Nays1D+ is a one-dimensional (1D) solver for river flows and bed level deformations in the iRIC platform.
For simulating rivers, we shold choose an adequate simulation engines from various models with different spatial dimensions. In iRIC, 1D, 2D (two-dimension) and 3D (three-dimensionL) models are available. 1D means a “line” like space (see figure 1). Usually, the spatial scale in the streamwise direction in rivers is mach larger than the lateral and the vertical scales. Due to this feature, many phenomena can be reproduced well by applying one-dimensional quations. Figure I.2 shows the basic concept of a 1D model for rivers. The most important advantage of 1D models is computational efficiency. A 1D models require much less CPU time and computational memory. It means that 1D models are capable of simulating long term and large scale phenomena in rivers with reasonable computational infrastructures.

Nays1D+ can simulate not only steady/unsteady flows bat also bed level change considering bedload transport. Therefore, the field of application for Nays1D+ is considerably wide. For instance, this model can be applied to the following phenomena.
– Temporal water level change during flood
– Assesment of effects of river training works, such as river width extension, cut-off works, constructing flood plain, etc.
– Predictions of long term morphological changes after constructing dams, weirs, bridges or other river structures.