Larcombe, P.

Morrison-Saunders, A.

Research Repository

Piers Larcombe Angus Morrison-Saunders  piers.larcombe@rpsgroup.com.au             “             @uwa.edu.au a.morrison-saunders@murdoch.edu.au       EIANZ, Perth Thu. 29th Oct. 2015. 15 +5  mins Getting the Physical Science right in  Marine Environmental Assessment (EA):  The critical need to challenge the status quo Australia’s offshore pipelines (D. White, UWA, 2013) Not HOW science is used in the EA process, but that key science is omitted. 1.5 - 2 TCs / yr 1 - 1.5 TCs / yr 30,000 TCs  in last 9000 yrs Bed sediment transport pathways  Multi-decadal  Episodic Regionally and locally, such pathways   profound implications for   marine environments & habitats Analogy:  Traffic ≡ bed sediment grains  Roads ≡  transport pathway Parks, reserves, lakes don’t have cars  ≡ sediment-free habitats.  Road Network  Completely inter-connected  Empty road ≡ lag surface  Busy road ≡ sediment present  Traffic jam ≡ sediment immobile.  KEY is that each road type  ≡ different benthic habitat.  ... each (habitat) controlled by:  the nature of traffic  & the long-term net movement of vehicles. 3 Bed sediment transport pathways  – what are they?   So ... EA application requires us to know how sediment moves through the system, controlling habitats Designing & managing new road developments require an understanding of how the network functions  Habitat = f (sediment transport pathway) Key aspects:   Sediment type  Presence / absence  Mobility (magnitude, frequency, nature)  Thickness  Form (micro-habitats)   Superposed & related are:   Biology  Chemistry  etc  4 .. depend on sediment from here All habitats here...       ~20 km      Most marine habitats = sediment-dependent (type, presence, absence, mobility, etc)       Mangroves  open coasts  & in deltaic systems    Seagrass beds  In mobile sands   & in muddy embayments.   Most reef flats      Detrital coral communities (turbid-zone reefs)         Middle-shelf benthic systems    5      Northwest Shelf, Australia 6 Dredged channels, up to >30 km long Permanent  - effectively for evermore Multi-decadal bed sediment pathway to SW The importance of physical science: 1: James Price Point Reports from ~2007.  Surely all relevant information is clear by now! 7 The importance of physical science: 1: James Price Point 7 km-long dredged channel...    Will cut entire nearshore transport pathway, risking:  removing surface sediments to S,  permanent habitat change  Would be an indisputable result of development, but issue missed in EA process.  Why?  EA            ‘Characterisation’ & ‘Models’  But better to understand & test physical science Large fields of sandwaves <few m high & 600-1200 m long  southward bed sediment transport  8 Turbidity ISN’T  TSS concentration (SPM)  Light availability  Sediment transport (or rate)  Sediment flux to the seabed  Etc In natural environments: Turbidity = f  [particle size, nature of PSD (esp. multimodal, i.e. mixtures),   shape, surface roughness, flocculation, Refractive Index,  composition, concentration...]                       (Bunt et al., 1999)  ~25 years - mainstay of EA  Q - Still useful for marine EA?  Optical backscatter (OBS) The importance of physical science: 2: Turbidity (NTU, FTU) Days Turbidity...    9 Tides plus waves Settling of  v. fine-medium sands  (63 - ~250 µm) at concs. >100x   35 mg/l 44 mg/l Neaps plus  small waves NTU (sondes) c.f. TSS (LISSTs) Green & Boon, 1993 Issue = Can be blind to major sedimentary events,  maybe of critical environmental relevance  Quantitative use unjustified Qualitative tool at best Silty v. fine sand A little silt or lots of sand? Environmental Assessment - Current Marine Regulatory & Guideline Documents  (e.g. dredging) Similarly:   WA EA guidelines 10 (2013) (2015) Key Federal document on dredging has limited physical & sedimentary science.  GBR/Qld documents & associated influential reports Performance Objectives:  are reported to WA Minister of Environment.  require an understanding of habitat dynamics,   so bed sediment dynamics  are expanded upon in associated WA EAG documents,   but in which physical & sedimentary science is weak or absent.  11  Wrt marine environment...                       (EAG8).  Environmental Protection Authority, Western Australia, 8 pp.  Revised Jan. 2015.  Key environmental factor (marine)  Performance Objectives   Benthic communities and habitat To maintain the structure, function, diversity, distribution and viability of benthic communities and habitats at local and regional scales. e.g. EAG8 “Environmental Principles, Factors and Objectives” (e.g. WA EPA)  Coastal processes To maintain the morphology of the subtidal, intertidal and supratidal zones and the local geophysical processes that shape them.  Marine environmental quality To maintain the quality of water, sediment and biota so that the environmental values, both ecological and social, are protected MESSAGE...  If you are relying on existing EA Guideline documents to guide your EIA practice,  you are getting poor scientific advice! Terrestrial environments.  Habitat understanding matters... 12 e.g. Habitat of the Wollomi Pine  highly valued, location secret   & we work to understand it e.g. Bushfire  Once = ‘ecological disaster’.  Now = understood as part of natural pattern of habitat renewal. e.g. James Price Point (SAR 2010)  “Once equipment is removed from site, rehabilitation would commence to ensure that the condition of the site reflects the existing surrounding environment.   “This would involve contouring the surrounding landscape and revegetation of native flora species.” But no reference to  the marine environment. Sediment-dependence matters! All these marine habitats are intimately related to sediment.  Exactly how is unknown 13 Pitcher et al. (2007) 1            2     3                4   yet this knowledge is critical to our approach to management.  As EA practioners,   you wouldn’t (and don’t) work like this on land.    So why is it ok to work like this offshore?  14 Physical science underpins habitats & ecosystems  but is weakly implemented in marine EA.  Weak in understanding benthic habitats & resilience, measurement techniques & programs...  EA principles include:  “best practicable science, methodologies & techniques appropriate to the problems being investigated, relevant, cost effective, efficient, focussed”  Out of sight, out of mind? &/or lag in level of knowledge c.f. terrestrial?  Have we just been lucky so far?  Environmentally-perhaps, costs-perhaps not.  Meeting international and national regulations requires an improved approach Observation              Implication 15 Responsibility lies with YOU,  the EA practioners:  1. Probably means some behaviour change 2. Fully acknowledge the key significance of the physical environment 3. Encourage measures to  • establish the logic • perform the background science  4. Help future regulations use these concepts to underpin the EA approach & practical application.  1. Misdirected effort 2. Unnecessary environmental damage  3. Regulation bypassed by ‘habitat science’.   All would discredit the EA process Situation demands a paradigm shift. Physical science is fundamental to EA conduct. Risks are great: 

Getting the physical science right in Marine Environmental Assessment (EA):  The critical need to challenge the status quo

https://researchrepository.murdoch.edu.au/id/eprint/28883/1/marine_environmental_assessment.pdf

Getting the physical science right in Marine Environmental Assessment (EA): The critical need to challenge the status quo

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