URBAN ROUGHNESS MAPPING VALIDATION TECHNIQUES AND SOME FIRST RESULTS

Because of measuring problems related to evaluation of urban roughness parameters, a new approach using a roughness mapping tool has been te sted: evaluation of roughness length z(o) and zero displacement z(d) f rom cadastral databases. Special attention needs to be given to the va lidation of the tool, and the roughness formulas therein. After a roug hness formula validation using laboratory data, three other validation tests have been applied sucessfully, using roughness classifications, comparison with an established roughness model, and spatial averaging consistency tests. The latter is an interesting, new approach which a llows to rank the performance of the otherwise largely similar models. Further results of interest are the sensitivity of the Raupach model to some of its parameters, and the need to include the drag of forest, town and obstacle group edges in an effective, spatially averaged rou ghness. (C) 1998 Elsevier Science Ltd. All rights reserved.