Hunter

Flooding on the Paterson & Williams Rivers

Paterso

n R iver

HINTON

MORPETH

MAITLAND

GREEN ROCKS

SEAHAM

RAYMOND TERRACE

HEXHAM

PATERSON

Seaham Weir

Wi l l

iam

s R

iver

Hunter R i v er

floodplain

Figure 1. Lower Hunter Catchment, from Maitland to Hexham

Hunter River catchment area: 22 000 sq km Mean annual runoff: 2 000 000 ml

Catchments contributing to runoff: Goulburn River (15%), Upper Hunter (45%), Paterson & Williams (40%) Lower Hunter catchment area: 380 sq km

Paterson River in flood, Hinton 1998 (photo courtesy Maitland SES Unit).

Rural flooding in Maitland 1989 (photo courtesy CMA).

The Lower Hunter River and its major tributaries are prone to flooding. Floods typically occur in the Paterson and Williams rivers in summer due to cyclonic depressions moving south off the Queensland coast. The area of the Paterson and Williams catchments comprises only 11% of the total Hunter River catchment area, and both streams meet the main channel well below Maitland (Figure 1). Despite the relatively small catchment sizes, runoff from these catchments contributes 40% of the total runoff to the Hunter River catchment.

HUNTER COMMUNITY RECOVERY FUND

Better FloodSafe than sorryFloods have been recorded on the Paterson River since 1929 and on the Williams River since 1950. On the Paterson, 26 major floods (greater than 12.2 m (AHD*) at Gostwyck Bridge) have been recorded. Figure 2 shows floods greater than 13.5 m (AHD). The highest flood on record peaked at 15.24 m (AHD) in March 1978. On the Williams River five major floods (greater than 8.50 m at Dungog gauge station) have been recorded (Figure 3).

1955 flood In the 1955 flood, the Williams and Paterson rivers contributed a massive amount of floodwater to the Hunter River, approximating 308 000 megalitres—enough to more than half-fill Sydney Harbour. Fortunately, the peak discharges from these two rivers occurred on 24 February, one day in advance of the main Hunter River flood. If the three rivers had reached their peaks on the same day, the impacts of the flooding would have been even worse. The rural areas from Maitland to Raymond Terrace were inundated. The water was 1.4 m deep in the Victoria Hotel at Hinton and 0.5 m deep in the Clare Castle Hotel at Raymond Terrace.

Recent floods Floods higher than the 1955 flood have continued to occur on the Williams and Paterson rivers, and often strike with little warning. The recent floods in 2007 are a timely reminder to prepare for floods—have a home emergency kit ready and know your evacuation route. Even minor floods can affect rural properties and cause flooding on roads and causeways.

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Figure 2. Floods greater than 13.5 m (AHD) recorded on the Paterson River at Gostwyck Bridge since 1929.

Figure 3. Floods greater than 8.5 m recorded on the Williams River at Dungog Station since 1950.

➜Rural properties at Morpeth flooded in 1998 (photo courtesy Maitland SES).

Road cut off by floodwaters at Phoenix Park in 2001 (photo courtesy John Lane).

* Australian Height Datum (AHD)—a datum used to measure vertical height based on mean sea level as zero.

References NSW Public Works 1994, Lower Hunter Flood Mitigation Scheme Fact Sheets 1994-1, 1994-6 & 1995-1a.

www.ses.nsw.gov.au For emergency help in floods, call the SES on 132 500