Environment Waikato Best Practice Guidelines for Waterway Crossings
Report: TR 2006/25R
Authors: David Speirs, Greg Ryan
Abstract
These best practice guidelines have been prepared to assist regional and local authorities, consultants, roading engineers and contractors with the design of appropriate waterway crossings within the Waikato region. By following the recommendations in this handbook, proposed waterway crossings:
- will be designed to have the minimum possible adverse impact on the environment
- will be consistent with the requirements of the Waikato Regional Plan.
- will not compromise the levels of service provided by regional and district flood protection or land drainage schemes.
The topics covered by this best practice guideline handbook include:
- the Waikato Regional Plan
- flood control schemes and land drainage areas
- best practice design guidelines for waterway crossings.
Environment Waikato Best Practice Guidelines for Waterway Crossings
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Table of Contents
| 1 Introduction |
1 |
| 1.1 What is best practice? |
1 |
| 2 The Waikato Regional Plan |
1 |
| 3 Flood control schemes and land drainage areas |
2 |
| 4 Type of waterway crossings |
2 |
| 4.1 Single span bridge |
2 |
| 4.2 Single barrel arch culvert |
3 |
| 4.3 Multiple span bridge |
5 |
| 4.4 Single barrel circular culvert |
5 |
| 4.5 Multi-barrel circular culvert |
7 |
| 4.6 Box culverts |
8 |
| 4.7 Fords |
8 |
| 5 Maintaining & restoring ecological values |
9 |
| 5.1 Design and construction considerations |
10 |
| 5.1.1 Water velocity |
11 |
| 5.1.2 Crossing inlet conditions (culverts) |
12 |
| 5.1.3 Physical barrier to aquatic invertebrates |
13 |
| 5.1.4 Flow turbulence |
13 |
| 5.1.5 Light requirements |
14 |
| 5.1.6 Water depth and wetted margin |
14 |
| 5.1.7 Perched culverts |
15 |
| 5.1.8 Timing of works |
16 |
| 5.1.9 Structure location and stream alignment |
16 |
| 6 Designing waterway crossings for flood events |
17 |
| 6.1 Definition of a reasonable flood event or design standard |
17 |
| 6.2 Estimation of design peak flood flow |
17 |
| 6.2.1 Define the waterway catchment |
18 |
| 6.2.2 Calculate the average slope of the main waterway |
19 |
| 6.2.3 Calculate the time of concentration for the catchment |
20 |
| 6.2.4 Define the design storm for the proposed crossing |
20 |
| 6.2.5 Calculate the design peak flood flow for the proposed crossing |
20 |
| 6.3 Design strategies using the design peak flood flow |
21 |
| 6.3.1 Bridges |
21 |
| 6.3.2 Culverts |
22 |
| 6.3.3 Fords |
23 |
| 7 Conclusion |
23 |
| 8 Recommended reading |
23 |
| Appendix 1 Contacts-territorial authorities |
25 |
| Appendix 2 Useful equations |
26 |
| Appendix 3 Average slope worksheet |
29 |
| Appendix 4 Technical memorandum 61 work sheet |
30 |
| Appendix 5 Associated hazards table |
31 |
Note: This report was originally published in May 2006 as Technical Report 2006/25. This new edition corrects a minor data error which appeared in Appendix 2, on the first line of page 27. The word ‘minutes’ was accidentally substituted instead of ‘hours’ in a ‘time of concentration formula’. While addressing this error, the opportunity was taken to make some other minor typographical changes. These changes make no difference to the conclusions or recommendations in the report, but in the interests of data accuracy we are re-releasing this publication.