"Nature's Plan For Parkways – Recreational Lands" was published in 1932 and proposed a regional plan that would place Darby and Cobbs Creeks in an interior network of parks. These streams were chosen due to the fact that the flowed through some of the most densely populated areas in Southeastern Pennsylvania and it could serve as buffers through urban areas. During the 1930s there were a number of projects undertaken on Darby Creek by the Army Corps of Engineers. The dikes along the southern end of the creek were repaired by a joint force of the Works Progress Administration, the Pennsylvania legislature, and Delaware County. A series of ditches in the Tinicum marshland were constructed by the Corps in 1935 as a means of mosquito control. The dredged material was deposited throughout the marsh over the next few years.