MORPHOLOGIC AND HYDROLOGIC CHARACTERISTICS

The length of the river Tanaro as far as its confluence with the river Po is about 236 kilometres.
The stretch from the source to Fabbrica (46 km) shows a more marked slope than in the following ones; the stretch between Fabbrica and Lequio Tanaro (60 km) shows a lesser and lesser slope.
The rest of the watercourse runs from Barbaresco onward almost on the plain with the smallest slope of one degree.
So the first stretch flows in mountain territory, the second in the Piedmont one and at last the third stretch on the plain.
Also the planimetry shows clearly that from Niella onward the river starts to wind in broad meanders, the peculiar ones of the plain rivers, while upstream the course is definitely straighter, contained between high mountainous bastions.
The flow is typical of a river flowing in the foothills of the Alps, characterised by a maximum flow between spring and summer when the melting waters of the winter snows add to spring rains and a secondary maximum flow, due only to autumn rains, with moderate waters in the summer period. The catchment area is about 8,000 kilometres square.
The hydrographic system of the area was subject in the past, and still it is, to a gradual transformation  through opposite processes: erosion and sedimentation.
The former in fact causes the ditching of the river-beds and the latter causes their uplift, but together with these processes there are also lateral changes.
At present the subsidence of the river-beds (1m – 1.50m) is occuring; the process is due to the fact that a new erosive cycle has begun in consequence of the slow and progressive subsidence of the Po delta (everybody knows about the slow subsidence of Venice). The phenomenon of about 2-3 mm per year tends to rejuvenate all the streams flowing into the river Po with an erosive cycle from downstream to upstream.
The Tanaro, especially in the curved stretches, overflows easily and causes periodical floods in wide flat areas and deposits thin strata mainly of slimy sand and slime.

Map of the catchment area of the Tanaro

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