Hydrological Systems

Geographial Inquiry Question

How do hydrological systems shape the creek system at Bobbin Head?

Shape and size of the Catchment

Use the River Runner Global animated map to identify where water travels in the Cockle Creek/Cowan Creek catchment.

This website will show you where any raindrop that falls in the world will end up with an animation of the length of the river system.

Enter Bobbin Head Picnic Area in the search bar or zoom in until you find the location.

https://river-runner-global.samlearner.com/

(Note, the map is not accurate if you enter a destination in the catchment above Bobbin Head - it will erroneously direct you to Berowra Creek.  But, if you drop a "rain drop" by clicking on the map in the catchment above Bobbin Head, it will show you the full animation of Cockle Creek).

Precipitation patterns and cycles - The Water Cycle of Hornsby

Using the Hornsby Council infographic below as a guide, draw your own diagram of the water cycle using arrows to show direction.

Catchment functioning

Land use patterns in a water catchment can affect the function of the water cycle. 

Using the Hornsby Council poster below, identity 5 ways in which human land use has affected the water cycle in Cockle Creek.  (Cockle Creek is next to Berowra Creek and has much the same impacts).

Tidal inundations

Cockle Creek is a tidal creek that flows to the ocean via Cowan Creek and the Hawkesbury River over a distance of about 25km. The water at Bobbin Head is therefore brackish - a mix of salt and fresh water. Salt content in the water goes up on a high tide and is lower after significant rain in the catchment and an outgoing tide.  The water level can vary up to 2 metres depending on tides and rainfall in the catchment. 

You can estimate the time and height of the tide at a given time at Bobbin Head by using a tide guide. 

Estimate the time and height of the tide on the day of your excursion using the link below.

Ku-ringai Yacht Club at Cottage Point is the closest location to Bobbin Head. You will get a more accurate time by adding about 30 minutes to that location.

King Tides at Bobbin Head

"King Tide" is a non-scientific term that refers to any high tide that is much higher than normal.  Some of the conditions that cause king tides include the position of the moon, ocean currents and coastal storm activity.

At Bobbin Head, king tides have been responsible for flooding of parts of the carpark and grassed areas in the picnic area. 

View the video below taken by Gibberagong staff with a time lapse camera of a king tide December 6th, 2017.

King Tides at Bobbin Head 6:12:17

Video footage of a king tide at Bobbin Head in December 2017

Youtube (0:27min)

Climate change and water levels at Bobbin Head

Want to know what the Bobbin Head may look like in 2100? 

This BETA version of Coastal Risk Australia (CRA) is an interactive map tool designed to communicate coastal inundation associated with sea level rise in the year 2100.  

Enter Bobbin Head Picnic Area into the search bar to view the predicted inundation caused by sea levels rising by 2100.