Riga is an assault river crossing by the Swedes and so they have minimal cavalry support at first. The Saxons and Russians are spread out along the river line and so only some will be available. In the real battle the Swedes arrived in a series of 'waves'. The first 'wave' brushed aside the small Saxon force near the landing point and then the Saxons/Russians mounted a series of assaults to dilodge them. With extra forces arriving on both sides as time went on. The Swedes were covering a ponton bridge that was being set up by them for the rest of the army to use. The Saxon/Russians didn't manage to defeat the covering force and once the bridge had been built they withdrew in the face of the Swdish cavalry. This scenario covers the battle after the bridge has been completed.

Von Liewen (+1)
Reserve Rhenskold (+3)
4 x Swedish Horse 8 SP
Fire Support