The Shifting Sands of Stockyard Creek: the geomorphic response to large wood reintroduction in a sand-bed stream

In April 2002, 26 Engineered Log Jams (ELJs) were built within a 2 km treatment reach of what was a degraded

ephemeral sand-bed stream at Stockyard Creek, Wollombi, NSW. Coupled with ~ 20 years of ongoing native revegetation

this project aimed to increase the geomorphic diversity and ecological characteristics of the ephemeral stream. The

experiment was set up as a standard Before-After Control- Impact (BACI) design, with a control reach situated in the

upstream limit of the study site and the incorporation of an external control reach in an adjacent valley. This paper aims

to assess the geomorphic response to the re-introduction of wood by comparing treatment and control reaches. Since

construction, the ELJs have experienced a 5 year period of low or no flow conditions, as well as two major bed mobilising

flood events which occurred in June 2007 and February 2013, and a number of smaller flow events. Four detailed

topographic surveys of the study reach were completed during the 11 year study period and have been used to

construct Digital Elevation Models (DEMs) of the in-channel bed topography. Geomorphic change detection analysis

suggests the magnitude of change within the treatment reaches was much greater than that of the control, with the

most pronounced response to ELJ introduction being the development of persistent pool habitat.