Greater Des Moines design firm Confluence plans to open an office in Minneapolis by the end of the month, principal Brian Clark said. Confluence built its reputation in landscape architecture. However, it is broadening its range of services by launching a city and district planning division that will be headed by Christopher Shires, current development manager for the city of West Des Moines. The division will be based in Des Moines. Confluence also has offices in Kansas City, Mo., Sioux Falls, S.D., and Iowa City.