Question A4 i Explain how climate change may lead to an incr

Question A4

(i) Explain how climate change may lead to an increase in river flooding? (1 mark)

(ii) Explain methods of estimating design flood for catchments with and without streamflow measurements? (Describe at least one method for each catchment type). (2 marks)

(iii) In establishing flood series for flood frequency analysis, what do we mean by independent floods? Explain the implications of using dependent floods for design flood estimation? (2 marks)

(iv) Suppose a spillway of a certain reservoir is designed to withstand a 1 in 100 year flood. What is the probability that you will encounter a 1 in 100 year flood in a 100 year life span of the reservoir? (4 marks)

(v) What design ARI would you use to ensure that the chance of flooding in a 50 year life of a project is no more than 5%? (4 marks)

(vi) How would you test the stationarity of a given time series? (1 mark)

(vii) What are the key differences between ARR 1987 and 2016? (2 mark)

(viii) What is probability neutrality? (1 mark)

(ix) What are the effects of urbanisation on the flow/hydrograph (2 mark)

(x) What are the effects of catchment storage on the outflow hydrograph? (1 mark)

Solution

Answer question i-

As warmer atmosphere can hold more water hence it can be said that with increasing temperature of the atmosphere with each passing day the events of strong rainfall will increase causing more flooding. But it cannot be said for each location, It will vary primarily with location to location and other factors too.

According to IPCC report the atmosphere is about 0.75 degrees warmer as compared to the temperature it had at the start of the century. and it will hold 5-6 percent more water in it. It doesn\'t guarantee the strong rainfall as the weather pattern will govern the rainfall amount, timing and distribution. But it definately means more water in the atmosphere.

If I explain weather pattern in more detail, you can say weather pattern change over time in every region and bring different weather with them with each change. Excess rainfall occur when it is stuck at one particular weather pattern for a long time at specific location causing flooding.

Also flooding will depend also on human activities such as more paving area and less green area hence, less penetration of water into the ground and more surface runoff. Also, condition of local sea also effect the flooding condition. Storm condition in sea will also lead to the flooding of river.

Hence, for conclusion you can say that climatic conditions effect the flooding but this is not the only causing factor.