Ithilien is dominated by overlapping and coalescing alluvial fans made of material derived from the Mountains of Shadow. The MofS seem to be extrusive igneous rock, weathering to angular fragments, locally clayey and silty.  The alluvial fans are somewhat eroded, and thus there are bridges over watercourses at regular intervals.  Total depth of the alluvial deposits vary, but generally range from about 500 feet near the mountains to about 200 near the Anduin.  The soils are very fertile, because of the igneous source rock that provides lots of trace minerals and breaks down into clays and silts that retain water through the summer.  Nearer the Anduin, the westward-trending fan materials meet the southward-trending fluvial deposits of the Anduin(consisting of a 500-to1000-foot sequence of layered  channel sands and overbank silts), which are coarser, more permeable, and more extensive.
  Soil development in Ithilien is extensive, with agricultural types resembling Tujunga Stony Loam near the bedrock outcrops, with well-drained Yolo loam in the midfan segments.  Near the river, some soils are waterlogged and resemble adobe clays.  Depth to groundwater is about 60 feet near the head of the fan, decreasing to about 10 feet near the river.
Wather quality is hard, with calcium and magnesium the dominant cations, and concentrations ranging from 25 to 75 mg/L, and concentrations of the domainant anion, bicarbonate, ranging from 125 to as much as 200 mg/L.  Locally, iron and manganese staining is a problem, and in some areas, excessive fluoride is present from erosion of hydrothermal deposits.  Local groundwater quality can be poor where associated with industrial activity, as in the well-known area near Minis Ithil.   There, metals mining and smelting, and disposal of garbage into the mine pits, have caused acid-mine drainage problems.  This is manifested a both low pH, in places as low as 1.8-2.3 pH units, and high metals concentrations.  In many places, the streams are devoid of fish and riparian vegetation, and the water and rocks are stained red, green, orange, and black.  Because of the lack of diversion of surface runoff from both mine workings and tailings, these severe water quality problems will be quite persistent, and no current plans for remediation have been presented to the lead environmental agencies.

Some who wander are lost.