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Environment Bay of Plenty i

Date of last update: 24 June 2010

Cover Photo: Text to follow.

Flood Warning Manual July 2008

Environment Bay of Plenty iii

Contents

Chapter 1: Introduction ...... 1

1.1 Flood manual purpose...... 3

1.2 How to use this manual ...... 3

1.3 The climate and weather of the Bay of Plenty Region ...... 3

1.4 Setting up the flood room...... 4

1.5 IT Equipment During Power Cuts ...... 6

1.6 Communication...... 6

1.7 Security...... 7

Chapter 2: Flood Warnings and Flood Warning Procedures...... 9

2.1 Flood warning procedure...... 11

2.2 Emergency response work assistance ...... 11

2.3 Meteorological office warnings ...... 11

2.4 Issuing warnings to the media ...... 12

2.5 Telemetered sites ...... 13

2.6 Civil defence ...... 16

2.7 Police...... 17

Chapter 3: Otara River...... 19

3.1 Warnings and warnings lists ...... 21

3.2 Otara River telemetry sites ...... 22

3.3 Otara Catchment hydrological characteristics ...... 22

3.4 Current stopbank design standards (includes Waioeka)...... 23

3.5 Predicted warning stages and travel times ...... 23

3.6 Previous floods ...... 25

3.7 Flood warning phone lists...... 27

Flood Warning Manual July 2008 iv Environment Bay of Plenty

Chapter 4: Waioeka River...... 29

4.1 Warnings...... 31

4.2 Waioeka telemetry sites ...... 31

4.3 Waioeka Catchment hydrological characteristics...... 32

4.4 Current stopbank design standards (includes Otara)...... 33

4.5 Predictable warning stages and travel times...... 33

4.6 Previous floods ...... 35

4.7 Flood warning phone lists ...... 37

Chapter 5: Waimana River ...... 39

5.1 Warnings and warnings lists ...... 41

5.2 Flood warning phone list ...... 43

Chapter 6: Whakatane River ...... 45

6.1 Warnings and warning list ...... 47

6.2 Whakatane and Waimana telemetry sites...... 47

6.3 River floods ...... 48

6.4 Previous floods ...... 49

6.5 Culverts, floodgates and pump stations ...... 50

6.6 The Whakatane River spit...... 50

6.7 Flood protection stoplog structures ...... 53

6.8 Te Rahu basin and spillway ...... 55

6.9 Rangitaiki Plains...... 56

6.10 Flood warning phone list ...... 57

Chapter 7: Rangitaiki River ...... 59

7.1 Rangitaiki Catchment hydrological characteristics ...... 60

7.2 Historical flood protection...... 60

7.3 Warnings and warning list ...... 60

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7.4 Telemetry sites ...... 61

7.5 Rangitaiki rainfall ...... 61

7.6 Culverts, floodgates, and pump stations...... 62

7.7 Flood control system and spillway ...... 62

7.8 Minor floods ...... 63

7.9 Major floods ...... 63

7.10 Landowners in Rangitaiki floodway ...... 64

7.11 Flood estimation ...... 64

7.12 Fonterra Limited Edgecumbe ...... 67

7.13 Pressure Relief Trench Monitoring Procedure...... 67

7.14 Matahina Dam ...... 67

7.15 Aniwhenua Dam ...... 71

7.16 Wheao Dam...... 72

7.17 Landowners in the Rangitaiki Floodway ...... 74

Chapter 8: Tarawera River ...... 75

8.1 Introduction and history ...... 77

8.2 Hydrology ...... 77

8.3 Telemetry sites ...... 78

8.4 Rain gauge sites...... 78

8.5 On track...... 78

Chapter 9: Kaituna River...... 81

9.1 Introduction and history ...... 83

9.2 Warnings and warning list...... 83

9.3 Telemetry sites ...... 84

9.4 On Track...... 84

9.5 Rain gauge readers ...... 85

9.6 Lower Kaituna River: sensitive areas...... 85

Flood Warning Manual July 2008 vi Environment Bay of Plenty

9.7 Flood warning phone list ...... 89

Chapter 10: Lakes ...... 91

10.1 Lakes Rainfall ...... 93

10.2 Lake Rotoiti ...... 93

10.3 Lake Rotorua ...... 96

10.4 Lake Okareka...... 97

10.5 Okere Gates...... 99

Chapter 11: Coastal ...... 101

11.1 Introduction ...... 103

11.2 Rainfall: Rangitaiki Plains...... 103

11.3 On track ...... 103

11.4 River Levels: major rivers...... 104

11.5 Tides ...... 104

11.6 Barometric pressure...... 104

11.7 Sea storms...... 104

11.8 Whakatane River Stoplogs...... 105

11.9 Storm Surge Data Collection Triggers...... 106

11.8.1 Astronomical Tidal Height ...... 106

11.10 Kope-Orini, Old Rangitaiki Canal pumps...... 114

11.11 Awaiti-Omeheu floodgate...... 114

11.12 Fortunes Rd Pump Station...... 114

11.13 Te Rahu Rd Pump Station ...... 114

11.14 Duke St Pump Station...... 114

Appendices...... 115

Appendix 1 – Contacts List ...... 117

Appendix 2 – Emergency Equipment...... 127

July 2008 Flood Warning Manual Environment Bay of Plenty vii

Flood Warning Manual July 2008

Chapter 1: Introduction

Chapter Summary

1.1 Flood manual purpose...... 3

1.2 How to use this manual ...... 3

1.3 The climate and weather of the Bay of Plenty Region ...... 3

1.4 Setting up the flood room...... 4

1.5 Communication...... 6

1.6 Security...... 7

Flood Warning Manual July 2008

Environment Bay of Plenty 3

1.1 Flood manual purpose

The purpose of this manual is to assist the flood controller and other personnel on duty during flood events to carry out their functions in the most efficient and effective way, with the objective of avoiding or reducing the risk to life and property from floods.

1.2 How to use this manual

This manual is broken into 12 parts, see chapter headings in contents for details.

Note 1 Parts of this manual require updating annually to verify telephone lists, property owners, telephone numbers etc.

Note 2 For information on dams - consult the appropriate river.

Note 3 This manual includes several plans, which have tracings that are stored for editing as conditions change. Most charts are in this manual, however copies of the following plans should be stored in the Flood Room: W118/95/1 (2 sheets), RDB 448 (1), R450/27 (2), M566 sheet 1, (M566 2- 22, M567)

Note 4 The 2007 update of this manual was written with the help of various staff. If needed, contact these individuals during an emergency as they may have something to offer.

Area Individual Phone River Works and Tony Dunlop 307 0773 Maintenance Pump Stations and Flood Tony Dunlop and Arthur 307 0773 and Gates Rangihika 308 8254

Kaituna River Roger Waugh 312 5216

Telemetric Data Glenn Ellery 312 4657

River Modelling Phillip Wallace and Peter West 021-238 7515 and 312 9742

1.3 The climate and weather of the Bay of Plenty Region

Examples of storm types typical of the Bay of Plenty weather described in ‘The Climate and Weather of the Bay of Plenty Region’, a Meteorological Service Publication by A M Quayle - Environment Bay of Plenty Library Number 1523 or 15629, are summarised below.

1.3.1 Typical weather patterns

Because the Bay of Plenty is sheltered by high country to the west, south and east, day-to-day variations of the weather are largely determined by the direction of the wind. While high country areas may receive rain with airstreams from any direction, most of the Bay of Plenty area receives a large part of its annual rainfall during periods of onshore north to northeast winds.

Flood Warning Manual July 2008 4 Environment Bay of Plenty

1.3.2 North to northeast airstreams

Airstreams from the north to northwest frequently have long trajectories over the warm ocean to the north of New Zealand and, as a result, the air flowing onto the Bay of Plenty under these conditions is very humid. As the whole region is exposed to the north, these airstreams often produce widespread and heavy rain when the moist air is forced to ascend over the rising ground of the North Island. Such flows are normally associated with one of two types of situation.

Firstly when a cold front, orientated north south, is approaching from the west, the northerly winds ahead of the front spread over the region, bringing widespread rain until the passage of the front when there is usually a clearance.

The second type occurs when depressions cross the northern half of the North Island. These lows often move only slowly east, and the north to northeast flows on the eastern side of the centre may bring prolonged rain to the region.

1.3.3 Disturbed west to southwest flows

This common situation occurs most frequently during the spring months, but because the Bay of Plenty is sheltered by high ground to the south and west, only a few showers are normally experienced.

1.3.4 Tropical cyclones

Occasionally, during the months November to April, cyclones originating in the tropics move onto northern New Zealand. Because of their origin over very warm tropical oceans, these depressions normally contain very moist air. Although the structure of tropical cyclones is much modified as they move into higher latitudes they may still produce very strong winds and heavy rain (Lew's rule of thumb - if they come down from New Caledonia, to the West of Lord Howe Island, and then start heading east - WATCH OUT).

1.4 Setting up the flood room

1.4.1 Flood manager

On receiving information from EDS staff that river levels are rising or likely to rise, turn to the appropriate section of this manual and follow the procedures outlined there.

The contacted staff member will generally proceed to the office and establish themselves in the flood monitoring room.

In the early stages of an event, monitoring may be able to be carried out at home.

It is essential that a log of events be kept from the Very Start of event. Actual time of despatch or receipt of all information / warnings is to be recorded.

The following general procedures should be followed in all cases.

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Advise the following people:

• Engineering staff in charge of river works.

• Works Supervisors.

• Group Manager, Rivers and Drainage.

• Contractors etc who may have plant working on or near rivers.

1.4.2 Admin support

If you are the first person called in for Admin support, please do the following:

(a) Status of rivers This will be the main question callers will ask.

Get a current status report for ALL rivers from the Flood Manager, keep recording throughout the event. The flood team should have this information already recorded on the whiteboard, if not ask an EDS staff member to provide this information. Please make notes, especially recording times and levels each river peaked at or is due to peak at and when high tide is due for each river, on the form found under ‘River Status’.

All the forms mentioned are found in the blue ‘Flood Manual’ kept by the phones.

(b) Care of field staff

• Record names of staff members in the field, their names and time they started into the ‘Staff Flood Roster’, remember staff are only required to work a 7 hour shift, however depending on the event this may not be practical.

• Advise Flood Manager when staff are due to finish their shift. Some staff may be asked by their supervisor to extend their shift time – please keep a special eye on these staff members.

• Meals:

• Remind staff to ensure they have plenty to drink and eat in their vehicles to tie them over till their first meal break. They may need to stop for snacks before heading out.

• If it is decided not to call on catering staff, ask the staff (if able to) to buy meals, keep the receipt and claim through petty cash on the next working day.

• If meals are needed contact the appropriate catering staff identified in the ‘Caterers’ folder, if unable to contact them, contact another staff member to take food to the depot in question (this is not what we want happening as a rule but sometimes plans fail and we have to think outside our square).

Flood Warning Manual July 2008 6 Environment Bay of Plenty

• You will need to turn the phones over (see section 1.5.2 below) and begin recording calls and events happening around you into the ‘Flood Log’. Record as accurately as possible, you may need to tell people to slow down and repeat themselves until you can read back to them and they confirm you have the correct details. Pass all messages onto the appropriate person to action, once they have confirmed that they will see to that particular job put an ‘A’ in the action box on your sheet.

Ensure that an up to date EBOP phone list is in the Flood Room.

• You will be required to manage security, see section 1.6 below.

• The Flood Manager will let you know when they feel the Flood Room can be closed down, please do the following:

- Phone and RT all remaining staff out in the field that you will be closing the Flood Room down at such and such a time. Staff may have information to impart to you and may ask you to hold on till they have got this information through.

- Ensure that you have left all your staff roster lists and Flood Logs organised and tidy on the desk, if you have chosen to record everything electronically please print this off. This will allow any staff coming through after you have left to know the status to date of the event.

- Turn the phones back over as per instructions on the flood room wall.

- Ensure that all dishes etc are taken up to the canteen and that the Flood Room is left in a tidy condition.

- Also, check that no coffee urns etc are left on in the staff room, check that staff have left this area tidy as well.

1.5 IT Equipment During Power Cuts

There is a generator in the server room in the depot that automatically starts in the event of a power cut. It will automatically shutdown when the power comes back on.

There is another generator in the Quay Street building that maintains power to an “essential services” circuit. This circuit covers the IT communications room on the third floor and the EDS/Flood Room and CMR 2. This generator is NOT automatic and needs to be manually started and shutdown.

Should all power to Quay Street be cut off, the IT systems will stay on line for about half an hour, using battery backup. Once power is lost, the phone system and Internet access (basically all of comms) is down. There are analogue phones and CD lines in CMR 2. Contact the IT Technical Services Supervisor on 029 368 9274 or Manager Information Technology on 029 368 9201.

1.6 Communication

1.6.1 Pager

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EDS staff have a pager used for flood warnings. Messages can be sent via:

• Direct dial the pager 026 255 9651 and type in contact telephone number, on your telephone keypad.

• NSL Security (Environment Bay of Plenty after hours security) 07 578 8233.

The pager is linked to the Telemetry system operated by Environment Bay of Plenty and sends alarms from the equipment to the officer on duty.

Operations staff should phone the EDS Pager to establish who from the EDS staff is on duty.

The Flood Warning pager should be worn by the officer on duty from operations. The number is 026 252 8438.

1.6.2 Phone system

All flood related calls go to the flood room telephone, normally set to voicemail. The Flood Managers pager is also activated.

To enable the phone to ring, press 543, then enter times.

To divert the phone back to voicemail, press 541.

To listen to messages, press 51, (#9845 if at another phone), 1111

All three phones have the messages diverted to 9845.

1.6.3 RT system

When calling someone do the following: “Regional * *, Regional * * this is Flood Base, over”, they will respond with: “Flood Base this is * * over” you then continue until the natural end of the conversation which the person who initiated the call can only finish by saying: “Flood Base Out”. Remember at the end of each time you talking to finish with ‘over’, this allows the person you are talking to know they are free to answer.

1.7 Security

After 8:00pm during week Mon- Fri the alarm has a two hour alarm which needs to be reset. At weekends and public holidays the two hour alarm applies as well but for 24 hours. If you are in the building after hours, you will need to phone NSL Security (07 578 8233), our pass word is CHUBB. Problems with the alarm – contact Annabel (021 190 9244).

Flood Warning Manual July 2008

Chapter 2: Flood Warnings and Flood Warning Procedures

Chapter Summary

2.1 Flood warning procedure...... 11

2.2 Emergency response work assistance ...... 11

2.3 Meteorological office warnings ...... 11

2.4 Issuing warnings to the media ...... 12

2.5 Telemetered sites ...... 13

2.6 Civil defence ...... 16

2.7 Police...... 17

Have you:

Received Warning?

Log Started?

Notified Anyone?

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Environment Bay of Plenty 11

2.1 Flood warning procedure

At the “inform operations” level, one of the following operations personnel will always be available to receive a flood alert.

The Flood Managers pager number is 026 252 8438.

Home phone numbers are also found in Appendix 1

Flood Manager home phone numbers:

Tony Dunlop 307 0773

Roger Waugh 312 5216

Bruce Crabbe 307 0825

Glenn Ellery 3124657

Graeme O’Rourke 312 4689

Peter West 312 9742

The appropriate staff member will generally proceed to the office and establish themselves in the flood monitoring room.

2.2 Emergency response work assistance

Arrangements have been made with key outer office staff for emergency assistance during events in the Rotorua and Tauranga area. Their details are as follows:

Richard Mallinson: 07 350 1169 (home), 021 753 420

John Mather: 07 544 2376 (home), 021 649 7346

Brian Clements: 07 533 1383 (home), 021 707 975

Daryll Hall: 07 576 5242 (home), 021 923 350

Greg Corbett: 07 533 3149 (home), 029 368 7571

Phil Dykzeul: 07 544 8117 (home), 021 922 339

2.3 Meteorological office warnings

Meteorological Office Telephone 04 470 0783

The Metrological Office issues warnings that can fall into one of two categories.

2.3.1 Severe weather watch

Prospect of heavy falls but situation uncertain at this stage. Alert may be updated to a "Severe Weather Warning" at a later time.

Flood Warning Manual July 2008 12 Environment Bay of Plenty

2.3.2 Severe weather warning

Good likelihood of heavy falls. Quantities and times are usually predicted at this point. These forecasts are also supplied by the Meteorological Service to the New Zealand Police and Civil Defence Headquarters in Wellington.

Now also issued by the Meteorological Service to the media who have been asked to pass them on without their own interpretation.

Warnings are telephoned to Council during working hours or to staff members at their homes after hours. The list supplied to the meteorological Office is updated from time to time and can be found in the Contacts List at the back of this manual.

Receiving a warning should not be considered a guarantee with respect to flooding. The Meteorological Service acknowledges the value of ‘local interpretation’ which results in some 70-80% of Meteorological Service heavy rainfall alerts and forecast never reaching a flood warning situation.

2.3.3 Weather MAPS

Upon request, the Meteorological Office will provide weather maps to be transmitted by fax during severe rainfall events. The cost is not high (see file 14/2 4 October 1988).

The Meteorological Office has been known to fail to issue warnings for what have turned out to be significant events. If the Meteorological Office has not issued a warning and you feel uneasy about the weather conditions - give them a ring, (04) 470 0783.

2.4 Issuing warnings to the media

Warnings may be issued by fax to Radio IXX (fax number 307 1242) - use double lined if possible. Tell the station the fax is coming (ph 308 6239).

This function should be carried out by Senior Operations staff. Examples of warnings are:

2.4.1 Examples of flood warnings - for distribution to the media

Fax number:

Radio BOP (Tauranga) 07 578 9564

Radio IXX (Whakatane) 07 307 1242

All fax transmissions of flood warnings should include information about frequency of announcement, time of announcement etc (do not forget - farmers milk between 0500 and 0800 - and they usually have a radio in the cowshed).

You are still required to contact the announcer and discuss the warning with him/her.

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Example 1: General Alert - low key

The following flood alert was issued by Environment Bay of Plenty at *** (enter date/time).

"Environment Bay of Plenty advises that because of the possibility of heavy falls this evening, farmers in the *** and *** catchments should check stock before nightfall.

Environment Bay of Plenty staff will continue to monitor the situation throughout the evening."

Example 2: Specific warning

The following flood warning was issued by Environment Bay of Plenty at *** (enter date/time).

"This warning is issued by Environment Bay of Plenty in response to steady/heavy rainfall in the *** catchments.

Farmers with stock on low lying areas adjacent to the *** and *** rivers are advised to move stock to higher ground."

Example 3: Extreme warning

If you are in this situation it is desirable that this type of warning should be discussed with the Regional Controller (Bill Bayfield) before issue.

Example 4: Prediction of peak

The following flood information was issued by Environment Bay of Plenty at *** (enter date/time).

"Environment Bay of Plenty advises farmers in the *** catchments that rainfall has eased in the upper catchment and the *** river is expected to peak in the *** area at approximately *** (time)."

Example 5: Follow Up

The following flood information was issued by Environment Bay of Plenty at *** (enter date/time).

"Environment Bay of Plenty advises that the *** and *** rivers have peaked and flood waters are now expected to recede."

PLEASE NOTE: For data shared with Whakatane District Council the following sentence should be added: “This data is currently being processed”.

2.5 Telemetered sites

Copies of these pages should be sent with site status summaries given to media by EDS or Operations staff. These cover sheets explain the layout of the summaries.

