The Mulkear River rises in the Slievefelim and Silvermines mountains and flows through a picturesque landscape, before joining the Shannon near Annacotty, Co. Limerick. The main channel of the river is approximately 21.5 km long, and together with its tributaries, it drains a catchment area of approximately 650 km². This catchment area spans both Counties Limerick and Tipperary. The principal tributaries are the Dead River, the Bilboa River and the Newport River.
The catchment consists of upland and lowland areas, typical of many Irish river systems. The upland area is extensive and has numerous mountain peaks in excess of 400m. The lowland area is largely a flat river plain.
The catchment topography reflects the underlying solid geology. The upland channels rise and flow over a sequence of Old Red Sandstone and Avonian Shales, before descending to the lowland corridor underlain with Carboniferous Limestone. The village of PallasGrean if this lies at the eastern extremity of an area known as the east Limerick volcanics. This is a plateau of land, which stretches for approximately 8 km towards the Herbertstown and Hospital area. It is an area of former volcanic activity and the strata lie as a series of igneous rings surrounding an elevated limestone core. One low lying pair of rings underlies the area of confluence of the Dead River and the Mulkear River and is evident as a narrow gorge through which the Dead River flows immediately downstream of Old Bridge at Sunville.
The soil type on high ground consists mostly of peaty podzols (75%) and blanket peat. The most widespread soil in the remainder of the catchment is composed of gleys (75%) and peaty gleys (25%), which are of sandstone glacial till origin. This soil is typical of rolling lowland but reaches higher altitudes than normal in the Mulkear catchment. It is a poor draining soil and underlies most of the sub-catchments of the Newport River, Annagh River and Bilboa River, and is also prominent along the line formed by the main Mulkear River and Dead River channels. The other major soil types lying in the Mulkear/Dead lowland are podzolics and gley.
Finch and Ryan (1966) classified soils in the Mulkear region relative to drainage conditions. They indicate that the majority of soils in the Co. Limerick area of the Mulkear River catchment are poorly drained. Much of this area has soils of very low permeability and a deep water table. The area of well drained soils is found at the lower end of the catchment near Annacotty.
In 1993 Teagasc issued a comprehensive survey report, which concentrated on the lands in the flood plain of the Mulkear River. The report concludes that 81% of the soils in the flood plain are constituted of Varved silts and clays, 9% of cutover peatlands, 4% loams.
Rainfall in the Mulkear catchment varies from moderate to heavy by Irish standards. Heavier rainfall is encountered in higher ground as would be expected. This, together with nature of some of the upland areas, i.e., steep hillsides, means that many tributaries are subject to rapid runoff, which can result in flash flooding.
Rainfall statistics for stations in the Mulkear catchment (average 1961-1990, courtesy of the Irish Meteorological Service)