ANNUAL SURVEY REPORT 2018 Hurst Spit to Hengistbury Head

Southeast Regional Coastal Monitoring Programme

ANNUAL SURVEY REPORT 2018

Hurst Spit To Hengistbury Head

AR 152 November 2018

Cover photograph: New Forest District Council - Coastal Team Annual Survey Report Christchurch Bay 2018

Channel Coastal Observatory National Oceanography Centre European Way Southampton SO14 3ZH

Tel: +44 (0)23 8059 8467 Fax: +44 (0)2380 596320 e-mail: [email protected] Website: www.channelcoast.org

Document Title: Annual Report 2018

Hurst Spit to Hengistbury Head

Reference: AR152

Status: FINAL

Date: 18 March 2019

Project Name: Southeast Regional Coastal Monitoring Programme

Author: P. Alderton

Checked By: S. Hawkins

Approved By: C. Thompson

Annual Survey Report Christchurch Bay 2018

Southeast Regional Coastal Monitoring Programme

Annual Survey Report 2018 – Hurst Spit to Hengistbury Head

1. Introduction

Analysis presented in this report provides an overview of beach changes since the commencement of the Southeast Regional Coastal Monitoring Programme in 2002. The first beach surveys took place during the summer of 2002 (i.e. the Baseline year) and changes are reported until September 2018.

The results are given for individual Survey Units spanning winter 2017 to autumn 2018. The Survey Unit report is updated following each survey and distributed to coastal engineers. In this way, a rapid assessment is made of changes from survey to survey, in addition to a comparison of longer term changes. On completion of the autumn surveys, the individual reports from all Survey Units are collated into this Cell‐wide annual survey report, to provide a useful long‐term record of short‐term changes.

Data are presented at several levels: • Comparison with previous survey • Tables with 2018 CSA change and m2 as % • Graphs of change in cross‐sectional area through time • Survey Unit maps summarising beach profile change from 2017 to 2018 • Survey Unit maps summarising beach profile change from Baseline year to 2018 • Topographic difference models

The Survey Unit maps indicate the location of the profiles, superimposed on the 2016 aerial photography (note that the profile lines may have been extended, for clarity).

2. Profile analysis

Where possible, longer‐term records from earlier programmes are also presented in the profile analysis, although historical data was often collected using significantly different survey techniques, or specifications. Cross‐sectional area is measured relative to a Reference Level which, typically, is the elevation of Mean Low Water Springs (Figure 1).

Annual Survey Report Christchurch Bay 2018

Figure 1: Profile cross‐sectional area

The trend in cross‐sectional area above MLWS is presented as a graph for each profile (Figure 2).

Figure 2: Example of cross‐sectional area above Mean Low Water Springs, through time

3. Hydrodynamic data

Wave reports for all coastal monitoring programme wave buoys within the Cell are included. The wave reports include summary statistics for the period spanning November 2017 to October 2018 for the Waverider buoy deployed at Milford‐on‐Sea.

ii Annual Survey Report Christchurch Bay 2018

Survey Unit 5fSU01 Location Hurst Spit

Survey Survey type Comments dates This period is characterised by minimal change in beach level. There has been some low level Autumn to 22/09/2017 accretion at profiles 5f00017, 20, 37, 49, 52, 54 and Spring 30/04/2018 56 of between 5 and 10%. The most erosion can be seen at profile 5f00064 at just ‐3.3%. The general trend of change over this period is of Spring to 30/04/2018 low level erosion with minimal change across the Autumn 27/09/2018 survey unit. Profiles 5f00037, 52 and 66 show the most significant erosion. Minimal changes have occurred over the past 12 Profile months. There has been some low level accretion at Spring to 11/04/2017 the distal end of the spit at profiles 5f00015, 17 and Spring 30/04/2018 20 and at profiles 5f00049, 52 and 54, the area of spit immediately east of the breakwater. There has been some significant change to the spit over this period. The most accretion has occurred to the distal end of the spit at profiles 5f00012, 15 and Baseline to 07/11/2003 17 of up to 43%. While erosion and accretion is Spring 30/04/2018 variable across the spit the biggest area of erosion is west of the elbow where profiles 5f00037, 39, 42, 45 and 47 have all eroded by more than 10%. Most erosion over this period has occurred to the Spring to 11/04/2017 lower beach both east and west of the breakwater. Spring 30/04/2018 There has been some accretion above this band of erosion suggesting a change in berm position. Topographic There has been significant erosion immediately east difference of the breakwater with only the back slope of the model Baseline to 07/11/2003 spit accreting in this area. To the east of the spit the Spring 30/04/2018 lower beach has accreted and the back of the beach has eroded. There have been numerous beach operations across the spit during this period.

