1. Hydrology and fluvial geomorphology

1.1 The drainage basin system

• Outputs: evaporation, evapotranspiration and river discharge.

• Stores: interception, soil water, surface water, ground water, and channel storage.

• Flows: above ground – throughfall, stemflow, overland flow, and channel flow.

below ground – infiltration, percolation, throughflow, groundwater, and baseflow.

• Underground water: water tables, ground water, recharge, and springs

1.2 Discharge relationships within drainage basins

• Components of hydrographs (storm and annual).

• Influences on hydrographs.

• Climate: precipitation type and intensity, temperature, evaporation, transpiration, evapotranspiration, and antecedent moisture.

• Drainage basin characteristics: size and shape, drainage density, porosity and permeability of soils, rock type, slopes, vegetation type, and land use.

1.3 River channel processes and landforms

• Channel processes

• Erosion: abrasion/corrasion, solution, cavitation, and hydraulic action.

• Load transport: traction, saltation, suspension, and solution.

• Deposition and sedimentation: the Hjülstrom curve.

• River flow: velocity and discharge, patterns of flow (laminar, turbulent and helicoidal), and thalweg.

• Channel types: straight, braided, and meandering.

• Landforms: meander (river cliffs, point bars, oxbow lakes), riffle and pool sequences, waterfalls, gorges, bluffs, floodplains, levées, and deltas.

1.4 The human impact

• Modifications to catchment flows and stores and to channel flows by land-use changes (deforestation, afforestation, urbanisation), abstraction and water storage.

• The causes and impacts of river floods; prediction of flood risk and recurrence intervals.

• The prevention and amelioration of river floods to include:

  • forecasts and warnings

  • hard engineering – dams, straightening, levées and diversion spillways

  • soft engineering – floodplain and drainage basin management, wetland and river bank conservation and river restoration.

Case study: candidates must study a recent river flood event showing the causes of the flood, impacts on both people and the environment, and evaluate attempts to reduce the impact of the flood.