# Two-dimensional physically based finite element runoff model for small agricultural watersheds I Model development

##### Anil Bhardwaj; M.P.K.ushal

#### Hydrological Processes 23(3): 397-407

#### 2009

**ISSN/ISBN: 0885-6087**

DOI: 10.1002/hyp.7150

Accession: 026028108

Soil erosion by water is the root cause of ecological degradation in the Shiwalik foothills of Northern India. Simulation of runoff and its component processes is a pre-requisite to develop the management strategies to tackle the problem, successfully. A two-dimensional physically based distributed numerical model, ROMO2D has been developed to simulate runoff from small agricultural watersheds on an event basis. The model employs the 2-D Richards equation with sink term to simulate infiltration and soil moisture dynamics in the vadoze zone under variable rainfall conditions, and 2-D Saint-Venant equations under the kinematic wave approximation along with Manning's equation as the stage-discharge equation for runoff routing. The various flow-governing equations have been solved numerically by employing a Galerkin finite element method for spatial discretization using quadrilateral elements and finite difference techniques for temporal solutions. The ROMO2D computer program has been developed as a class-based program, coded in C + + in such a way that with minor modifications, the model can be used to simulate runoff on a continuous basis. The model writes output for a runoff hydrograph of each storm. Model development is described in this paper and the results of model testing and field application are to be presented in a subsequent paper. Copyright