Introduction 

The CCHE1D modeling system was designed to simulate steady and unsteady flows and sedimentation processes in dendritic channel networks. The model simulates fractional sediment transport, bed aggradation and degradation, bed material composition (hydraulic sorting and armoring), bank erosion, and the resulting channel morphologic changes under unsteady flow conditions. 

CCHE1D's software design uses a watershed-based approach that provides straightforward integration with existing watershed processes (rainfall-runoff and field erosion) models to produce more accurate and reliable estimations of sediment loads and morphological changes in channel networks. 

CCHE1D has a GIS-based graphical interface that provides support for automated spatial analysis, channel network digitizing, digital mapping, and visualization of modeling results. 

CCHE1D is a general one-dimensional model, which is particularly effective in the estimation of long-term sediment loads and morphologic changes in channel networks, evaluation of the effects of erosion control and channel remediation measures on sediment yield, and analysis of the influence of land use changes and agricultural management practices on sedimentation.

Main Features of CCHE1D

The CCHE1D software includes features such as:

• Unsteady, one-dimensional channel network flow simulation, including in-stream hydraulic structures;

• Non-equilibrium, non-uniform sediment transport and channel morphology modeling, including bank stability analysis;

• ArcView-based graphical interface and control module;

• Extraction of the channel network and corresponding subwatersheds from ground elevation data;

• On-screen digitizing of channel networks based on aerial photographs, scanned imagery, etc.;

• Generation of the computational mesh for the channel flow and sediment transport computations;

• Data management system for automatic transfer of data among modeling components;

• Data interface to watershed modeling programs.
 

Main Capabilities and Applications

CCHE1D 3.0 can be applied to a variety of flow and sedimentation problems in natural channel networks. The model has been validated against a number of laboratory tests, as well as applied to several real-life applications. 

The Report CCHE1D - Model Capabilities and Applications exemplifies the types of flow and sediment transport problems that can be analyzed with CCHE1D.

Model Limitations

The most important limitations of the current version of CCHE1D 3.0 are:

• The CCHE1D model must be applied to dendritic channel networks with a single outlet only.

• Flow must be primarily subcritical in all reaches of the channel network. However, it can handle local supercritical and transcritical flows without hydraulic jumps in isolated cross sections through the hybrid dynamic/diffusive wave model.

• The model has not been tested for tidal flow conditions.

• The model cannot be applied to dam-break type of flows.

New Developments for CCHE1D Model

A new pollutant transport and water quality module has been developed, and will be made available for public testing in 2005. The new module will include modeling of transport and fate of general pollutants, nutrient dynamics (Nitrogen, Phosphorus, and Carbon Cycles), and water temperature, all under unsteady flow conditions, and with facilities for integration with upland pollutant loading models.

A new flow model for channel networks is also under development, and it should be applicable to rapidly varying flow conditions over initially dry beds, allowing CCHE1D to be applied to dam-break situations.