Presented By: RAJAT DEO SNEH SPARSH SWAPNIL SINGH 1.Geological works by river 2.Streams and its various types 3.Drainage system and various types of drainage patterns

A drainage system is the pattern formed by the streams, rivers, and lakes in a particular drainage basin. They are governed by the topography of the land whether a particular region is dominated by the hard or soft rocks, and the gradient of the land. A drainage basin is the topographic region from which a stream receives runoff, throughflow. Drainage basins are divided from each other by topographic barriers called a watershed.

Types of drainage patterns are: 1.Dendritic drainage patterns: Many contributing streams, joined together into the tributaries of the main river. 2.Superimposed drainage pattern: It is developed in geologically old and complex folded regions. It was initially developed in accordance with the geological formations at the top, which were subsequently removed due to the erosive work of these streams.

3. Trellis drainage pattern: When a consequent stream receives a number of subsequent stream from right and left at approximately right angles to its direction of flow, a trellis drainage system is said to develop. 4. Radial drainage pattern: In a radial drainage system, streams radiate outwards from a central high point. Volcanoes usually display excellent radial drainage. 5. Antecedent drainage: Those system of streams that existed prior to the uplift of the area to present status and that have succeeded in maintaining their courses through the uplift block form the antecedent drainage.

Rivers carry excess water from land to sea. In doing so they erode valleys and help in shaping the earth`s surface.They transport rock debris and dissolved materials and eventually they deposit most of their sediments in the oceans. River activity in combination with weathering and mass-wasting predominates by far over other types of erosion such as wind, ice or marine. The geological works of river is divided into three parts: 1.Erosion. 2.Transportation. 3.Deposition.

Breaking down of rocks by the dynamic action of any geomorphic agent like moving water, glaciers etc. The sum total of the process of wearing away of the rocks by the physical forces and chemical factors associated with the natural agencies. Rivers flowing over various rocks break them purely mechanically. The chemical action is minimal.

Every river receives enormous amount of material during its flow from head to mouth. This material includes the rock and soil particles that the river acquires by its own work of erosion along channel. The other part is the load eroded and contributed by its tributaries in the form of variously shaped particles, sediments and fragments.

The process of dropping down of load by river by any moving natural agent is technically called deposition. Types of deposition by river(fluvial deposit): 1. Alluvial fans and cones: Cone shaped accumulations of stream deposits that are commonly found at places where small intermittent streamlets coming down from hill slopes enter the low lands. 2.Flood plains: 3. Deltas: Alluvial deposits of roughly triangular shape that are deposited by major rivers at their mouths. 4. Channel deposit: When deposits is along the river- beds. Often, the materials so deposited take the shape of long narrow ridges called bars.

A stream is a body of water with a current, confined within a bed and stream banks. Depending on its location or certain characteristics, the stream may be referred to as branch, brook beck etc. Streams are important as conduits in the water cycle, instruments in ground water recharge and corridors for fish.

Consequent Streams : They invariably start flowing downslope and then gradually develop their channels essentially along the available slopes. Subsequent streams : These streams follow the routes carved out by themselves by selectively eroding the softer rocks making the topography.  Obsequent streams : These are tributaries to the subsequent streams. Prevailing relief is the controlling factor for determining the course of the obsequent streams.  Insequent stream : These are found to flow in channels that show no well defined relationship with either the slope of the area or the character of the rock.