Flood Monitoring cover sheet (To be used in conjunction with HydroTel™ Site Summary Reports)

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Site Abbreviations (in alphabetical order)

Grid Site Name Comments Agency Reference EAST CAPE CATCHMENTS Rain gauge at summit of Haparapara Haparapara Y15: 370 620 EBOP catchment in the eastern ranges NIWA river and rain in the Motu near Motu @ Waitangirua X16: 147 233 NIWA Motu village. Updated 12 hourly NIWA river and rain in the Motu Motu @ Houpoto X15: 181 609 located at the state highway bridge. NIWA Updated 12 hourly WAIOEKA & OTARA

CATCHMENTS Rain gauge situated at the top of the Koranga W17: 883 026 EBOP Waioeka catchment. River level/flow and rainfall in the Waioeka @ Cableway W16: 878 222 EBOP middle of the Waioeka gorge Rain gauge in the upper Pakihi Rakanui X16: 063 219 catchment which is a major tributary EBOP of the Rotorua River level and rainfall in the Pakihi Pakihi @ Pakihi Stn X16:979 325 EBOP which is a major tributary of the Otara River level/flow in the lower Otara Otara @ Browns Br. W16: 893 378 EBOP River but above Opotiki township Rain gauge positioned between the Tutaetoko X16: 926 282 EBOP Otara and Waioeka catchments. River level and rainfall in the lower Waioeka @ Mouth W16: 862 366 EBOP Waioeka but above Opotiki township River level and rainfall at the Otara @ Opotiki Wharf. W15: 861 469 confluence of the Otara and Waioeka EBOP rivers. Tidal effects present. WAIMANA & WHAKATANE

CATCHMENTS River level and flow site near the SH2 Nukuhou @ Quarry W16: 729 388 bridge. Feeds into the Ohiwa Harbour EBOP and floods Wainui Rd when high. Rainfall at the top of the Whakatane Huiarau W18: 628 786 EBOP catchment River level/flow and rainfall site on the Waimana @ Ranger Stn W16: 696 154 Waimana in the heart of the Urewera EBOP National Park. River level and rainfall situated in the middle of the Whakatane catchment. Whakatane @ Huitieke W17: 606 080 EBOP Give approx. 12-18 hrs lead into flood peak reaching Whakatane River level in the Waimana in the middle of the Waimana Gorge. Give Waimana @ Gorge W16: 644 367 EBOP approx. 12-18 hrs lead into flood peak reaching Whakatane River level in the Whakatane at Whakatane @ Ruatoki W16: 609 324 Ruatoki. River level/flow in the Whakatane at Whakatane @ Valley R W15: 609 475 the upstream end of Whakatane NIWA/EBOP township. Whakatane Airport W15: 599 525 Rainfall in Whakatane town. EBOP

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Grid Site Name Comments Agency Reference Level/flow in the Wainui-te-whara Wainui-te-whara W15: 611 522 EBOP which feeds the Awatapu lagoons. River levels at the lower end of Whakatane @ Wharf W15: 620 539 Whakatane township. Tidal effects EBOP present. RANGITAIKI & TARAWERA

CATCHMENT Rainfall in the upper Rangitaiki near Kokomoka V18: 129 592 EBOP Napier/Taupo highway. Levels/flow in the Rangitaiki at Rangitaiki @ Murupara V17: 329 984 NIWA Murupara. Rainfall situated between Whakatane Tarapounamu V17: 473 803 NIWA and Rangitaiki catchments River levels/flows and rainfall in the Whirinaki @ Galatea V17: 370 960 Whirinaki upstream of the confluence NIWA with the Rangitaiki Rainfall in the Waihua tributary of the Waihua Rain V16:471 171 Rangitaiki. Representative of mid NIWA catchment rainfall Rangitaiki@Aniwhenua V16: 418 163 River levels nera the Aniwhenua dam NIWA Rangitaiki@Matahina V16: 446 360 River levels above Matahina dam. NIWA River level/flow and rainfall in the Rangitaiki @ Te Teko V15: 436 444 NIWA/ebop Rangitaiki at Te Teko Noord Veirboom W15: 503 560 Rainfall in lower Rangitaiki plains area EBOP River level and rainfall in lower Rangitaiki @Thornton W15: 508 579 EBOP Rangitaiki. Tidal effects present. River level/flow and rainfall in the Tarawera @Awakaponga V15: 412 556 EBOP central Rangitaiki plains Levels and rainfall in the Tumurau Tumurau Lagoon V15: 383 523 lagoon which flows into the lower EBOP Tarawera. River levels and rainfall in the lower ORC Pump Station V15: 434 606 EBOP Tarawera. Tidal effects present. KAITUNA CATCHMENT Whakarewarewa U16: 959 329 Rainfall in Rotorua city area EBOP Lake Rotoiti U15: 030 447 Rainfall and lake levels at Okawa Bay EBOP Rainfall at the top of the Kaituna Kaharoa U15: 970 495 EBOP catchment River level/flow immediately Kaituna @ Taaheke U15: 035 499 downstream of the Okere Gates NIWA control structure River level/flow and rainfall in the Mangorewa which is a major tributary Mangorewa @ Saunders U15: 046 634 of the Kaituna catchment. Subject to EBOP rapid rises in water level up to 8 metres. Rainfall in the mid Pongakawa Pongakawa V15: 166 604 EBOP catchment. River level and rainfall site in the Kaituna @ Te Matai U14: 064 734 lower Kaituna catchment near Te EBOP Puke. River level in the lower Kaituna. Tidal Kaituna @ Clarke’s U14: 053 778 EBOP effects present. River levels at the bottom of the Kaituna @ Fords Cut V14: 109 775 Kaituna catchment. Tidal effects EBOP present.

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WESTERN BAY OF PLENTY CATCHMENTS Moturiki Tidal U14: 913 918 NIWA tidal site at Mount Maunganui NIWA River levels/flows and rainfall in a tributary near eastern end of Waimapu @ McCarrolls U14: 871 770 Tauranga Harbour EBOP River levels and rainfall in a tributary near western end of Tauranga Tuapiro @ Woodlands T13: 661 059 Harbour EBOP

HYDROTEL™ Site Summary Status Reports

Note #1 #2 #3 #4 #5 #6 #7 #8

Site Name Latest Water Data Rain Data Data Time Stage Flow Change Abv Alrm Intsty 24Hr

#1 SITE NAME Abbreviated site name. #2 LATEST DATA TIME the time of the most current data value in the format of dd/mm/yy hh:mm #3 STAGE (mm) - River level in mm. #4 FLOW (m3/s) - Flow in m3/s (not normally supplied) #5 CHANGE (mm/hr) - Change in water level over the previous hour. #6 ABV ALRM- The amount in mm that a river is above or below its alarm level. #7 INTNSTY - Hourly rainfall intensity in mm/hr. #8 24 HR - The total amount of rain that has fallen in the preceding 24 hours.

2.6 Civil defence

Under the Civil Defence Emergency Management Act 2002 Environment Bay of Plenty is required to participate in and administer a Civil Defence Emergency Management Group for the region. All employees of the Council may be required to undertake duties in the fulfilment of this role, including the staffing of an emergency operations centre. The Emergency Operations Centre Standard Operating Procedures manual details these staff functions. This is maintained by the Manager Emergency Management Office, John Thurston, in the Tauranga office, with copies distributed to all involved staff in Whakatane.

Flood warnings must be notified to the Group Controller (Bill Bayfield) and to the Manager of the EMO (John Thurston) where the nature or extent of the flood may lead to a declaration of a civil defence emergency. A declaration will be made if the situation is likely to go beyond the capacity of the normal responders (Police, District Councils, Hospitals etc). Information to be provided should include:

• Expected extent and area of flooding;

• Damage to property and works expected; and

• Numbers of people likely to be adversely affected, if known.

Note — Where the flood warning manager suspects that a flood may develop the Manager of the EMO should be advised at an early stage.

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The Group Controller/Manager EMO, or another member of the Regional Council's civil defence organisation will notify the affected district(s) if required.

A level 3 or level 4 state of local emergency will be declared, if required, by the Group Chairman after consultation with staff of the Regional Council and the affected territorial authority civil defence organisation(s).

It must be clearly understood that once a level 4 state of local emergency has been declared, ALL warnings must be issued through the Group Controller.

Although there may be no foreseeable serious flood threat, the flood warning manager should directly warn the appropriate District Council of the situation at the levels shown on the staff gauge tree for each river. If a local emergency (level 3) declaration has been made, the local Civil Defence Controller and the flood manager must mutually decide the procedure for the issue of flood warnings (media releases). A close connection should be established.

In all instances where the possibility for loss of life exists (whether or not a declaration of civil defence is being considered), flood warnings shall be advised to a responsible officer of the relevant district council. At the same time as this warning is given, a general description of the area likely to be flooded is to be provided.

Level Definition Responsible Level 3 Local Event within a district where an District Council Emergency emergency plan needs to be put into action. Level 4 Local Region wide state of emergency Regional Emergency requiring widespread assistance. Council

See report titled “Bay of Plenty Civil Defence Emergency Management Group Plan 2005” Civil Defence Publication 2005/01, particularly page 33 for more detailed information.

2.7 Police

Environment Bay of Plenty doesn’t usually have direct contact with the police during the flood event, unless a specific situation requires their assistance. The public are usually the police’s first warning of a sizeable event, and are always their priority.

Police will be asked to be on alert by the local Civil Defence (usually the district council) when an event requires this. If a Civil Defence Emergency is called they will have a representative stationed at the headquarters to assist with liaison, hence they are called upon more in the recovery stage of larger events.

Flood Warning Manual July 2008

Chapter 3: Otara River

Chapter Summary

3.1 Warnings and warnings lists ...... 21

3.2 Otara River telemetry sites ...... 22

3.3 Otara Catchment hydrological characteristics ...... 22

3.4 Current stopbank design standards (includes Waioeka)...... 23

3.5 Predicted warning stages and travel times ...... 23

3.6 Previous floods ...... 25

3.7 Flood warning phone lists...... 27

Have you:

Received Warning?

Log Started?

Notified Anyone?

Flood Warning Manual July 2008

Environment Bay of Plenty 21

3.1 Warnings and warnings lists

To read in conjunction with the Otara River staff gauge tree.

(a) EBOP Operations Staff (especially Tony Dunlop);

(b) Wardens or Farmers - Phone Lists are on blue paper at back of the chapter

(d) Civil Defence

(e) Contractors;

(f) Police;

(g) Radio Stations;

IMPORTANT The Principal Works Engineer (Tony Dunlop) must be notified early (at first warning level) so that his works gang can check all floodgates.

Because the time of concentration of these catchments is so short, any rainfall event that looks like it will cause river levels to rise to the first warning, should be responded to by issuing a warning. As a rule, even if in doubt, we should issue a warning (particularly if nightfall is approaching). Farmers prefer to be warned - even if nothing eventuates, rather than not be warned and be caught out. Generally 75mm or more will be sufficient to warrant a warning.

3.1.1 Warning lists

A series of "Warning Lists" have been developed to help with the transfer of warnings and alerts to the farmers of the Otara Catchment. Please note that it is normally only necessary to contact the Wardens (Heads) of each group. The members of each group are given here only in case of the Wardens not being available. Phone lists are located on blue paper at the back of this section.

Flood Warning Manual July 2008 22 Environment Bay of Plenty

3.2 Otara River telemetry sites

EDS Channel 1 – E191 - Environment Bay of Plenty Telemetry Channel

Grid Site Name Comments Agency Reference Otara Catchment Rain gauge in the upper Pakihi Rakanui X16: 063 219 catchment which is a major tributary EBOP of the Rotorua River level and rainfall in the Pakihi Pakihi @ Pakihi Stn X16:979 325 EBOP which is a major tributary of the Otara Otara @ Browns River level/flow in the lower Otara W16: 893 378 EBOP Br. River but above Opotiki township Rain gauge positioned between the Tutaetoko X16: 926 282 EBOP Otara and Waioeka catchments. River level and rainfall at the Otara @ Opotiki W15: 861 469 confluence of the Otara and Waioeka EBOP Wharf. rivers. Tidal effects present.

In addition to the above sites, the Waioeka at Cableway rain gauge, Mouth of Gorge rain gauge, and the Koranga rain gauge may help to better define total catchment rainfall.

The Tutaetoko rain gauge is sited on the ridge between the Tutaetoko and Te Waiti sub catchments.

3.3 Otara Catchment hydrological characteristics

The Otara Catchment is made up of three, roughly parallel sub catchments which join within a 5.6 km reach of the river. From east to west the sub catchments are:

Pakihi Sub catchment 140.0 km2 Te Waiti Sub catchment 96.0 km2 Tutaetoko Sub catchment 59.0 km2

TOTAL 295.0 km2

Relevant river distances (measured from the Confluence of the Otara River with the Waioeka River) are as follows:

River Section Distance Otara/Waioeka Confluence 0 km Upper limit of town 5.50 km Start of urban banks 8.70 km Start of rural banks 17.20 km Tutaetoko Confluence 17.95 km Browns Bridge telemetry site 19.00 km Pakihi Confluence 22.90 km

July 2008 Flood Warning Manual Environment Bay of Plenty 23

The present telemetry system includes water level recorders on the Pakihi River (at Pakihi Station (approximately 6.2 km up the Pakihi River) and at Brown Bridge (approximately 1.0 km upstream of the Tutaetoko Confluence).

ANY assessment of Flooding is therefore based on a GUESS of what is coming down the Tutaetoko.

The best guess at this stage should be based on an estimated contribution of Tutaetoko = 17% of Browns Bridge.

3.4 Current stopbank design standards (includes Waioeka)

Location Design Level Waioeka Urban Right Bank 100 year plus 450 mm freeboard Waioeka Rural Right Bank 20 year plus 300 mm freeboard Waioeka Urban Left Bank 100 year plus 450 mm freeboard Waioeka Rural Left Bank 20 year plus 300 mm freeboard Waioeka Rural Coastal Left Bank 2 year plus 300 mm freeboard Otara Urban Left Bank 100 year plus 450 mm freeboard Otara Rural Lower Right Bank 20 year plus 300 mm freeboard Otara Rural Coastal Right Bank 2 year plus 300mm freeboard Otara Rural Left Bank 10 year plus 300 mm freeboard Otara Rural Right Bank 10 year plus 300 mm freeboard Gault Ring Bank 50 year plus 400 mm freeboard

Design levels of the Waioeka-Otara stopbanks were reviewed in 2002 (Wallace).

3.5 Predicted warning stages and travel times

Historical data together with hydrological model simulations have been used to predict flood warning stages and lag time.

3.5.1 Flood warning stages

The Otara River flood warning system is based almost entirely on the stage at Browns Bridge. This is a reliable site with an accurate rating curve for levels below 4.5 m to which it has been gauged. The site has two main disadvantages:

(i) It is above the confluence of the Tutaetoko River, which has a catchment area of around 17% of the total at the top of the scheme.

(ii) It offers very little warning time.

Flood Warning Manual July 2008 24 Environment Bay of Plenty

3.5.2 Stage relating to rural overflow

There is no set stage at Browns Bridge for which overflow of the rural banks will occur due to the uncertainty of the contribution from the Tutaetoko River. The overflow of the rural scheme is most likely to occur for stages at Browns Bridge of above 5 m.

3.5.3 Stage relating to urban overflow

The left bank urban stopbanks were restored to the 100 year level plus 450 mm freeboard in 2001/02. (Lower reaches near confluence actually upgraded to 200 yr + 450mm freeboard)

Therefore overflow of the right bank is most likely to occur well before the left bank.

Overflow of the urban banks is unlikely to occur until stage levels in excess of 6.0 m occur at Browns Bridge.

The lower reaches are influenced by the Waioeka River

Probably a more reliable indicator of the likelihood of flooding of the town is rural overtopping as this takes into account such uncertainties as the Tutaetoko discharge. It seems likely that if significant overflow occurs in the rural area and the stage at Browns Bridge continues to rise, the urban banks will be overtopped. This may also give additional warning time.

3.5.4 Time of travel

Typical travel times for flood waters are as follows.

Pakihi to Browns Bridge 1.5 to 3 hours Browns Bridge 5.3 m till urban overflow 2 to 3 hours Urban overflow until water in town 1 to 2 hours Rural overflow until urban overflow 2 to 3 hours Rural overflow until water in town 3 to 5 hours

Note — A breach of the town banks could occur at any time without warning.

3.5.5 Discussion of results

The close proximity of the Browns Bridge staff gauge to the Scheme, combined with the catchment characteristics, makes for very short warning times. Assuming an Urban warning level of 6.0 m this would give 2 to 3 hours until overflow of the scheme banks and 3 to 5 hours before water enters the town. There is of course no certainty that flooding will occur for this level and so there may be a longer warning period or no flooding at all.

July 2008 Flood Warning Manual Environment Bay of Plenty 25

3.6 Previous floods

Top 10 recorder flood in the Otara River at Browns Bridge

Otara River at Browns Bridge Flood Peak Stage and Discharge Record Year Stage Discharge Rank

(m) (m3/s) 1964 984 1 1965 765 2 2003 5.11 728 3 1998 4.50 550 4 1999 4.39 519 5 1989 4.76 517 6 1976 4.50 512 7 1986 4.68 496 8 1996 4.64 483 9 1966 (-4.25) 447 10= 1967 (-4.25) 447 10= 2004 4.10 445 11

Note — Bracketed ( ) stage figures are assessed values only.

Graphs on the following pages cover:

• Otara at Browns Bridge rating

• Otara at Browns Bridge staff gauge prompter

• Pakihi Stream provisional rating

• Five graphs of previous events.

Flood Warning Manual July 2008

Environment Bay of Plenty 27

3.7 Flood warning phone lists

Farmers on Low Lying Land on the Left Bank of the Upper Otara River

First Warning

Name Telephone Number Liam and Spela Marshall (Warden) (07) 315 5343 (J Hedley’s Sharemilker) 027 484 2102 Donald Brown (07) 315 7694 / 027 749 5237 Cowshed (07) 315 5073 Preston Craig (07) 315 7803 Mike Gebert (Sharemilker) (07) 315 7631

Second Warning All those above plus those below:

Name Telephone Number Peter Jerram (07) 315 7829 Des Conner (07) 315 7827 Stephen Gebert (Sharemilker) (07) 315 7454 John Hedley (07) 315 7807 T (Buddy) Bennett (07) 315 7677

Farmers on Low Lying Land on the right bank of the Upper Otara River

First Warning

Name Telephone Number (07) 315 7465 (H) B Riesterer (Warden) (07) 315 6165 (W) Terry and Shannon Edwardson (07) 315 4688 Dean and Sharyn Petersen (Reserve (07) 315 6740 Warden) 027 622 7009 Peggy Hita (07) 315 6009 Malcolm Carter (07) 315 7859 David Keller (07) 315 7863

Second Warning All those above plus Ross Jerram (07 315 7864).

