Simulating realistic sedimentary bodies while conditioning all the available data is a major topic of research. We present a new method to simulate the channel morphologies resulting from the deposition processes. It relies on a formal grammar system, the Lindenmayer system, or L-system. The L-system puts together channel segments based on user-defined rules and parameters. The succession of segments is then interpreted to generate non-rational uniform B-splines representing straight to meandering channels. Constraints attract or repulse the channel from the data during the channel development. They enable to condition various data types, from well data to probability cubes or a confinement. The application to a synthetic case highlights the method's ability to manage various data while preserving at best the channel morphology.