185 424329.54 369579.31424330.04 369579.56 128.261 369579.85 128.401 424331.05 128.256 424331.51 369580.44 369580.71 128.224 424332.55 129.238 369581.31424333.82 129.249 369582.05 129.150
Northing Northing Northing 424382.36424382.78 369345.06424382.82424383.04424383.06 369345.39 127.715 369345.42424383.14 369345.60424383.43 369345.61 127.733 424384.07 127.982 369345.68 128.025 369345.90424384.50 123.932 369346.40 126.629 424384.92 127.014 369346.74 123.898 424385.67 369347.07424385.80 123.825 424385.91424385.96 369347.66 123.898 424385.97 369347.76424386.00 369347.84424386.18 369347.89 127.022 424386.26 369347.90 123.942 369347.91 123.946 369348.06 124.121 369348.12 126.647 128.001 128.082 128.053 424376.99424378.43 369389.44 369389.42 134.113 135.503 424379.66424380.32 369389.40424380.52424380.54 369389.39 135.510 369389.39 369389.39 127.33 134.618 424382.22 134.924 369389.36424383.71 135.503 369389.34 134.066 424376.94424377.41424377.43 369357.81424377.94 369357.82 369357.82 127.893 369357.83 127.920 128.146 125.210 424381.62424381.93424382.01 369357.88424382.66 369357.89 369357.89 128.133 369357.90 128.146 128.071 127.976
Section 11 Chainage : 540.0 (a) Section 12 Chainage : 550.0 (a)
Section 9 Section 10 Chainage : 484.5 (a) Chainage : 507.0 (a)
WL: 120.19m WL : 120.04m
WL : 120.04m WL: 120.49m Vt Scale 1:100 Hz Scale 1:100 Vt Scale 1:100 Vt Scale 1:100 Vt Scale 1:100 Hz Scale 1:100 Hz Scale 1:100 Hz Scale 1:100 Datum 118.00m Datum 119.00m Datum 118.00m Datum 118.00m Chainage
Chainage Chainage Chainage 0.000 7.888 14.459 16.889 17.856 20.229 20.617 22.836 25.999 0.000 0.403 1.215 2.491 3.282 4.869 5.265 0.000 7.213 10.344 11.893 14.769 14.886 17.502 17.867 20.939 27.073 0.000 1.338 1.795 3.670 3.860 5.213 5.866 7.882 Level : Points
Level : Points Level : Points Level : Points
Easting
Easting Easting Easting
Northing Northing Northing Northing 424530.58 369110.61 121.982 424530.36 369118.50 122.098 424530.19 369125.07 120.129 424530.12 369127.49424530.10 120.044 369128.46 119.881 424530.03424530.02 369130.83 369131.22 119.977 120.548 424529.96 369133.44 121.177 424529.88 369136.60 122.652 424492.31424492.70 369132.49 369132.58424493.49 120.759 119.891 369132.77424494.73 120.192 369133.07424495.50 119.468 369133.26 119.588 424497.05424497.43 369133.63 369133.72 119.971 121.045 424522.68 369112.11 122.559 424521.21 369119.17 122.385 424520.58 369122.23 120.922 424520.26 369123.75 120.226 424519.68424519.65 369126.57 369126.68 120.171 119.967 424519.12424519.04 369129.24 369129.60 120.111 120.494 424518.42 369132.61 121.419 424517.17 369138.61 123.671 424488.30 369155.16424489.64 121.266 424490.09 369155.25 369155.28 121.006 120.361 424491.96424492.15 369155.41 369155.42 120.239 424493.50 120.491 424494.15 369155.51 369155.56 120.383 121.089 424496.17 369155.69 121.950
Section 14a Section 14b Chainage : 598.0 (a) Chainage : 600.5 (a)
Section 13 Chainage : 586.5 (a)
WL : 119.85m WL : 119.86m Vt Scale 1:100 WL : 119.36m Vt Scale 1:100 Vt Scale 1:100 Hz Scale 1:100 Hz Scale 1:100 Hz Scale 1:100 DRAINAGE DISCLAIMER Datum 118.00m Datum 118.00m Datum 118.00m ONLY DRAINAGE DISCOVERED WHILST ON SITE IS DISPLAYED ON THIS DRAWING FURTHER INVESTIGATIONS MAY NEED TO BE CARRIED OUT TO ASCERTAIN Chainage Chainage Chainage THE FULL EXTENT OF THE DRAINAGE FOR THE SITE 0.000 7.433 7.710 7.979 8.999 9.268 10.086 11.927 13.872 16.009 16.125 16.571 24.216 0.000 6.872 11.065 14.404 16.385 16.950 25.218 0.000 6.796 11.065 14.987 16.505 16.983 25.218 KEY DIMENSIONS SHOULD BE CHECKED ON SITE Level : Points Level : Points Level : Points BEFORE COMMENCEMENT OF ANY WORKS
Easting Easting Easting NOTE
Grid and Level related to OS Northing Northing Northing using active GPS data network OSGB36 424542.63 369100.45 121.842 424549.97424550.24424550.51 369101.63 369101.67 369101.71 121.901 424551.51 119.947 424551.78 121.051 369101.87 369101.92424552.59 119.761 119.860 369102.05 121.729 424554.41 369102.34 119.579 424556.33 369102.65 120.986 424558.44424558.55 369102.99424558.99 369103.00 121.731 369103.08 119.947 121.728 424566.54 369104.29 121.980 424542.33 369094.18 122.511 424549.04 369092.70 122.072 424553.13 369091.80 119.709 424556.39 369091.08 119.849 424558.33424558.88 369090.66 369090.54 119.709 121.195 424566.95 369088.76 121.455 424541.73 369091.49 122.485 424548.37 369090.03 122.072 424552.54 369089.11 119.327 424556.37 369088.27424557.85 119.364 424558.32 369087.94 369087.84 119.327 121.264 424566.36 369086.07 121.425 and transformations OSTN15/OSGM15
Amendments Date Surveyor Description of work
Section 16 Section 15 Chainage : 647.0 (a) Chainage : 617.0 (a) Section 17 Chainage :657.0 (a)
Pipe : 600Ø WL : 119.32m WL : 119.35m WL : 119.21m Vt Scale 1:100 Hz Scale 1:100 Vt Scale 1:100 Vt Scale 1:100 Hz Scale 1:100 Hz Scale 1:100 Datum 118.00m
Datum 117.00m Datum 117.00m Chainage Chainage Chainage 0.000 6.249 11.065 13.899 14.987 16.505 16.983 25.218 0.000 5.190 7.034 7.355 8.099 9.437 9.907 10.168 10.965 12.409 12.768 13.021 13.225 16.081 18.052 18.233 18.678 18.876 25.219 0.000 6.284 6.982 8.578 9.001 9.799 11.196 12.473 13.325 16.087 16.126 16.390 18.100 19.675 25.222
Level : Points Level : Points Level : Points Meridian House 58/60 Hillside Road, Frodsham, Cheshire WA6 6AG Tel: 01928 734473 Fax: 01928 735573 Email: [email protected] Easting Easting Easting www.powerstiltman.co.uk Davy Field Brook Northing Northing Northing Darwen, Blackburn 424538.12 369075.06 122.701 424544.22 369073.72 122.753 424548.92 369072.68 119.296 424551.69 369072.07424552.75 119.236 369071.84424554.23 119.346 424554.70 369071.51 369071.41 119.240 121.338 424562.74 369069.64 121.425 424531.81 369046.43 122.237 424536.88 369045.31 121.903 424538.68424538.99 369044.91424539.72 369044.84 121.355 369044.68 121.556 424541.03 120.671 424541.48424541.74 369044.40 369044.30 369044.24 119.313424542.52 120.671 120.254 369044.07424543.93 121.064 424544.28424544.52 369043.76424544.72 369043.68 369043.63 119.888 369043.58 119.243 119.315 119.081 424547.51 369042.97 122.887 424549.44424549.62424550.05 369042.54424550.24 369042.50 369042.43 120.930 369042.37 119.090 121.468 121.518 424556.44 369041.00 121.511 424531.75 369035.68 122.135 424537.89424538.57 369034.33 369034.18 121.752 121.618 424540.13424540.54 369033.84 369033.75424541.32 120.890 119.187 369033.57424542.68 121.191 369033.27424543.93 119.155 369033.00424544.76 121.600 369032.82 119.210 424547.46424547.50424547.76 369032.22 369032.21 369032.16 121.191 119.254 424549.43 120.701 369031.79 121.296 424550.96 369031.45 121.461 424556.38 369030.26 121.477 River Sections
Client : Betts Associates
Surveyed By : PD/JL Date : 05/06/19 Scale
Drawn By : PD/JL Drawing No : 8397/02a 1:500
