HOST Classification

Hydrologists are often required to predict river flows, for example, when designing flood protection or river management schemes. Where historical records exist, flow indices can be calculated statistically but where there are none, or few records, other methods need to be used. The HOST classification makes use of the fact that the physical properties of soils have a major influence on catchment hydrology.

While it is recognised that the soil hydraulic conductivity, soil water storage capacity and the pathways of water movement through the soil are the most important, these attributes are spatially and temporally variable making them costly and time consuming to measure. As a consequence, they are only available for a limited number of British soils. However, Systematic soil surveys within the UK have resulted in complete map coverage and extensive databases in excess of 24 000 soil profiles of other observed and measured soil properties which were used to derive new attributes. These attributes were determined by means of pedotransfer and expert knowledge and used in the development of HOST.

The HOST classification is capable of predicting river flow levels of ungauged catchments (r² =0.79, s.e.e =0.089 in the case of Base Flow Index) and can be used in predictions of water quality, land suitability and environmental assessments.

HOST was a collaborative venture between MLURI, SSLRC and IH (now CEH).