Profile cross‐sectional area change: seasonal changes

Autumn to Spring Spring to Autumn Elevation of Profile Sept 2017 to Apr 2018 Apr 2018 to Sept 2018 Reference Surface (OD) (m2) % (m2) %

5f00012 ‐2.5 ‐1.0% 0.0 0.0%

5f00015 3.2 1.4% ‐0.6 ‐0.3%

Annual Survey Report Christchurch Bay 2018

5f00017 14 6.7% ‐8.8 ‐3.9%

5f00020 17 7.5% ‐11 ‐4.3%

5f00022 ‐1.1 ‐0.4% 2.9 1.0%

5f00024 1.0 0.4% ‐3.1 ‐1.2%

5f00027 0.5 0.1% ‐1.4 ‐0.4%

5f00029 2.9 1.1% ‐0.7 ‐0.3%

5f00032 ‐7.2 ‐2.7% 4.3 1.6%

5f00034 7.5 2.9% ‐8.6 ‐3.2%

5f00037 13 5.3% ‐13 ‐5.1% MLWS 5f00039 8.2 3.7% ‐6.1 ‐2.6% ‐1.13m

5f00042 ‐3.1 ‐1.3% ‐3.6 ‐1.6%

5f00045 ‐3.8 ‐1.7% ‐5.1 ‐2.3%

5f00047 2.6 1.0% ‐0.2 ‐0.1%

5f00049 24 9.3% ‐7.1 ‐2.5%

5f00052 38 12% ‐29 ‐8.4%

5f00054 22 7.7% ‐12 ‐3.9%

5f00056 27 6.5% ‐15 ‐3.3%

5f00058 1.6 0.5% 3.1 1.0%

5f00060 ‐5.0 ‐1.8% 3.9 1.4%

5f00062 ‐4.6 ‐1.8% 5.5 2.3%

5f00064 ‐7.1 ‐3.3% 7.1 3.4%

5f00066 4.5 1.9% ‐16 ‐6.5%

Annual Survey Report Christchurch Bay 2018

Profile cross‐sectional area change: annual and longer‐term changes

Spring to Spring Baseline to Spring Elevation of Profile Apr 2017 to Apr 2018 Nov 2003 to Apr 2018 Reference Surface (OD) (m2) % (m2) %

5f00012 ‐3.7 ‐1.5% 38 18%

5f00015 12 5.3% 69 43%

5f00017 21 10% 57 33%

5f00020 18 7.7% 20 8.8%

5f00022 1.5 0.5% ‐9.5 ‐3.1%

5f00024 ‐1.5 ‐0.6% ‐18 ‐6.4%

5f00027 ‐1.0 ‐0.3% 3.3 1.0%

5f00029 1.5 0.6% 19 7.4%

5f00032 ‐7.0 ‐2.6% 28 12%

5f00034 8.2 3.2% 27 11%

5f00037 9.7 4.1% ‐30 ‐11% MLWS 5f00039 10 4.7% ‐45 ‐16% ‐1.13m 5f00042 0.5 0.2% ‐38 ‐14%

5f00045 ‐8.2 ‐3.6% ‐31 ‐12%

5f00047 ‐4.0 ‐1.5% ‐43 ‐14%

5f00049 16 5.9% ‐10 ‐3.5%

5f00052 22 7.0% 41 14%

5f00054 26 9.4% ‐3.2 ‐1.0%

5f00056 13 3.0% 15 3.6%

5f00058 ‐5.8 ‐1.8% ‐11 ‐3.3%

5f00060 ‐13 ‐4.5% ‐15 ‐5.2%

5f00062 ‐5.6 ‐2.2% ‐15 ‐5.9%

5f00064 ‐2.4 ‐1.1% ‐4.4 ‐2.1%

Annual Survey Report Christchurch Bay 2018

5f00066 7.4 3.2% 18 8.0%

Topographic net volume change: annual and longer‐term changes

Spring to Spring Baseline to Spring Survey Unit/ Elevation of Groyne Bay/ Apr 2017 to Apr 2018 Nov 2003 to Apr 2018 Reference Surface Section (OD) (m3) % (m3) %

