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 tested: evaluation of roughness length z(o) and zero displacement z(d) from cadastral databases. Special attention needs to be given to the validation of the tool, and the roughness formulas therein. After a roughness 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 allows 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 roughness. (C) 1998 Elsevier Science Ltd. All rights reserved.