Spotlight on river health: Rescuing the Serpentine River with an in-depth Action Plan

Earlier this year, the Mandurah Mail shone a spotlight on the health of the rivers in the Peel region, which continues to decline.

Assessments have revealed, of more than 4000 kilometres of waterways throughout the Swan Coastal Plain, only about 1 per cent is in "near pristine condition".

In an effort to uncover why local waterways are not in the condition they should be, the Mandurah Mail will be interviewing environmental experts to gauge the health of local rivers and report on the research being conducted and initiatives in place to help restore them.

After speaking with leaders from the Peel-Harvey Catchment Council (PHCC), who sounded grave concerns about the condition of Mandurah's waterways, the series continues with another significant initiative to help restore the health of the Serpentine River.

Over the past year, the PHCC has partnered with Urbaqua Land and Water Solutions, a not-for-profit organisation who specialise in supporting environmental projects to deliver better on-ground outcomes, to complete and deliver the Serpentine River Action Plan.

The aim of the assessment is to provide insights for future on-ground restoration projects to improve the overall ecosystem and function of the river.

The Serpentine River has a catchment area of almost 1700 square kilometres and is one of three main rivers feeding into the Peel-Harvey Estuary, which is recognised under the Ramsar convention as a wetland of international importance.

Since European settlement of the region in 1830, local waterways have undergone a number of changes from extensive clearing for agricultural and urban development to the creation of an artificial drainage network to try to combat flooding.

It also included the de-snagging and re-engineering of the river to increase it's capacity and the construction of the Serpentine Dam for drinking water.

The significant modifications have caused a severe deterioration of water quality and resulted in a decline in water flows and aquatic biodiversity of the river corridor.

As a result, the Serpentine River was in desperate need of rescuing.

The River Action Plan was developed as part of the Connecting Corridors and Communities - Restoring the Serpentine River project.

Funded by the Alcoa Foundation, the three-year program commenced in 2018 with assessments of the condition of the river bank and foreshore, along the middle and lower sections of the river.

The team of scientists, assisted by community volunteers and graduates from the Alcoa environmental program, worked their way along eight reaches of the river, covering 40 kilometres on foot, making observations and identifying the issues impacting the health of the river.

They gathered data on geomorphology, vegetation condition, aquatic habitat and water quality, took more than 5000 photographs and made 40 assessments across the entire study site.

These have been compiled into the River Action Plan to identify sites at which priority actions should be implemented to improve the Serpentine River's health.

PHCC science and waterways program manager Dr Steve Fisher said the field work made up just one part of the Serpentine River Action Plan.

"Infrastructure such as bridges, weirs and drains, land uses, river connectivity, abundance and diversity of fish, freshwater crayfish and aquatic invertebrates, as well as threats such as the prevalence and spread of the noxious weed water hyacinth, have all also been assessed to ground-truth and fill knowledge gaps from earlier desktop studies," he said.

"There has also been detailed observations made from the air by helicopter and drones capturing aerial footage, as well as from the water and on foot.

"Other attributes, such as the cultural significance of the river, have also been captured through on-going consultation with the local Noongar people and private landholders in the catchment."

PHCC chairperson Caroline Knight said she was looking forward to seeing how the River Action Plan would guide future restoration works.

"By setting a baseline for the current condition of the Serpentine River, the plan enables us to measure the improvement in river health as a consequence of our actions," she said.

"Improvements in the condition of the Serpentine River will also complement PHCC's efforts in protecting the values of the Peel-Harvey Estuary.

"The estuary is a major component of the Peel-Yalgorup Wetlands System and recognised under the Ramsar Convention as a wetland of international importance due to the habitat it provides for waterbirds, including migratory shorebirds, fish, invertebrates and threatened ecological communities."

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The River Action Plan is the first in a number of initiatives to help restore the health of the Serpentine River.

The field work was conducted using standardised methods so condition comparisons can be made between each segment of the river.

The documentation and mapping of all sites where field work was undertaken will also allow for future replication of the methodology.

In addition to the River Action Plan, the PHCC has carried out river health assessments at five sites along the Serpentine River to attain a snapshot of the current condition.

These include both in-stream assessments, made by measuring the abundance of native fish and freshwater crayfish, and vegetation assessments along the foreshore.

Following restoration works recommended as a result of the River Action Plan, future assessments will be conducted to indicate whether the health of the river is improving, declining or being maintained.

In the next installment of the Spotlight on River Health series, the future uses of the river health assessments will be further explored as well as the next phase of the Connecting Corridors and Communities - Restoring the Serpentine River project.