Flood Warning Manual July 2008 28 Environment Bay of Plenty

Farmers on Low Lying Land on Both Banks of the Lower Otara River

First Warning

Name Telephone Number Jill Wingate (Warden) (07) 315 7884 Nigel Gebert (07) 315 6361 Stuart McKay (07) 315 8488 Alan Gault (07) 315 7855 Graham Gault (07) 315 6828 Chris Patchett (Sharemilker) (07) 315 7764 Gordon Estate: Glen Thorn (07) 315 7585 or G Hill (07) 315 7563 Gavin Young (Otara River, Duke Street) (07) 315 5981 Thornton Park Rest Homes (07) 315 7867 Gordon Dennis (07) 315 7883 Alan Rowe (07) 315 7332 John Dane (Te Rere Pa Block) (07) 315 7484

Second Warning (100 year bank) All those above plus those below (at Browns Bridge = 5.3):

Name Telephone Number Ross Moody (07) 316 7925 Gordon Dennis (07) 315 7883

July 2008 Flood Warning Manual 29

Chapter 4: Waioeka River

Chapter Summary

4.1 Warnings ...... 31

4.2 Waioeka telemetry sites...... 31

4.3 Waioeka Catchment hydrological characteristics ...... 32

4.4 Current stopbank design standards (includes Otara)...... 33

4.5 Predictable warning stages and travel times ...... 33

4.6 Previous floods ...... 35

4.7 Flood warning phone lists...... 37

Have you:

Received Warning?

Log Started?

Notified Anyone?

Flood Warning Manual July 2008

Environment Bay of Plenty 31

4.1 Warnings

To read in conjunction with the Waioeka River staff gauge tree.

(a) EBOP Operations Staff (especially Tony Dunlop);

(b) Wardens or Farmers - Phone Lists are on blue paper at back of the chapter

(d) Civil Defence

(e) Contractors;

(f) Police;

(g) Radio Stations;

IMPORTANT The Principal Works Engineer (Tony Dunlop) must be notified early (at first warning level) so that his works gang can check all floodgates.

4.1.1 Warning lists

A series of "Warning Lists" have been developed to help with the transfer of warnings and alerts to the farmers of the Waioeka Catchment. Please note that it is normally only necessary to contact the Wardens (Heads) of each group. The members of each group are given here only in case of the Wardens not being available. Phone lists are located on blue paper at the back of this section.

4.2 Waioeka telemetry sites

EDS Channel 1 – e191 - Environment Bay of Plenty Telemetry Channel

Grid Site Name Comments Agency Reference WAIOEKA CATCHMENT Rain gauge situated at the top of Koranga W17: 883 026 the Waioeka catchment. EBOP River level/flow and rainfall in the Waioeka @ Cableway W16: 878 222 middle of the Waioeka gorge EBOP Rain gauge positioned between the Tutaetoko X16: 926 282 Otara and Waioeka catchments. EBOP

Flood Warning Manual July 2008 32 Environment Bay of Plenty

Grid Site Name Comments Agency Reference River level and rainfall in the lower Waioeka but above Opotiki Waioeka @ Mouth W16: 862 366 township EBOP River level and rainfall at the confluence of the Otara and Waioeka rivers. Tidal effects Otara @ Opotiki Whf. W15: 861 469 present. EBOP

In addition to the above sites, the Otara at Browns Bridge rain gauge, and to some degree the Pakihi rain gauge may help to better define total catchment rainfall.

The Waioeka at Cableway site has additional telemetry equipment that is operated by NIWA. In the event of a failure at Cableway, telephone:

• NIWA - Rotorua 07 346 1950

• After hours (Wayne McGrath) 07 347 9071

• After hours (Graham Timpany) 07 348 8829

4.3 Waioeka Catchment hydrological

4.4 Waioeka Catchment characteristics

The Waioeka Catchment is bulbous in shape and extends inland from the sea for about 60 km.

Catchment widths range from 10 km wide for the 28 km nearer the coast, to 20 km wide throughout most of the southern part of the catchment.

Relevant river distances (measured from the confluence of the Otara River with the Waioeka River) are as follows:

River Location Distance Otara/Waioeka Confluence 0.0 km Upper limit of town 2.10 km Start of urban banks 2.65 km Start of rural banks 11.25 km Gorge Mouth telemetry site 35.10 km Waioeka cableway telemetry site 12.21 km Pakihi Confluence 22.90 km

The present telemetry system includes water level and rainfall recorders on the Waioeka River at the mouth of the gorge as well as at 'Cableway' in the middle of the catchment.

July 2008 Flood Warning Manual Environment Bay of Plenty 33

4.5 Current stopbank design standards (includes Otara)

Design levels of the Waioeka-Otara stopbanks were reviewed in 2002 (Wallace).

4.6 Predictable warning stages and travel times

Historical data together with hydrological model simulations have been used to predict flood warning stages and lag time.

4.6.1 Waioeka flood warning sites

Waioeka River flood warning is based primarily on the Cableway site, located approximately 21 km upstream of the scheme, with a secondary site at the gorge mouth (at the top of the scheme). Approximately 15% of the catchment area at the gorge mouth lies between the two sites.

The Cableway site is the most important for flood warning. It is reliable (and has NIWA backup) and offers a reasonable length of warning. The gorge mouth site is really only useful as a backup.

River stage records have been kept for the cableway site by the MWD (and its successor) since 1958. In 1987 major changes were made to the upper end of the rating curve, which had the effect of reducing the estimated discharges of larger events (including the floods of 1964 and 1967).

The gorge mouth site was established in 1984 and is really only useful for flood warning as a rainfall recorder and as a backup to the Cableway site. Being right at start of the scheme it offers virtually no warning time to farms on the Plains and very limited time to the township. No gauging is possible at the site so no rating curve exists. The reach on which the site is located is prone to erosion of the banks and aggradation and degradation of the riverbed. There are also a number of stud groynes upstream of the site (SH2 protection), which can have a marked effect on river levels. It has been useful in estimating the time of travel from the Cableway site.

Flood Warning Manual July 2008 34 Environment Bay of Plenty

4.6.2 Stages relating to rural overflow

The rural stopbanks are designed to a 20yr level with 300mm freeboard.

Overflow of the left bank of the scheme is likely to occur for stages at Cableway of above 7.8m. This does not discount the possibility of it being lower or higher because of the influence of the catchment below Cableway.

Overflow of the rural scheme may occur at stages at Cableway above about 9.2m.

Table 1 - River Levels

Stage Cableway Time of Affect on Date G/Mouth Travel Rural Scheme (mins) Dec 87 8.22 m 5.37 m 90 Top of Harfords banks (2.25 mile) plus trickle at river bank 5.25 mile cross section July 88 7.79 m 5.08 m 93 Overflow at Harfords (2.25 mile) requiring sandbags.

Table 2 – Rainfall

Date Gorge Tutaetoko Cableway Koranga Mouth Dec 87 44 mm 139 mm 213 mm 181 mm July 88 154 mm 196 mm 201 mm 153 mm

4.6.3 Stages relating to urban overflow

The right bank stopbanks were restored to the 100-year level plus 450 mm freeboard in the construction seasons in 2001/02. (Lower reaches near confluence actually upgraded to 200 yr + 450mm freeboard).

Overflow of the urban banks is unlikely to occur until stage levels in excess of 13 m occur at cableway.

The lower reaches are influenced by the Otara River and tides.

If high tide or the peak of the Otara occurs at the same time as the peak of the Waioeka this will have the effect of raising the water levels in the lower reaches of both rivers.

4.6.4 Vulnerability of Waioeka State Highway 2 Bridge

The bridge has a low soffit, as well as large number of piers. In large flood events the bridge is vulnerable, and will need to be closed if water is high enough. In 1998, for instance, the bridge was closed and diggers were used to clear debris from the bridge.

Also potential for SH2 on the Whakatane side to go under, and/or for the Waioeka Gorge to be affected.

Otara bridge (SH35) not so much of an issue

July 2008 Flood Warning Manual Environment Bay of Plenty 35

4.6.5 Correlation of cableway and gorge mouth stages

The typical time of travel of floods are summarised below:

Section Location Time Cableway to Gorge Mouth 1.5 to 2.0 hours Gorge Mouth to first rural overflow 0.5 to 1.0 hours Gorge Mouth to first urban overflow 1.0 to 1.5 hours

4.7 Previous floods

Waioeka at Cableway top 10 Annual maxima.

Waioeka River at Cableway Flood Peak stage and Discharge Record

Stage Discharge Year (m) (m3/s) Rank 1998 10.53 1521 1 1964 10.67 1494 2 1967 10.42 1447 3 1987 8.22 1026 4 1995 7.96 1002 5 1970 7.96 976 6 1988 7.79 943 7 1958 7.62 911 8 2003 7.36 907 9 1991 7.50 887 10 1999 7.23 882 11

Graphs on the following pages cover:

• Waioeka at Cableway rating

• Waioeka at Cableway staff gauge prompter

• Waioeka at Gorge staff gauge prompter

• Correlation between Gorge and cableway sites

• Five graphs of previous events

Flood Warning Manual July 2008

Environment Bay of Plenty 37

4.8 Flood warning phone lists

Farmers on Low Lying Land on the Left Bank of the Waioeka River

First Warning

Name Telephone Number Will Maxwell (Warden) (07) 315 7651 or 027 499 6641 Robert Anstis (Reserve Warden) (07) 315 5684 or 027 282 4351 Bern McDonald (07) 315 5248 Ian Rowe (07) 315 7994 or 027 755 9088 Alan Rowe (07) 315 7332 Robbie Peterson (07) 315 7361 or 027 454 3726 Kevin Black (07) 315 8832 or 027 251 3622 Keith Curtis (07) 315 6333 Kathy Shelley (07) 315 7953 or 027 487 0975

Second Warning All those above plus those below:

Name Telephone Number I Rowe (must be alerted at S/G = 7.4m (07) 315 7994 (20 year bank)

Farmers on Low Lying Land on the Right Bank of the Waioeka River

First Warning

Name Telephone Number Guy Nicol (Warden) (07) 315 7686 Grant Nicol (07) 315 8300 Jimmy Brown (Reserve Warden) (07) 315 7693 or Ian Brown (07) 315 7692 Norma Atkinson (07) 315 7712 John Dane (Manager) (07) 315 7484 or 027 204 6390

Mike Hughes (07) 315 5553 Whakatohea (07) 315 5715 or 027 728 6467 Allan and Michelle Polglaze Marylynn Langbein or Nick Hanne (07) 315 8425

Second Warning All those above

Flood Warning Manual July 2008

Chapter 5: Waimana River

Chapter Summary

5.1 Warnings and warnings lists ...... 41

5.2 Flood warning phone list...... 43

Have you:

Received Warning?

Log Started?

Notified Anyone?

Flood Warning Manual July 2008

Environment Bay of Plenty 41

5.1 Warnings and warnings lists

To read in conjunction with the Waimana River staff gauge tree.

(a) EBOP Operations Staff (especially Tony Dunlop);

(b) Wardens or Farmers - Phone Lists are on blue paper at back of the chapter

(d) Civil Defence

(e) Contractors;

(f) Police;

(g) Radio Stations;

5.1.1 Warning lists

A series of "Warning Lists" have been developed to help with the transfer of warnings and alerts to the farmers of the Waimana Catchment. Please note that it is normally only necessary to contact the Wardens (Heads) of each group. The members of each group are given here only in case of the Wardens not being available. Phone lists are located on blue paper at the back of this section.

Note — Telemetry sites and rain gauges are described in the Whakatane River Section together with "Time of Travel" analyses etc.

Graphs on the following pages cover:

Waimana at Ranger Station provisional rating

Waimana at Ogilvies Bridge staff gauge prompter

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Environment Bay of Plenty 43

5.2 Flood warning phone list

Waimana Confluence to Hausers Cliff Harper (Warden) 312 9983 Len Dunstan 312 9119 John Hall 312 9293

W Hausers to Waimana West Bridge Kevin Clark (Warden) 312 3319 027 626 4378 (note no cellphone reception in Waimana) Kelvin Wallace (Reserve Warden) 312 3109 Chris Schadler 312 3278

Waimana West to Waimana East Bridge Bernie Clark (Warden) 312 3185 Roger White 312 3183 Tony De Groot 312 3351 Kevin Flemming (Reserve Warden) 312 3337

Waimana East Bridge to Tanatana Allen Wardlaw (Warden) 312 3077 Les Wardlaw 312 3338 Robert Mexted 312 3119 Mary and David Faulkner 312 3129 Joseph Huges 312 3110 Fred Savage 312 3256 Carl Amrein (Sharemilker) 312 3863

Group 3 Clark Takao (Warden) 312 3134 Tom Brown 312 3123 Johnny Boy Rakuraku 312 3127 Jim Scholten (passed away trying to find out new owner) 312 3130 Phone not in service ???? Spud Kutia (Andersen’s) 312 3139

Flood Warning Manual July 2008

Chapter 6: Whakatane River

Chapter Summary

6.1 Warnings and warning list...... 47

6.2 Whakatane and Waimana telemetry sites ...... 47

6.3 River floods...... 48

6.4 Previous floods ...... 49

6.5 Culverts, floodgates and pump stations...... 50

6.6 The Whakatane River spit ...... 50

6.7 Flood protection stoplog structures...... 53

6.8 Te Rahu basin and spillway...... 55

6.9 Rangitaiki Plains ...... 56

6.10 Flood warning phone list...... 57

Have you:

Received Warning?

Log Started?

Notified Anyone?

Flood Warning Manual July 2008

Environment Bay of Plenty 47

6.1 Warnings and warning list

To read in conjunction with the Whakatane River staff gauge trees.

(a) EBOP Operations Staff, especially Principal Works Supervisor, Tony Dunlop - for pump stations etc

(b) Whakatane District Council - for floodgate inspections / the spit

(d) Wardens or Farmers - Phone Lists are on blue paper at back of the chapter

(e) Civil Defence

(f) Contractors;

(g) Police;

(h) Radio Stations;

Warning lists

A series of "Warning Lists" have been developed to help with the transfer of warnings and alerts to the farmers of the Whakatane Catchment. Please note that it is normally only necessary to contact the Wardens (Heads) of each group. The members of each group are given here only in case of the Wardens not being available. Phone lists are located on blue paper at the back of this section.

6.2 Whakatane and Waimana telemetry sites

EDS Channel 1 – E191 - Environment Bay of Plenty Telemetry Channel

EDS Channel 2 – E115 – NIWA Telemetry Channel

Site Name Grid Reference Comments Agency Waimana and Whakatane catchments Nukuhou @ Quarry W16: 729 388 River level and flow site near the EBOP SH2 bridge. Feeds into the Ohiwa Harbour and floods Wainui Rd when high. Huiarau W18: 628 786 Rainfall at the top of the EBOP Whakatane catchment Waimana @ Ranger W16: 696 154 River level/flow and rainfall site on EBOP Stn the Waimana in the heart of the Urewera National Park. Whakatane @ Huitieke W17: 606 080 River level and rainfall situated in EBOP the middle of the Whakatane catchment. Give approx. 12-18 hrs lead into flood peak reaching Whakatane

Flood Warning Manual July 2008 48 Environment Bay of Plenty

Site Name Grid Reference Comments Agency Waimana @ Gorge W16: 644 367 River level in the Waimana in the EBOP middle of the Waimana Gorge. Give approx. 12-18 hrs lead into flood peak reaching Whakatane Whakatane @ Ruatoki W16: 609 324 River level in the Whakatane at Ruatoki. Whakatane @ Valley W15: 609 475 River level/flow in the Whakatane NIWA/EB R at the upstream end of OP Whakatane township. Whakatane Airmon W15: 599 525 EBOP Rainfall in Whakatane town. Wainui-te-whara W15: 611 522 Level/flow in the Wainui-te-whara EBOP which feeds the Awatapu lagoons. Whakatane @ Wharf W15: 620 539 River levels at the lower end of EBOP Whaktane township. Tidal effects present.

6.3 River floods

6.3.1 Minor floods

200 - 300 cumecs Waimana River

400 - 600 cumecs Whakatane River

Low lying land adjacent to the rivers is likely to be flooded when above flows are reached. Warnings are not normally required unless a rapid rise in water level is expected during the hours of darkness, in which case:

SEE GRAPH OF GAUGE HEIGHT AT VALLEY ROAD VS EFFECT ON LAND.

6.3.2 Floods up to 10 year bank

300 - 600 cumecs Waimana River

600 - 1200 cumecs Whakatane River

Widespread flooding of all flat land adjacent to rivers will occur when river flows specified above are reached.

Flat land in the Taneatua-Ruatoki and Waimana areas where no 10-year banks exist will be most affected.

Warnings should be much the same as for minor floods except that the warning should be a little stronger in its wording.

SEE GRAPH OF GAUGE HEIGHT AT VALLEY ROAD VS EFFECT ON LAND.

6.3.3 Floods 1200 cumecs (10 year bank level) and above

24-hour rainfalls will likely need to be in excess of 100 mm over the main part of the catchment to cause floods above the 10yr bank level. First indications are usually from the Waimana area.

Suitable warnings should be broadcast over local radio stations (see chapter 2).

July 2008 Flood Warning Manual Environment Bay of Plenty 49

When floods are greater than the 10-year banks, preparations should be made to ensure that the stoplogs for the Big Game Fishing club and Waioho Stream are readily available should they be required.

If necessary a staff member can be sent to the Ruatoki Bridge to read the staff gauge.

6.4 Previous floods

6.4.1 Gauge heights

Oglivies/ Huitieke Waimana Valley Discharge Date Ranger (m) (m) (m) Road (m) Valley Rd (m3/s) Sep 70 5.05 5.10 6.35 1400 Oct 83 3.81 2.20 4.30 6.35 1040 Dec 83 4.73 1.62 5.20 6.20 1100 Dec 84 3.89 1.90 4.37 5.55 770 Apr 85 3.34 2.05 3.70 5.13 772 Jul 88 4.62 2.30 4.66 5.66 860 Feb 91 3.47 1.42 5.1 5.37 870 Jul 94 4.23 2.23 3.57 5.41 884 Sep 95 4.72 2.51 4.88 5.67 983 2 Jul 98 7.65 3.5 7.1 7.13 2240 10 Jul 98 4.17 2.33 5.24 6.21 1130 11 Jul 98 5.37 3.05 6.0 7.06 2100

6.4.2 Time of travel (hours)

Date Ogilvies/Ranger to Waimana to Huit to Valley Waimana (hrs) Valley Road (hrs) Road (hrs) Oct 83 4 6.0 11 Dec 83 6 4.5 8 Dec 84 6 5.5 9.5 Apr 85 7 5.5 9 (flat peak) Jul 88 5 4 9 Feb 91 3.25 5.5 7.25 Jul 94 9 8.75 Sep 95 5.5 4.5 8.5 2 Jul 98 Approx 5 4 11 Jul 98 4.75 1.75 7.25 Average 6 5 9 Minimum 3.25 1.75 7.25

Flood Warning Manual July 2008 50 Environment Bay of Plenty

6.5 Culverts, floodgates and pump stations

The Operations staff are responsible for the inspection of pump stations, floodgates, and culverts. Inspections are made in response to a heavy rainfall warning or following heavy rainfall. Whakatane township floodgates are the responsibility of the district council.

Always have someone check the Kope – Orini Floodgates are working

Note — The pump operation is described in Chapter 11 (Coastal).

These sites are detailed on Plan Numbers W118/95/1 (2 sheets) and Plan Number RDB448. Copies of these plans are kept in the Flood Room.

