Penwith District Council Hayle Harbour Hydrodynamic Modelling Report Final Report – Revision R02 BTI200141 28/11/02 Babtie Group 95 Bothwell Street, Glasgow G2 7HX Tel 0141 204 2511 Fax 0141 226 3109 Penwith District Council Hayle Harbour Hydrodynamic Modelling Report Document review and issue history Babtie Group BTI 200141 Revision Status Issued to Date Check by Reviewed by number R01 First draft Penwith District 04/11/02 L P McGregor J McKenna Council J Young J Wark R02 Final issue Penwith District 28/11/02 L P McGregor J McKenna Council J Young Copyright Babtie Group Limited. All rights reserved. No part of this report may be copied or reproduced by any means without prior written permission from Babtie Group Limited. If you have received this report in error, please destroy all copies in your possession or control and notify Babtie Group Limited. 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It should be noted and it is expressly stated that no independent verification of any of the documents or information supplied to Babtie Group Limited has been made. 1 Penwith District Council Hayle Harbour Hydrodynamic Modelling Report Contents Executive Summary............................................................................................................................... 5 1.0 Introduction ................................................................................................................................. 8 2.0 Background ................................................................................................................................. 9 3.0 Coastal Processes Overview................................................................................................... 11 3.1 Tides........................................................................................................................................ 11 3.2 Waves...................................................................................................................................... 11 3.3 Littoral Sediment Transport .....................................................................................................13 4.0 Hydrodynamic Model................................................................................................................ 14 4.1 Model Set-Up........................................................................................................................... 14 4.2 Model Calibration .................................................................................................................... 14 4.2.1 Calibration of Water Levels.............................................................................................. 15 4.2.2 Calibration of Flow Velocities........................................................................................... 16 4.3 Conclusions of Calibration Exercise........................................................................................ 18 5.0 Wave Model ............................................................................................................................... 19 5.1 Model Set-Up........................................................................................................................... 19 6.0 Model Runs................................................................................................................................ 21 7.0 Modelling Results and Analysis.............................................................................................. 23 7.1 St. Ives Bay ............................................................................................................................. 23 7.2 Hayle Beach ............................................................................................................................ 23 7.3 Hayle Estuary .......................................................................................................................... 27 7.3.1 ‘Existing’ Bathymetry........................................................................................................ 28 7.3.2 Lowered Beach Effects .................................................................................................... 28 7.3.3 Discussion........................................................................................................................ 29 7.3.4 Effect of Dredging ............................................................................................................ 30 8.0 Coastal Protection Measures................................................................................................... 32 8.1 Groynes ................................................................................................................................... 32 8.2 Beach Replenishment .............................................................................................................33 8.3 Rock Armouring....................................................................................................................... 34 8.4 Sand Filled Container Systems............................................................................................... 34 8.5 Dune Management Techniques .............................................................................................. 34 8.6 Summary ................................................................................................................................. 35 9.0 Summary and Conclusions...................................................................................................... 36 9.1 Summary ................................................................................................................................. 36 9.2 Concluding Comments ............................................................................................................38 2 Hayle Harbour Hydrodynamic Modelling Report List of Tables Table 1 – Model Calibration Points.......................................................................................... 41 Table 2 – Analysis of Peak Velocities...................................................................................... 42 Table 3 – Comparison of Nearshore Wave Modelling Results................................................ 43 Table 4 – Predicted Nearshore Wave Condition at Hayle Beach............................................ 43 Table 5 – Comparison of Potential Sediment Transport Rates ............................................... 44 Table 6 – Potential Wave and Tide Induced Sediment Transport........................................... 44 Table 7 – Potential Sediment Transport Rates........................................................................ 45 Table 8 – Potential Sediment Transport through Cross Sections during a Spring Tide.......... 45 Table 9 – Distribution of Predicted Sediment Transport across Section B (‘Existing’)............ 46 List of Figures Figure 1 – Location Plan .......................................................................................................... 48 Figure 2 – Hayle Estuary circa 1789........................................................................................ 49 Figure 3 – Typical Beach Profiles ........................................................................................... 50 Figure 4 – Longshore Transport .............................................................................................. 51 Figure 5 – Extent of Hydrodynamic Model Grids ..................................................................... 51 Figure 6 – Grid A: Mike21 (100m Grid).................................................................................... 52 Figure 7 – Grid B: Mike21 (30m Grid)...................................................................................... 52 Figure 8 – Location of Calibration Points................................................................................. 53 Figure 9(a) – Comparison of Water Levels at Point A ............................................................. 54 Figure 9(b) – Comparison of Water Levels at Point B ............................................................. 54 Figure 9(c) – Comparison of Water Levels at Point C ............................................................. 54 Figure 9(d) – Comparison of Water Levels at Point D............................................................. 55 Figure 9(e) – Comparison of Water Levels at Point E ............................................................. 55 Figure 9(f) – Comparison of Water Levels at Point F .............................................................. 55 Figure 10(a) – Comparison of Current Flow Velocity at Point 1 .............................................. 56 Figure 10(a) – Comparison of Current Flow Velocity at Point 2 .............................................. 56 Figure 10(a) – Comparison of Current Flow Velocity at Point 3 .............................................. 56 Figure 10(d) – Comparison