Introduction
The urbanization of a catchment is a drastic change in land use, and has major effects on the hydrological cycle during heavy rainfall events because of its impermeable surfaces (G. E. Hollis). By recording the discharge in a catchment the data can be used to create a hydrograph. It is often useful to analyse a hydrograph because it shows how quickly rainwater moves to the stream channel (Holden J. 2012.) The aim of this study is to compare an urban and rural catchment, and to find out why they are different. To achieve this a model was used to simulate both catchments, and an accurate hydrograph for those two scenarios was made. This hydrograph will be used to explain the differences in flow, and be compared to a real world example …show more content…
The foam represented the permeable soil in rural areas. Roles where determined in the group, with one timer, pourer and recorder. Exactly 1 litre of water was measured into a bucket with holes on the bottom that was supposed to simulate rainfall. A measuring cylinder was then placed beneath the catchment model’s outflow point so that the water poured from the bucket would be delivered into this. After 30 seconds the rain was poured over the entire foam surface to measure the rural environment and every 15 second the volume in the cylinder was recorded. The volume was recorded every 15 seconds during 5 minutes, and the data was filled in to a table. The same process was then repeated, only now a plastic sheet was put in top of the foam to simulate an urban …show more content…
It what hypothesized that urban catchment would have greater runoff and discharge and that it would arrive earlier than the rural catchment. An urban catchment will give a hydrograph with a high peak, short lag time with steep rising limb and receding limb. A rural catchment surface will give a hydrograph with lower peak, greater lag time and a longer receding limb. It all comes down to the permeability of the surface. A rainfall event in forested environment will cause the water to intercept the soil resulting in either water storage or baseflow. The baseflow gives the long and gentle receding limb, while the water coming from the canopies or overland flow gives a lag time and a low peak. The impermeable surfaces in an urban environment results in a quick flow, because of the low infiltration characteristics. As a result of this it is common that a urban hydrograph has a higher peak, with a steeper rising and receding limb, and the hypothesis is true. The data from Leith indicates that this is mostly a rural catchment as it matches the results from the rural simulation. This could work as a proof that the simulation model used in this study
The urbanization of a catchment is a drastic change in land use, and has major effects on the hydrological cycle during heavy rainfall events because of its impermeable surfaces (G. E. Hollis). By recording the discharge in a catchment the data can be used to create a hydrograph. It is often useful to analyse a hydrograph because it shows how quickly rainwater moves to the stream channel (Holden J. 2012.) The aim of this study is to compare an urban and rural catchment, and to find out why they are different. To achieve this a model was used to simulate both catchments, and an accurate hydrograph for those two scenarios was made. This hydrograph will be used to explain the differences in flow, and be compared to a real world example …show more content…
The foam represented the permeable soil in rural areas. Roles where determined in the group, with one timer, pourer and recorder. Exactly 1 litre of water was measured into a bucket with holes on the bottom that was supposed to simulate rainfall. A measuring cylinder was then placed beneath the catchment model’s outflow point so that the water poured from the bucket would be delivered into this. After 30 seconds the rain was poured over the entire foam surface to measure the rural environment and every 15 second the volume in the cylinder was recorded. The volume was recorded every 15 seconds during 5 minutes, and the data was filled in to a table. The same process was then repeated, only now a plastic sheet was put in top of the foam to simulate an urban …show more content…
It what hypothesized that urban catchment would have greater runoff and discharge and that it would arrive earlier than the rural catchment. An urban catchment will give a hydrograph with a high peak, short lag time with steep rising limb and receding limb. A rural catchment surface will give a hydrograph with lower peak, greater lag time and a longer receding limb. It all comes down to the permeability of the surface. A rainfall event in forested environment will cause the water to intercept the soil resulting in either water storage or baseflow. The baseflow gives the long and gentle receding limb, while the water coming from the canopies or overland flow gives a lag time and a low peak. The impermeable surfaces in an urban environment results in a quick flow, because of the low infiltration characteristics. As a result of this it is common that a urban hydrograph has a higher peak, with a steeper rising and receding limb, and the hypothesis is true. The data from Leith indicates that this is mostly a rural catchment as it matches the results from the rural simulation. This could work as a proof that the simulation model used in this study