The Entrance Channel EarthCache

The Entrance is aptly named after the channel by which the ocean enters into Tuggerah Lakes. The ocean feeds the extensive and complex Tuggerah Lakes system via The Entrance channel, preserving the ecological structure and values of the lake as well as maintaining a low flood risk to life and properties in the low-lying areas surrounding Tuggerah Lakes. It also extends its significance and importance to the surrounding coastal bird life by way of carrying a stream of fish and crustaceans ensuring their survival.

However, the channel is controlled by tides, currents and storms and thus, it is ever changing.

The Tuggerah Lakes system is comprised of three major interconnected lakes. Lake Munmorah, the smallest of the lakes, flows into Budgewoi Lake, the second largest lake, which in turn flows into Tuggerah Lake, the largest of the three. Tuggerah Lake offers the main connection to the Tasman Sea through the The Entrance channel.

The channel or "inlet" is comprised of a "mouth" and "throat" and both the lakes and the channel are tidal. The tidal delta found at the inlet is developed by both flood and ebb deltas. The shallow nature of the lake and channel cause the flood and ebb tidal currents to disperse and reduce their intensity. The formation of delta shoals are the result of the rapid flow of the flood and ebb tidal currents. The channel is stable in the sense that is a certain "S" shape to it when it is open and flowing well. It's throat is the deepest part but also the narrowest part with the mouth being shallower and wide.

Erosion from storms along the coastline dump extra sediment into the ocean that is held in motion and moved with the tidal currents. When the flood tidal current entering the mouth of the channel hits the ebb tidal current leaving the channel, the force of the impact during this period of saltation, allows the grains of sediment to settle building sand shoals. The adverse effect of the building sand shoals is that the water traversing the channel may be forced to be redirected or blocked altogether resulting in flooding around the low-lying properties around the lakes.

The Central Coast Council will dredge the channel when it is required to keep it open but locals are calling for breakwalls to be erected to keep the channel permanently open. This comes with both positive and negative consequences.

Positive reasons include a lowered risk of flooding, possible lessening the risk of erosion around the immediate area of the breakwalls, the possible deepening of the lake system encouraging more diversity in the marine life currently sheltering and living in the lakes as well as better filtration of the three major lakes avoiding stagnation.

The structural changes to the channel can impose negative impacts as it causes changes to the behaviour of the tidal currents encouraging accretion of sediment which in turn can cause an excessive salient build up. Over time, this can attribute to a tombolo formation further impacting the transport of sediment by way of longshore drift reduction leading to beach sediment starvation and causing erosion.

At the posted coordinates, message or email me the answers to the following questions:

1. Why do you think the channel is constantly changing?
2. Do you think Tuggerah Lakes would be devastatingly impacted if the channel closed?
3. Do you think we, as humankind, could override mother nature and force the channel to stay open by way of walls?
4. Do you think breakwalls would have a positive or negative affect on the Tuggerah Lakes system?
5. Take a photo from the posted coordinates to show me what The Entrance channel looks like and add it to your log. Make it a selfie, give me a thumbs up or include your GPS in your photo.

References:

https://link.springer.com/referenceworkentry/10.1007/0-387-30843-1_461

https://link.springer.com/referenceworkentry/10.1007/0-387-30843-1_464

https://en.wikipedia.org/wiki/Tuggerah_Lake

https://en.wikipedia.org/wiki/Breakwater_(structure)

https://www.centralcoast.nsw.gov.au/environment/coastlines/estuaries-lagoons-and-wetlands/tuggerah-lakes-estuary/dredging-entrance

https://www.researchgate.net/profile/Wayne_Erskine/publication/259079234_Flood-tidal_and_fluvial_deltas_of_Tuggerah_Lakes_Australia_Human_impacts_on_geomorphology_sedimentology_hydrodynamics_and_seagrasses/links/00b7d529e7cda5d963000000.pdf?origin=publication_list

https://www.lakesmail.com.au

https://www.facebook.com/wheresourBreakwallatTheEntranceChannel/