Not total confident on ID as there are similarities with T.irritans and T.scariosa but the following suggest T.compacta.
Coastal location/habitat, tightly imbricate florets, spikelets with predominantly 8 florets, glumes 1/2-3/4 length of spikelet, lemma notched with no mucro.
https://spapps.environment.sa.gov.au/SeedsOfSA/speciesinformation.html?rid=4605