MLWS 5fSU01 ‐6,902 ‐1.1% 180,909 39% ‐1.13m

Volume above reference surface (m3)

Date of survey 5fSU01

Nov 2003 464,542

March 2007 533,983

March 2008 558,544

March 2009 556,793

April 2010 556,268

April 2011 534,295

March 2012 574,170

March 2013 591,117

March 2014 583,272

April 2015 678,739

March 2016 690,517

April 2017 652,353

April 2018 645,451

Annual Survey Report Christchurch Bay 2018

Survey Unit 5fSU02 Location Milford‐on‐Sea

Survey Survey type Comments dates The general trend over this period is accretion. Profile 5f00074 has accreted the 08/09/2017 Autumn to Spring most with an increase in material of 16m2. 29/05/2018 There has been some low level erosion at profiles 5f00068, 76, 83, 84, 86 and 98. There has been low level accretion at the east of the survey unit with some more substantial 29/05/2018 Spring to Autumn losses to the profiles in the west. Profiles 28/09/2018 5f00079A and 80A have eroded by 18m2, with a further 5 profiles eroding by ≥10m2. The general trend over this period is accretion, with the most significant gains in 23/05/2017 beach material >15m2 at profiles 5f00074 and Spring to Spring Profile 29/05/2018 79A. There has also been significant erosion at profiles 5f00083, 84 and 85 west of the White House. The changes over this period are mixed, with some varying levels of both accretion and erosion. Profile 5f00080 has eroded the most over this period losing 21m2. The changes at profile 5f00091 are down to the difference in 13/07/2009 Baseline to Spring modelling over the rock armour and are not 29/05/2018 an accurate representation of change in mobile sediment. Changes to the section of beach east of the White House are mitigated by management of the sediment levels through recycling works. The lower beach over much of the survey unit has accreted over this period. The four groyne 23/05/2017 Spring to Spring bays west of the White House have eroded. A Topographic 29/05/2018 difference narrow band of the upper beach has also model eroded to the east of the White House. 01/11/2000 The trend over this period is erosion across Baseline to Spring 29/05/2018 the survey unit.

Annual Survey Report Christchurch Bay 2018

Profile cross‐sectional area change: seasonal changes

Autumn to Spring Spring to Autumn Elevation of Profile Sept 2017 to May 2018 May 2018 to Sept 2018 Reference Surface (OD) (m2) % (m2) %

