Mud sticks. Once accumulated it’s very hard to shift.
Sand rolls. In the wind, in storms. In water with tidal and current movements.
From the 11 to the 13th of October a group of Whangamata Camping Association (WCA) members walked and examined, around low tide, the recently excavated channel from the dugout marina basin down to the boat ramp. This part of the channel has never been dredged or altered previously.
The dredging and excavation is from a natural depth of .25 to .5 m to an artificial depth of 2m (at low tide). Rock walls and a weir structure have been placed in parts of the channel at the entrance to the excavated basin.
The most noticeable thing at such an early stage is the mud. The numerous black rock structures, only in the water months, are already deeply stained. Thick mud 5 to 10 cm thick has accumulated on the low tide flats behind the rock walls. All the marina structures are mud stained including the concrete pontoons.
The recently built weir has mud building on its surface. The structure is nearly always in moving water.
Where the rock wall ends a micro channel has formed. It runs from the low tide mark to a point 3 to 4 meters out from the rock wall and then runs (roughly) parallel to the dredged channel and joins up with (what was) a dead end channel opposite the boatramp (click on photos to enlarge.) The dead end channel opposite the boat ramp has been there for some time. The micro channel is new and came after completion of the rock wall around September 2009.
The most noticeable change is the increase in heights of the sediment banks on the western side of the causeway bridge. The increase in height has meant the channel has now carved faces into the sediment banks along its low tide meander, something that never happened previously.
The damming effect caused by the cauceway (built in 1974), is well documented. It has caused rapid infilling up stream with associated encroachment of flora. It was a known ecological disaster. Has this infilling now been accelerated?
While walking around the intertidal flats, WCA members were told by HeB workers on the site that crayfish had started living in the rock walls, and the marina is going to have problems with the channel and basin filling in.
