Tararu flood protection scheme design report
TR 2013/46
Report: TR 2013/46
Author: Megan Wood (Wainui Consulting Limited)
About this report
The purpose of this Design Report is to provide a summary of the works that have been undertaken at Tararu to reduce the flood hazard from the Tararu Stream, including the rationale behind the scheme development, the agreed levels of service, the design details, as built information, the operation and maintenance requirements of the scheme, the residual flood risk and the scheme review requirements.
The Design Report includes the following sections:
- Catchment overview
- Hydrological assessment
- Hydraulic model development
- Flood protection scheme
- Agreed levels of service
- Operation and maintenance
- Flood hazard assessment
- Residual flood risk
- Planning controls, and
- Scheme review.
Read or download the report
Tararu flood protection scheme design report [PDF, 6 MB]
| Contents | ||
| Executive summary | vii | |
| 1 | Introduction | 1 |
| 1.1 | Background | 1 |
| 1.2 | Scope of report | 1 |
| 2 | Catchment overview | 3 |
| 2.1 | Catchment description | 3 |
| 2.2 | Tararu Stream | 4 |
| 2.2.1 | General | 4 |
| 2.2.2 | Pre-scheme condition of Tararu Stream | 5 |
| 2.3 | Flooding issues | 6 |
| 3 | Hydrological assessment | 9 |
| 3.1 | Technical information | 9 |
| 3.2 | Catchment characteristics | 10 |
| 3.3 | Rainfall | 10 |
| 3.4 | Flow estimates | 12 |
| 3.5 | Hydrograph | 13 |
| 4 | Hydraulic model development | 14 |
| 4.1 | Introduction | 14 |
| 4.2 | Model build | 14 |
| 4.3 | Model inputs | 14 |
| 4.3.1 | Model datum | 14 |
| 4.3.2 | Channel cross section data | 14 |
| 4.3.3 | Upper boundary condition | 14 |
| 4.3.4 | Lower boundary condition | 14 |
| 4.3.5 | Roughness | 15 |
| 4.3.6 | Model location | 15 |
| 4.4 | Bridge representation | 15 |
| 4.4.1 | Background | 15 |
| 4.4.2 | Model set up | 15 |
| 4.4.3 | Description of modelling scenarios | 16 |
| 4.5 | Design models | 16 |
| 4.6 | Model validation | 17 |
| 4.7 | MIKE-11 model assumptions and limitations | 17 |
| 4.8 | Peer review | 17 |
| 5 | Flood protection scheme | 19 |
| 5.1 | Scheme history | 19 |
| 5.2 | Scheme evolution | 20 |
| 5.3 | River and catchment works | 21 |
| 5.4 | Channel improvements | 21 |
| 5.5 | Flood defences | 22 |
| 5.6 | SH25 Bridge upgrade | 24 |
| 5.6.1 | Bridge design | 24 |
| 5.6.2 | Bridge modelling | 25 |
| 5.6.3 | Preferred SH25 bridge design | 25 |
| 5.6.4 | Constructed SH25 bridge | 27 |
| 5.6.5 | Reduced freeboard | 27 |
| 5.7 | Future works | 27 |
| 6 | Agreed levels of service | 28 |
| 7 | Operation and maintenance | 29 |
| 8 | Flood hazard assessment | 31 |
| 8.1 | River flood hazard classification | 31 |
| 8.2 | River flood hazard map | 32 |
| 9 | Residual flood risk | 34 |
| 10 | Planning controls | 36 |
| 11 | Scheme review | 37 |
| 12 | References | 38 |
| Appendix 1: Flood protection scheme design | 40 | |
| Appendix 2: As-built survey | 50 | |
| Appendix 3: Bridge modelling results | 54 | |
| Appendix 4: Bridge assessment | 56 | |
| Appendix 5: Bridge upgrade drawings (design) | 58 | |