Problem Areas (historically)

Site Name Site Number Description Maloney's Floodgate M1 1050 dia Maloney's Floodgate M1a 900 dia Maloney's Floodgate M2 900 dia Maloney's Floodgate M3 900 dia Tait/Boheemen Floodgate TB 1 1800 dia Kopeopeo/Orini Floodgate KO 2 triple box culvert Te Rahu Floodgate TR 1 triple box culvert

Note — Access to the main Kopeopeo /Orini floodgate is via the 100-year stopbank off Keepa Road. (The gate is not always locked – standard stopbank key).

For emergencies Scottie McLeod (308 7731) has 2 AMI submersible pumps available (one is free standing).

6.6 The Whakatane River spit

Background The Whakatane Harbour mouth is continually constricted by the movement of sand along the beach from the west. The steady sand movement has formed a sand spit that impacts on flood conveyance at the mouth due to narrowing; but also on vessel navigation through shallowing.

During large floods such as 1970, the spit had been observed to erode rapidly enough to accommodate the peak of the flood. The natural mechanism of erosion is thought to be a side-ways action at the tip that widens the channel. The rocks at the spit, Turuturu (Statue Rock) and others, do impede this action but not critically during large floods.

In 1994 Whakatane District Council, with their interests in the Port, obtained a short term resource consent to construct the rock training wall at the mouth of the Whakatane River on the left bank (the Western Training Wall; see figure). The intention was for the wall to improve navigability of the harbour entrance by concentrating the flushing tidal flows. The 2004 flood removed approximately 50% of the wall. This has not been repaired. The consent was updated in 2004 (file 1370 51110) but has now expired.

July 2008 Flood Warning Manual Environment Bay of Plenty 51

It is recognised that the wall could seriously impede erosion of the sand spit during floods. To mitigate this effect, conditions of consent require that Whakatane District Council maintain a fuse-channel in the spit to encourage the spit to erode during floods. The fuse is a 50 metre wide channel excavated in the sand to join the river to the sea. The bottom level of this channel should be maintained below 1.4 metres Moturiki Datum (this is the equivalent of: 101.4m WDC Datum). A level of 2.0 metres triggers maintenance action by the consent holder. Height poles are in place in the vicinity of the fuse channel. They have colour-coded height markings painted on them (figure below).

To counter the effects of sea waves damaging the channel, a bund is left at the seaward end with a nominal maximum width of 20 metres. It is thought that, during a large river flood, this bund would erode by fluidisation from the pressure of the river water behind it. There is no condition constraining the height of this bund. The batter angles of the bund are determined by the beach face angle on the sea side, and wind-wave action on the river side (waves wash over the fuse-bund during high seas). The conditions of consent do not specify how to measure the 20 metre maximum width. High sea and wave conditions can impede the fuse action of this bund by washing sand back into the fuse and/or causing a resistance to failure through high downstream (sea) levels.

Flood Management The responsibility to maintain the spit fuse channel and bund lie with the Whakatane District Council. However during the flood warning phase on the Whakatane River, the Environment Bay of Plenty flood manager should ensure that the spit has been prepared correctly. If a storm event is expected to exceed 150mm of rainfall in the Whakatane and Waimana catchments then the level of the spit should be confirmed. This is usually possible using binoculars to sight the height poles from the Signal Station on the Right Bank of the river. If levels are higher than 2.0 metres R.L. or if the bund at the seaward end appears wider than 20m (measured at a level of 2.0m) then contact Peter Cavanagh, Harbour Superintendent at the Whakatane District Council on 3060500 or 027 570 8283. For the severe events (significantly greater than 150mm) Whakatane District Council will lower to 101.4m on request even if the fuse is found to be below the 2.0m trigger.

Flood Managers should be aware that the fuse has not yet been observed to function as it was intended and there remain misgivings about its performance. These notes are intended to assist flood management staff, they do not necessarily reflect Environment Bay of Plenty’s public opinion. It should be noted that parts of these notes are at variance with a published report by river engineering expert Gary Williams in 2005.

If making flood management decisions impacted by the action of the spit fuse, it is safer to assume it will not perform in time.

Flood History During the 1998 flood the sand spit widened by lateral erosion from the tip once river levels enabled a flow path to form behind the training wall (Photo CN 140004). Although a similar flood size to 1970, peak levels were approximately 0.5m higher in 1998 in the lower river. This difference was attributed to the effect of the Western Training Wall.

During the July 2004 flood the sand spit did not erode significantly until after river levels had reached 3.05m and the tide was well receded. Overtopping of the river bank at Mataatua Reserve caused flooding of houses along Muriwai Drive. Sandbagging efforts narrowly averted flooding of Quay Street and the Whakatane CBD. Unfortunately evacuation efforts had not been adequately prepared, due in part to confidence in the spit fuse. Once the spit eroded the river levels dropped by more than a metre in 1.5 hours. Due to the darkness, the action of the spit fuse was not observed.

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6.7 Flood protection stoplog structures

The stoplogs take approximately one hour to fit. The Whakatane River flood protection system relies on stoplogs being fitted at multiple locations as follows (note all levels quoted in the lower river are in terms of the Moturiki Datum, including the Wharf gauge).

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6.7.1 Whakatane urban area stoplogs

Install the stoplogs at the BOAT RAMP slot First as the rising water arrives at this slot earlier, and install the rest travelling Upstream from there.

Bolts to secure the Whakatane Boat ramp stoplogs in place are kept in Graeme O’Rourke’s office.

Stoplog Number Trigger Invert Stored Fitting Generic Traffic Location of Level method Management Stoplogs Plan Number Whakatane The five stoplogs (three Hiab Boat Ramp 5 logs @ at boat ramp slot and Truck (boat trailer 2 2.2m two at waka shelter slot) N/A parking area) locations are located adjacent to 1.5m @ the two slots. Whakatane Wharf The stoplog is located Hiab Fishing Club 1 gauge or if 2.5m on site adjacent to the Truck 3 Valley slot. Quay Street Road is The stoplogs are Hiab (in front of 2 expected 2.6m located on site adjacent Truck N/A EBOP office) to exceed to the slot. 6.5m. Information The gate is padlocked Closed Centre – 1, open when not in use, by hand, Whakatane needs to be unlocked use a small 2.8m N/A Green Wharf hinged and padlocked closed stopbank gate until the flood peak padlock passes. key

A hiab truck fitted with lifting chains and shackles is required to lift and place the stoplogs. Phil Sisson (Sisson Engineering) 308 5596 (work) or 307 1115 (after hours) is familiar with fitting these stoplogs.

6.7.2 Road closures due to stoplog instillation

As the stoplogs involve district council roads, a generic traffic management plan has been approved and must be implemented (see Rivers & Drainage Section Generic Traffic Management Plans Manual plan number 3).The plan includes the setting out of the road signs and cones etc. Contact Jack Higgs, Opus, 027 494 2720 to advise that generic traffic management plan number 3, is to be activated. If possible also advise the local radio station.

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6.7.3 Whakatane rural area stoplogs

Stoplog Num of Trigger Level Stored Fitting Generic Traffic Location Stoplogs Method Management Plan Number Te Rahu No trigger level yet, Field Stored at Lightweight Canal, staff should be asked to EBOP’s aluminium, Paroa Rd 4 monitor site at the same Edgecumbe so can be 4 Bridge time as monitoring the Maintenance fitted by Waioho Canal site. Depot (in hand (two Waioho Stoplogs to be installed if the railway person Canal, water level rises above 5.4m wagon). crew Rewatu at site, about 7.1m on the minimum). Road gauge at Valley Road. OR If Bridge 4 levels rise above 6.8m at 5 Valley Road, the stoplogs should be installed. The extra rise is likely to take at least an hour.

6.7.4 Road closures due to stoplog instillation.

As the stoplogs involve district council roads, a generic traffic management plan has been approved and must be implemented (see Rivers & Drainage Section Generic Traffic Management Plans Manual plan number #).The plan includes the setting out of the road signs and cones etc. Contact Jack Higgs, Opus, 027 494 2720 to advise that generic traffic management plan number # , is to be activated. If possible also advise the local radio station.

6.8 Te Rahu basin and spillway

The Te Rahu catchment has its origin in the hills above Awakeri. It has a catchment area of 30 km2 and includes the Otarere, Mangaroa, and Upper Te Rahu Streams.

The Te Rahu was formed as part of the Whakatane River Major Scheme. The Basin consists of 405 ha ponding and storage area that is expected to function about once every 20 or 25 years when water levels in the Te Rahu Canal exceed design levels.

Discharge into the Basin occurs through the Te Rahu Spillway that has been constructed upstream of Te Rahu Road.

The spillway is 600 metres long and has a base level that is 0.76 m below the design stopbank level of 4.57 metres. Any water flowing into the basin will find its way to the Whakatane River by either:

• Flowing back into the Te Rahu Canal when water levels in the canal recede.

• Flowing towards, and being pumped by, the Te Rahu pump station.

Contact Scottie McLeod if it is predicted that the spillway will come into operation.

Scottie McLeod, Te Rahu Road, telephone: 308 7731

The spillway operated in July 1998.

Note — Water will rise quite slowly in ponding area and is unlikely to cause any real problems unless it occurs overnight.

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6.9 Rangitaiki Plains

Warnings are to be given if a flood in Whakatane River is expected to exceed 1400 m3/s at Valley Road and in excess of 100 mm rainfall has occurred on the Plains.

Once staff gauge at the Powdrell Road Bridge gets to approximately 1.350 m it will overtop the right bank near the sluice gate at the west end of the Kope Canal. This will be superseded once stopbank works are complete.

Graphs on the following pages cover:

• Whakatane at Valley Road rating,

• Whakatane at Valley Road staff gauge prompter,

• Whakatane at Huitieke staff gauge prompter,

• Te Rahu storage area map,

• Whakatane-Waimana Flood Monitoring sheet,

• Whakatane-Waimana extreme rainfalls at rain gauge sites.

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6.10 Flood warning phone list

6.10.1 Environment Bay of Plenty Licensees

Right Bank Rob and Toni Martin 3126322 or 027 465 3662 Left Bank Mick Doherty 308 7174 or 0274 921 992 Left Bank David and Joanne Fretwell 308 0601 or 0274 976 516 Left Bank Peter Schlepers 3070386 or 021 627 623 Left Bank Danny or Meredith Deegan 3085552 or 027 408 5552 Left Bank Shane Moore 021 037 2971

6.10.2 Treatment Plant Upstream to Pekatahi Bridge

Right Bank Bill Roberts (Warden) 312 9415 Rob Simpson 322 8783 Alan and Ian Dunstan 312 9446 Jim Houston 312 5898 or 027 450 2138 Steven Byford 312 3213 or 027 288 7751 Phil Byford 304 6110 or 0274 821 064

Left Bank Tony Langenberger (Warden) 308 5884 Graham Brownlee 307 9481 Nathan Jones (Reserve Warden) 312 9666 (Worker) Grant Ingles 312 9838 John Fairbrother 312 9008 Paul and Maureen Groom 312 9994 Terry Andresen (Contact P Groom – Terry’s 312 9063 house currently been rebuilt as result of July 2004 floods)

6.10.3 Pekatahi Bridge to Waimana Confluence

Right Bank Bruce Fowell (Warden) 312 9019 027 254 1247 Bruce Rutherford 312 9177 Left Bank Tony Hopgood 312 9623 Dairy 1 Manager Sisam & Sons Ltd Janette Mitchell 312 9121

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6.10.4 Waimana Confluence to Ohotu Bridge

Right Bank Group 1 Rob Lyford (Warden) 312 9087 Stu Reid (Reserve Warden) 312 9093 Diane and Gary Maxwell 312 9334 Graham Lyford 312 9495 Pip Richardson 312 9135 John Lillas 312 9225

Group 2 Gavin McGougan (Warden) 312 9107 Ken McGougan (Reserve Warden) 312 9108 Tuhoe Trust Sharemilker Grant Perkins 312 9357 or 0274 393 912 Alan and Heather Mitchell 312 9963 Alan Wilson 312 9195 Lawrence Rawson 312 9396

Left Bank Richard Sisam (Warden) 312 9045(Home) 312 9048 (Office) Bruce Sisam (Reserve Warden) 312 9039 307 9182 Richard Holmes 027 422 3129 Tiwi Black ? Wayne Dylan 312 9175 Ohutu Bridge to Limeworks Noema Watene 312 9377 312 9906 Neil and Laura Bowater 027 452 9822

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Chapter 7: Rangitaiki River

Chapter Summary

7.1 Rangitaiki Catchment hydrological characteristics...... 60

7.2 Historical flood protection ...... 60

7.3 Warnings and warning list...... 60

7.4 Telemetry sites ...... 61

7.5 Rangitaiki rainfall ...... 61

7.6 Culverts, floodgates, and pump stations...... 62

7.7 Flood control system and spillway ...... 62

7.8 Minor floods ...... 63

7.9 Major floods ...... 63

7.10 Landowners in Rangitaiki floodway ...... 64

7.11 Flood estimation ...... 64

7.12 Fonterra Limited Edgecumbe ...... 67

7.13 Pressure Relief Trench Monitoring Procedure...... 67

7.14 Matahina Dam ...... 67

7.15 Aniwhenua Dam ...... 71

7.16 Wheao Dam...... 72

7.17 Landowners in the Rangitaiki Floodway ...... 74

Have you: Received Warning?

Log Started?

Notified Anyone?

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7.1 Rangitaiki Catchment hydrological characteristics

The Rangitaiki River is one of the three major rivers, which cross the Rangitaiki Plains. It has a catchment area of approximately 3,000km2 rising in the Central Volcanic Plateau region of the North Island. Its main tributaries rise in the bush covered greywacke country of the Ikawhenua Ranges. The river flows down through a gorge, where it is harnessed for hydro electric power generation then onto the Rangitaiki Plains, past the townships of Te Teko, Edgecumbe and Thornton. The Rangitaiki River flows across the central part of the Plains and is sourced on the Kaingaroa Plateau. It has a very high bed load of coarse pumice sands and had undoubtedly been the major contributor of alluvial sediments to the Plains. The Rangitaiki River is perched above the surrounding Plains making flooding an ever present threat.

The Rangitaiki Plains cover an area of approximately 270 km2. They are an in-filled graben, filled by a combination of alluvial and marine processes. In many areas substantial swamps have contributed to the infilling and thick layers of peat have built up.

7.2 Historical flood protection

Early attempts to provide flood protection and drainage of the Rangitaiki Plains were begun around the turn of the century by the Rangitaiki Drainage Board. The Rangitaiki Drainage Board was taken over in 1911 by the Lands and Survey Department and by 1924 a new mouth was cut for the Rangitaiki River. This was a major project and had a significant effect on lowering the water table and discharging floodwaters to the sea at a much faster rate. In addition, a number of drainage canals were constructed using floating draglines. Because of the perched nature of the river systems the canal outlets had to be as close as practicable to their point of discharge to the sea.

7.3 Warnings and warning list

To read in conjunction with the Rangitaiki River staff gauge trees.

(a) EBOP Operations Staff, especially Principal Works Supervisor, Tony Dunlop- for pump stations etc

(b) Fonterra Limited -main water intake in river

(d) Landowners in Rangitaiki Floodway - Phone Lists are on blue paper at back of the chapter

(e) Landowners upstream of Te Teko

(f) Civil Defence

(g) Contractors;

(h) Police;

(i) Radio Stations;

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7.4 Telemetry sites

EDS Channel 1 – E191 - Environment Bay of Plenty Telemetry Channel

EDS Channel 2 – E115 – NIWA Telemetry Channel

Grid Site Name Reference Comments Agency RANGITAIKI CATCHMENT Rainfall in the upper Rangitaiki Kokomoka V18: 129 592 near Napier/Taupo highway. EBOP Levels/flow in the Rangitaiki at Rangitaiki @ Murupara V17: 329 984 Murupara. NIWA Rainfall situated between Whakatane and Rangitaiki Tarapounamu V17: 473 803 catchments NIWA River levels/flows and rainfall in the Whirinaki upstream of the Whirinaki @ Galatea V17: 370 960 confluence with the Rangitaiki NIWA Rainfall in the Waihua tributary of the Rangitaiki. Representative of Waihua Rain V16:471 171 mid catchment rainfall NIWA River levels near the Aniwhenua Rangitaiki@Aniwhenua V16: 418 163 dam NIWA Rangitaiki@Matahina V16: 446 360 River levels above Matahina dam. NIWA River level/flow and rainfall in the Rangitaiki @ Te Teko V15: 436 444 Rangitaiki at Te Teko NIWA/EBOP W15: 503 Rainfall in lower Rangitaiki plains Noord Veirboom 560 area EBOP W15: 508 River level and rainfall in lower Rangitaiki @Thornton 579 Rangitaiki. Tidal effects present. EBOP

7.5 Rangitaiki rainfall

Selected rain gauge observers contact Environment Bay of Plenty in the event of heavy rainfalls or when more than 50 mm has fallen in the previous 24 hours. Generally no appreciable floods are anticipated until reports of 125 mm in 24 hours are received. If the rainfall on the previous day has also been heavy then some estimation of the flood should be made.

Reports of heavy rainfall are forwarded to Trustpower at Matahina Dam and the station may be brought onto full load.

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Observers within the Rangitaiki who can provide rainfall information are:

Telephone Approx. Map Site Operator Number Reference Matahina Dam Trustpower 07 322 8014 V16: 440 860 07 366 4782 Aniwhenua Dam BOP Electricity V16: 410 160 07 3062705 Lake Rerewhakaaitu S Wicks 07 366 6753 ?? V16: 140 200 Galatea Bob Cavell 07 366 4827 V17: 410 030 Gordon J & J 07 366 4568 or Grant Road V17: 420 010 Gordon R & S 07 366 4771 07 377 0372 Wheao Dam Trustpower V18: 210 790 (John) 027 4325 836 Tarawera (Kawerau) Timberlands 07 343 1040 V16: 310 370 Omataroa Timberlands Timberlands V16: 480 380 has telemetry Galatea Timberlands for all these V17: 360 030 Kaingaroa (Goudies) Timberlands sites, normally V17: 210 040 Waiotapu Timberlands interrogated at U16: 090 150 midday, but can Tauhara Forest Timberlands U17: 900 180 be more Waimahia Timberlands frequent if U18: 950 600 requested. Minginui Timberlands V18: 350 780

7.6 Culverts, floodgates, and pump stations

Staff should be aware of the large number of culverts, pump stations, and floodgates in the lower Rangitaiki Catchment. The Principal Works Engineer (Tony Dunlop) normally has these structures checked from time to time.

For a plan of the position of these structures, contact the drafting office and request the plan on microfilm.

The relevant plan numbers are: R450/27 (2 sheets)

The rain gauge sites are marked on plan M566 sheet 1.

Copy of plans should be held in the flood room.

7.7 Flood control system and spillway

The flood control system on the lower Rangitaiki River relies initially on flood forecasting methods to determine the expected flood size, which enables the required amount of storage in Matahina Dam to be provided. Flood estimates must initially be based upon rainfall as the river gauges at (Whirinaki, Murupara, Aniwhenua) peak too late to enable full storage to be provided in the dam. Storage needs to be provided in the dam for floods with a peak greater than about 500 cumecs (20 year return period). A controlled release of water from the dam is specified in the "Operating Rules" refer section 7.10.