5f00068 ‐0.5 ‐0.7% 0.7 1.0%

5f00069 0.9 8.1% 6.8 55%

5f00070 0.4 2.6% 4.0 29%

5f00071 3.6 32% 4.5 30%

5f00072 1.4 26% ‐0.2 ‐2.3%

5f00073 2.0 54% 0.0 0.4%

5f00074 16 25% ‐1.9 ‐2.3%

5f00074A 9.4 12% ‐5.1 ‐5.8%

5f00075 8.3 18% 0.1 0.2%

5f00075A 5.6 11% 0.2 0.3%

5f00076 ‐3.7 ‐11% 1.3 4.1%

5f00076A 2.7 8.1% ‐0.4 ‐1.2% MLWS ‐0.7m 5f00077 7.1 19% ‐7.6 ‐18%

5f00077A 9.9 25% ‐12 ‐25%

5f00078 5.2 9.8% ‐16 ‐27%

5f00078A 3.2 4.4% ‐9.9 ‐13%

5f00079 3.5 6.3% ‐11 ‐18%

5f00079A 7.2 14% ‐18 ‐30%

5f00080 3.8 7.4% ‐12 ‐22%

5f00080A 15 43% ‐18 ‐35%

5f00081 7.0 26% ‐3.0 ‐8.8%

5f00082 ‐ ‐ ‐ ‐

5f00083 ‐0.5 ‐1.8% ‐0.9 ‐2.9% Annual Survey Report Christchurch Bay 2018

5f00084 ‐1.9 ‐5.1% ‐5.0 ‐14%

5f00085 1.6 5.0% ‐11 ‐32%

5f00086 ‐0.8 ‐4.4% ‐0.9 ‐5.1%

5f00088 2.5 13% ‐7.9 ‐36%

5f00091 5.5 63% ‐2.9 ‐21%

5f00098 ‐0.4 ‐0.6% ‐2.6 ‐4.5%

5f00099 5.2 10% ‐1.5 ‐2.8%

Profile cross‐sectional area change: annual and longer‐term changes

Spring to Spring Baseline to Spring Elevation of Profile May 2017 to May 2018 July 2009 to May 2018 Reference Surface (OD) (m2) % (m2) %

5f00068 ‐3.0 ‐4.4% ‐7.4 ‐10%

5f00069 ‐1.8 ‐13% ‐12 ‐49%

5f00070 0.1 0.5% ‐7.4 ‐35%

5f00071 2.3 19% ‐9.0 ‐37%

5f00072 ‐0.2 ‐3.4% ‐2.0 ‐22%

5f00073 2.0 54% 0.1 1.6%

5f00074 17 26% ‐6.1 ‐7.0% MLWS ‐0.7m 5f00074A 13 18% 1.0 1.1%

5f00075 11 25% 0.0 0.0%

5f00075A 1.8 3.3% 6.1 12%

5f00076 ‐5.7 ‐15% 6.3 25%

5f00076A 0.0 ‐0.1% 11 42%

5f00077 2.3 5.5% 9.0 26%

5f00077A 4.0 9.0% 13 36%

5f00078 10 21% 9.6 20% Annual Survey Report Christchurch Bay 2018

5f00078A 10 15% 1.5 2.0%

5f00079 8.8 17% ‐2.9 ‐4.7%

5f00079A 16 35% ‐2.5 ‐4.1%

5f00080 11 26% ‐21 ‐27%

5f00080A 14 41% ‐16 ‐24%

5f00081 3.6 12% ‐5.6 ‐14%

5f00082 ‐ ‐ ‐ ‐

5f00083 ‐6.3 ‐17% ‐3.5 ‐10%

5f00084 ‐12 ‐26% ‐5.0 ‐12%

5f00085 ‐6.1 ‐16% ‐7.2 ‐18%

5f00086 3.5 25% ‐7.8 ‐31%

5f00088 8.6 65% ‐3.7 ‐14%

5f00091 4.7 50% 13 741%

5f00098 0.5 0.9% ‐0.8 ‐1.3%

5f00099 0.7 1.2% ‐1.5 ‐3.0%

Topographic net volume change: annual and longer‐term changes

Spring to Spring Baseline to Spring Survey Unit/ Elevation of Groyne Bay/ May 2017 to May 2018 July 2009 to May 2018 Reference Section Surface (OD) (m3) % (m3) %

MLWS 5fSU02 ‐1,982 ‐2.7% ‐36,661 ‐34% ‐0.7m

Annual Survey Report Christchurch Bay 2018

Volume above reference surface (m3)

Date of survey 5fSU02

Nov 2000 53,291*

June 2006 54,080*

August 2008 21,351**

July 2009 28,553**

May 2010 30,763**

May 2011 61,650*

March 2012 67,379*

March 2013 101,758

March 2014 97,032

April 2015 107,297

March 2016 101,957

May 2017 106,220

May 2018 111,963

Annual Survey Report Christchurch Bay 2018

*Surveys from November 2000, June 2006, May 2011 and March 2012 extend across the entire survey unit. However, the method of data collection means that there is no data across the rock armour. From March 2013 – May 2018 baseline surveys were completed with a laser scanner and this data includes the rock armour hence the higher volumes. **Surveys from August 2008 ‐ May 2010 cover just the area east of the White House which is why these volumes are so low.

