Origin and Evolution of Dry Valleys South of Ronkonkoma Moraine

• Main Authors: Soma Sen, Gilbert N. Hanson
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2007
• Subjects: Long Island; permafrost
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.558.7197; http://www.geo.sunysb.edu/lig/Conferences/abstracts07/abstracts/soma-sen-cmprsd-5.pdf

with few tributaries. The north-south valleys are clearly visible on a digital elevation model (DEM) of Long Island (Figure 1). These valleys are dry upstream. However further downstream water is present where the bottom of the valleys intersect the water table. We have named the Dry Valleys based on the ponds and lakes associated with the valleys. For example, Swan Dry Valley includes Swan Lake in Medford. According to Schmitthenner (1925-1926), small and shallow dry valleys are also known as ‘dells’. Katasonova (1963) refers to dry, straight and parallel valleys as ‘delly’. They both suggest that these are runoff valleys developed on a permafrost terrain. There are two kinds of Dry Valleys south of the Ronkonkoma Moraine. One has straight, parallel drainage networks with few tributary valleys, low sinuosity (less than 1.5), low slope of the main trunk channel (0.0016-0.004), rectangular watershed, and an angulated transverse profile, which is V-shaped with steep walls (Figure 2). Typical examples are the Canaan Dry Valley and the Swan Dry Valley. Further east is the other kind of Dry Valleys which have dendritic drainage patterns with both gentle and steep slopes such as the Setuck Dry Valley at East Moriches (Figure 3). An interesting feature occurs at the Scuttlehole Ponds which are immediately south of the interlobate zone of the Ronkonkoma Moraine (Figure 4). Here the tributaries of the Hayground Cove Dry Valley