κατ' ἐνιαυτόν, τῆς ἑορτῆς ἐν τῇ κόμῃ γιγνομένης, οἱ κωμῆται τὸν τοῦ χρίστου σταυρὸν ἔφερον πομπεύοντες, τῆς δὲ πομπῆς πρὸς τὸ φράγμα ἀφικομένης ὁ ἱερεὺς τῷ ποταμῷ καθιέρωσιν ἐνετίθει ἵνα ὁ ποταμὸς μὴ μανικῶς ἔχοι καὶ τῇ κώμῃ ποσφέροιτο.
I am fairly sure that I understand what Coderch has written (see below). What I can't understand is why there is no full stop after πομπεύοντες. Either I don't understand Ancient Greek punctuation or my translation is off.
Every year, the festival in the village happening, the villagers would carry the cross of Christ (while) parading,
the procession up to the fence having arrived, the priest a dedication would place-in the river so-that the river should not be crazy and should behave in ordered way towards the village.