Checked By : DG Amendment : Chainage :681.0(a) Chainage :813.0(a) Chainage :116.6(b) Section 31 Section 25 Section 21 Section 18 Chainage :340.0(b) Datum 132.00m Hz Scale1:100 Vt Scale1:100 Datum 121.00m Hz Scale1:100 Vt Scale1:100 Datum 115.00m Hz Scale1:100 Vt Scale1:100 Datum 117.00m Hz Scale1:100 Vt Scale1:100 Level :Points Level :Points Level :Points Level :Points Chainage Chainage Chainage Chainage Northing Northing Northing Northing Easting Easting Easting Easting
424815.86 369334.72 135.569 0.000 424699.74 369153.49 123.603 0.000 424659.48 368991.91 118.620 0.000 424532.18 369006.94 120.677 0.000
424700.22 369153.14 122.930 0.600 WL :123.05m
424700.65 369152.84 123.052 1.118 424659.47 368992.96 118.620 1.049 424659.46 368993.33 116.829 1.416 424701.15 369152.49 123.007 1.732 WL :119.86m
424701.71 369152.09 124.091 2.424
424703.00 369151.17 124.327 4.004
424819.83 369332.89 135.292 4.375 424659.43 368996.44 116.950 4.533 424659.43 368996.68 116.750 4.769
424704.09 369150.40 124.750 5.333 424537.50 369008.28 120.341 5.487
424538.15 369008.44 120.040 6.152
424821.71 369332.03 134.297 6.442 424538.18 369008.45 118.940 6.189 WL :119.15m 424821.92 369331.93 133.836 6.671 424659.41 368998.69 116.915 6.776 424538.80 369008.60 119.150 6.820 WL: 133.90m
424538.97 369008.64 118.802 6.997 424822.53 369331.65 133.898 7.345 424822.61 369331.62 133.761 7.426 424659.40 368999.54 118.681 7.633
424823.30 369331.30 133.847 8.191 424823.51 369331.20 134.075 8.421
424824.22 369330.88 134.331 9.197 424541.25 369009.22 119.094 9.348 Chainage :294.5(b) Section 26 Datum 124.00m Hz Scale1:100 Vt Scale1:100
424542.59 369009.55 119.182 10.727 424825.84 369330.13 135.138 10.986 Level :Points 424543.05 369009.67 119.406 11.210 Chainage Northing Easting
424659.37 369003.84 120.453 11.933
424544.92 369010.14 119.643 13.132
424828.15 369329.06 136.458 13.532
424729.45 369189.45 125.754 0.000
424729.85 369188.88 125.678 0.692 Chainage :0.0(c) Section 22 424730.24 369188.32 125.294 1.375
Datum 115.00m Hz Scale1:100 Vt Scale1:100 424548.13 369010.94 119.923 16.440 WL: 125.24m
424730.64 369187.75 125.143 2.075 424730.70 369187.67 125.242 2.178 Level :Points 424731.10 369187.10 125.090 2.874 Chainage Chainage :98.5(b) Section 32 Northing 424731.26 369186.87 126.157 3.151 Easting Datum 132.00m Hz Scale1:100 Vt Scale1:100 Level :Points Chainage Northing Easting Chainage :716.7(a) Section 19 Datum 117.00m Hz Scale1:100 Vt Scale1:100 424732.87 369184.58 127.424 5.954
424674.29 368984.75 117.488 0.000 Level :Points Chainage Northing Easting
424829.06 369346.87 135.831 0.000 Chainage :250.0(b) Section 27 Datum 126.00m Hz Scale1:100 Vt Scale1:100
424830.53 369346.59 135.452 1.500 424670.86 368984.99 116.212 3.435 424830.69 369346.56 134.637 1.659 424569.04 368986.53 121.102 0.000 WL: 134.77 424670.11 368985.04 117.001 4.190 424569.02 368986.76 118.930 0.223 Level :Points 424569.02 368986.80 118.937 0.265 Chainage Northing 424831.81 369346.35 134.648 2.799 Easting 424568.99 368987.09 118.934 0.561 424831.82 369346.35 134.772 2.811 WL :117.12m WL :116.22m 424568.99 368987.12 118.585 0.585
424832.99 369346.13 134.597 3.998 424668.46 368985.16 116.218 5.838
424833.11 369346.11 134.934 4.125 424568.84 368988.77 118.281 2.247
424568.80 368989.18 121.980 2.654 WL: 118.73
424834.63 369345.82 135.298 5.672 424568.74 368989.93 118.296 3.413
424738.30 369236.15 129.126 0.000 424666.26 368985.31 116.241 8.040
424665.54 368985.36 116.906 8.772 424568.62 368991.23 118.734 4.712 424665.15 368985.39 117.122 9.155 424568.62 368991.26 118.421 4.749 424836.49 369345.47 136.308 7.565
424568.52 368992.38 121.101 5.866 424837.33 369345.31 137.922 8.418 424568.49 368992.71 118.713 6.197
424568.46 368993.08 121.609 6.576
424740.29 369232.91 128.897 3.803 424662.46 368985.58 116.546 11.853 424740.40 369232.71 128.982 4.030 424662.42 368985.58 116.997 11.895
424740.61 369232.37 128.042 4.427 WL: 128.133m
424741.27 369231.30 128.133 5.685
424741.32 369231.22 128.970 5.778
424741.40 369231.10 128.002 5.926 Chainage :735.0(a) Section 20 424741.70 369230.61 128.036 6.496 Datum 116.00m Hz Scale1:100 Vt Scale1:100 Chainage :73.0(b) Section 33 Datum 135.00m Hz Scale1:100 Vt Scale1:100 424742.18 369229.82 128.764 7.425
424742.24 369229.72 129.142 7.544 Level :Points Chainage Northing Easting Level :Points Chainage Northing Easting
424657.02 368985.96 116.726 17.310 424743.19 369228.17 129.024 9.355 424656.90 368985.97 117.132 17.424
424586.60 368988.56 120.953 0.000 424586.58 368988.77 118.832 0.214
424831.55 369371.53 137.390 0.000 424586.54 368989.12 118.240 0.561 424831.75 369371.41 138.211 0.235 424586.54 368989.10 118.834 0.540
424832.04 369371.24 136.978 0.566 Chainage :209.0(b) Section 28 424832.25 369371.12 136.427 0.815 424586.47 368989.82 121.804 1.265
424832.32 369371.07 137.007 0.899 Datum 127.00m Hz Scale1:100 Vt Scale1:100 424653.15 368986.20 118.620 21.182 424832.39 369371.04 138.051 0.973 424832.48 369370.98 136.537 1.080 424832.66 369370.88 136.339 1.286 424832.72 369370.84 136.969 1.357 Level :Points
424833.24 369370.53 136.624 1.960 WL: 118.76m Chainage Northing
Easting 424586.29 368991.47 118.271 2.932 424833.75 369370.23 137.322 2.558 Chainage :499.5(b) Section 23 424586.05 368993.70 118.756 5.169 Datum 116.00m Hz Scale1:100 Vt Scale1:100 424586.03 368993.83 118.459 5.299 424585.94 368994.68 118.553 6.161
424752.97 369272.19 131.678 0.000 424585.93 368994.81 120.949 6.287 Level :Points 424585.92 368994.91 121.793 6.389 Chainage Northing Easting Chainage :57.0(b) Section 34
Datum 136.00m Hz Scale1:100 Vt Scale1:100 424754.36 369271.00 131.176 1.829 424754.40 369270.96 129.813 1.883
424755.08 369270.38 129.909 2.783
Level :Points 424755.18 369270.29 131.445 2.912 750Ø Pipe:
Chainage 424755.36 369270.14 129.922 3.147 WL: 129.42m Northing Brick culvert Easting 424755.37 369270.12 129.418 3.169 Code 424755.44 369270.07 129.236 3.254 424659.16 368999.54 118.681 0.000 750Ø Pipe: 424756.18 369269.43 129.922 4.235
424756.51 369269.15 129.877 4.668 424756.57 369269.09 131.402 4.752 Concrete platform 424757.00 369268.72 129.856 5.319
FPA 424838.73 369385.20 139.934 0.000 424758.17 369267.72 131.612 6.858
GL 424840.67 369384.27 139.302 2.149 424664.07 368999.57 119.529 4.909
424664.23 368999.57 119.909 5.069
GL 424841.32 369383.96 138.612 2.869 424664.55 368999.57 117.629 5.397 WL :117.22m GL 424841.62 369383.82 138.004 3.192
WA 424841.77 369383.75 138.078 3.366
Chainage :189.0(b) Section 29 424665.79 368999.58 117.219 6.632 WA 424842.67 369383.32 137.820 4.358 WL: 137.73
GL 424842.76 369383.28 137.659 4.457 Datum 128.00m Hz Scale1:100 Vt Scale1:100 424666.33 368999.58 118.355 7.172 SOF 424842.78 369383.27 138.803 4.484 WL1 424842.82 369383.25 137.724 4.522 424666.69 368999.58 117.664 7.533 WA1 424843.18 369383.08 137.733 4.924 424666.92 368999.58 117.696 7.766 424667.00 368999.58 120.465 7.843 Level :Points GL 424843.77 369382.80 139.007 5.577 424667.23 368999.58 120.358 8.075 Chainage Northing Easting