From the dam the flood wave passes along 11.3 km of natural channel where it attenuates slightly before entering the stopbanking system immediately above the

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Te Teko Bridge. Full flood capacity is available in the stopbank system down to 14.9km above the mouth, where, at a predetermined discharge, a controlled overflow of the right bank will occur which will discharge into the floodway. The floodway will limit the volume of water in the lower river so that levels do not exceed the known safe limits. The floodway rejoins the river 600 metres from its point of discharge to the ocean.

The floodway also provides a drainage outlet for some 3,700 ha on the plains, the main drainage systems being Reid's Central Canal (2,490 ha), Kopeopeo West Canal, and Western Drain (1,237 ha).

7.8 Minor floods

Matahina Dam is required to keep Environment Bay of Plenty informed of the lake level and flow rate from the dam “…to the satisfaction of the General Manager…”, but is allowed control in floods of less than 500 cumecs. The spillway comes into operation above about 160 cumecs.

Whenever the spillway is operating, a radio warning is advisable.

7.8.1 Floods up to 170 to 210 cumecs at Te Teko

Low lying land adjacent to rivers is liable to flood, particularly upstream of Te Teko.

7.8.2 Floods from 210 to 580 cumecs at Te Teko

These will affect all low lying areas above Te Teko and all areas within stopbanks below Te Teko (but not the floodway).

7.9 Major floods

7.9.1 Floods in excess of 580 cumecs at Te Teko

Following Edgecumbe earthquake restoration works, the river has full flood capacity but some areas below the Edgecumbe Bridge have minimal freeboard available. Floods in excess of 580 cumecs will affect landowners who may have stock in the Rangitaiki Floodway. (See section 7.8). The combined design capacity of the channel and spillway is 756 cumecs.

7.9.2 Critical levels: Rangitaiki floodway

The floodway is designed to come into effect at a flow of 580 cumecs (approximately).

The design capacity of the floodway is 103 cumecs, which requires a water level in the Rangitaiki about 0.33m above the spillway.

The design capacity of the main channel is 653 cumecs downstream of the spillway.

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7.10 Landowners in Rangitaiki floodway

Landowners who may have stock inside stopbanks on Reid's Central Canal and in the Rangitaiki Floodway area. (This list should be checked for accuracy in June of each year). Last updated June 2007. List located at back of this section on blue paper.

Whakatane District Council for road closures:

• Hydro Road

• McCracken Road

• McLeans Road

7.11 Flood estimation

An early estimation of flood size is required in order to lower the Matahina Dam before the main flood. That estimates should initially be based on rainfall reports and then confirmed by river level reports.

Two methods can be used for estimating floods in the Rangitaiki River and these are detailed below.

7.11.1 Flood estimates based on past records

From the isohyets of previous storms and the design storm, a prediction can be made of flood sizes from rainfall reports.

It should be realised that when rainfall reports are received, rain may still be falling and that the rainfall totals shown on the isohyets are generally for three or four days. The factors affecting flood size are:

• Maximum rainfall;

• Depth: area of storm;

• Locality of storm centre;

• Antecedent conditions

These factors are not all independent and will therefore be treated together.

Except for the 1944 storm when the maximum fall within the catchment was 375 mm, maximum falls have been in the order of 250-275 mm although this is no criteria for flood size. The depth area ratio of the storm is most important.

IF the distance between the isohyets IF the distance between the isohyets is small the storm is localised and is large then the storm is widespread the flood will be SMALL. and the flood will be much GREATER.

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The runoff characteristics of the Rangitaiki Catchment vary considerably and so the location of the storm is important. The runoff in the east of the catchment (steep greywacke ranges) is about ten times as great as that occurring to the west (the flat, pumice covered, Kaingaroa Plains). For similar storms the largest floods will occur when the centre is just to the east of the Murupara/Waiohau area.

If the antecedent conditions are wet the runoff will be greater, and so the flood greater, than if the ground is dry.

If the storm can be shown to be similar to one of the previous storms, it can be assumed the flood size will be of the same order. This method provides a preliminary estimate of flood size only.

7.11.2 Flood estimates by the rainfall/runoff/unitgraph method

This method gives an estimate of the complete hydrograph at Te Teko including the time of peak. Because the runoff characteristics of the catchment are so variable, a simple unitgraph could not be derived for the whole catchment. So it has been divided into seven subcatchments, as shown on plan M566 sheet 1, and a unitgraph has been derived for each of these and routed to Te Teko to form the composite unitgraph shown on M566 sheet 2.

This method is only valid when:

• There is widespread rainfall similar to previous events,

• Rainfall intensities < 25mm/hr

• Total average rainfall > 125mm in 48hrs.

Judgement must be used outside these criteria, as does the prediction of peak time at TeTeko.

The average rainfall for each subcatchment is calculated as follows:

• Plot isohyets (25mm) on sheet M566/1.

• Planimeter areas between isohyets for each subcatchment.

• Interpolate as necessary to give an average rainfall.

The hydrograph at Te Teko is obtained by the following:

• Write in average rainfall for each subcatchment on M566/2

• Multiply by appropriate runoff coefficient. Typical values are shown for each catchment - the higher figure represents wet antecedent conditions (and to some degree higher rainfall intensities).

• Multiply this runoff factor by the ordinates for each time step.

• Add all results in a row (including baseflow) to get the hydrograph at Te Teko.

This method can be done manually or by using the spreadsheet on V:\TS_RD\Flood Warning\Unithydrographs\unitrang.xls

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7.11.3 Discharge and time of travel: Whirinaki to Te Teko

In the table below a summary is given for several floods on the Rangitaiki River, showing the time of travel of the flood peak between the Whirinaki at Galatea gauging station (site number 15410) and the Te Teko gauging station (site number 15412) as well as the relative flood size at each site.

Note — that the total between Matahina and Te Teko is about 4 hours and that the storm events after January 1967 will have their total affected by the construction of the dam.

Date Whirinaki Te Teko Peak Time of Peak (m3/s) (m3/s) Travel (hours) February 1958 278 385 24 December 1958 227 414 27 May 1962 93 221 27 May 1962 119 374 15 June 1962 48 416 17 July 1964 127 272 21 January 1965 28 255 13 February 1965 337 596 21 Average 21 Minimum 13 Dam constructed, Time of Travel and Discharge Affected

February 1967 280 567 18 August 1970 285 637 11 May 1971 117 457 7 April 1974 101 316 13 February 1976 193 306 29 October 1983 158 371 21 August 1991 114 198 29 July 1998 437 Average (including 21 some not in table) Minimum 7

Since most of these storms have occurred, the Aniwhenua Dam has been constructed and this will increase the time of travel slightly. From these storms and in particular the study of the isohyetal maps, several facts emerge:

(iii) If the storm is widespread with similar depths of rain over the whole catchment, the time of travel from Galatea is approximately 18 to 24 hours and the peak at Galatea is about half the peak at Te Teko.

(iv) If the storm is centred to the north of the catchment the travel time is short and the Galatea peak is much smaller than that at Te Teko.

(v) If the storm is centred to the south, the time of travel is longer and the peak at Galatea is comparatively larger.

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7.12 Fonterra Limited Edgecumbe

Fonterra Ltd have an arrangement with TrustPower for notification when flow will exceed 140 cumecs. They will then keep a check on the river at Edgecumbe but should be advised as flows increase substantially above this figure.

Fonterra Ltd is manned 24 hours day. Telephone 07 304 7000 and ask for the "Energy Centre" extension 4808.

7.13 Pressure Relief Trench Monitoring Procedure

When the Rangitaiki River level rises through Edgecumbe to above the toes of the stopbanks it is recommended that the following monitoring procedure be carried out.

• Make regular inspections of the pressure relief trench outlet drains.

• Record the river level when flow is first observed from each outlet drain.

• At regular intervals while the river level remains above the toe of the stopbank:

o measure the turbidity of the water flowing from the drains,

o measure the flow coming from each drain and

o record the river level at the time the measurements were taken.

• Analyse the information to see if the assumptions made during design appear to be conservative and to enable re-estimation of likely outflows when the river reaches its peak design level.

• If there is increasing turbidity of the outflow water or if excessive outflow volumes are expected consider further remedial measures for that section of stopbank.

7.14 Matahina Dam

7.14.1 Introduction

Matahina dam is owned and operated by TrustPower Ltd and comprises an earth dam, a concrete spillway structure and hydroelectric power station. TrustPower has a comprehensive Emergency Action Plan (EAP) and procedures that outline how floods, earthquakes and volcanic activity will be jointly managed by its own management staff, emergency services, Whakatane District Council and Environment Bay of Plenty. Discharges from the dam spillway gates and power station penstocks are controlled by its resource consent conditions.

Minimum reservoir level (flood pending) 71.6m Minimum normal operational level 73.15m Maximum normal operational level 76.2m Design flood level 76.8m

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Matahina Dam has the capability of reducing the peak of the flood, providing storage is made available well before the peak of the flood passes the dam. A notable aspect of floods in the Rangitaiki River is the very high volume of discharge of which the dam is capable of storing only a small portion. After removing maximum station discharge and baseflow from the recorded 1970 flood, the dam was capable of storing between minimum drawdown level (RL 73.15) and design flood level (RL 77.05) only 10% of the flood volume. During the 100-year flood figure is expected to decrease to around 6%.

The other aspect of operation of the dam is that minimum drawdown level must be reached approximately 12 hours before the peak of the flood reaches the dam, and approximately 10 hours is required to attain the minimum level in the dam. Early estimation of the size of the flood is therefore vital to maximise the use of the dam in a flood event.

In order to provide an estimate of flood size reliable communications are necessary.

7.14.2 Telephone Communication

Telephone communication is available under normal circumstances. The lines are however vulnerable to storm damage and cannot be fully depended upon. Matahina Dam (ph 322 8014, fax 322 8024), is in telephone communication with TrustPower Te Maunga 24hr Control Centre ph 07 574 7958 or 07 574 4888 ext 777.

7.14.3 Radio communication

Matahina Dam has a radio telephone set which is normally switched to Channel E115 - a NIWA frequency. Channel 7 on the Environment Bay of Plenty fleet radios is programmed with E115 and should therefore be able to communicate with Matahina. Matahina and Te Maunga can also contact each other and via their Fleetphone trunk radio system.

7.14.4 Operation of Matahina Dam during floods

When a flood of about 500 cumecs or greater is expected, Environment Bay of Plenty will ask TrustPower to provide storage. The dam outflow and the lake level will fall to a minimum of RL 71.6m. The dam will be kept at RL 71.6m and the outflow to a maximum of 600 cumecs until:

• The inflow increases to more than 600 cumecs in which case the lake level will rise and the discharge may be increased to 755 cumecs;

• The peak at the upstream gauges indicates that the flood will be less than 600 cumecs in which case the dam may be refilled; or

• The peak passes the dam and the lake has not risen again to RL 76.2 m in which case the dam may be refilled. Details of this procedure are given later in Dam Operators Instructions.

TrustPower have a contingency plan in the event of imminent dam collapse.

Given the downstream stopbanks are designed for a 100 year design flow at 780 cumecs TrustPower has developed a three staged approach to flood management. The procedures allow TrustPower to optimise the power stations production and yet still comply with its consent conditions. Brief descriptions of the flood management stages follow (TrustPower, 2006):

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Stage 1 Alert: TrustPower receives a severe weather warning from the Met Service and alerts operations staff of a potential flood situation

Stage 2 without Lake Drawdown: For floods that are expected to be less than 500 cumecs TrustPower will increase generation with discharges up to 135cumecs. If lake level rises above the normal operating maximum level then the spillway gates will begin opening.

Stage 3: with Lake Drawdown: For floods that are expected to be greater than 500cumecs and/or upon request from EBOP to lower lake level. TrustPower will lower lake level and maintain it at a level below the normal operating minimal level. If the lake inflow exceeds 550cumecs then TrustPower will manage outflows so that it maintains a 550cumec outflow. If lake level still continues to rise above the normal operating maximum level then TrustPower will increase the total discharge to 600cumecs.

Since July 2004 TrustPower and EBOP have embarked upon a joint contract with NIWA to improve flood forecasting at Matahina dam. TrustPower and Environment Bay of Plenty are also preparing a joint Memorandum of Understanding that will improve dam operation during flood events.

7.14.5 Aims of operation

In order to provide flood storage when required without any loss of power production, the two basic aims of the dam operation outlined here are:

• To lower the lake to the minimum level before the main flood reaches the dam;

• To ensure the dam is refilled after the flood.

7.14.6 Limitations on outflow

• The capacity of the lower Rangitaiki Channel is 580 cumecs before overtopping of the Reids Central spillway. There is a further provision for 100 cumecs down the floodway and 75 more in the main channel. Outflow should therefore be restricted to 580 cumecs and only go to 755 cumecs when the lake is rising so rapidly that it will exceed its maximum level.

• When the lake is being lowered, a maximum outflow of 550 cumecs has been specified which allows a safety margin of 30 cumecs.

7.14.7 Limitations of lake lowering

• A maximum drawdown rate of lake level of 0.3 m per hour has been specified to avoid slumping of the banks. This implies a maximum excess of outflow over inflow of 200 cumecs.

• A maximum increase in outflow of 280 cumecs per hour or 70 cumecs per 15 minutes has been specified in order to limit the rate of rise downstream of the dam.

7.14.8 Limitation on Lake filling

Sudden reductions in river level downstream of the dam would result in slumping of the banks. So the rate of river level drawdown is limited to 1.2 m in 8 hours, with the proviso that the actual reduction may be made in a period of 30 minutes, with the outflow then kept constant for the following 7½ hours.

Flood Warning Manual July 2008 70 Environment Bay of Plenty

7.14.9 Request to draw lake down

Environment Bay of Plenty can request Lake drawdown. This should occur only rarely when:

• Meteorological forecasts clearly indicate that the Rangitaiki Catchment is likely to receive a major storm event.

• The rainfall data that has been collected and analysed using the existing empirical model indicates that discharges in excess of 450 cumecs are likely at Te Teko.

7.14.10 Procedure for station operators

As soon as possible after the System Controller, Tauranga (07 574 7958), has accepted a request for lake drawdown by Environment Bay of Plenty, the station shall be brought to full load and the total station discharge increased to the value assessed by Environment Bay of Plenty.

Lake drawdown in accordance with this procedure shall not exceed a rate of 0.3 metres per hour and total station discharge shall be limited accordingly.

When drawing down, the outflow will not exceed 200 cumecs more than the inflow or at any stage exceed 550 cumecs. Total station outflow shall be maintained at this rate until the lake falls to elevation 71.6m. When the lake reaches this level, the discharge shall be regulated in accordance with …

At elevation 71.6m or such higher level at which the lake may cease falling, the total station outflow shall be maintained equal to the inflow until it reaches 550 cumecs. If the inflow starts falling before 550 cumecs is reached, as indicated by a falling lake level, the outfall shall be restricted progressively to that required for system load and the lake brought back to elevation 76.20 m as quickly as possible.

When the inflow exceeds 550 cumecs, the total station discharge shall be kept at 550 cumecs until one of the following conditions is reached:

• The lake level begins to rise then the discharge can be increased to 600 cumecs, (note this is over spillway design start level). If the lake level commences falling before elevation 76.2 is reached, the spillway gates shall be closed until the total station discharge again equals the inflow. If Environment Bay of Plenty advises that the flood peak has passed, the gates shall be progressively closed and the lake level returned to elevation 76.2 as quickly as possible. Any residual flood shall be discharged in a similar procedure as above.

• If the lake level continues to rise with a discharge of 600 cumecs above elevation 75.0, or at a rate higher than 0.3 metres per hour, the discharge shall be increased to 755 cumecs, until the lake level begins to fall, in which case the lake level can be brought back to elevation 76.2 m. If the lake level continues to rise above elevation 76.7, normal spillway procedure will come into operation.

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7.14.11 Sudden Failure Procedure

TrustPower have outlined the potential consequences of a sudden failure of Matahina earth dam on a sunny day in the EAP. The EAP also documents the emergency management controls TrustPower will implement in such an event. If a large flood causes the Emergency then the incremental consequence will be less at most but not all downstream locations. A flood map showing inundated areas resulting from a dambreak of Matahina Dam during a dry day is shown in drawing 8/1275/92 provided in Figure A2.4, Appendix 2, Rangitaiki-Tarawera Floodplain Management Strategy (2007).

7.15 Aniwhenua Dam

Aniwhenua Power Station is controlled and monitored from Bay of Plenty Electricity control room at Commerce Street, Whakatane. The control room is manned on normal working days between 0730 and 1700.

The information regarding any aspect of the scheme that is monitored via SCADA can be gained from the control room by telephoning 07 3062705. If calling outside normal working hours, there may be a delay in response as the telephone transfers to the Duty Controllers mobile telephone.

Aniwhenua Power Station attendants can be reached via the control room, `or at the Power Station (telephone 07 366 4782).

Ask to be put in touch with someone from generation.

7.15.1 Inflows to Lake Aniwhenua

The continuous readout in the control room is based on the water level at Bay of Plenty Electricity's gauge on the Rangitaiki River at Galatea (near the Galatea substation). The water levels at this site are measured with a pressure transducer and telemetered back to the control room via their own Leeds and Northrup telemetry system, through UHF radios.

The rating curve for this site has not been derived by normal gauging methods. The discharge for the stage/discharge relationship has been calculated by:

• Noting the discharge at the tailrace at which the lake level is constant and plotting this discharge against gauge height at the Galatea site.

The Galatea site cannot record over 100 cumecs and because of its position does not take into account flooding on the Horomanga.

The BOP Electricity's water right states that inflow to Lake Aniwhenua shall be calculated according the equation:

Inflow = 1.35 G + 1.49 M + 3.54 cumecs,

Where G is the flow in cumecs in the Whirinaki at the Galatea gauging station and M is the flow in cumecs in the Rangitaiki River at the Murupara gauging station. This equation is only suitable for use with mean daily flows and should not be used for calculating flood flows.

Flood Warning Manual July 2008 72 Environment Bay of Plenty

7.15.2 Outflow from Aniwhenua

Outflow from the lake can be either through the radial gates at the northern end of the lake, or along the canal and down through the powerhouse to the tailrace. Provision has also been made for emergency discharges from the lake through an emergency gate that is tripped at a predetermined water level.

(i) Radial Gates

The setting of the gates is telemetered back to Whakatane and BOPE has a relationship between gate setting and discharge.

(ii) Tailrace

BOP Electricity and NIWA have telemetered flow sites at the outlet.

7.15.3 Aniwhenua Dam: Water Right 190

This water right was issued in December 1975 with a later variation in December 1981.

The information contained below is a precise of the relevant requirements of the right as they relate to the control of the dam during flood flows.

"1.1 ...the discharge from the powerhouse shall not exceed 75 cubic metres per second. The rate of change of discharge shall not exceed 10 cubic metres per second per minute.

2.2 The water level of Lake Aniwhenua shall be maintained between 146.6 metres and 146.8 metres under normal operating conditions.

3 The spillway gates incorporated in the dam must be capable of passing a flow of 850 cubic metres per second at a water level of 146.8 metres. Additional spillway capacity must be provided so that a total flow of 1270 cumecs can safely pass through or over the dam at a water level not exceeding 147.5 metres.

The opening and closing mechanism of all spillway gates shall be provided with an alternative means for their operation in the event of any electrical power failure.

8 The 'grantee' shall provide BOPRC with information regarding "the occasions when water was discharged through the spillway structures and an estimate of such discharges and their duration."

