Abstract

The catchment of the Mangatoetoe Stream experienced heavy rainfall during the period 16-17 July 2005. This rainfall caused high flows in the Mangatoetoe Stream through Waihi township and resulted in overtopping of the culvert at the junction of Consols Street and Baber Street and flooding of one dwelling at 20 Baber Street.

This report provides assessment of the magnitude of the recent flood event, the 50 year flood levels and recommends the appropriate minimum floor levels of buildings within this reach of the stream. It also defines the responsibilities of Environment Waikato for maintaining the Mangatoetoe stream under the Waihou Valley Scheme.

The objectives of this report are:

to estimate the magnitude of the event downstream of the Consols Street - Baber Street culvert in terms of both peak flow and Average Recurrence Interval (ARI)
to assess the 50 year ARI flood level for 20 Baber St.
to assess the effect of the stream condition on water levels.

Flooding of Mangatoetoe Stream, Waihi : July 2005 [PDF, 1 MB]

Contents
1 Background	1
2 Objectives	1
3 Rainfall	1
4 Stream flows	2
5 Catchment characteristics and design flows	2
6 Assessment of the recurrence interval of the July 2005 flood event	4
7 Waihou Valley Scheme	4
8 Hydraulic modelling	5
9 Assessment of 50-year flood levels	7
10 Conclusions	8

Flooding of Mangatoetoe Stream, Waihi: July 2005

Abstract