Deepen the river

AS A long time resident of Grafton and living near the river the writer is concerned by the accumulation of silt on the Grafton side of the river and the likely effect on the height of floods.   It is a natural phenomenon for silt to build up on the inside of a bend in a river while the outside of the bend is scoured away but, in this case, the writer is only concerned with the accumulation of silt in this section of the river. In the last 60-70 years this build up has become most noticeable. What is visible on the surface is evidence of the silt that has made and is making the river so much shallower.   How much soil is there in that build-up? If there is a million cubic metres it represents a million cubic metres of water which, during a flood has to be accommodated elsewhere! It must have an effect on height of the flood so far as Grafton and South Grafton are concerned and it leads the writer to question whether, in terms of the quantity of water, the latest flood was the biggest!   As a boy I remember that, with a younger brother, from Carrs Creek we rode bicycles into town to see the sailing ship Huia which was loading timber at Frazer's Mill. (That sawmill was just upstream of where the Readymix concrete works are today). I very much doubt that such a deep draft vessel, putting aside the presence of the bridge, could get near that site today.   As this section of the river is made shallower the flow of the river is slowed and more and more silt is deposited. And the more silt that is deposited the more the flow is reduced! That silt is good soil, as any farmer who can take advantage of it will confirm, but it is in the wrong place at the moment! The writer suggests deepening the river as an alternative to raising the levee.   In a way we are fortunate. There is a large area in South Grafton, between the riverbank and the South Grafton hill that would benefit by being raised. If dredges were used to pump the mud out of the river the pipe lines might be located in what were at one time creeks draining those low areas.   In time, the writer believes, both sides of the river would benefit if the river could be made deeper by the removal of silt. What would be useful as an indication of the changes that are taking place would be cross sectional diagrams at several points in the area which show if and where the worst build-up is taking place. If taken at regular intervals or after a flood, such diagrams would be very useful.   As a matter relating to the slowing of the flow of the river on the Grafton side, it is believed that between the upriver end of Susan Island and the mainland on the northern side, what used to be a channel has become silted up. (In the natural course of events, probably in time Susan Island will become a peninsula!) As another restriction on the flow it must have an effect on the build-up of the silt with which the writer is concerned.   Nearly every day the writer sees trucks bringing fill into town. In most cases local soil would be just as effective and we have plenty right on our doorstep, if it was made available.   Ken Weeks, Grafton

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