424669.46 368999.59 120.666 10.304
424765.65 369287.55 133.378 0.000 Chainage :0.00(b) Section 35 Datum 138.00m Hz Scale1:100 Vt Scale1:100 Chainage :375.5(b) Section 24 Level :Points Datum 120.00m Hz Scale1:100 Vt Scale1:100 Chainage Northing Easting 424767.73 369285.70 132.515 2.792
424768.03 369285.44 132.270 3.189 424768.22 369285.27 130.484 3.444 Level :Points Chainage 750Ø Northing Pipe: Easting WL: 130.51m 424768.67 369284.87 130.409 4.050 Brick culvert
424769.00 369284.57 130.507 4.489 750Ø Pipe: 424769.47 369284.16 130.371 5.109 424769.71 369283.95 130.406 5.431 424769.90 369283.78 132.333 5.686 424872.93 369434.50 145.911 0.000
424770.90 369282.89 133.207 7.031 424668.23 369122.60 125.387 0.000
424772.44 369281.52 134.205 9.084
424875.82 369430.91 145.426 4.608 Chainage :156.5(b) Section 30 Datum 130.00m Hz Scale1:100 Vt Scale1:100 424673.73 369122.53 125.511 5.504 Level :Points Chainage Northing Easting
424878.73 369427.29 142.654 9.249
424879.76 369426.00 141.710 10.904
424786.02 369313.10 135.170 0.000
424678.75 369122.46 123.288 10.523 424880.57 369424.99 140.682 12.197
424881.87 369423.38 140.579 14.267 424681.32 369122.43 122.888 13.095 424882.08 369423.11 140.201 14.604 424787.95 369310.69 134.602 3.089 424681.59 369122.42 121.796 13.360 WL: 140.20m
424882.63 369422.42 140.108 15.491 424682.44 369122.41 122.214 14.217 WL: 121.81m
424883.03 369421.93 140.134 16.125
424883.13 369421.80 140.580 16.282 424683.27 369122.40 121.647 15.045 424683.29 369122.40 121.812 15.063 424683.84 369122.39 122.214 15.608 424684.13 369122.39 121.811 15.900
424684.47 369122.38 121.934 16.246 424684.73 369122.38 122.148 16.503
424790.24 369307.83 133.203 6.747 424685.16 369122.37 122.650 16.935
424791.32 369306.48 132.601 8.480
424791.63 369306.10 131.654 8.968
424885.96 369418.28 142.249 20.805 WL: 131.71m
424792.13 369305.47 131.547 9.777 424792.27 369305.30 131.713 9.988
424792.56 369304.93 131.589 10.463 424792.67 369304.80 131.890 10.638
424887.21 369416.73 143.074 22.790
424793.91 369303.26 132.472 12.611
424691.65 369122.29 122.635 23.424
424888.83 369414.71 144.098 25.380 424794.66 369302.31 133.206 13.824 Amendments Checked By :DG Drawn By:PD/JL Surveyed By:PD/JL Date NOTE BEFORE COMMENCEMENTOFANYWORKS KEY DIMENSIONSSHOULDBECHECKEDONSITE and transformationsOSTN15/OSGM15 using activeGPSdatanetworkOSGB36 Grid andLevelrelatedtoOS 58/60 HillsideRoad,Frodsham,CheshireWA66AG Client : Surveyor Tel: 01928734473Fax:735573 Darwen, Blackburn Email: [email protected] Davy FieldBrook River Sections Description ofwork www.powerstiltman.co.uk Betts Associates Amendment : Drawing No:8397/02b Date :05/06/19 Meridian House 1:500 Scale Milking Lane, Darwen Hydraulic Assessment
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APPENDIX F: MODEL SCHEMATIC
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Milking Lane, Darwen Hydraulic Assessment
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APPENDIX G: FLOOD ZONE PLAN
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Milking Lane, Darwen Hydraulic Assessment
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APPENDIX H: PREDICTED FLOOD DEPTH AND LEVEL PLANS
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Milking Lane, Darwen Hydraulic Assessment
APPENDIX I: PROPOSED SCENARIO FLOOD DEPTH AND LEVEL PLANS
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Milking Lane, Darwen Hydraulic Assessment
APPENDIX J: BLOCKAGE PLANS
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Milking Lane, Darwen Hydraulic Assessment
APPENDIX K: DAVY FIELD DRAIN CULVERT CCTV SURVEY
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HYD397_MILKING.LANE.DARWEN_HYDRAULICASSESSMENT Drainage Report
Prepared For Site BARNFIELD CONSTRUCTION LTD BARNFIELD/BLACKBURN 8 Kenyon Rd, GREENBANK TERR Brierfield BLACKBURN Nelson LANCS BB9 5SP BB3 0RN
NDDS LTD GREG GREER [email protected] 01254 876654/234475
Total Defects for Project Total DRB Grades for Project Inspection Report
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BARNFIELD BLACKBURN GREENBANK TERR - CCTV Survey Report : 28/10/19
Name : NDDS LTD Contact : ALAN GREER Location : UNIT BN4 JUNCTION 7 BUSINESS PARK Town : BLACKBURN Region : LANCS Postcode : BB5 5JW Email : [email protected] Contact Number : 01254 876654/234475 Surveyor : GREG GREER Valid Certification No : L974
Client Information
Name : BARNFIELD CONSTRUCTION LTD Contact : TRACY BATE Location : 8 Kenyon Rd, Town : Brierfield Region : Nelson Postcode : BB9 5SP Tel : 01282 442300 Mobile : Email : [email protected] Fax : Site Information
Name : BARNFIELD/BLACKBURN Contact : TRACY BATE Location : GREENBANK TERR Town : BLACKBURN Region : LANCS Postcode : BB3 0RN Tel : 01282 442300 Mobile : Email : [email protected] Fax :
Total Defects for Project Total DRB Grades for Project Inspection Report
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Total Defects for Project Total DRB Grades for Project Inspection Report
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Overview
Section: 1 DRB Grade: A Pipe Size: 1050 From: MH1 Grade A To: INLET Material: Concrete Use: Surface Water
Section: 2 DRB Grade: A Pipe Size: 1050 From: MH1 Grade A To: MH2 Material: Concrete Use: Surface Water
Section: 3 DRB Grade: A Pipe Size: 1050 From: MH2 Grade A To: MH3 Material: Concrete Use: Surface Water
Section: 4 DRB Grade: A Pipe Size: 2100 From: OUTFALL Grade A To: MH3 Material: Concrete Use: Surface Water
Total Defects for Project Total DRB Grades for Project Inspection Report
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Site: GREENBANK TERR, BLACKBURN Section 1
Client: Location (Street Name): City/Town/Village Cust Job Ref. Surveyors Name: Date: BARNFIELD GREENBANK TERR BLACKBURN DAVID FISHER 28/10/2019 CONSTRUCTION LTD
Start Node Ref: MH1 Finish Node Ref: INLET Direction: U Height/Dia: 1050 Start Node Depth: 3,100.00 Finish Node Depth: 0.00 Use: S Shape: C Start Node Coordinate: Finish Node Coordinate: Material: CO Cleaned N
Drain Type Lining Type Lining Mat. Year Const. Weather Flow Cont. Length Remarks
A Z D N 10.3
Position Code Description CD Pic Video Ref 00.00m MH Start node type, manhole 0_0 00.00m WL Water level 5% 0_1 0:00:00 10.29m REM General remark 0_2 0:01:23 10.30m BRF Finish node type, major connection without 0_99 manhole 99
Total Defects for section DRB Grade for Section Inspection Report
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Descriptive Report with Remarks and Observation Images Section 1 Pos Video Ref Code Description Image 00.00m MH Start node type, manhole Image Provided - Ref: 0_0 MH1
00.00m 0:00:00 WL Water level: 5% Image Provided - Ref: 0_1 Height/Diameter
10.29m 0:01:23 REM General remark Image Provided - Ref: 0_2 DEBRIS BUILT UP AT MOUTH OF CULVERT
Total Defects for section DRB Grade for Section Inspection Report
