This paper presents a simultaneous solution algorithm for one-dimensional unsteady flow routing through channel networks. This direct solution algorithm is based on the double-sweep method and utilizes separate recursion equations for continuity, momentum and energy equations for each of the individual components of channel networks. Through separate recursion equations for each of the components, the new algorithm converts the channel network problem into a single-channel problem. The new algorithm is utilized in conjunction with a linearized unsteady flow model using full dynamic flow equations. The required computer storage for the coefficient matrix of the whole system is reduced significantly from the 2N¿2N matrix to a 2N¿4 matrix, where N is the number of cross sections used in the computation of flow variables in the channel network. The algorithm presented in this paper provides an efficient and accurate modeling of unsteady flow events through channel networks. ¿ American Geophysical Union 1993