WESTERN ARM.

Hutt News, Volume 2, Issue 36, 13 February 1930, Page 2

WESTERN ARM.

.. What is known as the " Western Aim" is the old branc&l of the river which fowed on the west'side of Gear Island.* This arm was closed a good! many years ago by the Board constructing- dams near the north "end and at the south end. The' embankment at the north end is a complete dam with no culvert or opening of any kind through it. The embankment at the ' south' end is provided with flood-gates.

Before the arm was closed by embankmeats serious flooding used to occur as t&is arm was subject to the same height of ""flood as the eastern arm which is now the whole river. At tie time tie ann was closed the' streams from the western hills drained into it and the floodgates in the southern em--bankmant were provided to control flood and tide waters and to allow discharge of the stream waters from what had now become a collecting basin. ; "

In- subsequent years Percy's Creek (called also Moran's Creek) was^divert"ed down Nelson Street culvert, though the creek still functioned as a channel for the lower lands. Everest's Creek is broughtdirectly into, tie closed arm by a culvert, but I am n&t abl* from remory to say .whether this culvert was constructed prior tb the closing of the arm or subsequently to its •being eJosed. Te Momi- Creek whi<j2i had its source in tie, Normandale Hills was .diverted by culvert and discharges into .the Hutt River a little, north of Riverbank Road, and the western arm is'tnus relieved of this volume. Thus a .period was arrived at wheii only Everest's Creek and a very much reduced volume from Percy's (Moran's) and TeMomi Creeks was discharged into the western arm. During ensuing years up to the present jfche great improvement to the lower reaches of the Hirtt iiiver has resulted in a lowering of the river bed and a better discharge of flood waters, with a result t&at the general level of the ground water .for a considerable distance both east and west >f the Hubfc River in both Hutt and Petone has been -materially lower cd. The actual level of water in the closd .trm at normal times is lower than. it was in years gone by. Recently Percy's Creek and other waters Sxava again been brought into the closed western arm and" the impression has been gained by adjoining land owners •that the volume of water now dis-

ehargiag into tie dosed western arm during periods of heavy rain &as teen so increased that the level of the water in the closed western arm acting as a collecting basin ha's "been materially Taised and that this raising has had t&e effect of causing the level of the ground water in the area adjacent also

to rise. Though. I dp not at present concur in this impression it is possible that it is correct. The establishment of gauges which is being attended to "will enable tests to be made during the ensuing winter when it may be discovered that possibly the flood-gates are not large enough, or that silting of the western, arm below the southern dam is having the effect of jestricting the disefiarge so that full advantage of the fall of the tides is not being gained.

It is not unreasonable to suppose that the level of the ground wa^er could be affected even w&eri periods of high level in enclosed arm are short, because it is wH. known the sub-soil of much of the lower ptrtion of the Hiitt Valley consists of a fine water bearing sand with almost a net work of underground -streams which axe -the courses of ancient stream beds* The rise and fall of the tide has ai immediate effect for a considerable distance from t&.e sea coast. - ' |. A few years ago complaints wef* made that the enclosed arm during dry summer periods tended .to- become foul and it^ is a fact that though -it may' not' have actually been unhealthy the water was somewhat offensive. TSris may have been contributed to by gas works effluent which was at that time discharged , via Moran's ,Creelc. For the last several years my ; personal impression .from . regular inspections has been that there is 'practically nothing offensive, even in summer time, but this may be > due only to the fact that recent summers have not been particularly hot and dry.. At the time that the water appeared to be offensive a proposal was made, and 2ias since been kept in view by the Boai'd that the enclosed arm could be flushed. This flushing would be done by the construction of a cul-. vert through the northern dam to which water would be led from a filter box constructed under the- shingle of the river ted in a location between the shingle plants, pf Messrs Goutts" and McAllxnn. The steady lowering of the riverbed would Ihaye made it- inadvisable np to the present to embark upon this costly work unless the closed western arm had.become actually unhealthy. . : ■■-,:,..;_...:

However in view of future possibilities arrangements were -made with the Public' Works. Department, to construct a eulveTt under the Railway embank* merit when that embankment was being made for the railway across the head of Gear Island. This culvert was constructed at great ekpense as it was necessary to keep it'at such, a low level that it would function during^periods of low summer flow of the rivet, these' being Ihe periods at which the closed arm would be offensive and the peridds. at which it would not be necessary to reserve the closed arm as a collecting basin for large volumes of flood water from the 'western hills. .

To complete the provision fot flushing the western arm would entail costly con? struetion of culvert extension through the northern dam and of the intake filter and culvert under the river bed and of sluice gate and tower.- A rough estimate of this is £2000.;' There is at present a considerable growth of Tushes and weeds in the tipper portion yf-the closed arm which is" decidedly unsightly, but I think can scarcely be considered unhealthy. The water is "dead '"■ for that reach of t>he closed aim upstream from the Everest Creek rjulvert and therefore to clear a channel through the weed would not be of much avail.Tlie water-is shallow and if this aTea develops into an-offensive swamp then it may ( be better to consider filling it in. On the other hand future development of Gear Island, as an Air Base may make it desirable to retain "as lalsge an aTea of water as possible. It-seems to me that while it.is not desirable to incur much immediate expenditure "" those v ratepayers more, immediataly concerned might iike to call a meeting at wMch members of the Board and Clerk and Engineer could be presant for an informal discussion.