CHAPTER X
Plant Winning of Tidal Lands—Salt Marshes
   The Salt Marsh is tidal land par excellence. Its basis consists of silt and mud, that is, of the most finely-divided erosion products. These materials carried in suspension into estuaries or other sheltered positions, such as the lee side of spits, &c., tend to be precipitated at slack water. In these positions the mud is normally colonized by vegetation to form salt marsh. When in fullness of time a vigorous mixed vegetation has arisen, occupying a level overrun by the spring tides only, the marshes are termed “saltings”.
   Salt marshes, more than any other type of maritime land, show continuous change, both in the details of their topography and in their vegetation covering. In the case of shingle it is the exceptional storm or super-tide that determines important topographic re-arrangements, whilst for effective movements of sand on a dune system winds of considerable velocity are necessary. With mud, on the other hand, the normal daily flow and ebb of the tide are entirely adequate to transport and redistribute the particles. The most gentle of currents will lift and carry particles of clay, e.g. one flowing at 0.17 mile per hour (0.25 foot per second). The process operates at every tide; mud is being moved from one place and deposited in another. The aggregate result is topographic change. Creeks meander like rivers; ground is eroded away; silt is deposited on the saltings and their level rises. The change in level affects the physical character of the soil, whilst, with a rising level, the period of tidal submergence is shortened. Such changes unfit
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