of the Waipaoa River Flood Control Scheme (19 Sept 2018) Applicants - - PowerPoint PPT Presentation

An Introduction to the Upgrade

• f the Waipaoa River Flood

Control Scheme (19 Sept 2018)

Applicants Team

Name Position Role

Neil Daykin Operations Manager Project Business Owner Joss Ruifrok Senior Project Engineer Project Manager Stella Morgan Director of Sage Planning Planning Consultant Rachael Zame Associate with CooneyLeesMorgan Legal Representative Craig Goodier Principal Engineer with Hawke’s Bay Regional Council River Modelling Technical Expert Janic Slupski Senior Policy Advisor Landscape expert

Contents

 1.0 Background  2.0 Project Overview  3.0 Investigations  4.0 Modelling & Design  4.1 Flood capacity  4.2 Design Flood Levels  4.3 Stopbank Design  4.4 Ormond Bypass  4.5 Mulloolys Bend  4.6 Upstream Properties  5.0 Wi Pere

1.0 Background

 The Waipaoa Flood Control Scheme (WFCS) began over 60 years

ago.

 The WFCS was substantially completed by 1969  The WFCS consists of:

 64km of stopbanks,  Stopbank top widths of 2m,  Stopbank heights range up to 6m,  638ha of productive land between the river & stopbanks (floodable berm),  76+ culverts, concrete walls, floodgates and related infrastructure.

 The WFCS protects $7 billion worth of land and property  In the 2006 LTCCP, Gisborne District Council (GDC) continued its

commitment to investigating upgrading the WFCS.

 In the 2009/19, 2015/25, & 2018/28 Long Term Plans, GDC

committed to a WFCS upgrade resilience project.

1948 Flooding

June 2018 Flood, photo by Jordon Perry

2.0 Project Overview

 Project involves the upgrade of the existing the Waipaoa Flood

Control Scheme (WFCS)

 Project also includes for the provision cycle trails along the

stopbanks,

 Flows (discharges) are forecast to increase by 25% between

now and 2090 due to a warming climate,

 Design will cater for a 1:100 yr flood event, accounting for

climate change factors out to the year 2090, plus ‘freeboard’,

 ‘Freeboard’ is an additional height allowance to compensate

for variables inherent in the design (0.6m applied),

 Will provide a ‘theoretical’ uniform LoS up to the design event  Stopbank top width to be increased to 4m

OLD

• Top width = 1.8 m
• Height = 3 m (example)
• Freeboard = 0.3 m

NEW

• Top width = 4 m
• Height = 4.3 m (example)
• Freeboard = 0.6 m

1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Height (m) Distance (m)

Stopbank Comparison

OLD

• Top width = 1.8 m
• Height = 3 m (example)
• Freeboard = 0.3 m

NEW

• Top width = 4 m
• Height = 4.3 m (example)
• Freeboard = 0.6 m

1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Height (m) Distance (m)

Stopbank Comparison

3.0 Investigations

3.1 - Stopbank Foundations

Results:

Stability generally

good,

Lateral bank

erosion a problem in some locations,

Narrow berms in

several places

 Ground Penetrating Radar (GPR)  Cone Penetrometer Tests (CPT)  Scala Penetrometer Tests (SPT)

3.2 - Stopbank Strength / Stability

Results:

 Stability generally very good. However 2m top widths too narrow for

safety and robustness. 4m now the industry norm.

 Instability under earthquake conditions - generally not significant

(exceptions).

 Liquefaction under seismic conditions is a risk (settlement and lateral

spreading) in the lower to mid reaches. Little that can be practicably done.

3.3 - River & Berm Width

Results:

Generally good berm width Some locations in critical areas have narrow berm widths Strengthening or berm widening may be necessary in places

4.0 Modelling & Design

4.1 - Flood Capacity

Cyclone Bola event used as our calibration event (4500

cumecs)

Design event is Bola plus 25% (Accounts for Climate Change

effects (2.1 deg.C out to the year 2090)

Bola +25% additional flow = 5625 cumecs = 2090 1% AEP

discharge

5625 cumecs is our ‘Design Event’ Stopbank heights are modelled flood levels from a 5625

cumec event, plus 0.6m of freeboard.

4.2 - Design Flood Levels

Updated the hydraulic model of the river 1D-2D ‘coupled model’ being used for design Updated model reviewed by DHI modelling specialists Model assumes that all floodwaters are contained by the

stopbanks (no leaks)

4.3 Stopbank Design

Stopbank Long Section based on cross sections every 100m’s for Stages 1 & 2

0.5m variation in stopbank level Higher stopbank, likely to account for Super Elevation

• n outside of bend

0.5m variation in stopbank level

4.4 Ormond Bypass

Proposed bypass

4.5 Mulloolys Bend

4.6 Upstream Properties

A B C D E

5.0 Wi Pere Trust

Wi Pere Trust Land

END OF PRESENTATION