Briefly describe four possible impacts of the flood on different types of traffic movement in the area shown on the satellite image.

Explain two ways in which agriculture and/or irrigation on flood plains can affect water quality.

Examine the factors that affect the response of a stream hydrograph to a rainfall event.

Award [1 mark] for each of four statements clearly relating to the photo, such as:

• airport under water (air traffic)
• Bruce Highway flooded (road vehicles)
• river transport disrupted (river traffic)
• isolation of Rockhampton from places to the west
• possible closure of bridges
• difficulty in crossing the flood plain (by any means of transport)
• some city streets likely to be impassable
• credit other valid suggestions eg “car parks flooded”.

Responses must make some reference to two types of traffic (road, air) for maximum [4 marks] but do not expect every point to be explicitly linked to a particular type of transport.

Explanations are likely to refer to two of the following – salinization, eutrophication, the impacts of agro-chemicals, effluent run-off. In each case, award [1 mark] for the identification and up to [2 marks] for the explanation/developed exemplification.

The most likely focus for candidates will be:

Eutrophication [1 mark] occurs when fertilizers/nitrates are washed into a lake/river [1 mark]. Algae grow, and then die, leading to oxygen depletion [1 mark].

Response of hydrograph should be addressed in terms of lag time, peak discharge, rising and recessional limb, overland flow/throughflow contributions, etc. Likely factors will include: basin shape, antecedent rainfall, rainfall intensity and duration, seasonality of rainfall, basin land use, type of farming soil and rock type, affecting porosity and permeability, basin relief, degree of urbanization, forest cover and seasonal changes.

Possible responses include “flashy” response hydrographs (short time lag and very high peak flows), or a response that does not differ markedly from baseflow under some conditions (chalk lithology).

At band D at least two factors should be described and linked to a valid response/change that may be observed in stream hydrographs.

At band E, either a range of factors should be explained and linked with hydrograph features, or there is an examination of how certain factors interrelate eg, human/physical combination leads to very flashy response.

At band F, expect both.

Marks should be allocated according to the markbands.

There were few problems in the interpretation of the satellite image. Some candidates did not keep to the question, and described impacts of flooding that were not related to traffic movement.

This was either done very well, identifying eutrophication and salinization as the main impacts of agriculture and/or irrigation, or missed the point all together.

There were some very good answers, showing clear understanding of the hydrograph and associated responses. Good knowledge was shown of factors affecting the stream hydrograph. The best responses included an annotated diagram of a stream hydrograph. However, many candidates either wrote about a flood event or tried to discuss the hydrological cycle, demonstrating a lack of understanding of the term “stream hydrograph”.