Some effects of discharge upon the transport of animals and peat in a north Pennine headstream

(1) The paper examines data on concentration (quantity per unit volume of water) and transport (quantity passing a point per unit time) of suspended peat and animal drift relative to discharge in a small north Pennine stream. (2) Within individual spates, suspended peat concentration and animal drift (in terms of numbers) peaked before the discharge but animal drift concentration (in terms of weight) remained high during the discharge peak, and mean weight per drift animal peaked at the same time as the discharge. The differences in time of peaking of animal drift, as between weight and numbers, reflect the fact that the concentration of most of the aquatic components of the drift was depressed during the spate peak but that the concentration of terrestrial material (of greater mean weight individual$^{-1}$) peaked with the discharge. (3) Data from 212 sampling units were used to examine the relationships between peat concentration/transport and stream discharge. The best fits were to power law relationships between concentration and discharge and transport and discharge. However, a logistic curve relating log$_{10}$ discharge and log$_{10}$ transport was also a good fit. (4) A similar analysis of the data for concentration/transport of animals in suspension showed significant positive correlations between concentration/transport in terms of animal numbers and discharge and suggests power law relationships. Animal concentration/transport, in terms of weights, were also positively correlated with discharge but the relationships were exponential. (5) The results show that at least 80% of the peat transported annually by the stream was carried by spates of over 5.6 times the annual mean discharge. These spates occupied less than 3% of the total time in the year, but accounted for 30% of the annual discharge.