Presentation on theme: "Rivers – Fluvial Environments. The River Ouse- York The River Ouse is the drainage basin in Yorkshire. The river itself is formed by the River Ouse."— Presentation transcript:
Rivers – Fluvial Environments
The River Ouse- York The River Ouse is the drainage basin in Yorkshire. The river itself is formed by the River Ouse Gill Beck and the River Ure. It flows southwards and is joined by the River Nidd north of York. Eventually it meets the Humber Estuary. Physical influences on the Ouse Relief- Some of tributaries flow west wards from the North York Moors. The river travels through hills which gradually descend in height through to the vale of York. The relief affects the flow of the river, higher velocities are found at the upper and middle stages while they are slower through York. Geology- High up land there is limestone. The rocks become younger downstream. The rocks are permeable and precipitation infiltrates in summer affecting the discharge of the upper sections of many tributaries. Vegetation- The upland parts are moor land with heathers, grasses and trees. Interception is therefore lower. Middle and lower stages are farmland. The landscape is open and interception is lower. Soils- Peat soils absorb great deal of precipitation which affects discharge. Downstream there are brown soils suitable for farming. Climate- The topography of the Ouse basin is almost flat. The annual precipitation rates are between mm. High rainfalls over the tributaries makes the river prone to flooding. Human influences on the Ouse Farming- Most of the area is used for farming both pastoral and arable. ‘Gripping’ (drains) was carried out on the Ouse in the 1970’s to lower the water table. This leads to larger peak flows downstream and reduction in lag times. Dry weather base flows are higher because water reaches the channels more quickly. Management of soils in the lower parts of the basin increase infiltration. Forestry- Afforestation varies along the river. They increase interception and reduce discharges. Urban developments- New housing areas, out of town shopping areas have been built in the area. These create impermeable surfaces in the basin. This increases run off rates because infiltration is increased. Drains also carry this water to local streams and rivers which increases the frequency of flooding. Key Words Run off rates Drainage basin River Discharge Flooding Interception Infiltration precipitation
↑ Photos of York during the 2000 floods ↑ Flood control schemes Clifton Ings – this is a flood washlands scheme. Here, embankments surround the land, which is allowed to flood, preventing the city of York from flooding (it can hold 2.3m cubic meters of water) Leeman road – the embankments that have been built here are made of residue from the sugar beet factory. The channel’s capacity is increased by their distance from the rivers edge. Almery terrace – the houses here are protected by concrete floodwalls with rubber sealed gates - the walls are situated directly in front of the housing, offering a small amount of protection. General Accident offices – this building’s bottom floor is a car park, meaning that in the event of a flood nothing too valuable is damaged or lost (it is a planning measure to limit flood damage). Foss Barrier – this prevents the River Ouse water backing up the river Foss (a tributary), as this would cause damage to some of York’s most historical buildings - water from the Foss is pumped into the river Ouse. York is surrounded by rivers, several of which are tributaries to the River Ouse
Hot spots. Map of Hawaii. The Hawaiian Hot spot. The volcanic islands of Hawaii in the pacific ocean are acceptations to the general rule. They are not located at a plate margin. The Hawaiian islands have formed over a source of magma called a Hot Spot. Hot Spots are irregularly distributed around the world and they are though to result from rising plumes of hot mantle material originating far below the lithosphere. Over geological time, Hot Spots are thought to remain more or less stationary. So as the pacific plate has steadily moved over it, a while series of islands have been formed. The volcanoes themselves are very similar to those formed at constructive plate margins. They tend to be shield volcanoes and are formed by non-violent eruptions.
Conservative Plate Margins – San Andreas, California Conservative plates move sideways past each other and no land is subducted. The Pacific plate is moving faster than the N.American plate The slippage of these plates causes earthquakes. E.g., San Francisco, 1906, 700 people died
What is a lava plateau?? A lava plateau is an extensive, upland, extrusive igneous land form that is generally level and is made up of successive layers of lava and ash. How are they formed? These result from numerous eruptions of large volumes of extremely fluid, basaltic lavas. They gather as sheet-like flows covering large areas of land. Most plateau-type eruptions are fissure eruptions, often associated with volcanic centers. These eruptions tend to be long and narrow and are fed from dykes. Large plateaus do not necessarily have extraordinary rates of magma supply. For example, the Columbia River basalts accumulated over km3 of basaltic lavas over 10 million years at an average rate of accumulation of 2 km3 per century. :FACTS: The Siberian basalt region is probably the most important and is believed to have helped in the extinction of up to 95% of all life on Earth 225 million years ago. Life? Lava plateaus are hard, rocky, exposed areas and are therefore pretty inhabitable. Good case study site!
Ingleborough (Yorkshire dales national park) Limestone pavement Limestone areas frequently exhibit a bare surface (limestone pavement), criss – crossed enlarged joints (grykes), separating blocks of limestone, clints in between blocks. Surface depression pavement Surface drainage Swallow hole Sink holes also occur Caverns with stalactites & stalagmites Permeable limestone Thin soils Valley or gorge Spring at cave mouth Exposures of bare rock
4- Spurn Point The spit at Spurn Point forms a sweeping curve which continues the line of the coast. The sand forming the spit has been transported along the Holderness Coast by longshore drift. The energy in the waves transports the sediment in a southerly direction to where the North Sea meets the Humber Estuary. This process is known as deposition, and forms a spit 1- Flamborough Head Flamborough Head is at the most Northern part of the Holderness Coast. The chalk cliffs here were formed from the remains of tiny sea creatures millions of years ago. Above the chalk at the top of the cliffs is a layer of till (glacial deposits) left behind by glaciers during the last Ice Age. As the cliffs below are worn away by the action of the waves, the clay soil often falls into the sea making the coastline retreat. 2- Hornsea There has been coastal management put in place at Hornsea to stop the coast from eroding further. Defences in the form of a concrete seawall and timber groynes afford protection and an on going refurbishment programme ensure this has continued. Also, a stone gabion has been erected to the south of Hornsea. The Beach material is being transported south along the Holderness Coast by longshore drift. In Hornsea sand has accumulated where the groynes are. 3- Mappleton Management which has been developed at Mappleton includes two rock groynes and a rock revetment. Sediment has accumulated between the groynes halting erosion. However, further south the rate of erosion has increased significantly. This is because material which is being carried south is not being replaced (it is trapped within the groynes). Therefore there is no beach to protect the cliffs. Coastal Features found at the Holderness Coast: Wave Cut Platform Stack Wave Cut Notch Bay Headland Arch Cliff Spit Coastal Erosion Processes At the Holderness Coast: Corrosion Attrition Hydraullic Action Abrasion
The Dorset Coastline Along the Dorset Coastline there are many Geographical Landforms. One in Particular is the sequence of Caves, Arches, Stacks and Stumps. One well known example of this is Old Harry Rocks. This landform originally would have been the Coastline of Dorset, which due to erosion became a Cave, which lead to the formation of an Arch and eventually a Stack and Stump. This is caused by the erosion of the limestone cliffs by marine and sub – aerial processes. These include Hydraulic action and Abrasion. Sub – aerial processes are Oxidation and Carbonation. Fig 1. Key words: Old Harry Rocks, Marine erosion, Limestone and sub – aerial processes. Lulworth Cove was created approximately 10’000 years ago by erosion processes and has formed a horse shoe shape. Fig 2. Also, along the coast the is a Stack present at Flamborough Head. It has been left detached from the Dorset Coastline except for a joint which runs from it’s base. Fig 3. Fig 1. Fig 2.Fig 3. Old Harry, detached from the Dorset Coastline. Old Harry Rocks.