The map shows the concentration (annual load) of suspended sediments into rivers (in milligrams per litre). The load of sediment is lower in the Canadian Shield area and on the Arctic Islands. The greatest loads appear in the Prairie Provinces and in the Cordillera. The map also shows histograms of the mean monthly suspended sediment load in metric tons per day per square kilometre times 10-3 for ten rivers across Canada. Data are compiled from 1961 to 1970. Every year, about 300 million metric tons of sediment is carried by Canadian rivers to the oceans or across national boundaries. To appreciate the volumes involved consider that if the suspended sediment reaching the mouth of the Fraser River over a period of 1 year could be massed in a conical pile with 45-degree slopes, it would reach a height equivalent to a 100-story building (almost 300 metres). Transportation of soil particles from the land surface begins with the action of precipitation. The precipitation dislodges soil particles; the d