Complex sentence: First attempt to control the river, proposed in 1775 by Matvey Kazakov, materialized in 1792 Neglinnaya Canal, running parallel to the river; once the canal was running, old river bed was filled with earth.
Split into simpler sentences: First attempt to control the river, proposed in 1775 by Matvey Kazakov, materialized in 1792 Neglinnaya Canal, which was running parallel to the river. Once the canal was completed, the old river bed was filled with earth.