West River is a part of the Western Highland. The surficial geology of the area expresses principally the effects of glaciation. Features made by glacial erosion include striations and grooves, streamline hills, crag and-tail features. Till covers a great deal of the area, although over many ridges and hills it is thin or absent.
During dissection of the glacial drift, streams deposited alluvium, some of which caps low stream terraces. Swamp and marsh deposits, mostly thin show evidence of past plant population (glacial record) in the form of fossil pollen. Most of the marshes along the shore are tidal marshes, a product of the most recent part of the past-glacial rise of sea level against the land. The soils of the area include ( ground water) sand and gravel, humus, and clay.
Triassic rocks underlie the land around West River. The Arkose consists of pinkish, gray, brown and reddish arkosic sandstone and conglomerate, with interbedded layers of reddish siltstone. These rocks are variably and irregularly stratified.
The identities and outcrop pattern of various types of bedrock are important in the study of the surficial geology of New Haven and Woodmont area. The presence in the glacial drift of rock fragments with identifiable area of origin makes possible the determination of the direction of movement of the former glacier ice.
1
The depth of bedrock around West River from Derby Avenue to Whalley and Blake in Westville ranges from about 200 to 250 feet and greater above sea level (about 61 to about 76 metres). The most conspicuous feature of the bedrock surface is the scarp, as much as 200 feet high, which rises from the valley of West River. Most of the topographic features of the area tend to be elongate, reflecting general South to Southwest trends in the structures of both the Triassic and the metamorphic rocks.
2
The land elevation of West River at Derby Avenue and the Boulevard is 30 feet above sea level and at Blake and Whalley over by the Mite Corporation it is about 50 feet above sea level.
The very irregular shoreline and the abundant islands suggest that part of the Connecticut Coast has been submerged beneath the sea since the valleys and ridges were developed by erosion. There is a rather small depth of glacial erosion in the New Haven-Woodmont area. At no place is glacial diversion of drainage, a not uncommon feature of glaciated regions, clearly evident. Regardless, glaciation has influenced some stream valleys. The West River is now flowing in places at least, on thick deposits of glacial drift, and hence may now be at positions different from those occupied before glaciation. In a few places, also, there are ponds, some of them occupying shallow basins created by the irregular deposition of glacial drift. These basins are still present because of the recent glaciation. Time has been too short to permit the re-establishment of uninterrupted stream flow.
3
The drainage pattern of West River is closely related to composition and structure of the bedrock. West River does not occupy a wholly natural basin. The natural sweep and curve of West River has been altered by fill. The original fill has sunk so that the fresh water marsh and the filled area co-exist somewhat uneasily. Along the River near Derby and the Boulevard is some marsh land. Thousands of yards of costly fill covered the marshland; a lake was dredged in the west bay of the marsh to provide some of the fill.
There has been little or no rechanneling done to West River near Derby Avenue and the Boulevard. Very little consideration has been given to the upkeep of West River.