Appropriate spatial scales to achieve model output uncertainty goals

Appropriate spatial scales of hydrological variables were determined using an existing methodology based on a balance in uncertainties from model inputs and parameters extended with a criterion based on a maximum model output uncertainty. The original methodology uses different relationships between scales and variable statistics. It is extended with two different uncertainty propagation methods, the mean-value first-order second-moment (MFOSM) method and Monte Carlo analysis, and backward uncertainty propagation to obtain appropriate scales based on two uncertainty criteria. The methodology is applied to three flood estimation methods. The application to the River Meuse basin in western Europe revealed that the methodology can be used for the considered flood estimation methods under similar climatological and geographical conditions. The results showed different relative input and parameter uncertainties for the different flood estimation methods (3–6%) for a specific maximum output uncertainty (25%) and different appropriate spatial scales for the dominant variables.