Focusing on Andersen Inlet erosion risks

I guess there has been a lot of discussion in this blog about changes on the surf beach at Venus Bay but in reality the most significant erosion is going on all along Andersen Inlet.The deeper channels (think of them as a submerged meandering but tidal streams) are snaking back and forth changing position within the inlet progressively widening the inlet and eroding its banks (particularly at Inverloch, on the north eastern side, and around doyle’s road, on the western side. Sand is progressively  moving deeper into the inlet and this hinders the development of mangroves, which are really the only way to slow down eroding the shores. The open “beaches” allow waves to undercut the peat layer of the salt marshes and once compromised like this the salt marshes quickly wash away. Trees offer only slightly more resistance but they soon also succumb to the erosion.

Point Symthe – Geology walk to Inlet & Ocean Beaches

You will find this years geology walk out on Point Smythe area (not to Point Smythe itself) in the Summer by the Sea program list under Geology Rocks!. Sorry no rocks to see but plenty else, including geological processes in action. Perhaps a few experiments on the beach. The route this years has been trimmed (no big dunes to walk up) and there is still plenty to see, in less than 5km.
 

Fri 20 January 1.30pm – 3.30pm

Bookings Essential (03) 5674 3738

What is a Spit?

The geomorhpic definition of Spit is a sandy bar projecting from the mainland into open water. Spits are formed by deposition of sediments moved by longshore drift. (here is a wikipedia link on spits, if you want more details)

So the Big question; Is Point Symthe a Spit?

Well it is widely described as a spit in tourist literature guide books, Often as Victroia's largest spit. However there may be a few problems calling it a true spit

1) The Andersen inlet estuary is no longer "open water" and there is a very strong tidal inflow and outflow cutting across the longshore drift

2) Observations in this project suggest that the longshore drift does change directions and has been larger going southwards for the past few years

3) It doesn't have the characteristic hooked end.

Yet physically it is a very large continuous section of sand and the present situation may represent a very late stage of spit development. Where by the entrance to Andersen inlet may close over with a continous sand bar from Point Symthe to Inverloch.

However as Andersen inlet gradually fills with sediment (not sure if anyone is accurately measuring this) The effects of the tidal flows (it is the same amount of tidal change but in a progressively shallower inlet) mean that there is now considerable erosion cause along the main chanels giving outlet to the sea. These infact are behaving like a meandering streams thrashing back and forth across the inlet floor and heavily eroding the coast & beaches but just at very specific locations (where the chanels curve most).

Who will win? Longshore drift or the tidal flow from Andersen Inlet.