Coulson will remain connected with the larger club supporting the Worthing Juniors and Raiders Academy Programme.
Rene Draude, Director of Rugby, said: "I would like to thank Ian, Jody, Ben, James for their massive contribution to the club over the last four years and more recently Jack. This is especially true in recent months working in these very uncertain Covid restricted times.
"In this period of time, reflecting where we are as a club and the recent announcement of no National League rugby this season has led us to a place where changes were required."
An announcement on the appointment of the new head coach is imminent as the club plan for the future.