REGULARIZATION. 53 



impossible to exceed a certain degree of improvement, usually very limited. It must 

 be remembered, where the regularization has in view the discharge of flood waters, 

 that the reduction of level depends on the amount of fall, and if the latter is consider- 

 able, the reduction of level and the effect on the discharge of floods will also be consider- 

 able ; but quite different is the aim of regularization when it is a question of improving 

 the conditions of navigation. We have then to obtain a sufficient channel depth 

 in times of low water, and so called regularization works are in themselves usually 

 powerless to give a suitable depth unless the water-level is raised by means of dams 

 or other similar constructions." 



Notwithstanding these opinions there are numerous examples of fairly successful 

 improvements of this character on the Garonne, the Rhone, the Rhine, the Volga, the 

 Elbe, and other streams, and it is fair to conclude that when the river-bed is of a stable 

 nature and the discharge considerable, regulating works will be successful if the 

 plans are made with a view to the general rather than the local effect, and are designed 

 on correct principles and without a too great regard for economy. 



The greater number of regularization works in rivers rest on a purely theoretical 

 conception, the end to be attained being to realize in a natural stream with a bed 

 more or less movable a uniformity of slope and regularity of section. Had these streams 

 been cut through material capable of wholly resisting the action of the current the 

 conditions existing on artificial canals would have been found, and success would have 

 followed intelligent application. With the permeable material through which nearly 

 all rivers flow, the object attempted has rarely been realized. 



Some of the works of contraction, however, have been founded on observations 

 of natural phenomena over a long period of time, supplemented by patient and 

 intelligent experimental researches, and these have had a fair measure of success, 

 although not always meeting the full requirements of navigation. 



It will be interesting to summarize the results in a case of this kind. The example 

 is that of the Garonne and the notes are made from a paper by Inspector-General 

 Fargue,* under whose direction the works were executed. The general regime of the 

 flow, following the laws which govern all rivers, was as follows: 



The center line or channel followed the concave bank. 

 ' The bars were deposited along the convex bank. 



The channel was the deeper and the bar the more projecting as the concave or 

 convex curve was the more accentuated. 



The maximum or minimum of curvature corresponded respectively to the maxi- 

 mum and minimum of depth. This correspondence did not occur in the same trans- 

 verse profile, the deep place being below the concave summit, and the greatest pro- 

 jection of the bar below the convex summit. 



The least depth was below the points where the concavity was changed to 

 convexity. The channel presented regularity in its longitudinal profile when the 



* " Rational Direction of Artificial Banks," etc. 