7.16 Wheao Dam

7.16.1 General

The Wheao Power Station is situated on the left bank of the Wheao River approximately 25 km south of Murupara. The station is controlled from the Trustpower offices in Rotorua.

July 2008 Flood Warning Manual Environment Bay of Plenty 73

The Wheao River is partially sourced from the high runoff areas of the Urewera Ranges whereas the nearby Rangitaiki River originates in the low runoff Volcanic Plateau. The Flaxy Dam is too small to affect the height or timing of floods. In extreme events, an emergency spillway will divert water from the Flaxy system past the powerhouse to the Wheao River.

Time of travel between Wheao Dam and Murupara is of the order of 6-8 hours at normal flows.

See also consent number 1370 02 0253

7.16.2 Contact numbers

Tauranga office 07 574 4800 ask for the control room

Direct dial control room 07 575 2908

Telephone or fax the dam 027 399 3369

7.16.3 Rainfall and discharge data

Trustpower have two flow sites that are telemetered back to their Rotorua offices (The telemetry system is not one of ours).

(i) Wheao River downstream of the Powerhouse (i.e. total flow of Wheao River and Powerhouse);

(ii) Rangitaiki River at above canal intake (i.e. Total Rangitaiki River flow). This site was not rated until late 1988.

Flow at the Wheao/Rangitaiki confluence is therefore both these rates added together, minus the diversion in the canal (maximum 21m3/s).

Rainfall information can also be attained by telephoning either the dam direct or via the Rotorua control room. There is a rain gauge at the dam site (manual, to be automated 1997).

Graphs on the following pages cover:

• Rangitaiki at Te Teko rating,

• Rangitaiki at Murupara rating,

• Whirinaki at Galatea rating,

• Waihua at Gorge rating,

Flood Warning Manual July 2008 74 Environment Bay of Plenty

7.17 Landowners in the Rangitaiki Floodway

If in Doubt – Give them a Warning

Landowners who may have stock inside stopbanks on Reid's Central Canal and in the Rangitaiki Floodway area. (This list should be checked for accuracy in June of each year). Last updated June 2009.

Name Phone Dennis and Mary Sax 322 8091 Graham and Leeanne Reeves 304 8629 or workers 304 9326 John and Fiona Haultain 304 9509 Bridget Newdick 304 6353 Sullivan Estate (Barbara Sullivan) 304 8454 Bernie McCracken 304 9750 Awaroa Farm (Fonterra Owned) 304 9169 or 304 7000 extension 7716 G.K Evans 304 9037 Kevin Leech 304 9689 G.K. Lloyd 304 9116 P.D & R.L Askey 304 8246 Kathony Farms – Wayne Morgan 312 3330 David and Sue Law (Sharemilkers) 304 9760 Warren Olsen 304 9429 or 021 765 345 Walter Van Rossum 304 8033 P.R Baird 308 8881 or 0274 997 475 Shaw, Glen 304 8236 C Fraser and S Bignell Gerrit Van Den Top 308 5173 Craig Hammond 308 4713 or 027 297 6334

Contact Whakatane District Council for road closures:

• Hydro Road

• McCracken Road

• McLeans Road

July 2008 Flood Warning Manual 75

Chapter 8: Tarawera River

Chapter Summary

8.1 Introduction and history ...... 77

8.2 Hydrology ...... 77

8.3 Telemetry sites ...... 78

8.4 Rain gauge sites...... 78

8.5 On track...... 78

Have you:

Received Warning?

Log Started?

Notified Anyone?

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Environment Bay of Plenty 77

8.1 Introduction and history

The Tarawera River is situated on the western side of the Rangitaiki Plains and is covered in the volcanic areas of the lakes system. Large quantities of pumice sands have been deposited by this river and contributed to the infilling of the plains. The Rangitaiki and Tarawera Rivers once had a common outlet.

From 1971 through to the present, flood protection and drainage works, as set out in the Rangitaiki/Tarawera Rivers Major Scheme Report, have been completed with a series of large contracts. The materials used have largely been won from the adjacent river as the cheapest source available. This has caused some problems, where coarse pumice sand allowed excessive seepage and a grass cover would not grow. This has been overcome with the method of toe loading of the stopbanks and the use of special grass species.

In some areas underbank seepage and the potential for a piping failure required toe loading and special surcharge areas to be constructed. In some areas specially imported material was used to strengthen the stopbanks.

The March 2 1987 earthquake caused no overall subsidence to the Tarawera River stopbank system and its 100-year standard of protection has been restored with the completion of the earthquake repairs.

Surveys in 1998 indicated the bed level had dropped in most places; erosion and susceptibility of the banks to undercutting may have increased.

8.2 Hydrology

Two rated water level recording stations are located on the Tarawera River. Downstream of the outlet of Lake Tarawera is the Lake Outlet recorder site (NIWA) while much further downstream near the Edgecumbe/Matata highway is the Awakaponga recorder site (Environment B·O·P). In addition, there is a water level recorder near Matata, upstream of the main road bridge (tidally affected).

8.2.1 Lake outlet recorder site (statistics)

Minimum Q = 3.8 cumecs Mean Q = 6.7 cumecs Maximum Q in 1972 = 15.7 cumecs (average annual flood = 10 cumecs)

8.2.2 Awakaponga recorder site (statistics)

Minimum Q = 15 cumecs Mean Q = 30.4 cumecs Maximum Q = 92 cumecs in 1962 (average annual flood = 55 cumecs)

The above data should demonstrate that floods are caused in the catchment below the Lake outlet site rather than in the lake itself. It is generally felt that the portion of the catchment that most contributes to flooding is that area between Kawerau and the Lake outlet.

A typical Awakaponga hydrograph is extremely long and flat and generally occurs over days rather than hours.

Flood Warning Manual July 2008 78 Environment Bay of Plenty

8.3 Telemetry sites

EDS Channel 1 – E191 - Environment Bay of Plenty Telemetry Channel

Site Name Grid Reference Comments Agency TARAWERA CATCHMENT River level/flow and rainfall in the Tarawera @Awakaponga V15: 412 556 central Rangitaiki plains EBOP Levels and rainfall in the Tumurau lagoon which flows into the lower Tumurau Lagoon V15: 383 523 Tarawera. EBOP River levels and rainfall in the lower Tarawera. Tidal effects ORC Pump Station V15: 434 606 present. EBOP

The rating curve at Awakaponga varies considerably with changing bed levels. The latest HydroTel rating is likely to be the most accurate way of relating stage to flow, although high flows may not have been calibrated. Several but not all previous floods have had an increase of stage of around 0.15m per 10m3/s at higher flow rates.

8.4 Rain gauge sites

Lake Rerewhakaaitu S Wicks 07 366 6753 Waiotapu Timberlands 07 343 1070 Tarawera (Kawerau) Carter Holt Harvey Tasman 07 306 9050

8.5 On track

On Track need to be notified if high intensity rainfall is being recorded along their Tauranga-Kawerau railway line. Call Duty Network Control Manager 09 498 2066 or Network Control Manager (Kawerau) 021 440 112. The Flood Manager will need to advise On Track of the areas vulnerable to flooding after assessing the rainfalls and storm track.

In many cases the advice would be “there is major flooding throughout and On Track are advised to halt all train movements between Kawerau and Tauranga”, or if a storm only affects the Kaituna to Tauranga area, then the affected area may be Otamarakau/Hauone (where there is a train station) to Tauranga.

This was the advice that should have been heeded in the 1 May 1999 storm, when the tracks were moved sideways at the Raparapahoe Bridge and the Waiari Bridge was undermined.

The pager alarm trigger levels are set up as follows:

• Mangorewa at Saunders...... 60 mm in 3 hours

• Pongakawa ...... 30 mm in 1 hour

• Tarawera at Awakaponga...... 30 mm in 1 hour

• Tumurau Lagoon ...... 30 mm in 1 hour

• Ohinkoao ...... 30 mm in 1 hour.

July 2008 Flood Warning Manual Environment Bay of Plenty 79

Graphs on the following pages cover:

• Tarawera at Awakaponga rating

• Tarawera at Awakaponga staff gauge prompter

Flood Warning Manual July 2008

Chapter 9: Kaituna River

Chapter Summary

9.1 Introduction and history ...... 83

9.2 Warnings and warning list...... 83

9.3 Telemetry sites ...... 84

9.4 On Track...... 84

9.5 Rain gauge readers ...... 85

9.6 Lower Kaituna River: sensitive areas...... 85

9.7 Flood warning phone list...... 89

Have you:

Received Warning?

Log Started?

Notified Anyone?

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Environment Bay of Plenty 83

9.1 Introduction and history

The Kaituna River occupies some 1250 km2 in the Bay of Plenty region of the North Island, draining lakes Rotorua and Rotoiti and surrounding lands. The river rises at the Lake Rotoiti outlet and flows 51.5 km to the sea near Maketu, with several tributaries draining the adjacent area.

For the first half of its course, the river flows in a deep gorge through steep bush- covered terrain. It then emerges onto a gradually widened flood plain. The lower half of the river originally suffered from a tortuous alignment and inadequate flow capacity. The resulting high water levels restricted drainage from the adjoining low lying flat lands and caused frequent overtopping of the banks with consequent extensive flooding.

In 1980 the Bay of Plenty Catchment Board began the construction of a major stopbanking and drainage system.

9.2 Warnings and warning list

To read in conjunction with the Kaituna River staff gauge trees.

• EBOP Operations Staff (especially Tony Dunlop);

• Wardens or Farmers - Phone Lists are on blue paper at back of the chapter.

• Western Bay of Plenty District Council;

• Civil Defence

• Contractors;

• Police;

• Radio Stations;

IMPORTANT The Principal Works Engineer (Tony Dunlop) must be notified early (at first warning level) so that his works gang can check all floodgates.

Flood Warning Manual July 2008 84 Environment Bay of Plenty

9.2.1 Warning lists

A series of "Warning Lists" have been developed to help with the transfer of warnings and alerts to the farmers of the Kaituna Catchment. Please note that it is normally only necessary to contact the Wardens (Heads) of each group. The members of each group are given here only in case of the Wardens not being available. Phone lists are located on blue paper at the back of this section.

9.3 Telemetry sites

EDS Channel 1 – E191 - Environment Bay of Plenty Telemetry Channel

EDS Channel 2 – E115 – NIWA Telemetry Channel

Site Name Grid Reference Comments Agency KAITUNA CATCHMENT

Whakarewarewa U16: 959 329 Rainfall in Rotorua city area EBOP

Lake Rotoiti U15: 030 447 Rainfall and lake levels at Okawa Bay EBOP Rainfall at the top of the Kaituna Kaharoa U15: 970 495 catchment EBOP River level/flow immediately downstream Kaituna @ Taaheke U15: 035 499 of the Okere Gates control structure NIWA River level/flow and rainfall in the Mangorewa which is a major tributary of the Kaituna catchment. Subject to rapid Mangorewa @ Saunders U15: 046 634 rises in water level up to 8 metres. EBOP Rainfall in the mid Pongakawa Pongakawa V15: 166 604 catchment. EBOP River level and rainfall site in the lower Kaituna @ Te Matai U14: 064 734 Kaituna catchment near Te Puke. EBOP River level in the lower Kaituna. Tidal Kaituna @ Clarke’s U14: 053 778 effects present. EBOP River levels at the bottom of the Kaituna Kaituna @ Fords Cut V14: 109 775 catchment. Tidal effects present. EBOP

Additional information can be gained by interrogating the levels of Lakes Rotorua and Rotoiti - see Chapter 10.

9.4 On Track

On Track need to be notified if high intensity rainfall is being recorded along their Tauranga-Kawerau railway line. Duty Network Control Manager 09 498 2066 and Network Control Manager (Kawerau) 021 440 112. The Flood Manager will need to advise On Track of the areas vulnerable to flooding after assessing the rainfalls and storm track.

July 2008 Flood Warning Manual Environment Bay of Plenty 85

This was the advice that should have been heeded in the 1 May 1999 storm, when the tracks were moved sideways at the Raparapahoe Bridge and the Waiari Bridge was undermined.

The pager alarm trigger levels are set up as follows:

• Mangorewa at Saunders 60 mm in 3 hours

• Pongakawa 30 mm in 1 hour

• Tarawera at Awakaponga 30 mm in 1 hour

• Tumurau Lagoon 30 mm in 1 hour

• Ohinkoao 30 mm in 1 hour.

9.5 Rain gauge readers

9.5.1 Lower Kaituna

Cor and Christine Verwey Collins Lane Te Puke 07 573 6414

9.6 Lower Kaituna River: sensitive areas

These areas either have caused problems in the past, or are considered to have potential to cause problems.

9.6.1 Upper Ohineangaanga

This stream is subject to debris blocks in the upper catchment with rapid release of flood waters as they burst. In the area around the township, and upstream of the town where there are numerous orchards and deer farms that suffer flooding and erosion problems. The stream is considered too 'flashy' for warnings to be issued.

The Kopuroa, Raparapahoe, Parawhenuamea, and the Waiari are also considered to be in this 'too flashy' category.

9.6.2 Maketu Area

This drainage in this area is serviced by three main pump stations, Diagonal Drain, Ford Road and Maketu. Each station is telemetered and is monitored by the Kaituna Works Supervisor. Floodgates also require checking before and during events. Problems can occur when more than 70mm of rain falls over a couple of days and the catchment is moderately saturated.

Flood Warning Manual July 2008 86 Environment Bay of Plenty

The area also relies on gravity drainage out into the Maketu estuary through a number of floodgated culverts. In the past these have become silted up causing problems. An ongoing desilting program is in place but during events where water is lying on farms they should be checked at low tide for siltation. Contact the Kaituna Works Supervisor to arrange this.

The Maketu Diversion gates were installed in 1992 to improve the ecology of the estuary (following deterioration from the diversion of the Kaituna to the Te Tumu Cut in the 1950's). One gate has been removed. There is no longer a requirement to close the gates at a certain level. There have been problems in the past associated with large trees being caught on the culverts. If they are closed, Clem Tapsell, ph 533 2327 or Elaine Tapsell, ph 533 2503 and, DOC Rotorua, ph 349 7400, should be notified.

9.6.3 Left bank sand dunes

The sand hills on the left bank of the lower Kaituna, from Fords Cut up to Bells Road. May be susceptible to scour in high flows. Use contact E K Hickson, telephone 07 542 0148.Needs updating.

Not normally a problem.

9.6.4 Kaituna Wetland culverts

Four culverts let water into the Kaituna Wetland: two 600mm pipes at the upstream loop, a 1.8m pipe into the middle loop and a 450mm balancing culvert at the downstream loop. The 450mm and 600mm pipes have floats that are designed to close at levels above 1.5m. The 1.8m pipe has a sluice gate that will need closing manually. The 450mm culvert lets water back out if the level in the wetland is above 1m (and river levels are less than 1m).

A water level recorder inside the wetland monitors the level and this along with river levels is used to initiate a closure of the sluice gate. The target level in the wetland is 0.87m (Moturiki) and overtopping of the stopbanks around the wetland should be monitored once the level has reached 1.1m (Moturiki).

It is not expected there will be excess inflow through the Kaituna Wetland culverts unless levels rise above 1.5m R.L. This is expected to require at least 200m3/s (10yr flood) at Te Matai (3.5m on the gauge), or levels above 1.3m at Fords Cut during a storm surge event for a number of high tide cycles.

9.6.5 Bell Road Area

This area is serviced mainly by gravity drainage into the Kaituna River. There are also low stopbanks along the main Bell Road Drain that overtop in medium sized coastal rainfall events or if the lower Kaituna River is high because of storm surge or river floods. Floodgates require checking in this area before and during events. A key contact for this area is Lindsay Marshall, phone 07 573 4465.

Two small pump stations also exist and are looked after by on-site caretakers.

9.6.6 Upstream of Te Matai

These are various areas upstream of Te Matai with only 10 year banks or no stopbanking at all. Farmers in this area need warnings at the given warning levels in this manual. Wardens have been allocated a number of land owners each to phone.

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The Mangorewa River is a short catchment and subject to high intensity rainfalls in the southern catchment bordering Lake Rotorua. This river has the potential to cause large floods in the middle reaches of the Kaituna River. An overflow channel exists just upstream of the confluence with the Kaituna that spills water when the Saunders water level recorder reaches approx. 4.5 metres.

See chapter 10 regarding the lakes. Note that during high flows from the Mangorewa River and middle Kaituna area, the increase from opening Okere gates is a very small percentage of the overall flow.

9.6.7 Flood Pumps

Two flood pumps are stored in the Lower Kaituna area for use in flood events. Contact should be made through the Kaituna Works supervisor who would normally arrange their deployment.

Graphs on the following pages cover:

• Mangorewa at Saunders rating,

• Kaituna at Te Matai provisional rating (affected by tide at low levels)

• Kaituna at Te Matai staff gauge prompter,

• Drainage and Canal network plan.

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Environment Bay of Plenty 89

9.7 Flood warning phone list

Group 1 Mangorewa /Kaituna Confluence Area Stuart Steel (Warden) (07) 533 1069 or 021 949 128 Longridge Park Shop (07) 533 1515 Joan Scown (Reserve Warden) (07) 533 1076 Allister Reese (07) 533 1439 David Woodward (07) 533 6240 Peter Hareb (07) 533 1824 or 027 223 6052 Peter Melton (07) 533 1477 027 439 6667

Group 2 Weld Properties Richard Weld (Warden) (07) 573 6108 or 027 472 8146 Gerard Weld (Reserve Warden) (07) 573 9073 or 021 232 4850

Group 3 Upstream State Highway 2 Geoff McNaughton (Warden) (07) 533 1139 Graham and Isabel McNaughton (07) 533 1196 Gary and Tracey McNaughton (07) 533 1476 Brian Tanner (07) 573 7300 Murray Wootten (07) 533 1178 Dave Davis (07) 533 1126 Dennis Armstrong (07) 533 2270

Group 4 Downstream State Highway 2 – Left Bank (Also Ohineangaanga and Raparapahoe) Dave Marshall (Warden) (07) 573 7546 or 027 493 6781 Colin Armer (07) 573 9689 Cor Verwey (07) 573 6414

Group 5 Bell Road and Left Bank Craig Roughton (Warden) (07) 542 2538 Lindsay Marshall (Reserve Warden) (07) 573 4465 Dave Hurst (07) 542 2138 027 472 8643 Phillip Dovoston (07) 542 0024 Graham Thompson (07) 542 0915 Noel McLeod (07) 542 0762 Andrew Simmelink (07) 542 2800 Geoff Hickson (07) 542 1343 021 137 2673

Flood Warning Manual July 2008 90 Environment Bay of Plenty

Group 6 Right Bank from Mouth to State Highway Doug Pammant (Warden) (07) 573 4470 0274 918 450 Roger Hintz (Reserve Warden) (07) 573 6893 Alan Titchmarsh 025 416 421 Henry By de Ley (07) 533 2099 Ray Bushell (07) 533 2422 Roy Vercoe (07) 578 4787 G Boswell (07) 573 5425 Ronaki (07) 573 8015 Dennis Armstrong (07) 533 2270

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Chapter 10: Lakes

Chapter Summary

10.1 Lakes Rainfall ...... 93

10.2 Lake Rotoiti...... 93

10.3 Lake Rotorua ...... 96

10.4 Lake Okareka ...... 97

10.5 Okere Gates ...... 99

Have you:

Received Warning?

Log Started?

Notified Anyone?

