SYNOPSIS Part 1The Lynmouth floods of August 1952 were investigated before the evidence was put forward based on this evidence. The selection of values for the roughness co-destroyed, and assessments of the flow in different parts of the Lyn River system are efficient in Manning's formula is a controversial matter, but an overall check was provided by the figures fitting together into a reasonable pattern.Since it is unusual to h d a torrential river in England, some special topographical features are obviously involved. The explanation of geomorphologists is that on a coast showing the highest cliffs of England, the sea eroded away the valley side and captured the river. The main course, the East Lyn River, has been graded to a steep For the West Lyn River, joining the East Lyn nearest the sea at Lynmouth, the effect profile but the tributaries have not been equally graded and have been left hanging. is greatest and the profile is precipitous.works recommended follow European practice for torrential rivers. I n flood, the rivers attain very high velocities and carry heavy bedloads. Remedial Part 2 16th August, 1952, are briefly discussed, against a background of the average long-termThe meteoroIogical conditions leading up to the catastrophic rainfall of the 15conditions in the area. The rainfall on that day, and the resulting run-off, are described in relation to the geology, topography, and vegetative cover of the catchment.The run-off, as computed from site surveys, is compared with values calculated in accordance with the Interim Report of 1933 of the Institution Flood Committee.Mention is made of the obstruction of the natural channels of the L p rivers and their tributaries by dead vegetation and boulders and by recent building work.The scale model at the Imperial College, of a short section of the West Lyn suitable as a gauging site, is described. With its aid, a stage-discharge curve has been determined which will enable the site to be used as a permanent gauging station. This flood intensity during the night of the 15-16th August.curve, together with a record of high-water marks, has yielded a value for the peak Downloaded by [ University of Sussex] on [11/09/16].

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Discussion, 111 the ubseuce of the Author abroad, I r . A. B. Porter iuLroduced the Paper with the aid of a series of lantern-slides.The Chairman observed that some members might be surprised by the figures given in the Paper relating to dredging operations, but in works of that kind they were always of an astronomical nature. He had been given the following figures for similar operations a t American ports : Philadelphia 152 million cubic yards ; New York 124 million cubic yards ;Galveston 12if million cubic yards, per annum ; therefore the figures for the River Mersey were not so high as they appeared a t first glance. If those navigable channels were to be mdintained beyond their natural bed it was necessary to dredge, and Mr. A. G. Lyster had realized, in 1912, that the limit of improvement from dredging alone had been attained and that further improvement from dredging could not be expected except ill conjunction with the proposed training banks. The latter had been very successful.It might be asked why the works had taken such a long time. During Downloaded by [ UNIVERSITY OF IOWA LIBRARIES] on [11/09/16].

Discussion.The Authors introduced the Papers with the aid of lantern-slides. Mr. Seaton observed that his Paper had been written quite independently of Mr. Irving, and he was very glad to see that the latter had come to similar conclusions in many cases. He wished to stress the importance of research into the subject of coast erosion and sea defence and'the vital necessity of conserving land and even reclaiming land now inundated by the sea. He hoped that it would be found possible for The Institution to bring the subject to the notice of the responsible Minister (if he could be found), for, since no political kudos could be gained by ventilating the subject, the natural tendency was for Parliament to shelve it. The subject was of paramount importance to the well-being and, indeed, to the continued existence of the nation. A country whose leaders were continually urging the necessity of food production and which permitted agricultural land, even of small extent, t o be inundated was surely insane, and it had rightly been said that " those whom the gods wish to destroy they first make mad." He had seen many acres of agricultural -land given up to the sea which could have been saved by the expenditure of a few thousand pounds. Surely it was but fair and equitable for the State to appropriate, under the guise of nationalization, the liabilities of the individual as well as his assets.Mr. M. A. Henry observed that the South Wales main line formed a very important link with the West. Originally it had terminated a t Neyland, but when the Pishguard harbour extension was opened in 1909, the Neyland branch had become of secondary importance.A co,mparison of the coast defences of North and South Wales showed that the latter were of much smaller magnitude than the former. The Bristol Channel had a great range of tide, varying from about 45 feet a t Chepstow to about 28 feet a t Swansea.Apart from the natural protection afforded to the South Wales main line by sand dunes and intervening ground, the principal artificial defences were situated west of Llanelly, on the Burry estuary. From Llanelly to Burry Port a sea wall extended for about 2 miles. When the railway had originally been laid the sea was far removed from the line, with saltings between it and the sea. The construction of a river training wall in the Burry estuary had had the effect of eroding the whole of the saltings right up to the railway. The sea wall was a very simple structure, because it had not been expected that it would be subjected to the action of the sea. It was a curved wall, only about 18 inches t,hick, and it supported the line a t a level of about 10 feet above the original salt marsh. It was now exposed to the full effects of the sea and had been protected by the usual stone tipping.In addition, artificial beaching had been put down in the form of slag, and the beaching had to be made good from time to time ; otherwise there would be a risk of voids amongst the 2-ton blocks that protected the wall and failure might occur. There had been one or...

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