Erosion Management: Urban Case Study Exercise
Accompanying Exercise: (For students to print off, complete, and turn in for a grade)
Case Study: Managing Urban Construction Erosion- Exercise (pdf)
CASE STUDY
Managing Urban Construction Erosion
In the earlier lesson case study of Holmes Lake (view Holmes Lake case study), we discussed that the majority of sediment that entered the lake was due to urbanization. Construction of residential and commercial buildings, roadways, and utilities disturb soil and increase erosion.
Phase I Mass grading and land preparation of large subdivision. In large (> 1 acre) land grading, some erosion control measures are stipulated by state federal agencies to obtain permit.
Clearing the land. Image by M. Mamo
Land grading. Image by M. Mamo
The following case study shows a medium size (1/4 acre) residential home construction site in T9N R7E Section 14 Sixth Principal Meridian, Lancaster County, NE. The first step in construction is grading and preparing the foundation. The soil that is dug out is stockpiled during this process. As you can see, the soil is bare and thus susceptible to erosion.
Phase II Individual home or business development (less than 1 acre, currently not well regulated for erosion control measures).
Grading to prepare for construction. Image by M. Mamo
Laying the foundation. Image by M. Mamo
An early June rainstorm. Image by M. Mamo
A mid-June rainstorm. (Note the presence of vehicles on the lot) Image by M. Mamo
A mid-June rainstorm. (Note the closure of the structure) Image by M. Mamo
Step 1) Describe the causes of erosion for this lot.
Step 2) Evaluate the type of erosion occurring on this lot.
Step 3) How does the presence of the housing structure affect the type and amount of erosion?
Step 4) Recommend management practices that could be implemented during the grading and construction phases to minimize erosion.