Question re: Chalk Stream story

Hi Terry, (or anyone else who knows)


Here is your Question of the Day from a Kansas fly angler who is ignorant (but curious) about Great Britian fishing:

When you refer to a waterway as being a "chalk stream" does that mean the stream actually runs for some or all of its length across ancient chalk formations laid down as ocean sediment aeons ago?

Here in the U.S. we have lots of limestone streams. Some can be found in Kansas, even (although most of my state's limestone formations on rivers are confined to the area immediately before, within and immediately below riffles -- the rest of the river section having a sediment bottom).

In Kansas we have many chalk formations, but ours are buried beneath many feet of soil overburden. No chalk streams in Kansas. At least none that I know of.

Very pretty streams, in your story photos. Nice work by the company that did this restoration. They'll all go to Heaven when they die, for doing something this cool for trout.


Joe
"Better small than not at all."

Joe:

http://en.wikipedia.org/wiki/Chalk_stream

They are similar to limestone spring creeks like Letort Spring Run here in Pennsylvania but I BELIEVE the type of limestone found in here in PA is of a different type and not true chalk.

They do look exactly the same same as our PA variety though, with an abundance of weeds and watercress being one similarity.

One of my life long dreams has always been to fish the Test or Itchen.

Some day I hope!

:D

Maybe there's not that much difference -- not that big a leap geologically speaking -- between chalk and limestone streams.

Maybe there's no difference at all -- the terminology being simply a matter of national nomenclature.

It's just that when I think of a "chalk stream" I can't picture its natural morphology in my mind as easily as I can the morphology of a "limestone stream", like we have in parts of Kansas.

Does a "chalk stream" (in its natural state) have features like riffles and rapids, as limestone streams all do? Are chalk streams characterized by a pool/drop repetition, as limestone streams are?

On their curves and bends, do chalk streams have deep holes that years of erosion force have cut into the underlying chalk bed?

Sorry for all the questions, but the term "chalk" combined with that good story's photos made me curious.

As far as I can tell chalk streams and limestone streams are pretty much the same. The main feature of the chalk stream is that they are fed from the chalk aquifers so the water level and temperature stays pretty constant. They flow through low lying, flat country and many of the Hampshire streams are in fact man-made - by the Romans I am told - to drain the land which would otherwise be wetlands. Because of this, whilst there are some sections more pool-like or riffly they are pretty consistent along their full length.

Thank you, DragginFly. What you say here is interesting to the max -- that centuries ago the Romans may have been the ones who built some of the streams in Great Britian that people have been fly rodding for the past 100+years.

That certainly is possible. From everything I've read and seen of their technological capabilities the Romans had the engineering skills, plus at that time they'd long been among the world's foremost builders of water management projects.

While it's understandable from a manpower and project cost point of view, it's too bad that human-made waterways such as these chalk streams and also irrigation canals and such usually follow a straight-line course. Never designed in such a way as to mimic nature's lazy, random serpentines and structural interruptions.

I'm just glad that sport fish live in those chalk streams. That is very cool! My hat's off to the personnel who are rehabilitating those stream sections.


Joe
"Better small than not at all."

I can add a little. There is something called the Exe-Tees line that runs from north-east England - the river Tees - to south-west England - the river Exe. To the east of the line and running roughly parallel to it are Limestone formations and to their east there are chalk formations. I come from the county of Lincolnshire and we have limestone rivers in the west of the county and then in the east are chalk streams. There are limestone streams and chalkstreams all of the way between this imaginary line and the North Sea from SW to NE England. Some have trout, some don't.
In my experience, the streams run clear the majority of the time because they are mostly spring fed and the water is very filtered because the ground is very porous and the rain soaks in quickly. The dissolved minerals present in the water, probably helped by agricultural fertilizers, produce thick and lush weed growth. There are very few natural ponds and lakes as a result of the porous rock. Of course, when it rains heavily, there is some direct runoff that carries soil and mud into the streams and I believe that this varies by location - some of these chalk and limestone streams often run coloured, some rarely do.
As to what the topology of the streambed is like, the streams and rivers that I am familiar with are of a constant steady gradient with no rocks, no rapids, and are of a fairly constant depth. Because of hundreds of years of farming, many rivers and streams have been straightened but old maps will show the original meandering courses. In the southern part of the country where the classic chalk streams like the Test and Itchen are, I understand that many of the chalk streams there are really irrigation canals but I'll bet that many are straightened versions of the original streams and rivers and I would not be surprised if there is some Roman engineering in there.
In my home town of Lincoln, the River Witham, a limestone fed river, flows through a 2 mile gap in a north-south ridge of limestone hills. The land in the "gap" was a big swamp prone to flooding when the Romans arrived 2000 years ago. They built a "drain" that taps part of the river water upstream of the city to flow on a different route to rejoin the main river after the city some 15 miles downstream. When the river rises, more water flows over the upstream weir feeding the drain and it protects the city from flooding. It's still working as it did 2000 years ago.
Sorry to ramble on but since I now live in the US, it's interesting for me to compare the rivers that I fish here - mostly freestone with little plant growth, with the ones that I knew in England. I am often amazed, when I look into a US east coast river from a bridge, how often the rivers look fishless compared with the rivers I knew as a boy. Looking down from a bridge I could usually see dozens of fish holding in the current sipping flies as they floated by - trout if they were present but also chub, dace, roach, and rudd.

Wow! What a great addition. Thanks so much. 8)