THE NORFOLK BROADS. 



353 



site of the whole seven [sec Fig. 2) its velocity and carrying power 

 would be simultaneously reduced ; it would, therefore, drop all its 

 sediment as a delta or fan-shaped heap around its mouth. At times, 

 when the river was low, this might tend to form a bar across its 

 entrance, but during floods the river would unceremoniously re-cut 

 its channel through this pile of debris, and spread the fan further 

 outwards. As the fan grew, the whole face would not receive equal 

 amounts of detritus ; the middle would grow faster than the sides, 

 and thus project into the Broads ; rushes and plants growing on 

 the shallow sides of the fan would help to complete the embankment, 

 and confine the river to one narrow channel. Even during floods, 

 when the river swept over the embankments, the stems of the dense 

 rush grove would act as a sieve, and catch all the mud, and thus not 

 only raise the main walls, but prevent the silting of the Broads on 

 either side. All fresh supplies of sediment would, therefore, instead 

 of being spread evenly over the floor, be piled up on either side of the 

 mouth of the channel. In this way the embankment would in time 



Fig. 2. — The Hoveton Group of Broads ; occurring in a tract of alluvium (unshaded) the whole of 

 which was once occupied by the original Broad, (i inch to the mile.) 



run right across the large original Broad, dividing it into two smaller 

 ones, separated by the river and its embankments. The actual line 

 of the embankments would be deflected by the influx of lateral 

 streams, or follow the main current when it diverged from a straight 

 line to avoid higher land. Tributaries, moreover, would in the same 

 way cut up the two Broads into yet smaller ones, and the size of the 

 whole would be gradually reduced by the slow inward growth of the 

 rands around the margins. 



Various local modifications occur owing to the different directions 

 in which the rivers entered the Broads : thus at Ranworth the stream 

 struck the middle of an elongated Broad, and has cut it into two 

 nearly equal lobes. At Surlingham (Fig. i) the Yare was deflected 

 sharply to the north by the hill to the south of the Broad, which 

 marks the site of a sheet of " dead " water left in this angle. 



If this theory be the true one, then the Broads are gradually 

 decreasing in size, as is well-known to be the case, and those which 



2A 



