Final answer:
The discharge rate for a 10-year flood event cannot be determined without specific data or a flood frequency graph. However, yes, it is possible for a flood with a similar discharge to the 9/23/2009 event to happen again in the next 20 years.
Step-by-step explanation:
The student is asking about the discharge rate associated with a 10-year flood event for a particular river. This kind of question is typically related to hydrology, which is a branch of Geography or Environmental Science. To determine the discharge associated with a 10-year flood event, we usually refer to empirical data or a flood frequency curve that has been established for that specific river. Without the exact data or curve provided in the question, it's not possible to give a correct answer to which option (a. 1,200 b. 2,000 c. 400 d. 275 e. 600) corresponds to the 10-year flood event discharge.
Regarding the possibility of a flood similar to the event on 9/23/2009 happening again, the nature of probability and statistics tells us that yes, it is possible for a similar event to occur within any given time frame, including the next 20 years. The fact that a flood occurred in the past does not change the probability of it happening again in the future. Each year has an independent chance of experiencing such a flood, according to its recurrence interval.