Har­bour health on the im­prove

Kapi-Mana News - - NEWS -

A new sci­en­tific sur­vey of Porirua Har­bour shows much lower sed­i­men­ta­tion rates than those es­ti­mated five years ago.

The first com­pre­hen­sive sur­vey of the sea floor of the har­bour was done in 2009 as part of the re­search work to­wards its restora­tion.

Last Novem­ber Porirua City Coun­cil and Welling­ton Re­gional Coun­cil com­mis­sioned a five-year fol­low-up sur­vey, which has been com­pleted.

‘‘The find­ings are very en­cour­ag­ing – the sur­vey found sed­i­men­ta­tion rates over the past five years much lower than ex­pected,’’ said coun­cil­lor and Te Awarua-o-Porirua Har­bour and catch­ment joint com­mit­tee chair­woman Bron­wyn Kropp.

The study found the sed­i­men­ta­tion rate for the Onepoto and Pau­ata­hanui arms of the har­bour was 2mm per year on av­er­age.

That is sig­nif­i­cantly lower than those cal­cu­lated for the 1974-2009 pe­riod, but con­sis­tent with other sed­i­men­ta­tion ob­ser­va­tions by Welling­ton Re­gional Coun­cil.

‘‘While this is good news for the past five years, cau­tion is re­quired when in­ter­pret­ing th­ese rates,’’ Kropp said.

‘‘Th­ese new rates will be a com­bi­na­tion of nat­u­ral vari­a­tions and a lack of ma­jor storms over the past five years that would nor­mally de­liver more sed­i­ment to the har­bour. ‘‘But the re­sult is heart­en­ing.’’ The Porirua Har­bour Trust re­cently re­leased a pos­i­tive an­nual score­card for the har­bour and last year’s Guardians of Pau­ata­hanui In­let cockle sur­vey was also en­cour­ag­ing.

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