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Pos Video Ref Code Description Image 10.30m BRF Finish node type, major Image Provided - Ref: 0_9999 connection without manhole INLET
Total Defects for section DRB Grade for Section Inspection Report
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Site: GREENBANK TERR, BLACKBURN Section 2
Client: Location (Street Name): City/Town/Village Cust Job Ref. Surveyors Name: Date: BARNFIELD GREENBANK TERR BLACKBURN DAVID FISHER 28/10/2019 CONSTRUCTION LTD
Start Node Ref: MH1 Finish Node Ref: MH2 Direction: D Height/Dia: 1050 Start Node Depth: 3,100.00 Finish Node Depth: 0.00 Use: S Shape: C Start Node Coordinate: Finish Node Coordinate: Material: CO Cleaned N
Drain Type Lining Type Lining Mat. Year Const. Weather Flow Cont. Length Remarks
A Z D N 20.89
Position Code Description CD Pic Video Ref 00.00m MH Start node type, manhole 1_0 00.00m WL Water level 5% 1_1 0:00:00 20.89m MHF Finish node type, manhole 1_99 99
Total Defects for section DRB Grade for Section Inspection Report
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Descriptive Report with Remarks and Observation Images Section 2 Pos Video Ref Code Description Image 00.00m MH Start node type, manhole Image Provided - Ref: 1_0 MH1
00.00m 0:00:00 WL Water level: 5% Image Provided - Ref: 1_1 Height/Diameter
20.89m MHF Finish node type, manhole Image Provided - Ref: 1_9999 MH2
Total Defects for section DRB Grade for Section Inspection Report
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Site: GREENBANK TERR, BLACKBURN Section 3
Client: Location (Street Name): City/Town/Village Cust Job Ref. Surveyors Name: Date: BARNFIELD GREENBANK TERR BLACKBURN DAVID FISHER 28/10/2019 CONSTRUCTION LTD
Start Node Ref: MH2 Finish Node Ref: MH3 Direction: D Height/Dia: 1050 Start Node Depth: 4,170.00 Finish Node Depth: 0.00 Use: S Shape: C Start Node Coordinate: Finish Node Coordinate: Material: CO Cleaned N
Drain Type Lining Type Lining Mat. Year Const. Weather Flow Cont. Length Remarks
A Z D N 44.67
Position Code Description CD Pic Video Ref 00.00m MH Start node type, manhole 2_0 00.00m WL Water level 5% 2_1 0:00:00 44.67m MHF Finish node type, manhole 2_99 99
Total Defects for section DRB Grade for Section Inspection Report
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Descriptive Report with Remarks and Observation Images Section 3 Pos Video Ref Code Description Image 00.00m MH Start node type, manhole Image Provided - Ref: 2_0 MH2
00.00m 0:00:00 WL Water level: 5% Image Provided - Ref: 2_1 Height/Diameter
44.67m MHF Finish node type, manhole Image Provided - Ref: 2_9999 MH3
Total Defects for section DRB Grade for Section Inspection Report
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Site: GREENBANK TERR, BLACKBURN Section 4
Client: Location (Street Name): City/Town/Village Cust Job Ref. Surveyors Name: Date: BARNFIELD GREENBANK TERR BLACKBURN DAVID FISHER 28/10/2019 CONSTRUCTION LTD
Start Node Ref: OUTFALL Finish Node Ref: MH3 Direction: U Height/Dia: 2100 Start Node Depth: 2,800.00 Finish Node Depth: 0.00 Use: S Shape: R Start Node Coordinate: Finish Node Coordinate: Material: CO Cleaned N
Drain Type Lining Type Lining Mat. Year Const. Weather Flow Cont. Length Remarks
A Z D N 22.94
Position Code Description CD Pic Video Ref 00.00m OF Start node type, outfall 3_0 00.00m WL Water level 5% 3_1 0:00:00 22.94m REM General remark 3_2 0:01:37 22.94m MHF Finish node type, manhole 3_99 99
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Descriptive Report with Remarks and Observation Images Section 4 Pos Video Ref Code Description Image 00.00m OF Start node type, outfall Image Provided - Ref: 3_0 OUTFALL
00.00m 0:00:00 WL Water level: 5% Image Provided - Ref: 3_1 Height/Diameter
22.94m 0:01:37 REM General remark Image Provided - Ref: 3_2 APPEARS TO BE 3 X LIVE CONNECTIONS WITHIN MANHOLE 3
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Pos Video Ref Code Description Image 22.94m MHF Finish node type, manhole Image Provided - Ref: 3_9999 MH3
www.viewline.tv Inspection Report
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Surveyor Certificate
www.viewline.tv Milking Lane, Darwen Hydraulic Assessment
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HYD397_MILKING.LANE.DARWEN_HYDRAULICASSESSMENT Milking Lane, Darwen Hydraulic Assessment
APPENDIX L: SITE TOPOGRAPHICAL SURVEY
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HYD397_MILKING.LANE.DARWEN_HYDRAULICASSESSMENT Milking Lane, Darwen Hydraulic Assessment
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HYD397_MILKING.LANE.DARWEN_HYDRAULICASSESSMENT Survey Operations Limited 2018 Reproduction in whole or in part by any means is prohibited without the prior permission of Survey Operations Limited.
N
Note: The survey is plotted on a plane local Grid. Orientation to National Grid. All levels relate to Ordnance Datum, achieved using the OS National GPS Network.
Survey Control Markers established for Mapping purposes only and should not be used for Construction without the written approval of Survey Operations Ltd.
Levels in parenthesis indicate top of walls.
STANDARD REFERENCE & ABBREVIATIONS
(AR)...... Assumed Route IL...... Invert Level
AB...... Air Brick IP...... Inlet Pipe
AV...... Air Valve KO...... Kerb Outlet
B/W...... Barbed Wire LB...... Letter Box
BAR...... Barrier LP...... Lamp Post
BB...... Belisha Beacon MG...... Multi-Girth
BH...... Borehole MH...... Manhole
BL...... Bed Level MKR...... Marker
BOL...... Bollard MP...... Mooring Point
BS...... Bus Stop NP...... Street Name Plate
BT Box...... British Telecom Box O/H...... Overhead
BT...... British Telecom IC O/P...... Open Paling
BRTW...... Brick Retaining Wall OE...... Overhead Electric Wire
BW...... Brick Wall OP...... Outfall Pipe
C/B...... Close Boarded OSBM...... Ordnance Survey Bench Mark
C/I...... Corrugated Iron OT...... Overhead Telecom Wire 133.63 C/P...... Chestnut Paling P/C...... Post & Chain 133.75 G 133.68 CB...... Control Box P/R...... Post & Rail 133.78 TARMAC CBW...... Concrete Block Wall P/W...... Post & Wire 133.85133.94 133.75 CCTV...... Closed Circuit TV PAV...... Paving 133.88 CD...... Cable Duct PB...... Pillar Box W/M 134.01134.04 CEL...... Cellar Light PC...... Pedestrian Crossing 133.89 133.99 CH/L...... Chain Link PP...... Petrol Pump
CHY...... Chimney PT...... Post or Pillar 134.00 134.19 134.12 CL...... Cover Level RE...... Rodding Eye G 134.12 CM...... Cable Marker RS...... Road Sign 134.33 COL...... Column RTW...... Retaining Wall 134.20 134.33 CONC...... Concrete RWP...... Rain Water Pipe 134.57 134.29 134.32 CP...... Catch Pit SAP...... Sapling
CRTW...... Concrete Retaining Wall SL...... Sump Level
