Flood Management Techniques (Evaluate)
FLOODS
A river flood is a flow in excess of the channel capacity to accommodate the peak discharge, and occurs when the amount of water arriving on land exceeds the capacity of the land to discharge that water by infiltration, surface flow or drainage pipes. Flooding of river valleys and coastal areas is the most frequent of natural hazards and is one of the most significant in terms of death, injuries and long-term social and economic impacts. Flooding regularly claims over 20,000 lives a year and affects 75million people globally. Thus, strategies are put in place to minimize the impacts of these hazards. The 3 broad groups are prediction, mitigation and response. However, the effectiveness of these strategies vary depending on the level of development of the country, the level of cooperation between the authorities, population and private organizations and the severity of the hazard. It is also important to note that effective hazard management cannot rely on just a single strategy and generally, a multi-pronged approach, which is a combination of strategies, is necessary to minimize the severe impacts of the hazard.
Prediction
1. Prediction through the calculation of flood recurrence interval a. North Dakota – Accuracy and reliability of data b. Flood recurrence interval is defined as the probability that a flood of particular magnitude will occur once or more in any given year. It can be used to examine the flood frequency (how often an area will experience flood) and flood magnitude (the size of a flood event). The records of a river’s discharge over the longest time available are ranked according to the discharge volume. The formula (n+1)/R is used to calculate the recurrence interval, where n is the number of discharge levels in the record and R as the rank of discharge. The recurrence intervals then can be plotted against discharge to determine the statistical probability of flood events. c. Using the flood recurrence intervals,
A river flood is a flow in excess of the channel capacity to accommodate the peak discharge, and occurs when the amount of water arriving on land exceeds the capacity of the land to discharge that water by infiltration, surface flow or drainage pipes. Flooding of river valleys and coastal areas is the most frequent of natural hazards and is one of the most significant in terms of death, injuries and long-term social and economic impacts. Flooding regularly claims over 20,000 lives a year and affects 75million people globally. Thus, strategies are put in place to minimize the impacts of these hazards. The 3 broad groups are prediction, mitigation and response. However, the effectiveness of these strategies vary depending on the level of development of the country, the level of cooperation between the authorities, population and private organizations and the severity of the hazard. It is also important to note that effective hazard management cannot rely on just a single strategy and generally, a multi-pronged approach, which is a combination of strategies, is necessary to minimize the severe impacts of the hazard.
Prediction
1. Prediction through the calculation of flood recurrence interval a. North Dakota – Accuracy and reliability of data b. Flood recurrence interval is defined as the probability that a flood of particular magnitude will occur once or more in any given year. It can be used to examine the flood frequency (how often an area will experience flood) and flood magnitude (the size of a flood event). The records of a river’s discharge over the longest time available are ranked according to the discharge volume. The formula (n+1)/R is used to calculate the recurrence interval, where n is the number of discharge levels in the record and R as the rank of discharge. The recurrence intervals then can be plotted against discharge to determine the statistical probability of flood events. c. Using the flood recurrence intervals,