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Environment Bay of Plenty 93

10.1 Lakes Rainfall

Sources of Lakes Rainfall Information are:

Telemetered rain gauge at Kaharoa

• NIWA 07 346 1950

• J H Wright (Okere Falls) 07 362 4887

• A T Shaw (Rotoma) 07 362 0777

• Doug Morris (Rotorua Airport) 07 345 9836

10.2 Lake Rotoiti

10.2.1 Rotoiti telemetry

The system used is an iRIS320 which is linked to an SDI12 shaft encoder. The level of Lake Rotoiti at Okawa Bay can be gathered from HydroTel where it is normally updated on an hourly basis. If for some reason the Okawa Bay site fails secondary data may be obtained from NIWA (Phone 07 346 1950) as they operate an alternate recorder at Okere Falls; note that the Okere recorder is subject to draw-down from the Okere Gates control structure.

Flood Warning Manual July 2008 94 Environment Bay of Plenty

OPERATING GUIDELINES FOR OKERE GATES BETWEEN LAKE ROTOITI AND THE KAITUNA RIVER (As at 30 November 2005)

Note – Guideline levels were adjusted by –0.034m to synchronize with change in Bench Mark levels (GN O’Rourke)

Objective: To aim for the target level of 279.116m above Moturiki Datum and to remain within 75mm of this level as far as practicable.

The lake level is now measured by Environment Bay of Plenty’s new lake level recorder at Okawa Bay Marina. The lake level is measured as 278.908m (RL Zero) plus the telemetered reading from the recorder.

Guidelines:

1 Open or close gates between 8am and 9am or 4pm and 5pm whenever possible. 2. All three gates should be moved in unison. 3. Minimum gate openings are 100-200-100. Check ratings to ensure flow above 7.9m3/s. 4. If the lake remains above 279.166m for three days, open gates 3x100mm. 5. For lake levels above 279.191m, open 3 gates by 200mm each. 6. If levels are above 279.216m the next day open 3 gates a further 200mm each. In general, this setting should be 300mm or 400mm higher than the setting required for a stable lake level. 7. All three gates open full when lake rises to 279.266m unless the flood manager decides otherwise. 8. Gates can be closed by 3x100mm when level is below 279.166m if lake is falling and expected to continue falling at the new setting (including forecast rain and Lake Rotorua level). 9 When lake reaches 279.116m, close gates to the level expected to be most stable. 10 If lake drops below 297.101m, close gates 3x100mm. 11 Gates may be opened 3x100 or 3x200 (eg. if heavy rain is forecast or levels above 279.191m are likely) 12 Maximum change in flow rate is 5m3/s/hr when closing gates and 10m3/s/hr when opening gates. 13 Inform all rafting companies by fax when gates are to go outside or return to the range 3x200 - 3x500. 14 Keep a record of enquiries relating to lake levels.

10.2.2 Rotoiti Minimum and Maximum

• Rotoiti maximum is set at RL 279.406

• Rotoiti target is set at RL 279.116

• Rotoiti minimum is set at RL 278.856

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10.2.3 Rotoiti control gates

Keys are held by:

• Graeme O’Rourke

• Roger Waugh

• Rotorua Office (Craig Putt / Richard Mallinson)

• Gates record book in Graeme O’Rourke’s office, spare key taped in back of book.

Maintenance and repairs can be carried out by:

(i) Engineers:

Unique Sheetmetals 198 View Road Contact: John Mawer phone: 07 349 3426

Summit Engineering and Hydraulics Limited Telephone: 07 348 0464 After Hours: 07 345 5990 (Mike Klomp)

(ii) Electricians:

Control Tech (Opotiki) Geoff Indcavort 025 9939 44

10.2.4 Discharge through Okere Gates

*Minimum discharge 7.9 cumecs (This equates to gate settings of approximately 100,200,100)

Maximum rate of change up 10 cumecs/hr Maximum rate of change down 5 cumecs/hr

When opening the gate settings at Okere Falls you must not exceed a rate of change greater than 10 cumecs in an hour.

Discharge through the gates depends on lake level, but the following table should give approximate flows (m3/s):

Gate setting/ 200 300 400 500 600 700 800 900 1000 1200 1500 Lake level 279.116 12 17 21 25 27 29 31 33 34 36 36 279.216 13 18 23 27 30 32 34 36 38 41 44 279.231 14 19 25 29 33 36 39 42 44 48 52

Cumecs (m3/s)

When the Okere Gates are opened to greater than 3x200 or 3x500, the list of people on the contact list in blue at the back of this chapter need to be contacted, also when they are closed to below these

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10.3 Lake Rotorua

10.3.1 Rotorua telemetry

The system being used is a Kainga Interrophone (owned by Environment B·O·P) which is linked to a Leupold and Stevens water level recorder (owned by NIWA - Rot). The Dataphone is 230 v powered so beware of power failures in the area.

Note — the difference in RL Zero of the two staff gauges on Lake Rotorua i.e.

• Town Warf + 277.000 = Rotorua (RL)

• Lakefront Staff gauge + 279.010 = Rotorua (RL)

10.3.2 Lake Rotorua - minimum and maximum

• Rotorua maximum is set at RL 280.11

• Rotorua medium is set at RL 279.805

• Rotorua minimum is set at RL 279.50

10.3.3 Lake Rotorua outlet

The level of Lake Rotorua is controlled by a permanent 'choke' structure installed in 1989. Its principal purpose is maintenance of lake level during the typical summer low flow period. Fine tuning of this level is attained by steel stoplogs each 100 mm in height and placed on the bed of the channel which lies at the centre of the waterway. In order for the structure to discharge floods it is desirable the stoplogs be removed.

Tony Dunlop normally handles removal/installation of the stoplogs.

The crane hire companies familiar with the site are:

• Lakeland Steel Doug Stewart phone: 07 347 9585

• Todd & Pollock Crane Hire 136 Birch Ave Tauranga phone: 07 577 9849

• Todd McPhee Crane Hire Ltd phone: 0800CRANES, 0800 272 637

• Lakeland Plant Hire Ltd 142 View Rd, Rotorua, phone: 07 347 9585 fax: 07 347 9846

Bruce Morrison phone: 07 348 3658 Teeny Stewart phone: 027 4924 500

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10.4 Lake Okareka

LAKE OKAREKA OUTLET – GUIDELINES FOR OPERATION OF STRUCTURE

(i) Introduction

Lake Okareka has no natural outlet and outflow is controlled by a valve on a pipe that discharges into the Waitangi Stream (which flows into Lake Tarawera). The Operations Group of Environment Bay of Plenty holds consent (60776) for this structure, granted in May 2001.

(ii) Target Range

The lake level target range is 353.5m to 353.9m (to Moturiki Datum)

(iii) Day-to-day management

Responsibility for day-to-day management of the outlet structure is delegated to the Rotorua District Council.

(iv) Monitoring of Lake Level

Lake levels are to be checked and recorded by the Rotorua District Council at least once every two weeks.

(v) Regular Checking of Pipe Intake

The intake structure will typically be checked and cleared weekly when the valve is partially or fully opened.

A floating boom will be installed across the canal upstream of the intake to trap debris. This will be checked and cleared at the same time as the intake.

(vi) Valve Operation Guidelines

At the time of the regular intake inspection, as in (5) above, the valve will be adjusted as needed. Recommended settings are as shown in Figure 1 attached.

Figure 1 shows that there shall generally be four settings:

• fully closed (when the lake level is below 353.56m)

• open at approximately 100 l/s

• open at an intermediate flow approximately 150 l/s when the lake level is falling from the “valve fully open” situation

• fully open (approximately 239 l/s)

Discretion is available to vary the settings as considered appropriate to meet the objectives of maintaining lake levels within the target range and Waitangi Stream fish habitat protection.

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Any adjustment of the pipeline valve, i.e. changes to the rate of outflow into Waitangi Stream, will be made after consultation with Fish and Game New Zealand, with the owners (or representative of) of 303 Spencer Road (through which the Waitangi Stream runs, containing the trout nursery), and with the Department of Conservation.

Is level < 353.56?

Y N

Valve Closed Is level < 353.7? (Q= 0)

Y N

Valve Open 4½ Turns Is level < 353.75? (Q= 100 l/s) Y N

Was Valve Fully Valve Fully Open Open? (Q= 239 l/s)

Y N

Valve Open Valve Open 5 Turns 4½ Turns (Q= 150 l/s) (Q= 100 l/s)

Figure 1 Valve Operation Guidelines

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10.5 Okere Gates

The following are to be contacted when the Okere Gates are opened to greater than 3x200 or 3x500, also when they are closed to below these settings:

Company Contact Phone / Fax E-mail Kaituna Keith Hughes 07 345 4199 [email protected] Cascades 0800 524 8862, fax 07 357 4370 White Water Rod Phone/fax 07 [email protected] Excitement Caudwell 345 7182 River Rats Justin 0800 333 900, [email protected] 07 345 6543, fax 07 349 6567 Great Kiwi Greg, Phone/fax 07 Whitewater 348 2144 Note fax won’t work with phone on – may need to phone. Raft-a-bout Donna or Phone/fax 07 [email protected] Chris 343 9500, 0800 723 822 Environment Carl 021 976 178 [email protected] Bay of Plenty Magazinovic* Tauranga Longridge c-o Stuart (07) 533 Park Steel 1515, fax 07 533 1814 Kiwi River 07 377 6597 [email protected] Safaris Katikati 0800 338 736 [email protected] Adventures Wet N Wild 07 348 3191 [email protected] Tread and [email protected] River Adventure [email protected] Education Kaituna [email protected] Kayaks Barry [email protected] Bringans Sunspots Donald 07 362 4222, [email protected] Kayaks Calder fax 07 362 4324 Michael Gill *All done by email and text as required.

NB Speedfax: RAFT’G on downstairs fax may have all these numbers. E-mail also works well.

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101

Chapter 11: Coastal

Chapter Summary

11.1 Introduction...... 103 11.2 Rainfall: Rangitaiki Plains ...... 103 11.3 On track...... 103 11.4 River Levels: major rivers ...... 104 11.5 Tides...... 104 11.6 Barometric pressure ...... 104 11.7 Sea storms ...... 104 11.8 Storm Surge Data Collection Triggers ...... 105 11.8.1 Astronomical Tidal Height...... 106 11.8.2 Barometric Setup...... 107 11.8.3 Wind Setup ...... 108 11.8.4 Wave Conditions ...... 109 11.8.5 Estuary Effects ...... 110 11.8.6 Conclusion and Recommendations ...... 110 11.9 Kope-Orini, Old Rangitaiki Canal pumps ...... 114 11.10 Awaiti-Omeheu floodgate ...... 114 11.11 Fortunes Rd Pump Station ...... 114 11.12 Te Rahu Rd Pump Station...... 114 11.13 Duke St Pump Station ...... 114

Have you: Received Warning?

Log Started?

Notified Anyone?

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Environment Bay of Plenty 103

11.1 Introduction

A chapter dealing with coastal processes has become more significant on the Rangitaiki Plain since the earthquake of 2 March 1987.

This event lowered many hectares of land to the extent that a considerable portion of the Plains is now below mean sea level. This of course makes drainage under normal circumstances rather difficult. Flooding of the lower levels of the Rangitaiki Plains can now be affected by any or all of five factors:

• Rainfall;

• River levels;

• Tide, high, low, spring, neap

• Barometric pressure;

• Sea storms.

11.2 Rainfall: Rangitaiki Plains

See ‘The Climate and Weather of the Bay of Plenty Region’ Library Number 535 (normally in EDS Office) or see also section 1.3 of this manual.

11.3 On track

This was the advice that should have been heeded in the 1 May 1999 storm, when the tracks were moved sideways at the Raparapahoe Bridge and the Waiari Bridge was undermined.

The pager alarm trigger levels are set up as follows:

• Mangorewa at Saunders ...... 60 mm in 3 hours

• Pongakawa...... 30 mm in 1 hour

• Tarawera at Awakaponga...... 30 mm in 1 hour

• Tumurau Lagoon ...... 30 mm in 1 hour

• Ohinkoao ...... 30 mm in 1 hour.

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11.4 River Levels: major rivers

Under 'normal' circumstances rainfall events occur either in the upper catchment or the lower catchment (coastal).

11.4.1 Upper Catchment events

High flows in the major rivers but only moderate to low falls on the coast; therefore no problem with coastal drainage.

River levels are normally of concern only where major rivers are running high (in response to rainfall in the upper catchment) at the same time as coastal areas are receiving significant falls.

The effect of this is that where the outlet of a drainage system on the Rangitaiki Plains is dependant on floodgates (i.e. gravity drainage) then drainage will only occur when the river level has fallen or during low tide periods.

11.5 Tides

Copies of the most recent 'Nautical Almanac' are kept in the EDS Office and the Library.

11.6 Barometric pressure

A barometer is kept in the EDS Office. This unit was purchased in 1988 and can be calibrated by telephoning the airport control tower at Whakatane (308 8397) or Mount Maunganui (07 575 4144) or Rotorua (07 345 5199). Calibration should be carried out if an event is predicted.

Barometric pressure should now be recorded along with rainfall and river levels.

Tide predictions are computed for average barometric pressure. As barometric pressure falls below the standard pressure level (1014mb) sea level responds by rising above normal. The relationship of this response is that for every millibar drop in barometric pressure sea level rises by 1cm.The water level does not, however, adjust itself immediately to a change of pressure and it responds moreover to the average change in pressure over a considerable area.

For practical purposes the mean average barometric pressure for New Zealand may be assumed to be 1014 mbs.

Change due to barometric pressure alone seldom exceeds 30 cm.

11.7 Sea storms

Some Regional Council works are vulnerable to extreme sea levels associated with some coastal events. Exceptionally high tide levels can occur because of the combination of spring tide, low barometric pressure, and wind set up.

Events up to RL 1.8 metres are not uncommon and problems are not expected with these events, of concern are events which exceed RL 2.0 metres at lower estuary sites, particularly if accompanied by strong wave action.

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Problem areas may include:

• Lower Whakatane River Stopbanks;

• Lower Rangitaiki River Stopbanks;

• Lower Tarawera River Stopbanks;

• Rangitaiki Plains Drainage;

• Kaituna Plains Drainage;

• Kaituna Wetland Culverts;

• Maketu Estuary Stopbanks, Singletons Drain area:

• Maketu Estuary Diversion Gates at Ford Rd

• Tauranga Harbour especially Judea area;

• Little or no warning is likely to be given of such events.

Staff are required to be aware that the coincidence of a high spring tide and a deep depression (low pressures) may cause problems. It should be stressed that the occurrence of these events is rare and warnings should only be given after careful consideration of available data.

Agencies that may require warnings

Agency Area of Concern Phone

Tauranga District Council Judea Industrial Area Barry Low, Emergency Management 07 571 8008 or Western BOP District Maketu Residential 027 494 6556 Council Area Little Waihi

Because of the rarity of these events and the value of the data that can be gained from them it is important that inspections be made of the sensitive areas as soon as possible. The coastal cross sections may also require resurveying.

11.8 Whakatane River Stoplogs

Whakatane Township is vulnerable in big storm surge events to inundation from the ocean, as elevated water levels travel up the river and affecting local infrastructure.

There are a series of stoplogs set up to fill gaps where stopbanks are lowered for roads and walkways, reducing inundation risk.

If the recorder at Whakatane Wharf reaches 1.5m and is expected to go higher, installation of the stoplogs is recommended. Details of stoplog locations and installation instructions are in the Whakatane River section of this manual under the heading “Whakatane Urban area stoplogs”. With the most vulnerable area being the Whakatane boat ramp, any installation should start with the most downstream logs first and work upstream as deemed necessary.

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11.9 Storm Surge Data Collection Triggers

This memo is to help address issues that have been raised about what size storm events we should be recording in greater detail, i.e collecting storm surge levels reached along beaches and around harbours in the Bay of Plenty and compiling a storm surge report to document the event for future reference.

In the past after a significant storm surge event Peter Blackwood (previous Manager Technical Services) would commission the collection of maximum storm surge elevations along the coastline and prepare a short report of findings. Recognition of significant events was done through his knowledge of coastal processes and past storms and his experience with the Bay of Plenty coastal environment. With Peter Blackwood no longer working with us it is important our team has a basic knowledge and guideline for identifying what events require data collection and reporting on. This will enable us to remain confident that we have gathered this invaluable data for future studies on coastal hazards and inundation.

There are several components of storm surge that will give us an idea of the significance of a storm event, most of these we are able to monitor. These include:

• Astronomical tidal height

• Barometric set up

• Wind setup

Wave heights also play a key role in the amount of wave run-up experienced on the coastline.

11.8.1 Astronomical Tidal Height

The astronomical tidal height is the height that the tide has been forecast to reach under normal weather conditions. Tidal forecasts are provided in the Nautical Almanac and are the height that storm specific weather components build upon. In general this level needs to be raise by 0.1m at locations East of Matata and a further 0.1m East of Omaio.

Note: The tidal heights in the Almanac are given in Chart Datum and will need to be converted into Moturiki Datum, this is done by subtracting 0.963 from the Almanac height. It should also be noted that the primary level is for Tauranga, there are slight changes in predicted tide elevations and time of peak levels in different locations around the Bay of Plenty Coastline. In general peak levels predicted for Tauranga are the same as those predicted for Whakatane, Ohiwa and the open coastline in between. At Omaio the levels are higher by 0.2m. Within the Ohiwa harbour levels are predicted to be 0.1m higher than the open coastline. To get more exact predictions there is a spread sheet set up in: R:\Coastal\Tides\Secondary Tide Predictions.xls Remember that East of Matata these levels should be raised by roughly 0.1m and a further 0.1m East of Omaio in order to account for the effect of the earths spherical shape on mean sea level.

Red alert dates

Red alert dates are predicted by NIWA and constitute higher than normal tides. There is a greater risk of storm surge should a storm pass through the Bay of Plenty around these dates. The relevant web site is http://www.niwascience.co.nz/rc/hazards/dates

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11.9.1 Barometric Setup

As barometric pressure falls below the level of 1014 mb (defined as standard pressure) sea level rises. The relationship is that for every millibar drop in pressure sea level rises by 1 centimetre. Note: 1mb = 1hPa (hector Pascal)

The response of sea level to a change in barometric pressure is not instant and in the Bay of Plenty can range between 2-12 hours (Tonkin & Taylor, 1999).

The 1% AEP barometric pressure is 981 mb, and coverage is thought to be extreme with the central pressures expected to be even lower. Table 1 records some barometric pressures recorded in various storms in the Bay of Plenty.

Recorded Barometric Pressures for storms in the Bay of Plenty.

Storm Event Minimum Barometric Pressure

Cyclone Giselle (Wahine) 964 (Tauranga)

Cyclone Fergus 985.4 (Tauranga)

Cyclone Drena 998.8 (Tauranga)

Cyclone Ivy 989.6 (Whakatane)

Storm 18th September 2005 976.6 (Omokoroa)

Weather Bomb 12th June 2006 989.9 (Whakatane)

In general I recommend that:

1 If a noteworthy weather system is heading towards the Bay of Plenty with barometric pressures below 1000mb it would be wise to asses the magnitude of other associated components (wind speed and direction, predicted tidal level, wave heights) in order to asses the likelihood a storm surge resulting.