134.47 MG B\W CTV...... Cable Television SoL...... Soffit Level 134.53 134.69 134.65 CUL...... Culvert SP...... Sign Post MG MG 134.82 SO1 CW...... Concrete Block Wall SPL...... Springing Level 134.76 134.83 134.71 DC...... Drainage Channel SRTW...... Stone Retaining Wall 134.53 134.81 DPC...... Damp Proof Course SV...... Stop Valve (unspecified) 134.97 134.73 G0.8 PT MP5 134.94 DR...... Drain SVP...... Soil Vent Pipe PT B\W DSW...... Dry Stone Wall SW...... Stone Wall MG 135.03 W/M BT G P\W 134.90 ECP...... Electricity Cable Pit TAC...... Tactile Paving BUSHES 134.96 134.42 G0.6 135.13 TP SO9 EIC...... Electricity Inspection Cover TB...... Traffic Bollard 135.40 MG LP EJ...... Expansion Joint TBM...... Temporary Bench Mark 135.14 MG 134.94 135.01 135.23 EJB...... Electricity Junction Box TCB...... Telephone Call Box P/W 135.15 MG TREES 134.65 135.57 135.05 EL SUB STN..Electricity Sub Station TFR...... Taken From Records 135.19 LOWER DARWEN MG 135.02 135.15 MG EL...... Eaves Level TIE...... Anchor Point (Masts/Poles) PRIMARY SCHOOL MG C\B 135.31135.28 G0.7 135.29 ELB...... Electricity Box TL...... Traffic Light 135.69 134.77 BRICK WALL 134.93 MG EP...... Electricity Pole TLB...... Traffic Light Control Box 134.92 135.19 MG ER...... Earth Rod TM...... Ticket Machine 135.25 135.29 G1.0 135.40 135.42 ETL...... Electricity Transmission Line TMC...... Tarmac SO14 MG 134.92 MG FB...... Flower Bed TP...... Telecommunications Pole 135.53 C\B 135.38 WST 134.86 134.89 FH...... Fire Hydrant TPIT...... Trial Pit G1.1 G1.8 134.42 MG 135.43135.45 FL...... Floor Level TS...... Trash Screen MG 135.73 MG W/M ASSUMED FENCE LINE FP...... Flagpole U/C...... Under Construction 135.09 135.37 MG 135.48 133.89 134.94 MILKING LANE G*.*...... Girth (of tree) U/G...... Underground 135.45 G1.3 G...... Gulley UTL...... Unable to Lift (MH,IC etc) MG 135.57 135.61 MG GAB...... Gabion UTS...... Unable to Survey 132.75 135.36 135.57 WST G0.4 134.22 GIP...... Gas Inlet Pipe VDP...... Vehicle Detector Pad EXISTING G0.4 G0.4 135.54 C/B 135.41 BUILDING MG 135.55 133.71 B/W 134.66 Bw GMKR...... Gas Marker VP...... Vent Pipe 130.92 132.71 135.40 135.52 134.61 131.82 132.31 G1.0 MG 135.53 GST...... Gas Stop Tap (Domestic) W/M...... Wire Mesh 130.36 131.74 135.43 MG 135.57 130.63 134.94 135.39 GSV...... Gas Stop Valve (Mains) WL...... Water Level 135.37 MG 131.10 132.39 134.75 133.78 WST 135.58 HSE...... Housing WM...... Water Meter 127.72 129.46 135.38 120.63 129.23 137.01 120.68 121.05 120.54 129.16 C/B 135.42 Ht...... Height WO...... Wash Out B/W 134.62 MG 133.22 137.17 135.38 135.36 HV...... High Voltage WP...... Waste Pipe 130.37 135.51 120.64 135.48 SO2 120.56 120.69 124.24124.29 134.67 I/R...... Iron Railing WST...... Water Stop Tap (domestic) 121.41 126.64 MG TARMAC 126.08 127.18 127.57 WST 134.21 137.74 ROUGH GROUND / VEGETATION 134.22 IC...... Inspection Cover WSV...... Water Stop Valve (mains) 123.99 123.97 MG 133.36 121.00 135.11 WST 120.71 121.43 130.54 MG 120.68 122.31 125.42 120.56 135.48 124.23 BT B/W 121.64 CONC RTW 125.29 137.78 135.38 120.96 122.16 124.82 135.75 TREES/BUSHES TARMAC 120.74 TREES/BUSHES 133.99 135.02 SO13 MG 132.57 120.75 133.66 120.66 125.25 127.66 135.37 126.03 MP4 121.80 122.88 MG MG C/P 120.81 120.91 134.60 134.41 G 134.55 123.13 125.45 120.63 132.18 HOUSING G BS 133.53 122.48 122.93 MG 134.17 120.80LP 120.85 CONC 121.95 123.75 C/P 120.72 120.83 123.24 124.52 DENSE TREES/BUSHES B/W MG 134.84 MG 133.41 120.88 121.06 138.14 124.58 MG 135.06 MG 134.11
120.83 130.78 136.02 133.73 120.79 120.88 120.76 122.27 138.33 134.86 133.85 121.42 135.14 133.95 120.83 121.17 RUBBLE ROUGH GROUND / VEGETATION G0.8 132.42 MG 128.18 134.26 120.68 122.01 121.39 MOUND MG 131.69 121.23 120.77 121.31 SO8 133.21 120.72 MH 124.91 133.37 135.48 121.37 CL124.18 MG 120.91 122.00 MG 133.32 133.49 121.32 121.98 135.87 C/B MG G 124.32 132.30 MG 133.19 120.87 G0.7 133.27 MG 133.20 TREES/ 132.02 G0.4 133.20 133.44 MG 133.34 121.37 TREES/ 121.93 121.39 VEGETATION G0.8 121.08 121.78 120.81 120.74 ROUGH GROUND VEGETATION 134.86 G0.8 121.27 132.67 W\M 121.57 133.30 121.91 121.56 138.49 MG C/B MG SO3 120.79 135.12 MG TREES/ MG 133.41 122.17 121.47 MG 136.21 131.79 BUSHES MG 133.53 120.78 120.78 131.23 138.57 124.14 134.89 G0.7 129.30 MG OP OPx2 129.68 133.63 G 121.75 131.61 129.36128.55 129.49 150Ø 700Ø 120.75 123.75 123.78 134.39 MG 131.73 IL129.85 IL129.73 120.77 121.46 C/P 130.75 128.79 129.78 136.26 133.17 TREES/ OP 120.79 128.11 131.53 OP 121.47 BUSHES 128.80 129.32 150Ø 129.60 120.76 121.27 150Ø 128.99 129.25 129.87 123.96 121.74 G1.0 130.21 128.98 Bw IL129.87 133.95 CONC RTW 124.93 135.80 MG G0.8 129.41 G0.7 133.20 128.45 130.46 128.97 129.17 MG 134.04 G 130.58 MG MG MG 129.56 133.97 120.83 123.95 MG G0.5 129.20 134.16 G0.7 129.53 MG 133.80 121.27 IC 124.36 138.85 G0.7 130.29 135.93 Bw 128.90 MG 129.06 Cw 122.14 CL121.37 121.61 138.79 130.68 130.42 OP MG 121.52 MG OP 128.69 120.76 LP 121.70 MG 133.05 B/W 128.98 300Ø 121.10 MG 300Ø 128.51 IL130.21 MG 128.98 130.48 Bw BOL MG IL128.53 128.76 133.35 122.26 MG 120.82 G0.5 121.71 121.69 131.93 128.27 120.71 SP 135.44 G0.8 MG 129.05 SP 121.25 134.61 129.76 130.55 BOL 135.53 DENSE TREES/ MG 128.02 128.18 128.97 SO4 120.78 120.68 BUSHES FOOT- DENSE TREES/ 129.50 127.96 122.19121.34 124.64 124.87 138.09 MG 130.04 127.90 BRIDGE BUSHES MG 127.93 130.49 133.76 121.62 121.69 124.26 MG 134.90 134.73 121.28 135.75 MG 120.81 121.49 135.25 126.95 134.84 MG 129.38 133.70 127.48 MG 134.53 KO ROUGH GROUND 128.35 129.78 MG 122.34 MG 126.81 126.64 128.69 G 120.73 120.73 121.66 123.44 131.04 120.64 125.26 129.43 135.06 MG 126.80 127.36 132.55 Client 123.33 121.38 134.08 GREENBANK TERRACE 121.46 121.70 G0.5 MG 131.60 TARMAC 127.18 135.20 122.37 121.74 126.05 126.23 121.88 124.26 130.04 135.04 135.02 134.65 MG 126.41 MG MG 121.38 121.70 RUBBLE 135.31 MG 125.51 126.56 129.99 Blackburn with Darwen Borough Council 124.48 126.12 127.44 MOUND 134.55 134.85 MG MG MG 120.69 CONC WALL 134.44 125.90 MG MG 135.50 TREES/BUSHES 121.83 MG 125.39 126.26 126.00 MG 132.81 135.67 132.24 127.00 G0.4 130.86 133.46 ROUGH GROUND/ 135.60 120.67 MG 128.66 120.55 122.42 ML3 126.01 130.42 VEGETATION Drawing Title 125.88 MG 121.30 125.58 127.88 131.24 135.76 121.39 125.44 126.58 126.91 121.70 134.36 130.34 MG 121.74 125.77 MG 131.64 134.65 TARMAC 128.38 MG 120.65 122.35 134.26 G0.6 129.68 132.10 121.77 134.23 B/W MG Topographical Survey of Land at: 120.66 129.01 131.15 131.04 133.67 MG 124.41 SO12 G1.0 121.48 MG 131.90 124.18 128.33 133.29 VEGETATION 130.90 130.12 MG 135.44 136.16 125.28 125.35 132.62 121.71 129.45 133.19 G 129.41 126.46 MG 132.94 Milking Lane 121.22 125.20 136.31 121.77 125.68 127.02 124.88 130.26 133.29 126.34 MG 120.65 TREES/BUSHES 132.84 124.63 132.54 IC LP 128.77 MG 133.25133.16 G1.0 136.38 125.01 125.30 133.29 136.58 CL120.65 120.58 133.63 129.56 132.68 G1.0 136.48 120.51 132.47 134.06 121.79 125.10 MG 136.07 Darwen MG MG 133.76 121.55 121.91 124.87 127.67 G0.2 135.11 BUSHES G1.0 133.02 131.29 130.01 133.74 134.87 