Annual Survey Report Christchurch Bay 2018

Survey Unit 5fSU03 Location Hordle Cliffs

Survey Survey type Comments dates There has been some erosion to the east end 23/03/2016 of the survey unit with losses at profiles Spring to Spring 20/04/2018 5f00100, 101 and 103. The west has experienced some accretion. Profile Over this period there has been erosion across 15/08/2006 the survey unit. The biggest loses occurring at Baseline to Spring 20/04/2018 profiles 5f00100, 101 and 103, with profile 5f00100 eroding 25m2. The beach immediately west of the wooden groyne has eroded over this period with a thin 23/03/2016 band of erosion extending across the survey Spring to Spring 20/04/2018 unit along the lower beach. There has been Topographic some accretion to the upper beach at the difference western extent of the survey unit. model There have been two main bands of accretion during this period, to the lower beach and the 01/11/2000 Baseline to Spring upper beach. Much of the lower beach to the 20/04/2018 west of the unit and the mid beach throughout the unit has eroded.

Profile cross‐sectional area change: annual and longer‐term changes

Spring to Spring Baseline to Spring Elevation of Profile Mar 2016 to Apr 2018 Aug 2006 to Apr 2018 Reference Surface (OD) (m2) % (m2) %

5f00100 ‐2.5 ‐3.6% ‐25 ‐27%

5f00101 ‐6.6 ‐11% ‐13 ‐20%

5f00103 ‐2.6 ‐3.6% ‐10 ‐13% MLWS 5f00105 4.6 4.5% ‐5.0 ‐4.5% ‐0.7m

5f00107 8.4 6.3% ‐1.4 ‐1.0%

5f00111 8.0 5.1% ‐1.4 ‐0.9%

5f00114 8.6 4.1% ‐1.3 ‐0.6%

Annual Survey Report Christchurch Bay 2018

Survey Unit 5fSU06 Mudeford Quay to Location Highcliffe

Survey Survey type Comments dates There has been a loss of material at most profiles over this period. Profile 5f00284 has 19/09/2017 Autumn to Spring eroded 20m2. Meanwhile profiles 5f00235, 25/04/2018 239 and 292 have all accreted by more than 6m2. Changes to the beach have been variable over this period. The biggest changes have been at 24/03/2017 profiles 5f00276, 288 and 292, the latter Spring to Spring 25/04/2018 having accreted by 45m2. There have also been significant losses at profiles 5f00244, 248 Profile and 253. Changes to the beach have been significant and variable over this period. The biggest losses have occurred at profiles 5f00268, 272 03/06/2003 and 300 with losses of 33m2 at 5f00300. Baseline to Spring 25/04/2018 Profiles 5f00239, 244, 248, 288 and 292 have accreted the most over this period. Profiles 5f00244 and 248 both gaining more than 70m2. 25/04/2018 There has been some significant accretion at Spring to Autumn 24/09/2018 profiles 5f00268, 272 and 280. There has been mixed erosion and accretion across the survey unit. Highcliffe has accreted at the lower and upper beach with a band of erosion in between. The undefended section of beach between Highcliffe and Avon has 19/09/2017 Spring to Spring eroded at the upper beach and accreted at 25/04/2018 the lower beach. Avon beach has shown mixed change with patches of erosion and accretion. There has been some erosion Topographic immediately east of Christchurch harbour difference entrance. model The east of the survey unit at Highcliffe is characterised almost exclusively by accretion. The two groyne bays furthest east show more mixed change with some erosion and 28/08/2002 Baseline to Spring accretion. The 6 groyne bays furthest east at 25/04/2018 Avon beach have eroded as has the undefended stretch of beach 600m east of these groyne bays. The most western groyne bays in the survey unit have accreted with a Annual Survey Report Christchurch Bay 2018

Survey Survey type Comments dates channel of erosion extending from Christchurch harbour entrance. There have been numerous beach operations across the beach during this period.

Profile cross‐sectional area change: seasonal changes

Autumn to Spring Spring to Autumn Elevation of Profile Sept 2017 to April 2018 April 2018 to Sept 2018 Reference Surface (OD) (m2) % (m2) %

5f00229 ‐3.2 ‐5.4% ‐2.1 ‐3.8%

5f00230 ‐1.5 ‐4.9% ‐0.6 ‐2.1%

5f00235 6.8 16% ‐4.1 ‐8.1%

5f00239 6.1 4.5% 2.0 1.4%

5f00244 ‐8.6 ‐6.0% 7.0 5.2%

5f00248 ‐6.5 ‐4.5% ‐4.4 ‐3.2%

5f00253 ‐9.4 ‐8.2% ‐2.8 ‐2.7%

5f00257 ‐1.9 ‐1.3% 1.6 1.1%

5f00261 ‐4.0 ‐2.8% 2.1 1.5% MLWS 5f00264 ‐5.3 ‐4.2% 2.3 1.9% ‐0.31m 5f00268 ‐5.0 ‐7.5% 12 20%

