TERRESTRIAL LASER SCANNER BASED INSTREAM HABITAT QUANTIFICATION USING A RANDOM FIELD APPROACH Andy Large a , George Heritage b a School of Geography, Politics and Sociology, Newcastle University, Newcastle upon Tyne NE1 7RU – a.r.g.large@ncl.ac.uk b Built and Human Environment Research Institute, School of Environment and Life Sciences, Peel Building, University of Salford. Manchester M15 4WT – g.l.heritage@salford.ac.uk KEY WORDS: Terrestrial laser scanning, biotope, DEM, typology ABSTRACT Derivation of surface grain size is necessary for a variety of applications in river engineering, geomorphology and river ecology. Yet, characterisation of surface grain-size is notoriously problematic due to patchiness, incompatibility between sampling approaches and operational bias. To improve ecological status (viz. the EU Water Framework Directive) there is a need to advance the understanding of geomorphological, hydrological and ecological functional links. There is a need for adaptive tools, and a key question is whether hydromorphology can be characterised at a spatial scale that truly accounts for instream ecological dynamics. At the micro-habitat scale, water flow level in river channels is moderated by the interaction with the roughness of the surface over which it flows. This is vital for benthic community organisation. The interaction is highly complex and remains poorly understood despite its importance. Here, surface roughness has also been measured using a random field of spatial elevation data. The success of this approach has been tempered by the lack of high-resolution topographic data covering all roughness scales; improved data-point resolution is now achievable however, using terrestrial laser scanning technology. The aim here is to reliably quantify instream hydraulic habitat defined by water surface characteristics using random field terrestrial laser scanner x,y,z data. In addition, we look at the applicability of the technology to reach characterisation as this the working scale of policy drivers such as the EUWFD. Biotopes provide are applicable over a range of climate conditions, are hierarchical, provide a standard, descriptive assessment of instream physical structure based on consistent recognition of features over a range of spatial and temporal scales and, importantly, integrate ecology, geomorphology and hydrology. However, to become an alternative to hydraulic models, biotopes need a robust, empirical and practical channel typology/taxonomy to be developed to allow rapid characterisation of reaches. Introduction Recent research has demonstrated that the mosaic of hydraulic habitat types present in a reach are very important in determining biodiversity (e.g. Dodkins et al., 2005) A number of initiatives over the past decade have focused on characterisation of instream habitat using hydraulic variables as these are deemed central to the inhabiting biota. Biotopes provide a standard, descriptive assessment of instream physical structure based on consistent recognition of features (Padmore (1998). They have their basis in the development of typologies to underpin the ‘Habitat Quality Index’ developed as a framework for the protection of rivers (Raven et al. 1997), and provide a means of integrating ecological, geomorphological and water resource variables for management purposes. Essentially the biotope concept allows for a standard, descriptive assessment of instream physical structure based on consistent recognition of features over a range of