Geology & Hydrology

Today is another day of mild temperatures and heavy rain :-(. Tomorrow it is due to rain again, which allows a timely investigation of the geology and hydrology of the area, for it has quite a bearing on the natural history of the town.

Geology

Paddock Wood lies on a flat area of county, just 17 metres above sea level, which is part of ‘The Weald of Kent’. 

 

The town sits on a bedrock of Wealden Clay, topped off with a deposit of river silts and gravels, from the nearby River Medway. The Wealden Clay bedrock was deposited approximately 120 – 135 MYA, when the area was a small, shallow, tropical sea.

The name ‘Weald’ gives a clue to its historical use and natural vegetation cover. ‘The area was known to the Britons as Coed-Andred, Coed being the British word for wood. The Romans called it Silva-Anderida (Silva being latin for wood or forest). The word ‘weald’ also signifies in Saxon language a woody country or forest. The Saxons thus called it ‘Andredsweald’, for it retained the name of Andred for centuries after the Romans abandoned Britain’ (Archaeologia Cantiana Vol. 14 -1882  pages 38).

The small pockets of woodland dotted around the town are the remnants of this great ‘Andredsweald’ which for millennium covered a large area of the counties of Kent & Sussex and also parts of Hampshire. In Saxon times much of the extensive woodland around Paddock Wood was used extensively as 'pannage' -  autumn foraging for the local swine herds.

Whilst the weald clay soils around Paddock Wood provide poor drainage and are noticeably slow to warm up in the spring,  these conditions are excellent for the native English Oak trees (Quercus robur), which formed much of the Andredsweald of old and continue to form the basis of the small pockets of woodland found in the countryside surrounding the town.

Hydrology

The land occupied by Paddock Wood is flat and in the winter wet, flooding fairly easily; indeed many of the fields had surface water showing on them today, after just a few days of rain. 

As the following map shows there are parts of the town designated by the Environment Agency as either flood zone 2 - a 1 in 200 year river flood event (light blue), or flood zone 3 – a 1 in 100 year river flood event (darker blue). With climate change expected to pay a greater influence upon our weather patterns, as this century progresses, these flood zone designations may have to be amended, to include designations for more frequent flood events.

Fluvial flood map of Paddock Wood

In addition, the town's current drainage infrastructure is inadequate and causes urban runoff flooding in parts of the town. The following map shows the main surface water drainage system (blue & red), but also the natural drainage ditches and streams (purple & green) for area of this blog . As can be seen the main drainage streams (purple) are (west - east) : Tudeley Brook / Gravelley Way /  the West & East Rhoden Streams.

Surface drainage map of  Paddock Wood

Flooding remains a great source of debate among local residents, particularly regarding the wisdom of allowing further development in an area known to be prone to flooding. Of interest to the future changes in the natural history of the area is the planned extensive use of drainage ponds, which are currently proposed within the three main large housing developments planned over the next 10 years.

As I will report in future posts, because of its natural & man made drainage structures Paddock Wood is an already an attractive habitat for amphibian populations (frogs, toads, newts) in the area. Should there be a considerable increase in the number (& area) of drainage ponds then I would expect a further increase in the amphibian population living within the town & surrounding countryside.

So there you have it, a brief summary of the geology and hydrology of the area, with clues to how this affects the natural history of the area, as we may discover as the year progresses.