5f00272 ‐0.5 ‐1.2% 7.8 20%

5f00276 2.0 4.0% 3.4 6.6%

5f00280 0.1 0.1% 8.1 11%

5f00284 ‐20 ‐26% 5.7 10%

5f00288 1.6 1.2% 1.4 1.1%

5f00292 6.4 5.1% ‐7.8 ‐5.9%

5f00296 ‐5.1 ‐3.6% ‐3.2 ‐2.3%

5f00300 ‐0.9 ‐19% ‐0.9 ‐24% Annual Survey Report Christchurch Bay 2018

Profile cross‐sectional area change: annual and longer‐term changes

Spring to Spring Baseline to Spring Elevation of Profile Mar 2017 to April 2018 June 2003 to April 2018 Reference Surface (OD) (m2) % (m2) %

5f00229 ‐0.1 ‐0.1% ‐3.4 ‐5.7%

5f00230 1.4 5.1% ‐0.6 ‐1.9%

5f00235 7.2 17% ‐1.6 ‐3.1%

5f00239 5.1 3.8% 51 56%

5f00244 ‐7.5 ‐5.3% 74 121%

5f00248 ‐8.8 ‐6.0% 75 119%

5f00253 ‐9.1 ‐7.9% 28 36%

5f00257 1.4 1.0% 5.7 4.0%

5f00261 ‐1.0 ‐0.7% ‐0.4 ‐0.3% MLWS 5f00264 ‐1.4 ‐1.1% ‐17 ‐12% ‐0.31m 5f00268 ‐4.6 ‐7.1% ‐29 ‐32%

5f00272 4.7 14% ‐29 ‐42%

5f00276 10 25% ‐14 ‐22%

5f00280 9.0 14% ‐6.7 ‐8.0%

5f00284 3.1 5.7% 1.2 2.0%

5f00288 20 18% 38 40%

5f00292 45 53% 26 25%

5f00296 4.0 3.0% ‐1.2 ‐0.8%

5f00300 ‐1.8 ‐32% ‐33 ‐90%

Annual Survey Report Christchurch Bay 2018

Survey Unit 5fSU08 Location Mudeford Harbour

Survey Survey type Comments dates 08/03/2017 There has been minimal change over this Spring to Spring 25/06/2018 period.

25/06/2018 There has been minimal change over this Spring to Autumn Profile 21/09/2018 period.

05/11/2003 There has been a small increase in volume Baseline to Spring 25/06/2018 across the profile line over this period.

12/06/2012 There has been minimal change over this Spring to Spring Topographic 25/06/2018 period. difference 11/06/2007 There has been minimal change over this Baseline to Spring model 25/06/2018 period.

Profile cross‐sectional area change: seasonal changes

Spring to Autumn Elevation of Profile June 2018 to Sept 2018 Reference Surface (OD) (m2) % MLWS 5f00312 0.4 2.3% ‐0.31m

Profile cross‐sectional area change: annual and longer‐term changes

Spring to Spring Baseline to Spring Elevation of Profile Mar 2017 to June 2018 Nov 2003 to June 2018 Reference Surface (OD) (m2) % (m2) % MLWS 5f00312 ‐0.8 ‐3.5% 1.0 4.6% ‐0.31m

Annual Survey Report Christchurch Bay 2018

Topographic net volume change: annual and longer‐term changes

Spring to Spring Baseline to Spring Survey Unit/ Elevation of Groyne Bay/ June 2012 to June 2018 June 2007 to June 2018 Reference Section Surface (OD) (m3) % (m3) %

MLWS 5fSU08 ‐69 ‐0.6% 116 1% ‐0.31m

Volume above reference surface (m3)

