Keywords: 
• distributary channel /
• drainage system /
• fractal geometry

Abstract: Based on genesis, distributary channel systems (DCS) are subdivided into river and tide-dominated DCS. Taking into consideration the internal sedimentary architecture of channel fill and sand distribution patterns or geometric structure of drainage systems, the former is further divided into sinuous, branched and anastomostic systems, and the latter into tide-branched and tide-anastomostic DCS. Controlled by physical factors of environment, DCS reveal a certain characteristics of geometric structure and fractal geometry. Fractal dimensions of five types of DCS are calculated by means of fractal geometry. Results show that there is self-similarity in a distributary channel system, and fractal dimensions calculated vary from 1.046 to 1.763. In general the sinuous has simple geometric structure and low fractal dimension that is below 1.30; the anastomostic, the branched and the tide-anastomostic have complex geometric structures and high fractal dimensions that are above 1.40. Fractal dimension of the tide-branched is between above tow groups. In low delta plain, fractal dimensions of DCS are closely related to physical parameters of environment, especially to the gradient of offshore and average power of wave. Low fractal dimension corresponds to the great gradient of offshore and high average power of wave. Since characteristics of DCS reflect environmental parameter, types of deltaplains can be defined by types of DCS. The paper has defined five types of delta plains, including delta plains with sinuous, anastomostic, branched, tide-branched and tide-anastomostic distributaries. Delta plains of Rhone, Zhujiang and Mekong belong respectively to delta plain with sinuous, anastomostic and tide-branched distributaries. At least five types of combination modes of delta plains are found: type ¹ delta plains with sinuous → anastomostic → branched distributaries; type ² delta plains with sinuous → branched distributraries; type ³ delta plains with sinuous → tide-anastomostic distributaries; type⁴ delta plains with sinuous → tide-branched distributaries; type⁵ delta plains with single sinuous distributaries. Type¹ is found in Permian Coal Measures of North Anhui. Mississippi delta plain is a typical example of type ².