Interestingly, certain floods to which Washington is susceptible can be partially guarded against only by such approaches as the ones mentioned above, and not at all by upstream dams. One of them occurred in August of 1933, when a hurricane pushed the water in the estuary upstream and raised it to flood stage at the capital.
III. THE CLEANSING OF THE WATERS
Streams have always had to carry and digest wastes that enter them through drainage from the land. It is one of their functions in the scheme of things, and so well have they performed it through the millennia that human beings have been able to take it for granted. Within limits that might be considered normal, the ability of running water to handle loads of waste is phenomenal, and in earlier times those normal limits were seldom exceeded, for even in populated areas the general lack of sanitary sewer systems kept the loads from being concentrated.
In civilized parts of the modern world, however, there are now so many people generating so many wastes of one kind and another, which often enter the streams at concentrated points, that the streams can no longer digest them without help. Too often, in the face of uncontrolled human increase and expansion, that help has either been denied them or has been weak and perfunctory. The result is plain enough now in the sorry mess of sick or dead or dying waters that we Americans have on our hands, the heritage of having kept on taking them for granted long after we had bred ourselves out of the right to do so.
As civilized rivers go, the Potomac is rather lucky. It is polluted, but many parts of it are not nearly as dirty as people are sometimes led into believing by a look at the summertime estuary at Washington. The fabled and scenic German Rhine, for instance, is much more degraded in its main flowing reaches than is the Potomac, and so are a majority of the other rivers in the northeastern United States and many elsewhere in the country. Industrialization on the Potomac and its tributaries has been spotty so far, and there are no really big clusters of population in the upper parts of the Basin. Furthermore, pollution here has already been given quite a lot of dedicated and expert attention and some rectification. Thus anyone who travels up and down the river and its tributaries finds many miles of pleasant flowing streams capable of sustaining fish and the other things that are supposed to live in and around water, and fit to soothe frayed nerves.