Date of survey 5fSU08

June 2007 11,486

June 2012 11,671

June 2018 11,602

Annual Survey Report Christchurch Bay 2018

Survey Unit 5fSU09 Location Mudeford Sandbank

Survey Survey type Comments dates The change has been variable over this period. The biggest losses, up to 14m2 have occurred at profiles Autumn to 12/09/2017 5f00332 and 364A. Profile 5f00323 has shown the Spring 26/06/2018 most accretion with an increase in beach level of 11m2 at this profile. There have been some minor changes to the beach over this period. With some erosion at profiles Spring to 26/06/2018 5f00321, 323, 344, 356 and 367A. Whilst profiles Autumn 21/09/2018 5f00325, 332, 338, 361A and 364A have all experienced some low levels of accretion. Profile Change to the beach level has been minimal over Spring to 08/03/2017 this period. The most significant change occurring at Spring 26/06/2018 profile 5f00338 with a loss to the beach level of 9m2. There has been some significant changes over this period, mostly with an increase in the beach level. Baseline to 28/11/2003 Profiles 5f00338, 349 and 361A have eroded with Spring 26/06/2018 361A having lost just under 9m2. Profiles 5f00325 and 364A have experienced the most accretion with profile 5f00325 gaining 23m2. There has been minimal change over much of the beach. There has been some accretion to the lower beach in the 5th groyne bay from the distal end of Summer to 12/09/2017 the spit. The two groyne bays closest to the distal Autumn 26/06/2018 end of the spit have eroded over this period. The Topographic beach on the harbour side at the distal end has also difference accreted. model The most significant accretion over this period is to the distal end of the spit, while the groyne bays east Baseline to 07/11/2003 from the proximal end of the spit have also Autumn 21/09/2018 accreted. There has been some erosion to the upper beach around the dunes.

Profile cross‐sectional area change: seasonal changes

Autumn to Spring Spring to Autumn Elevation of Profile Sept 2017 to June 2018 June 2018 to Sept 2018 Reference Surface (OD) (m2) % (m2) %

5f00321 3.4 10% ‐3.0 ‐8.2%

Annual Survey Report Christchurch Bay 2018

Profile cross‐sectional area change: seasonal changes

5f00323 11 54% ‐1.8 ‐5.7%

5f00325 ‐0.7 ‐0.5% 0.3 0.2%

5f00332 ‐14 ‐11% 2.6 2.3%

5f00338 ‐3.9 ‐7.4% 4.6 9.4%

5f00344 2.8 2.6% ‐3.7 ‐3.4% MLWS ‐0.31m 5f00349 ‐0.4 ‐0.3% 0.0 0.0%

5f00356 7.1 5.7% ‐1.4 ‐1.1%

5f00361A ‐6.3 ‐16% 1.9 5.7%

5f00364A ‐10 ‐10% 0.6 0.7%

5f00367A 0.1 0.1% ‐4.7 ‐5.9%

Profile cross‐sectional area change: annual and longer‐term changes

Spring to Spring Baseline to Spring Elevation of Profile Mar 2017 to June 2018 Nov 2003 to June 2018 Reference Surface (OD) (m2) % (m2) %

5f00321 2.1 6.2% 1.8 5.1%

5f00323 1.2 3.9% 3.3 12%

5f00325 ‐0.2 ‐0.1% 23 17%

5f00332 ‐3.2 ‐2.8% 3.5 3.2%

5f00338 ‐9.1 ‐16% ‐8.5 ‐15% MLWS 5f00344 ‐0.4 ‐0.4% 1.8 1.7% ‐0.31 5f00349 1.6 1.2% ‐2.5 ‐1.8%

5f00356 3.8 2.9% 7.4 6.0%

5f00361A ‐1.5 ‐4.3% ‐8.9 ‐21%

5f00364A 3.4 3.8% 19.4 27% 0.8% 5f00367A 0.6 8.7 12%

Annual Survey Report Christchurch Bay 2018

Topographic net volume change: annual and longer‐term changes

Summer to Summer Baseline to Summer Survey Unit/ Elevation of Groyne Bay/ Sept 2017 to June 2018 Nov 2003 to June 2018 Reference Section Surface (OD) (m3) % (m3) %

MLWS 5fSU09 ‐1,995 ‐2.7% 4,689 7.0% ‐0.31

Volume above reference surface (m3)

