Middle Creek is a small watercourse that drains through the village of Pearl Beach on the New South Wales Central Coast. The creek is an ephemeral stream that drains a 58.3 ha catchment that is mostly undeveloped and which extends back from the coast to the escarpment (refer Figure 1).

As shown in Figure 1, the creek rises over about 2 kilometres west from the coastline to an elevation of 160 metres above sea level. The upper two-thirds of the catchment are extremely steep with an average grade along the streamline of more than 10%. The lower one-third of the catchment is much flatter and extends across a narrow floodplain before discharging through the back beach dune of Pearl Beach.

The lower reaches of Middle Creek flow through the central section of the existing urban areas of the village of Pearl Beach. The creek flows in an easterly direction along an alignment that generally follows the rear boundary of properties that front Pearl Beach Drive and Emerald Avenue (refer Figure 1). As a consequence, many of these properties fall within the adjoining floodplain and are therefore susceptible to flooding.

Available anecdotal and recorded data indicates that flooding has occurred on many occasions, most notably in January 1989, April 1989, February 1990 and January 1992. This flooding was particularly severe in the vicinity of the Diamond Road crossing of the creek (refer Figure 1) and led to significant damage to properties that adjoin the lower reaches of the creek. In recognition of this, Council undertook works in early 1994 to increase the capacity of the Diamond Road culvert. As a consequence, reports of damage in this area due to flooding are now less common.

Notwithstanding, over the intervening period, there has been encroachment into the creek corridor along the rear of those properties that front Pearl Beach Drive and Emerald Avenue. The encroachment has occurred as a consequence of individual property owners undertaking works to improve the amenity of their backyards. Unfortunately, this has often reduced the channel capacity and led to increased flow velocities during flood events. These changes have significantly impacted on the natural stream characteristics, resulting in increased bed and bank scour and a deterioration in channel condition in the lower reaches. In addition, the altered channel regime has increased the potential for localised flooding across private properties.

In recognition of these issues and the potential for flood damages to be incurred into the future, Gosford City Council decided to embark on the development of a Floodplain Risk Management Plan for Middle Creek. In 2003 Council completed the first stage in that process with the publication of the Middle Creek Flood Study.

The Middle Creek Flood Study documented design flood levels and flow velocities for each of the 5, 20 and 100 year recurrence flood events. The report provided “baseline” flood data for use in development assessments and the analysis of potential flood damage reduction measures. A range of floodplain management measures were developed and assessed as part of work to prepare the draft Middle Creek Floodplain Risk Management Study, which has recently been completed.

This report documents the preferred management options for Middle Creek and incorporates them into a program of works that identifies the likely cost of each measure and their projected benefit to the Pearl Beach community.