126.13 MG G1.0 126.50 130.16 133.78 135.49 133.56 MG Sheet 1 of 2 121.48 121.24 135.07 120.52 129.98 124.23124.86 132.65 133.22 134.20 126.37 130.50 124.54 131.98 123.27 130.64 130.23 133.86 134.94 128.91 134.13 MG MG SO5 122.00 125.76 130.16 133.59 SO7 136.30 137.06 121.71 125.88 124.66 131.93 134.45 137.16 124.78 PT 134.71 137.26 121.56 MG Scale(s) Surveyor 125.13 127.24 123.79 PT MG SO15 135.39 134.65 WST 120.47 MG 129.07 135.16 120.48 135.70 MG 120.52 127.91 124.62 137.22 MP 124.38 134.99 1:500 121.76 MG 137.24 SO10 125.67 123.69 124.68 132.87 MG 137.33 121.87 121.38 125.16 127.37 121.52 127.48 126.85 132.10 136.00 137.16 121.98 125.25 125.15 127.54 127.27 B/W 134.00 MG 120.53 125.82 Date Drawn 120.44 126.76 124.22 124.03 MG 129.28 132.78 134.46 123.23MG 136.80 137.39 120.52 121.61 MG 125.15 123.90 136.85 ROUGH GROUND/ 135.42 G PM 123.58 MG 136.95 AUG 18 123.33 VEGETATION 137.19 121.83 121.91 MG 132.69 136.35 G 120.50 121.66 121.49 124.10 122.67122.80 123.98 136.10 137.54 121.82 124.17 129.02 121.52 136.91 121.87 121.87 126.94 132.92 120.50 121.96 123.02 121.75 121.51 122.35 122.55 122.96 123.06 133.88 134.71 137.47 Job Number Checked OP 121.50 122.01 122.99 122.61 136.99 BT 120.50 .100Ø 122.38 122.95 137.28 120.51 Cw 122.78 122.82 122.88 135.52 136.89 137.40 121.84 IL121.50 122.39 122.32 122.96 132.51 TP IC 122.71 123.87 18G072 IC 123.03 123.06 132.18 137.42 122.40 122.87 122.69 121.67 122.92 CL120.41 133.33 133.84 120.33 CL122.07 137.63 122.20 122.48 122.40122.44 MG 137.37 123.05 137.48 MP3 122.33 136.90 122.40 123.13 123.80 132.35 121.94 123.07 132.95 133.62 120.35 123.11 123.22 123.31 135.32 135.83 123.58 131.96 132.59 137.77 120.48 121.95 123.26 122.01 134.42 PT 135.03 136.67 Sheet Size & Drg Number & Revision 135.40 G PT 121.92 122.14 132.33 123.06 132.29 PT 122.37 121.62 122.88 135.74 120.23 LP 122.68 133.79 134.22 120.31 122.50 123.58 122.81 120.25 120.42 121.93 131.54 133.43 133.45
B/W 137.74 137.64 SoL122.17 BL121.29 137.54 120.54 121.97 137.34 Cw ELEC 121.60122.15 134.50 138.00 123.60 A0 18G072/001 136.72 SUB 122.32 135.80 135.23
Bw 122.39 135.12 138.04 122.57 131.93 STN. WSV 123.14 122.80 132.06 134.19 133.69 120.37 123.00 123.08 124.61 135.06 120.36 120.44 123.25 120.28 124.47 130.62 137.67 135.16 136.05 137.25 120.52 122.37 123.01 135.32 135.31
134.09
122.02 135.26 120.37 124.61 120.36 120.44 120.28 124.47 135.32 ROUGH GROUND/ 135.31 122.98 ROUGH GROUND 134.09 122.21 122.89 VEGETATION 133.01 134.43 122.02 137.95 122.91 125.85 130.89 135.26 122.08 123.46 129.25 C/P Survey Operations Limited 2018 122.49 Cw CONC 135.28 137.25 MH CL 122.77 122.03 B/W 130.62 130.96 135.39 137.31 120.40 121.85 122.23 125.64 125.91 135.93 120.32 122.44 122.46 123.46 128.88 133.88 122.31 123.31 124.80 130.76 130.97 135.66 Reproduction in whole or in part by any means MH CL 122.78 129.00 122.26 MH 129.05 122.12 CL123.01 MH 136.51 CL123.49 128.29 136.16 121.97 128.87 is prohibited without the prior permission of 123.58 137.43 120.44 MH 123.46 138.31 123.02 123.41 132.67 137.87 SP CL122.12 123.22 123.46 138.26 Bw 122.70 MH 123.04 130.78 137.57 120.43 123.34 135.65 Survey Operations Limited. CL121.95 ML2 122.84 123.15 137.70 132.05 122.66 123.39 136.43 122.95 130.70 122.48 CONC 122.31 122.77 G 124.39 125.58 128.11 120.47 123.43 135.60 121.81 122.15 138.09 120.34 W\M 122.58 137.31 121.77 123.33 123.31 126.33 122.41 123.26 128.70 122.22 TARMAC 123.07 123.28 137.73 136.99 122.88 131.77 134.67 122.68 126.19 MH 123.29 130.66 121.91 122.51 138.28 CL122.11 130.48 122.32 123.40 120.52 120.42 122.19
128.20 128.69 MH CL 124.64 138.15 122.03 Bw MH TREES/BUSHES 123.66 133.50 136.62 137.29 123.52 CL122.01 122.89 123.59 126.15 122.45 130.62 132.32 137.64 DENSE BUSHES/ 120.55 122.33 122.78 122.82 137.68 138.51 TARMAC 122.17 VEGETATION PT MH CL Cw 122.64 Cw 136.23 122.00 121.95 122.45 136.32 MH CL TARMAC 130.47 136.31 121.70 IC 122.04 MH G MH 122.20 123.26 122.10 G CL122.24 135.29 138.55 CL122.00 OHC 122.30 122.14 120.42 CL122.04 122.11 137.81 128.32 122.28 126.34 123.38 VP 122.17 123.25 130.25 121.86 121.93 COL OHC 122.20 126.49 130.39 138.39 120.63 126.47 128.31 138.33 120.50 LP COL ROUGH GROUND 137.72 122.85 123.81 Bw 123.34
121.95 121.91 122.82 131.64 122.99 120.63 122.91 132.14 129.54 137.97 120.75 138.61 122.46 122.83 133.94 136.15 136.30 137.84
126.99 128.09 G ROUGH GROUND/ 126.85 128.89 120.48 121.93 137.87 120.68 DILAPIDATED BUILDING VEGETATION 120.57 123.40 121.96 123.01 123.11 137.94 HOUSING 122.99 SO6 123.12 131.55 135.34
121.95 121.81 123.23 137.67 122.67 ML1
124.31 123.47 130.53 137.73 IC 122.70 123.07 127.16 138.05 136.30 120.68 122.82 122.87 131.81 120.74 CL122.16 122.82 128.59 136.77 138.16 122.75
122.86 122.03 BT 122.71 125.18 123.19 122.88 136.14 138.41 121.92 122.76 134.39 122.65 122.64 126.84 138.14 122.49 122.53 122.52 138.49 122.48 120.83 122.43 122.33 122.42 135.33 136.07 122.38 122.61 137.83 122.16 122.31 127.02 122.03 122.01 122.31 122.20 122.27 122.23 131.78 136.42 137.87 121.88 122.16 122.18 127.25 136.57 120.85 122.07 122.04 122.57 125.31 127.06 132.71 135.93 138.08
121.95 121.91
122.83 122.69 125.05 120.80 MP 135.69 120.78 122.51 PT 120.71 124.37 122.43 122.42 122.59 137.77 122.33 125.21 N 122.21 G 125.11 134.90 121.94 122.07 122.42 134.36 136.02 137.16 137.40 122.57 TARMAC 122.43 136.30 120.94 121.96 126.91 BRICK RTW 121.85 122.52 G CB 121.73 121.97 121.70 122.12 120.70 121.82 122.05 136.58 G 138.28 120.90 120.78 121.10 G G 122.24 122.30 125.26 121.71 121.78 IC 122.23 134.25 TAC G 122.13 122.16 122.37 135.02 IC 122.10 122.26 125.72 136.08 121.07 G G 122.01 137.00 G G 121.79 121.89 121.90 G0.2 G0.2 124.38 121.81 122.16 G0.2 ER 122.35 122.27 121.74 121.92 122.04 IC G0.2 G0.2 121.80 121.82 122.40 126.92 G 121.68 G0.2 G0.2 G0.2 ER 121.80 125.19 G 122.50 G G0.2 122.37 TARMAC BT 121.79 121.83 120.90 121.12 121.50 121.79 G0.2 121.83 135.21 121.02 G0.2 121.97 ER 121.18 121.87 G0.2 125.04 135.06 136.20 Note: IC 121.77 121.94 122.00 121.84 122.02
CL121.74 121.78 121.78 128.53 TREES/ 133.76 122.35 122.00 IC 122.20 136.03 121.59 121.89 BUSHES 134.70 The survey is plotted on a plane local
121.85
G0.2 121.84 TAC 121.81 G0.2 G0.2 G0.2 G0.2 BUSHES 133.92 133.22 138.04
122.01 TARMAC 121.96 G0.2 122.17 136.39 121.20 122.22 DILAPIDATED BUILDING 122.11 121.09 CL121.27MH 121.48 DENSE BUSHES/ 133.57 Grid. Orientation to National Grid. 130.47 122.60 124.37 VEGETATION 131.84 136.65 121.22 123.00 123.12 121.90 122.80 125.36 126.10 121.46 121.55 121.81 136.72 All levels relate to Ordnance Datum, TAC 121.91 MP2 121.91 Bw 122.10 121.99 BUSHES/VEGETATION 122.49 124.89 131.92 136.29 121.42 121.55 121.85 124.30 128.55 121.32 COL 134.63 achieved using the 121.82 123.45 LP 121.82 ER 121.81 124.18 124.76 TARMAC 122.00 122.02 121.46 121.60 OHC 121.81 121.81 129.37 137.80 122.06 G0.3 G0.3 121.96 121.34 121.50 121.92 128.35 OS National GPS Network.