Date of survey 5fSU09

Nov 2003 66,971

July 2004 69,725

May 2005 73,111

May 2006 65,389

June 2007 70,388

June 2008 73,111

June 2009 74,356

June 2010 72,630

June 2011 71,720

June 2012 68,263

June 2013 69,556

June 2014 76,917

June 2015 81,551

June 2016 75,003

Sept 2017 73,655

June 2018 71,660

Annual Survey Report Christchurch Bay 2018

Interim Wave Report Milford-on-Sea 2017/18

Milford-on-Sea Directional Waverider Buoy

Location

OS 427261 E 90395 N Latitude: 50° 42.75' N WGS84 Longitude: 01° 36.91' W Instrument type Datawell Directional Waverider Mk III Buoy in situ off Milford-on-Sea. Location of buoy (Google Water ~ 10 m CD Photo courtesy of Fugro GB mapping, image ©2016 depth Marine Limited TerraMetrics)

Summary

The largest significant wave height (HS) measured was 2.95 m on 2 January 2018 and occurred at High Water, during spring tides, with a 0.30 m surge. Four more storms exceeded the storm alert threshold as described in the Storm Analysis. January experienced the highest average HS and, by a large margin, the greatest percentage of bimodal seas. Wave direction was predominantly from the SW by S.

Data Quality

Recovery rate (%) Sample interval 99 30 minutes

Monthly Averages – 2017/18 All times are GMT

Hs Tp Tz Dir SST Bimodal No. of Month (m) (s) (s) (o) (oC) seas (%) days November 0.64 7.1 4.0 215 12.3 2 30 December 0.88 8.8 4.4 213 8.6 5 29 January 1.09 10.9 4.9 208 8.2 14 31 February 0.61 11.2 4.5 204 7.0 1 27 March 0.68 9.7 4.5 203 6.0 2 31 April 0.65 10.4 5.0 211 9.1 5 29 May 0.33 9.4 4.1 208 12.9 0 31 June 0.34 7.0 3.8 209 16.6 0 30 July 0.38 5.9 3.3 213 20.2 1 31 August 0.54 5.6 3.5 215 19.9 0 31 September 0.54 7.5 3.9 212 18.0 2 29 October 0.47 8.6 4.3 209 15.2 2 31

Interim Wave Report Milford-on-Sea 2017/18

Storm Analysis

Tidal Water level Tidal Tidal Max. Hs Tp Tz Dir stage Date/Time elevation* range surge* surge* (m) (s) (s) (o) (hours (OD) (m) (m) (m) re. HW) 02-Jan-2018 23:30 2.95 7.7 5.8 214 1.44 HW 2.66 0.30 0.47 12-Oct-2018 23:00 2.92 11.8 6.9 211 0.56 HW -2 2.08 0.14 0.42 10-Dec-2017 12:00 2.91 9.1 5.4 218 0.17 HW -4 1.63 0.32 0.56 31-Dec-2017 03:30 2.86 10.0 6.1 217 -0.05 HW -5 1.96 0.59 0.64 18-Jan-2018 06:00 2.74 10.0 6.0 214 -0.40 HW +1 1.91 0.25 0.26

* Tidal information is obtained from the step gauge on the Royal Lymington Yacht Club Starting Platform. The surge shown is the residual at the time of the highest Hs. The maximum tidal surge is the largest surge during the storm event.

Distribution plots The distribution of wave parameters are shown in the accompanying graphs of:

 Monthly time series of HS (red line is 2.74 m storm alert threshold)  Incidence of storms during the reporting period and for all previous years. Storm events are

defined using the Peaks-over-Threshold method. The highest HS of each storm event is shown

 Percentage of occurrence of HS, TP, TZ and Direction from November 2017 to October 2018

 Wave rose (percentage of occurrence of Direction vs. HS) for all measured data General The buoy, owned by New Forest District Council, was first deployed on 20 May 1996. It was replaced with a Directional Waverider on 17 November 2005, at which time the magnetic declination at the site was 2.6° west, changing by 0.15° east per year.

Acknowledgements The step gauge is installed on their Starting Platform by kind permission of the Royal Lymington Yacht Club. Tidal predictions for Lymington were supplied by Fugro GB Marine Limited.

Interim Wave Report Milford-on-Sea 2017/18