the show, foil Hie rojajgrovfl triage 

 reduce tins effect, and therefore 



CrcatBS conditions favourable to nunc 

 rapid vertical accretion on the adjae 

 cut rriudfiaW, tn this way, mangrove-, 

 may he said to contribute to the 

 advance of the shoreline 



AtCRIllON on Mi ni I.MS 



I he standard method of mcasuiing 

 vertical accretion of sediment on 

 mudllats or marshlaiuls is to place 

 a layer of identifiable matetial (such 

 as brick dust) on the suif.ice, and 

 return subsequently to probe foi it 

 and measure the thickness of over- 

 lying accretion. An attempt was 

 made to use this method on mudllats 

 in front of the maiigiovcs south of 

 Yatmga. but it tailed because the 

 brick dust layer was quickly dis- 

 persed by waves and em rents, and 

 by burrow me crabs, and so did not 

 remain in position long enough to 



be of much use as a marker horizon 

 An Alternative method is to inseri 

 stakes and measure the level () f 

 accretion against these. In January 



I'HnX a set of 12 stakes (bamboo 

 canes) were implanted at various 

 sues up to ten yards seaward of the 

 mangrove fringe south of Yaringa. ] 



I lie nun! here is very soft, and can I 



onlj lie traversed on foot with n u . I 



aid of platehei -hoards attached to 

 one's shoes. I his results in disturb- 

 trace of the mudllat surface on a 

 scale which calls in question the 

 validity of measurements made in ot 

 near the disturbed area. It proved 

 nunc convenient lo work from ., 

 shallow -draught boat, moving toward 

 the mangroves on a rising tide. 



I tit- slakes were pushed into thv 

 mud until only 20 cm protruded 

 above the surface. Changes of level 

 on the inudllals were then measured 

 at monthly intervals with referent. 



Plate 4 Waves movint into the mangrove fringe at (ftfe Aftftf fife ™«h«rfY»rin^ 

 194 



Pkot*. Au< 

 V IC ( Nal Vol 86 



