| name the two types of hydrographs | flashy and subdued |
| state the differences in terms of lag time | subdued has a longer lag time
flashy has a short lag time |
| state the physical factors that would impact the shape of the hydrograph | drainage basin shape
slope angles
drainage density
antecedent (Prior) rainfall
ROCK TYPE
vegetation cover
amount and intensity of precipitation
drainage basin size |
| describe the impact on the hydrograph drainage basin shape has | drainage basins that are more circular in shape lead to more flashy hydrographs than those that are long and thin. this is because each point in the drainage basin is roughly equidistant from the measuring point on a river. |
| describe the impact on the hydrograph slope angles has | steeper sides tend to have flashier hydrographs than gentle slopes. this is because water flows quicker in any flow so gets to river faster. |
| describe the impact on the hydrograph drainage basin density has | the higher the density have flashier hydrographs ( drainage density is how many tributaries it has) |
| describe the impact upon the shape of the hydrograph antecedent rainfall has | soil already saturated therefore overland flow is increased and in turn the speed the water travels to the river. this means the hydrograph tends to be more flashy. |
| describe the impact that rock type has on the hydrograph | impermeable rock and soil types means that water can not be absorbed therefore overland flow increases, speed of water increases leading to a more flashy hydrograph (clay, shale rocks) |
| describe the impact that vegetation cover has on the shape of the hydrograph | thick vegetation cover means more will be intercepted and increased ETP rates, slowing the movement of water leading to a more subdued shape. it also reduces the peak discharge as less water will make it to the river as some is lost via ETP |
| describe the impact that amount and intensity of precipitation has the shape of the hydrograph | increasing the amount of water entering the drainage basin will increase the peak discharge and the intensity of the precipitation will determine the lag time, the greater the intensity the flashier the hydrograph |
| describe the impact upon the hydrograph the size of the drainage basin will have | the larger the drainage basin the greater the amount of precipitation will have a greater peak discharge. the smaller drainage basin will tend to have a shorter lag time as water has less distance to cover. |
| state the human factors that would impact the shape of the drainage basin | deforestation/afforestation
agriculture
growth of urban areas
soft engineering and flood management
water abstraction |
| describe the impact upon the shape of the hydrograph that deforestation and afforestation will have | deforestation is the removal of trees therefore reducing vegetation cover, the hydrograph will be more flashy. afforestation is the opposite, it is the planting of trees and therefore increasing vegetation cover meaning the hydrograph will be more subdued. |
| describe the impact upon the hydrograph agriculture will have | variety of effects:
ploughing fields breaks up top soil allowing greater infiltration and subduing the graph.
although this could be alternative that channels have been created and water may flow through these creating a more flashy hydrograph. also large number of animals on small areas can impact the soil leading to more overland flow, flashier hydrograph. |
| describe the impacts that growth of urban areas can have on the shape of the hydrograph | large impermeable surfaces created, greater overland flow more flashy hydrograph. |
| describe the impacts that flood management and soft engineering has upon the shape of the hydrograph | management schemes are designed to slow the lag time and reduce the peak discharge |
| describe the impact that water abstraction has upon the shape of a hydrograph | water abstraction is using up underwater stores of water. this reduces base flow and so more water must reach the channel flow the channel before it reaches bankfull capacity |
