The Time Rivers of Goro Adachi

Goro Adachi on http://www.goroadachi.com/timerivers/
creates an interesting theory on Topographic Imprints on a large scale, stating that the river Nile and others, such as the Tigris-Euphrates pf Messopotamia, are actually huge monuments left to us by a much higher intelligence countless aeons ago. He goes further by stating that the rivers are a blueprint of human history, not being clear however if they foretold history or where somehow related to historical events.
Admittedly his approach is somewhat suspect. It is the usual suspect to be blunt: Numerology and stellar connections. Having seen all kinds of theories "proven" by sketchy correlations between alignment, dimensions of monuments and trigonometrical data for every conceivable attribute of any given star and constellation, it looks more of the same old "I can prove that the Eiffel Tower was built by Aliens" stuff.
But although his proof is shaky at best, his theory makes an interesting point: Researchers have excluded Earth-scale monument research from their repertoire.. The reason can be easily traced back to the ridicule factor: Ridicule follows anyone arguing the Ancient Autronaut-God theory. If you add Terran-scale monuments to the description, even hardcore fanatics will probably think you are stretching things too far.. That is why all theorists try to back up their proposal using the only available tool: Mathematical relations.
I think this is the wrong way. Not only does it prove nothing, but also creates a sense of fringe to "normal people". There is a lot of research to be done, but not on a map using a ruler.. If these kinds of monuments exist, they are probably more than charts.
Why does everyone seem to forget the inherent usefulness rule? Let's assume the Nile is artificial..
Why would someone build a 6700 kilometer river simply for leaving an obscure and questionnable cryptic message countless centuries later?
Does it not make more sense that such an undertaking would have a very specific purpose?
Will return to the subject soon..