122.45 121.78 G0.3 121.87 121.44 121.78 121.81 121.97 133.20 121.74 122.16 121.41 BT W/M 121.87 G0.3 121.68 121.95
121.31 121.48 TAC MH ROUGH GROUND/GRAVEL C/P 124.54 CL121.35 122.68 121.87 MH 121.80 G TARMAC CL121.84 132.05 121.37 121.69 G 121.96 Survey Control Markers established for 121.27 121.45 121.60 121.80 126.21 121.35 121.21 122.03 121.52 G 134.94 121.50 121.89 CONTAINER 121.64 121.87 121.26 121.70 127.58 121.38 122.68 TARMAC 121.60 125.48 137.21 Mapping purposes only and should not be 121.49 MH 121.48 DP1 TBM1 121.35 G CL121.32 121.66 124.92 130.11 G 124.63 121.30 121.64 122.01 124.70 121.47 121.55 used for Construction without the written 122.46 G 121.43 121.42 122.61 121.17 137.42 BUSHES 126.34 G 121.25 121.33 121.84 ROUGH GROUND
PAVIORS 121.52 121.28 PAVIORS 121.14 121.28
128.39 121.42 121.52 ROUGH GROUND/GRAVEL 127.33 approval of Survey Operations Ltd. 121.77 MG
121.43 126.26 BT 121.83 121.75 135.45 121.62 121.69 IC MH 121.55 121.84 121.95 121.31 PT 121.57 CL121.45 121.45 121.76 121.70 121.62 121.32 121.61 121.78 126.28 121.80 121.60 133.60 TAC BT 121.46 126.04 136.28 137.96 FP 121.63 MP 122.08 135.59 121.55 124.63 PT BUSHES MH PAVING 121.72 121.61 122.03 121.49 121.84 121.81 121.82 121.87 125.81 121.59LP 121.53121.68 CL121.54 121.66 125.58 TREES/ 121.68 121.84 PT 121.87 138.24 121.88 122.16 124.76 125.15 DENSE VEGETATION CB 121.93 121.88 135.30 W\M 124.65 136.42 121.83 121.49 121.59 121.65 CB 122.37 121.96 SP DILAPIDATED 122.06 125.86 122.03 BT SUB STN. 125.07 138.61 121.53 122.39 121.97 132.35 MP1 121.73 122.48 121.46 121.67 135.23 G0.2 126.17 126.23 124.73 122.00 122.51 G0.2 122.36 122.46 121.35 121.35 121.62 136.35 121.66 121.32 121.47 121.49 122.53 CONC TREES/BUSHES 138.84 G 125.15 G0.2 G0.2 125.51 121.33 TAC 122.67 121.67 EP 121.22 121.22 131.94 121.46 122.59 G0.2 122.60 121.26 121.66 125.02 W\M 121.42 121.55 121.33 EP 121.50 121.85 122.39 121.43 121.20 126.22 134.84 119.78 121.84 126.32 139.04 121.62 121.26 (121.91) (121.76) 136.54 121.15 119.72 119.96 122.11 122.87 121.49 (122.19) 120.71 121.48 125.93 121.44 121.35 121.48 STONE RTW 119.23 125.13 119.96 131.64 121.58 WEIR 121.42 I/R 118.99 I/R 123.29
119.77 122.14 (122.29) 119.72 119.68 BRIDGE 118.96 119.48 120.36 139.40 PT 121.39 119.38 125.44 126.26 135.88 LP 119.33 MG 119.00 Bw 120.03 122.31 121.44 121.74 122.89 (122.13) 119.33 121.62 PT 120.08 124.20 Sw 126.18 120.16 119.31 121.61 PT RTW 134.39 121.85 121.55 125.77 121.46 119.23 SoL120.82 121.62 121.77 127.24 BRIDGE 119.49 TREES/BUSHES 140.17 121.67 123.88 125.18 125.97 126.10 121.98 121.82 122.44 130.57 122.08 119.83 119.22
121.65 124.43 121.70 123.52 122.82 (120.27) 126.06 TARMAC Cw 121.88 122.04 BL119.30 121.56 121.87PT 121.56 123.62 124.91 (120.52) ROUGH GROUND/ 140.46 HOUSING G VEGETATION 123.23 123.67 135.83 121.58 121.67 OP 122.10 122.58 125.40 127.35 134.13 .900Ø 123.22 125.32 121.89 123.18 124.42 125.73 SoL120.24 122.13 123.14 124.53 122.40 120.51 121.56 CONTAINER IL119.34 122.04 136.96 CONC RTW 122.02 CONTAINER 123.74 123.96 140.60 123.59 127.00 125.95 123.23 123.24 119.96 121.97 125.10 122.57 122.35 123.18 124.78 121.92 123.23 121.84 122.12 124.34 122.18 122.35 127.77 123.13 129.67 123.28 123.68 122.20 122.12 DP2 124.52 128.41 140.71 126.83 Levels in parenthesis indicate top of walls. 123.79 123.12 124.64 126.14 126.74 137.41 122.22 122.20 128.84 133.41 122.55 123.95 124.44 PT 123.19 122.51 123.82 128.91 123.21 123.82 123.83 127.12 MH 123.22 122.20 123.21 127.49 122.12 140.66 CL123.81 CONTAINER 127.97 120.15 123.73 129.15 122.38 124.49 DENSE BUSHES/ 127.64
122.60 123.78 TREES/ 122.33 124.45 VEGETATION 123.84 CONC 126.24 VEGETATION 129.12 123.26 124.08 129.75 G 123.77 124.34 128.28 C/B LOWER ECCLESHILL ROAD 123.28 ROUGH GROUND/ 123.28 123.84 138.38 128.28 STANDARD REFERENCE & ABBREVIATIONS 123.28 122.68 126.59 120.34 129.16 122.92 VEGETATION 124.56 120.25 124.53
122.54 Cw 122.45 123.80 123.82 128.31 133.95
123.84 140.92 122.92 129.31 (AR)...... Assumed Route IL...... Invert Level 123.83 123.25 124.38 123.39 123.18 123.89 126.36 123.17 128.90 128.28 123.92 123.15 IC 123.32 123.29 123.12 123.99 124.42 128.34 AB...... Air Brick IP...... Inlet Pipe DP4 128.88 140.90 W\M CONC 123.73 128.80 124.34 AV...... Air Valve KO...... Kerb Outlet 122.34 IC 124.55 123.73 126.34 124.28 120.22 122.88 122.79 123.35 124.18 123.71 126.79
123.26 124.26 128.97 RTW 123.77 128.53 129.42 128.59 130.50 B/W...... Barbed Wire LB...... Letter Box 123.84 123.60 CONTAINER 124.02 123.18 124.01 133.58 123.07 BAR...... Barrier LP...... Lamp Post TARMAC 123.11 140.95 123.80 123.34 124.13 120.23 123.15 123.68 128.99 128.92 TARMAC 123.18 123.83 123.78123.75 129.38 BB...... Belisha Beacon MG...... Multi-Girth 123.84 123.32 123.04 124.04 129.20
124.60 ROUGH GROUND DENSE TREES/ BH...... Borehole MH...... Manhole 123.72 129.32 123.56 123.41 DP3 123.49 VEGETATION CONTAINER 123.35 128.92 141.01
123.35 123.85 BL...... Bed Level MKR...... Marker 123.25 123.92 123.41 123.28 123.38 123.44 CONC WALL 123.43 123.26 127.29 123.85 123.39 123.47 123.94 129.31 130.76 133.29 BOL...... Bollard MP...... Mooring Point 123.29 123.38
124.64 141.31 123.83 124.08 129.44 BS...... Bus Stop NP...... Street Name Plate 123.69 123.45 120.03 123.31 129.36 BT 123.81 123.51 C/B 142.19 124.15 SP BT Box...... British Telecom Box O/H...... Overhead 123.84 123.47 120.35 123.51 141.51 123.66 120.55 129.52 123.70 124.79 123.37 141.74 123.65 123.80 BT...... British Telecom IC O/P...... Open Paling 123.88 C/B 123.81 123.84 MG C/B 123.65 120.20 132.61 134.78 141.60 123.83 123.45 123.34 120.54 124.17 DP5 BRTW...... Brick Retaining Wall OE...... Overhead Electric Wire RTW MON TARMAC 120.46 120.50 120.63 127.52 123.83 123.66 123.43 120.69 120.51 123.57 124.49 130.78 123.84 123.87 123.83 120.74 120.58 137.96 BW...... Brick Wall OP...... Outfall Pipe
