ABSTRACT
Combined micromorphological and soil-physical studies of water movement in saturated riverine and marine heavy clay soils in the Netherlands have demonstrated the occurrence of biporous flow: relatively rapid movement of water along soil cracks and slow movement through the fine-porous natural aggregates (‘peds’). These flow processes present measurement problems for Ksat and water table levels. Use of the column, cube and drain-cube method for measuring Ksat will be discussed.
Results obtained with the crust test for measuring Kunsat near saturation will be shown to demonstrate the sharp drop of Kunsat upon desaturation of the soil. This, in turn, results in very low drainage rates.
Tile drainage of both types of heavy clay soils resulted in a significant increase of Ksat. The increase in the young riverine soil was due to increased cracking, while formation of vertical worm channels caused a very high increase of Ksat in the older marine soil.
