Wetlands Australia 31: Buffers, sponges and moderators – why swampy meadows matter

Authors: Cam Wilson (Earth Integral) and Dr Siwan Lovett (Australian River Restoration Centre)

In the face of a changing climate, one that is expected to bring increased extremes in weather patterns, wouldn’t it be nice to have a riparian system you could describe as a ‘buffer, sponge and moderator’?

Wetlands and swampy meadows do just that, and they are gems when it comes to bringing resilience to the waterways, farms and wildlife of this dry old continent.

The swampy meadow is a riparian system that was very common in upland valleys of south-eastern Australia at the time of European contact. It is essentially a floodplain that doesn’t have a continuous channel. As the name ‘swampy’ suggests, the alluvial sediments that make up the landform are regularly saturated, creating conditions that support a dense ‘meadow’ of moisture-loving grasses, sedges and rushes. Some, but not all, swampy meadows contain chains-of-ponds, which are irregularly spaced along the valley floor.

The Rivers of Carbon program is working with landowners to protect and restore these very special swampy systems across the southern tablelands of New South Wales.

Intact swampy meadow at ‘Baarlijan’ with landholder Donna Hazell. Photo: Richard Snashall

So, how do they function as ‘buffers, sponges and moderators’?

Swampy meadows help to buffer peak flows as they move through the catchment, reducing the severity of downstream flooding. These systems also buffer the movement of sediment and nutrients, with the dense vegetation acting as an effective filter which can improve downstream water quality and habitat complexity while enhancing on-site productivity.

Over time, swampy meadows build vertically into an effective sponge, as captured sediment is combined with organic matter inputs from the highly productive vegetation. The sponge, or alluvial aquifer, fills and stores moisture during periods of flow, and then provides benefits during drier periods to downstream users, by slowly releasing moisture as baseflow, as well as benefits to on-site flora, fauna and primary production by providing access to moisture long after the rest of the landscape has dried out.

Swampy meadows are also moderators of energy. Any time that flowing water interacts with dense vegetation, the speed and energy of the flow is reduced. The ‘roughness’ provided by the tall tussocks, sedges and rushes that typify these settings is especially effective at moderating flow velocity, so it is important that management efforts aim to protect this vegetation and maintain good general groundcover. Dispersed flow also moderates energy, so efforts to prevent the formation of flow concentrating features such as erosion gullies, or stock and vehicle tracks are also important. Swampy meadows can also moderate the local microclimate via ‘air conditioning’ evapotranspiration effects.

We believe these systems are so important that, in partnership with South-East Local Land Services, Water New South Wales, local landowners and specialist experts, we developed a film that shares the science and stories behind swampy meadows.

Restored swampy meadow system at ‘Cadfor’, property owner Rod Hoare. Photo: Richard Snashall

Further information

To view the film and learn more about these wonderful swampy areas, visit http://riversofcarbon.org.au/.