DEVELOPMENT EFFECT ON FLOODING:

A doctoral student says his study of two small streams in eastern Pennsylvania appears to back up what inundated residents have long suspected: flooding along small creeks and streams is worsened when land is paved over. Joshua Galster watched the Little Lehigh and Sacony creeks for months, taking rainfall measurements at certain points along each one. The streams are similar in almost every respect, but there is a lot more development along the Little Lehigh, than along the Sacony. Galster found that discharge increased at a much greater rate as he moved downstream along the Little Lehigh than along the Sacony. Precipitation, climate and geology can all play a role in discharge, but Galster, a doctoral candidate in environmental sciences at Lehigh University, said his research has largely accounted for those factors — leaving development as a likely explanation for all that water.

Lehigh professor Bruce Hargreaves, one of Galster’s advisers, said paved, or impervious, surfaces cause more runoff, which in turn contributes to stream discharge.

Bill Muehler, who works in the planning division of the Army Corps of Engineers, said that when at least 10 percent of a given land mass is developed, runoff into nearby streams is increased significantly.

Many waterlogged residents along the Delaware River blame their flooding problems on development. But researchers say the latest round of flooding — which forced thousands to evacuate in New Jersey, New York and Pennsylvania and caused millions in property damage — was more likely caused by other factors, including back-to-back soaking rainstorms, melting snow and oversaturated ground.

Development may have a greater effect on smaller streams and creeks such as the Little Lehigh, which flooded in September in the wake of Hurricane Ivan, Muehler said.