Territory Stories

Sediment Quality Sampling Design for Darwin Harbour

Details:

Title

Sediment Quality Sampling Design for Darwin Harbour

Creator

Brinkman, Richard; Logan, Murray; Northern Territory. Department of Environment and Natural Resources; Australian Institute of Marine Science

Collection

E-Publications; E-Books; PublicationNT; Report Number 44/2019

Date

2020-01-06

Location

Darwin Harbour

Description

In the context of increasing development and associated pressures, this project aims to inform the development of a first systematic, long-term, sediment monitoring program for Darwin Harbour which takes into consideration the physicochemical nature of Darwin Harbour sediment and the oceanographic processes which will influence the movement of contaminated sediment in the Harbour. The rationale for the program is that seabed and estuarine sediments are both an extensive habitat and the ultimate repository for many contaminants that enter waterways. In addition, monitoring of contaminants in sediment may facilitate the identification of increasing contaminant loads in the Harbour which may not be detected by water monitoring programs due to the high flushing rate within Darwin Harbour and infrequent water sample collection.

Notes

Made available by via Publications (Legal Deposit) Act 2004 (NT).

Table of contents

1. Executive summary -- 2. Introduction -- 3. Methods -- 3.1 Overview of methodology -- 3.2 Tidal Hydrodynamics -- 3.3 Wave Dynamics -- 3.4 Sediment Modelling -- 3.5 Sediment sampling design analysis -- 4. Results -- 4.1 Tidal and wave driven hydrodynamic processes -- 4.2 Sediment transport modelling -- 4.3 Sediment characteristics from previous sampling programs -- 4.4 Sediment sampling design analysis -- 4.4.1 Existing chemical sediment data, Outer Harbour sediment monitoring data, and designated sampling sites -- 4.4.2 Hydrodynamic modelling layers -- 4.4.3 Exclusion zone masks -- 4.5 Spatial Model fitting -- 4.5.1 Background on statistical techniques for designing sediment sampling program -- 4.5.2 Results from statistically derived sampling design - East Arm -- 4.5.3 Results from statistically derived sampling design - Outer Harbour -- 4.5.4 Representation of sampling sites mapped with hydrodynamic and sediment modelling parameters -- 4.6 Harbour Sediment Zonation, and conceptual representation: -- 5 Conclusions -- 6 References -- 7 Appendix 1

Language

English

Subject

Sediment quality; Tidal hydrodynamics; sediment sampling; design analysis

Publisher name

Northern Territory Government

Place of publication

Palmerston

Series

Report Number 44/2019

Format

43, 74 pages : colour maps ; 30 cm

File type

application/pdf

ISBN

9781743502303

Use

Attribution International 4.0 (CC BY 4.0)

Copyright owner

Northern Territory Government

License

https://creativecommons.org/licenses/by/4.0/

Parent handle

https://hdl.handle.net/10070/755961

Citation address

https://hdl.handle.net/10070/765802

Page content

41 spatially balanced design) for generating candidate sampling configurations, for which an optimum sampling size and configuration is determined. Overall, 2D spatially balanced sampling designs for both Outer Harbour and East Arm would seem most appropriate. These designs are immune to any uncertainty in previous data and spatial modelling and should yield well balanced spatial configurations. A total of 100 samples collected from both East Arm and Outer Harbour is likely to yield representative samples from which to construct a variety of spatio-temporal models into the future. Knowledge of the dominant processes controlling sediment transport within the Harbour has enable the development of conceptual model of sediment movement within the Harbour. The proposition for the conceptual model of sediment transport is that fine sediment typically enters the Harbour during wet season flow events. This sediment is easily suspended and remains in suspension, due to large tidal currents within the central section of the Harbour until it is moved into more quiescent regions, via flood dominated tidal asymmetry, where it deposits. This system represents a mechanism of nett fine sediment movement into depositional areas in the upper reaches of the Harbour Arms. The movement of the fine sediment which has higher binding affinity for contaminants than sand, can be used to guide the selection of sediment sampling sites as depositional zones are potential sinks for contaminants within Darwin Harbour.


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