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2 If a pressure system has passed through the Bay of Plenty and produced unusually low Barometric pressure (say < 980), even if the other components are not considered to be out of the ordinary then it would still be worth while collecting surveyed water levels.

11.9.2 Wind Setup

The surface shear stress of the wind travelling over the sea surface drives water in the prevailing wind direction. An onshore wind thus drives a wedge of water against the land. The magnitude of the height of this wedge is called wind setup.

In the Bay of Plenty Region the highest storm surge elevations are recorded, in general when weather systems approach us with winds blowing in the Northerly to Easterly direction. Winds blowing in these directions have the greatest fetch. Prevailing wind direction in the Bay of Plenty is Westerly to South Westerly.

The size of the wind setup is complex to calculate and is dependent on several factors including:

• Intensity, duration and direction of high winds

• Coastline bathymetry. This affects the way the water interacts with the shoreline and thus the magnitude of set up.

• Coastline geometry. The concave shape of the Bay of Plenty coast is likely to enhance setup levels in some locations.

If coastline bathymetry and geometry is considered relatively constant on a day to day basis, then the intensity, duration and direction of winds become the factors of interest when estimating the magnitude of a storm surge. These elements are recorded at Environment Bay of Plenty’s wind recorders located in Rotorua, Tauranga and Whakatane and can be viewed on Hydrotel or by contacting EDS. Table 2 gives the return periods of wind speed (these were taken from NZS 4203: 1984 and are possibly not the most up to date for this region) and table 3 gives some recorded wind data associated with past storm surge events.

Basic wind speed (m/s) and their associated return periods as according to NZS 4203:1984

Recorder Location 5yr 25yr 50yr 100yr

Tauranga 27 30 32 34

Rotorua 28 32 34 36

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It is unclear whether the design wind speeds are a gust or a mean velocity over a short duration, say 10 – 12 minutes.

Wind speeds recorded in past storm events.

Storm Event Wind Direction Wind Speed (m/s)

Cyclone Giselle (Wahine, 1968) Northerly 40.3 (gust)

Cyclone Fergus (1996) Easterly 26.3 (gust), 17 (average)

Cyclone Dena (1997) East – North East 20.6 (gust), 14.9 (average)

Cyclone Ivy (2004) Easterly 22.14 (gust), 14.95 (average)

Storm 18th September 2005 Easterly 14.9 (gust)

Weather Bomb 12th June 2006 Northerly 29.3 (gust), 18.5 (average)

11.9.3 Wave Conditions

Waves are not specifically a component of storm surge although during storm surge events wave height is often higher than normal. Due to this wave characteristics during a storm event can give an indication of a possible storm surge being felt on the coast. Along the open coast especially, the effects of a storm are felt by the combined magnitudes of storm surge and wave run-up, the static water surface is raised due to the storm surge which then allows the breaking wave heights to be elevated this increases the amount of wave run-up on beaches and thus the possibility of inundation of assets along the coast.

Environment Bay of Plenty has a wave buoy located 13km off the coast of Pukehina beach in a central position within the curve of the Bay of Plenty. The wave buoy records data such as max wave height, average wave height, significant wave height, significant wave period, mean period, water temperature, wave steepness as well as other wave components. This data is useful in gauging the importance of waves during an event. The EDS team use wave buoy information to determine when data collection is required and usually send their team out to survey the coastal profiles if wave heights reach 10m or above.

Due to its distance off shore the wave buoy is not always a direct indicator of wave height at the coastline, however if waves do reach the 10m wave height it is recommended that investigation of other storm components e.g. height of wave run-up locally and tidal elevations at recorders, be carried out briefly in order to identify if more data collection is required.

Note: If EDS are carrying out their coastal surveys it is worth requesting them to record high water / debris levels at each of their coastal cross sections after an event. They often do this but a specific request will reconfirm it.

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Table 4 below gives current estimates of wave height return periods.

Wave Height return periods (as advised by PLB 27/08/07)

Wave Type 2yr 5yr 10yr 20yr 50yr 100yr Hs 3.3 5.4 6.8 8.1 9.9 11.2 H1% (1/100) 4.4 7.9 10.2 12.2 15.2 17.5

Hs = significant wave height

H1% (1/100) = mean height of the highest one-hundredth of the waves.

Note: at "A" Beacon during Cyclone Fergus the recorded wave heights were Hs = 9.7m and H1% (1 in 100 waves) = 11.404m - we also regarded that storm overall as 10% AEP.

11.9.4 Estuary Effects

Within estuaries there may be an additional set up or set down (may occurs with Tauranga Harbour) of water due to the

There are two components involved in estuary effects:

• Hydraulic effects relating to influx of freshwater, outlet controls, depth and channelling of water.

• Spatial differences in water levels due to the differential effect of wind stress.

11.9.5 Conclusion and Recommendations

Although there is not one specific trigger that will clearly let us know when the recording of a storm event is required there are a few variables that can help us to determine. In summary we should:

Storm Coming

• Check astronomical tidal heights and red alert dates around the time the storm is going to pass over the Bay of Plenty. If the tides are already higher than normal monitor the situation carefully.

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• If a cyclone or tropical cyclone weather system is heading towards the Bay of Plenty with barometric pressures below 1000mb then look at the magnitude of other associated components (wind speed and direction, predicted tidal heights, wave height) in order to asses the likelihood a storm surge resulting.

• Investigate the direction, and speed of predicted winds and estimate how long the high winds are predicted to last. Take more care when a weather system is producing winds coming from a north to easterly direction.

Storm Passed

• Advice from Peter Blackwood indicates it is worth surveying high water marks and debris levels whenever the Ohiwa / Moturiki recorders register anything above RL 1.5-1.6m Moturiki Datum.

• Collect surveyed water levels whenever a pressure system has passed through the Bay of Plenty that produced an unusually low / high storm component, be that wind speed, barometric pressure (say < 980mb), wave height (above 10-12m). A judgement call will need to be made.

• If EDS are carrying out their coastal surveys request them to record high water / debris levels at each of their coastal cross sections.

• When collecting debris / high water marks try, where possible, to collect information from the same location as data has been collected in the past (especially within estuaries / harbours). This will enable more accurate comparisons of storm events to be made in the future. Maps are shown below outlining possible data collection locations within the Tauranga and Ohiwa Harbours. For details on historic open coast sites see Graeme O’Rourke and/or the Coastal Profiles folder (blue).

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11.10 Kope-Orini, Old Rangitaiki Canal pumps

The Kope-Orini tide gates are capable of discharging whatever water is delivered to this point, provided Whakatane River levels (sea levels) are low enough. The canal hydraulics are limited by the energy (water surface) slope that can develop while the gates are open.

The capacity of the Kope-Orini Pump Station is 6 cumecs. The pump should be switched on when the floodgates begin to close and levels are above 0.3m on the gauge and further rain is expected.

Similarly, once the tide starts going out, the limiting factor in discharging water in the Old Rangitaiki Channel is the hydraulics of the channel rather than the capacity of the floodgates. The maximum flow out the tide gates is 14 cumecs. Capacity of Old Rangitaiki Pump Station is 2.5 cumecs. The pump should generally be turned on with levels above 0.85m at the pump, 1.0m at Smiths Rd, the gates closed and rain continuing.

11.11 Awaiti-Omeheu floodgate

The Awaiti-Omeheu floodgate has a fishpass and two slide gates for irrigation purposes. The irrigation gates should be closed when irrigation is not taking place. This is the responsibility of the irrigators: Eveleens 304 9157, Platt Gow Trust 304 9591, AC and M Martin 304 9544 and Steiner 304 8432. They can also be asked to close the gates during heavy rain or high water levels in the Tarawera (e.g. sea storms). The fishpass should also be closed at high levels, eg if above 1.8m is expected. (Roger Waugh).

Platt Gow also opens a floodgate on the Hawkins Drain off the Omeheu Canal.

Gary Stevens Ph 308 4207 has requested a warning for high levels in the Omeheu Canal. The only indicator for this is rainfall at Te Teko, combined with tide level at Matata. Issue a warning above 100mm in 24hrs at Te Teko.

11.12 Fortunes Rd Pump Station

11.13 Te Rahu Rd Pump Station

11.14 Duke St Pump Station

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Appendices

Appendix 1 – Contacts List

Appendix 2 – Emergency Equipment

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Environment Bay of Plenty 117

Appendix 1 – Contacts List

Name Work Phone Home Phone Cell Phone Fax No E Mail Address Airport Control Towers Whakatane 07 308 8397 Mt Maunganui 07 575 4144 Rotorua 07 345 5199

Awaiti-Omeheu Eveleens Floodgate Closures 07 304 9157 Platt Gow Trust 07 304 9591 AC & M Martin 07 304 9544 Steiner 07 304 8432

Bay of Plenty Electricity All Electrical Faults/No Power 0800 500 710 (press 1) Whakatane Office 07 306 2700 07 307 0922 Aniwhenua Power Station 07 366 4782 Fonterra Energy Centre (Edgecumbe Power Station) 07 306 2718 Commercial Manager: Chris Power 07 306 2704 027 457 6303 [email protected] Generation Mechanical Engineer: Gil Clark 07 306 2737 0274 751 468 [email protected] Generation Operations Engineer: Ken Dodson 07 306 2706 0274 750 145 [email protected] Generation Operations Manager: John Smyth 07 306 2709 0274 591 757 [email protected]

Civil Defence Environment BOP Greg Wilson 0800 368 267 021 284 8334 [email protected] Clinton Naude 07 579 3891 021 398 336 [email protected] Whakatane District Council Bill Wycherley 07 306 0538 07 308 6078 0274 906 775 07 306 0500 02611 4440 (Pager) Ian Maloney 027 476 9528 Jan Pryor 07 306 0527 07 304 9094 027 282 4891

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02611 4440 (Pager) Rotorua District Council Pauline Hitchcock 07 350 0209 extn 8312 07 349 1166 0274 545 402 07 348 0192 [email protected] Western Bay District Council and Tauranga District Council Alan Pierce 07 579 6781 07 549 0767 027 284 9550 Civil Defence plus Opotiki District Council Assets Ian Castles 07 315 3030 07 315 6770 027 399 018 Jim Finlay (Back up) 07 315 3030 026 104 129 (Pager) 07 312 5929 021 107 1073 Kawerau District Council Tony Moller 07 306 9009 07 322 8387 027 283 6949 07 306 9044 (Direct) 07 323 8072 Coastguard Coastguard Whakatane 07 308 7110

Contractors Bay Excavators (for Kaituna) 07 573 7064 0274 954 317 (Heavy Equipment and Murray Salt Contracting, (for Kaituna Area): Transport) 07 573 6673 0274 466 546 07 573 6672 Brian 07 573 6672 G McRobbie Contracting, (for Kaituna area) 07 322 8557 0274 953 513 Grant Farms: Tom Grant 07 308 8259 0274 960 558 Rust A & R 07 304 9146 0274 878 667 Waiotahi Contractors: Graham Mills 0274 945 694 Whakatane Office 07 308 8098 Opotiki Office 07 315 6580 NZ Generator Steven Andrews 07 574 2950 0274 490 490 [email protected]

Crane Hire Lakeland Steel (Doug Stewart) 07 347 9585 Todd & Pollock Crane Hire 07 577 9849 Todd McPhee Crane Hire Ltd 0800 CRANES 0800 272 637 Lakeland Plant Hire Ltd 07 347 9585 07 347 9846 Bruce Morrison 07 348 3658 Teeny Stewart 027 4924 500

July 2008 Flood Warning Manual Environment Bay of Plenty 119

Electricians Concord Technologies (Okere Gates and Upper Kaituna) Rob Cook 07 348 2368 07 349 0773 Brian East, (first choice for Rangitaiki Pumps, part of Whakatane Electrical Contractors) 07 304 9470 027 274 0540 Whakatane Electrical Contractors (24 hours) 07 308 0446 (for Kopeopeo and Thornton West Pump Station) Link Electrical, (first choice for Kaituna pumps) Tauranga 07 575 7056 Brian Percy 07 574 6506 027 492 2370 Opotiki Electricians Geoff Enkovort 0274 993 944 Control Tech (Opotiki) 07 315 8867

Emergency Response 0800 368 288 extn: Richard Mallinson: 7572 07 350 1169 021 753 420 Work Assistance (EBOP) 0800 368 288 extn: 021 649 7346 John Mather: 8501 07 544 2376 0800 368 288 extn: 021 707 975 Brian Clements: 7575 07 533 1383 0800 368 288 extn: 021 923 350 Daryll Hall: 8524 07 576 5242 0800 368 288 extn: 029 368 7571 Greg Corbett: 7571 07 533 3149

Engineering Sisson Engineering (Phil Sisson) 07 308 5596 07 307 1115 Unique Sheetmetals (Rotorua) 07 349 3426 Summit Engineering & Hydraulics Ltd 07 348 0464 07 345 5990

Flood Managers 0800 368 288 extn: [email protected] Roger Waugh 9519 312 5216 029 368 9519 0800 368 288 extn: [email protected] Bruce Crabbe 9513 307 0825 021 756 032 0800 368 288 extn: [email protected] Glenn Ellery 9449 3124657 0800 368 288 extn: [email protected] Graeme O’Rourke 9521 312 4689 0800 368 288 extn: [email protected] Peter West 9587 312 9742

Flood Warning Manual July 2008 120 Environment Bay of Plenty

Fonterra Edgecumbe Site 07 304 7000 07 304 7061 Energy Centre 24 hours 07 304 7001 – 1 - 4808

Harbour Master – Brian Spake [email protected] Eastern Bay 029 368 9415

Harbour Superintendent Peter Cavanagh [email protected] - Eastern Bay 07 306 0519 07 308 8271 027 570 8283 (remove boats from Whakatane Harbour) 027 275 2233 [email protected]

NIWA Rotorua (work hours) 07 346 1950 Wayne McGrath Graham Timpany

On Track 24 hour Help Desk 09 488 6886 Duty Network Control Manager 09 498 2066 Network Control Manager (Kawerau) 021 440 112 Wellington 04 498 3006 Bryon Briffault 0274 924 052 Andy Morris 0272 848 457 Gavin Smith 0275 726 116

Opus (road closures) Dave Roper 027 499 9358 [email protected]

Meteorological Service File 2760 03 Contact List EBOP: Glenn Ellery 0800 368 267 07 312 4657 [email protected] Shane Iremonger 0800 368 267 [email protected] 07 308 2151 Charl Naude 0800 368 267 [email protected] Meterological Office 04 470 0783

Muketu Diversion Clem Tapsell Closure 07 533 2327 Elaine Tapsell 07 533 2503 DOC Rotorua 07 349 7400

July 2008 Flood Warning Manual Environment Bay of Plenty 121

Police Edgecumbe 07 304 9004 Kawerau 07 323 1400 Mt Maunganui 07 575 3143 Murupara 07 366 1170 Opotiki 07 315 1110 Rotorua 07 348 0099 Taneatua 07 312 8070 Tauranga 07 577 4300 Te Puke (Kaituna area) 07 573 9147 Te Teko 07 322 8206 07 307 0873 Whakatane 07 308 5255

Postmaster Waimana (Bell & Hodgson: Agency) Ray Bell 07 312 3048 07 312 3046

Principal Works 0800 368 288 extn 021 933 879 [email protected] Engineer Tony Dunlop 9526 307 0773

Pumping Equipment Hi Tech Irrigation Services (Morrinsville) 07 889 7755 07 889 7755 [email protected] Hirequip Ltd (Kawerau) 0800 727 727 or 07 307 2545 East Bay Hire Ltd (Whakatane) 07 308 8821 or 07 308 8822 0274 428 635 Hauraki District Council (Clarky) 07 862 8609 Selwood Pumps, (Alistair MacDonald) 0800 800 837 0274 968 905 Hartley’s Pumps (Kawerau) 07 323 7790 07 323 7794

Radio Stations Whakatane: 1XX 07 308 6239 1XX Station Manager, (Emergency) 07 312 4123 0272 449 825 Sun FM 07 308 0403 Rotorua: Classic Hits 97 FM 07 348 9089 0800 002 527 Lakes 96 FM 07 346 3902 Te Puke: The Qube 99.3 FM 07 573 5012 Tauranga: Newstalk ZB (95 BOP FM) 07 578 9139 Coastline 93.4 FM 07 571 0444

Flood Warning Manual July 2008 122 Environment Bay of Plenty

Radio Hauraki 07 578 9139

Raingauge Readers Wharawhara Water Treatment Plant 025 978 930 Carter Holt Harvey (Tarawera @ Kawerau) 07 306 9050 Lower Kaituna: C&C Verwey 07 573 6414

Sack Supplies for Sand Textile Bag & Sack Co Ltd (Auckland) 09 629 0266 09 629 0656 Bagging

Sand Bagging Fed. Farmers Assistance Bruce Woods 07 322 8570 07 366 4730 025 814 148 Arthur Adam 07 308 7731 025 905 825 Scottie McLeod 07 308 4846 Brian Power 07 304 8236 Glen Shaw Tauranga Federated Farmers Office 07 587 5039 Te Puke Federated Farmers – John 07 533 3681 Scrimgeour

Traffic and Crowd Legion of Frontiersman: Whakatane Control 07 3080928 Edgecumbe 07 304 9578 Maori Wardens 07 308 0936

Transpower Edgecumbe Substation 07 838 0677 021 443 144 Bob Combs (Station Manager)

Transit NZ BOP Regional Office (Tauranga) 07 927 6009 07 578 2909

Trustpower Kaituna Area Operations Centre 24 hrs (Tauranga) 0800 878 787 Generation 24 hrs 07 574 7958 07 574 4777 Matahina Dam 07 322 8014 07 322 8024 Head Office (Tauranga) 07 574 4800 Control Centre (Te Maunga) 07 574 7958 07 574 4888 extn 777

July 2008 Flood Warning Manual Environment Bay of Plenty 123

Wheao Dam (Control Room) 07 575 2908 025 979 215 025 979 215 Power Lines: Western BOP 06 759 6565 Rotorua / Taupo 06 873 9397 Hydro Schemes (24hr): Kaimai 07 574 4777 Wheao 07 574 4777 Matahina 07 574 4777

Waimana Area Waimana School 07 312 3021 Marie Tiopira 07 312 3038 Helen Te Waara 07 315 4611

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Environment Bay of Plenty 125

On Track need to be notified if high intensity rainfall is being recorded along their Tauranga-Kawerau railway line. The Flood Manager will need to advise On Track of the areas vulnerable to flooding after assessing the rainfalls and storm track.

This was the advice that should have been heeded in the 1 May 1999 storm, when the tracks were moved sideways at the Raparapahoe Bridge and the Waiari Bridge was undermined.

The pager alarm trigger levels are set up as follows:

• Mangorewa at Saunders ...... 60 mm in 3 hours

• Pongakawa...... 30 mm in 1 hour

• Tarawera at Awakaponga...... 30 mm in 1 hour

• Tumurau Lagoon ...... 30 mm in 1 hour

• Ohinkoao ...... 30 mm in 1 hour.

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Environment Bay of Plenty 127

Appendix 2 – Emergency Equipment

Office

A check of the equipment should be carried out in June of each year.

An emergency box is available for those long nights when a flood has once again decided to peak in the early hours of the morning. The box is stored under the desk in Sharleen Augustus’ office. Food, torches, batteries, candles, soup and pasta are stored in the emergency box.

Food should be replaced together with batteries (whether they have been used or not).

Flood Warning Manual July 2008