| 1978 | A severe easterly storm battered the Mangawhai Harbour sandspit, opening up the south breach. Mangawhai Harbour started to 'back-fill' with sand at an estimated rate of 100,000 cubic metres per annum. | |
| 1985 | The flushing capacity of the North Entrance had decreased by 75% due to the South Breach capturing most of the tidal prism. | |
| 1987 | Cyclone Bola created more havoc and damaged the channel. | |
| 1989 | Both entrances to Mangawhai Harbour became extremely shallow and difficult to navigate. | |
| 1990 | Sedimentation of the North Entrance intensified. By the end of the year the entrance was blocked and Picnic Bay build-up increased. | |
| 1991 | On the 11th February the controversial "BIG DIG" started at 6.00am with over 40 machines and scores of volunteers. During 1991 the North Entrance was reopened (temporarily), a start was made on closing the South Breach by using a sand bridge, the rock groyne out to Sentinel Rock was partly rebuilt and, after gaining a sandbagging licence, 4000 sandbags were deposited across part of the South Breach. A small dredge was purchased through Mangawhai Endowment Fund - the dredge was officially named "The Spirit of Mangawhai". An application by the MHRS to dredge the northern channel and replace sand back into the spit island was made and approved by the Director General of Conservation, and dredging began in August. In October the Spit Wildlife Refuge and sand extracting licences came under the control of the Auckland Conservancy. | |
| 1992 | "The Spirit of Mangawhai" sank during a storm but was resurrected, then re-opened the Northern Entrance in time for the summer holidays. The entrance closed again shortly afterwards. | |
| 1993 | A coastal engineer was employed by MHRS, and a plan formed to clear sand from Picnic Bay and pump it into the Wildlife Refuge, but still leave the North Entrance closed. The dredge worked throughout the year widening the inner channel in preparation for a further opening. | |
| 1994 | Inner harbour topographical surveys were carried out and calculations indicated that approximately 268,000 cubic metres of sand needed to be removed to establish the desired channel inlet and throat cross-section. In May the MHRS Harbour Restoration Plan was released on evidence that the plan, as well as doing no harm to the environment, would succeed as long as it was executed in the proper manner. | |
| 1995 | Various permits were gained for work to commence, a larger dredge was purchased, and two 20 tonne diggers worked between tides to build the bund wall. | |
| 1996 | Stabilization of the bund wall and revegetation of the repositioned sand was introduced and, on 29 June 1996, the bund wall was completed. The South Breach was closed at a cost of $750,000 not counting the thousands of volunteer hours. |
From mid 1996 to 2000 the MHRS continued within the parameters of the resource consent with a programme of channel dredging and maintenance. The "nursery arm" had, in the previous four years, propagated and planted more than 100,000 Pingao and Spinifex plants, with excellent results and evident stabilization of the bund area. The "fencing" programme continued and fences incorporating wind breaks successfully built up the height and spread of the bund wall area.
The main work since 2000 has involved dredging, maintaining the harbour and bund wall, further wind fencing and planting more Pingao and Spinifex to better stabilize the sand dunes and restore the wildlife refuge.