Red River Gradient Boundary Survey Act This bill directs the Bureau of Land Management (BLM) to commission a survey to identify the South Bank boundary line with respect to land along a specified 116-mile stretch of the Red River in Oklahoma and Texas (the affected area). The survey shall adhere to the gradient boundary survey method; span the length of the affected area; be conducted by one or more independent third-party surveyors who are licensed and qualified to conduct official gradient boundary surveys, and selected by the Texas General Land Office and the Oklahoma Commissioners of the Land Office (the offices), and each affected federally recognized Indian tribe; and be completed within two years of enactment of this bill. The BLM shall only approve the survey, or a portion of it, that has the written approval of the offices and each affected tribe. Surveys of individual parcels in the affected area shall be conducted according to the requirements for the survey of the South Bank boundary line. After a survey for an individual parcel has been approved, the offices shall publish a notice of the approval of such survey, and furnish to any landowner a copy of such survey and any field notes related to the parcel of that landowner.