123.84 PT 123.41 142.26 142.73 CONTAINER 123.76 P/R 120.80 DAVY FIELD BROOK 124.39 C/B...... Close Boarded OSBM...... Ordnance Survey Bench Mark 123.41 123.99 124.91 123.92 123.86 123.34 120.93 124.44 133.30 142.75 C/I...... Corrugated Iron OT...... Overhead Telecom Wire 123.51 125.63 SP 138.10 143.01 123.99 125.34 130.77 124.08Cw CONC 123.43 123.82 121.27 C/P...... Chestnut Paling P/C...... Post & Chain 123.89 123.59 121.24 P/R 124.32 142.81 C/B MH 121.57 121.39 139.24 CB...... Control Box P/R...... Post & Rail CL124.02 123.89 (125.38) 124.80 124.57 MH CONTAINER 124.36 123.69 OP 143.03 CL124.30 CBW...... Concrete Block Wall P/W...... Post & Wire CONC WALL 125.45 123.64 150Ø 124.79 127.54 (128.27) P/R 124.02 126.69 IL121.36 125.69 128.83 CCTV...... Closed Circuit TV PAV...... Paving 124.25 P/R 122.70 133.28 143.13 124.35 (128.27) 128.05 121.42 121.15 123.48 134.45 140.41 143.22 W\M (126.64) 122.57 129.78 143.62 CD...... Cable Duct PB...... Pillar Box 127.97 121.41 CONC RTW 142.64 P/R 124.51 P/R 124.19 CB 123.64 121.74 131.11 CEL...... Cellar Light PC...... Pedestrian Crossing 126.17 128.15 132.48 133.92 124.57 142.78 124.67 124.94 123.75 127.36 PT 129.31 CH/L...... Chain Link PP...... Petrol Pump 121.57 125.41 124.89 124.47 122.62P/R 130.96 140.76 124.59 136.96 143.83 125.04 132.37 CHY...... Chimney PT...... Post or Pillar 133.66
124.82 125.08 124.92 P/R 125.69 P/R DP6 142.91 CL...... Cover Level RE...... Rodding Eye 125.71 126.08 125.24 138.13 123.84 127.13 134.83 CM...... Cable Marker RS...... Road Sign
128.77 139.83 143.63 143.58 130.55 P/R 138.59 140.64 143.03 COL...... Column RTW...... Retaining Wall 132.57 141.02 134.28 143.67 CONC...... Concrete RWP...... Rain Water Pipe 134.91 135.90 CP...... Catch Pit SAP...... Sapling 141.95 137.06 CRTW...... Concrete Retaining Wall SL...... Sump Level
138.09 CTV...... Cable Television SoL...... Soffit Level 138.76 140.38 139.16 CUL...... Culvert SP...... Sign Post
CW...... Concrete Block Wall SPL...... Springing Level
DC...... Drainage Channel SRTW...... Stone Retaining Wall
DPC...... Damp Proof Course SV...... Stop Valve (unspecified)
DR...... Drain SVP...... Soil Vent Pipe
DSW...... Dry Stone Wall SW...... Stone Wall
ECP...... Electricity Cable Pit TAC...... Tactile Paving
EIC...... Electricity Inspection Cover TB...... Traffic Bollard
EJ...... Expansion Joint TBM...... Temporary Bench Mark
EJB...... Electricity Junction Box TCB...... Telephone Call Box
EL SUB STN..Electricity Sub Station TFR...... Taken From Records
EL...... Eaves Level TIE...... Anchor Point (Masts/Poles)
ELB...... Electricity Box TL...... Traffic Light
EP...... Electricity Pole TLB...... Traffic Light Control Box
ER...... Earth Rod TM...... Ticket Machine
ETL...... Electricity Transmission Line TMC...... Tarmac
FB...... Flower Bed TP...... Telecommunications Pole
FH...... Fire Hydrant TPIT...... Trial Pit
FL...... Floor Level TS...... Trash Screen
FP...... Flagpole U/C...... Under Construction
G*.*...... Girth (of tree) U/G...... Underground
G...... Gulley UTL...... Unable to Lift (MH,IC etc)
GAB...... Gabion UTS...... Unable to Survey
GIP...... Gas Inlet Pipe VDP...... Vehicle Detector Pad
GMKR...... Gas Marker VP...... Vent Pipe
GST...... Gas Stop Tap (Domestic) W/M...... Wire Mesh
GSV...... Gas Stop Valve (Mains) WL...... Water Level
HSE...... Housing WM...... Water Meter
Ht...... Height WO...... Wash Out
HV...... High Voltage WP...... Waste Pipe
I/R...... Iron Railing WST...... Water Stop Tap (domestic)
IC...... Inspection Cover WSV...... Water Stop Valve (mains)
Client Blackburn with Darwen Borough Council
Drawing Title Topographical Survey of Land at:
Milking Lane
Darwen
Sheet 2 of 2
Scale(s) Surveyor 1:500 MP
Date Drawn AUG 18 PM Job Number 18G072 Checked TP
Sheet Size & Drg Number & Revision A0 18G072/002 Milking Lane, Darwen Hydraulic Assessment
APPENDIX M: NOTES OF LIMITATIONS
The data essentially comprised a study of available documented information from various sources together with discussions with relevant authorities and other interested parties. There may also be circumstances at the site that are not documented. The information reviewed is not exhaustive and has been accepted in good faith as providing representative and true data pertaining to site conditions. If additional information becomes available which might impact our l conclusions, we request the opportunity to review the information, reassess the potential concerns and modify our opinion if warranted.
It should be noted that any risks identified in this report are perceived risks based on the available information.
This report was prepared by Betts Hydro Ltd for the sole and exclusive use of the titled client in response to particular instructions. Any other parties using the information contained in this report do so at their own risk and any duty of care to those parties is excluded.
This document has been prepared for the titled project only and should any third party wish to use or rely upon the contents of the report, written approval from Betts Associates Ltd must be sought.
Betts Associates Ltd accepts no responsibility or liability for the consequences of this document being used for the purpose other than that for which it was commissioned and for this document to any other party other than the person by whom it was commissioned.
HYD397_MILKING.LANE.DARWEN_HYDRAULICASSESSMENT