John Allen, age 9, of North St. Paul, Minn., for his question:

HOW DO THEY PREDICT FLOODS?

A river causes a flood when it slops over its banks. A cloudburst may dump down a deluge of rainwater. A wild hurricane storm may wash a flood of sea water over the land. Not all floods are alike, and some are easier to predict than others. As a rule, river floods are the easiest to predict. Hurricane floods give a little warning, but a cloudburst flood gives hardly any warning at all. Rivers tend to flood over their banks in the spring, when melting snows run down the slopes and fill them to overflowing.

 So experts measure the winter snowfall far and wide. They also keep daily measurements of the spring rainfall. This helps them to figure out when the rivers will fill up and flood over. Weathermen watch the path of a hurricane to figure when it may flood over the shores. They also watch deluging showers in the hills to figure out when cloudbursts are likely to come flooding down the slopes.