Runoff Pond Design,Lutsen, MN

By Mark Greve

Problem

Poplar River increases in sediment load near Lutsen ski hills

Structure needed to slow flow and settle sediment out

Find a location for structure that does not interfere with ski runs

Computer Modeling

Used LIDAR data in ArcGIS to determine watersheds, slopes, lengths, etc.

Also mapped roads, culverts and other points of interest

Flow paths, culverts and watershed boundaries field-validated

Computer Modeling (cont.)Water Erosion Prediction Project (WEPP)

model used to create slope model

Inputs: climate data (10 yr), slope, land cover and soil types

Outputs: total runoff,sediment load by particle size and areas of erosion

Computer Modeling (cont.)WEPP outputs transferred to Excel

Hydrograph created from flow-routing table

Pond Design

Two-pond system connected by ditch

Trapezoidal cross-sections, 2:1 ratio on sides

Riser pipe in centeras outlet

Emergency spillwayincluded

More Computer ModelingUsed flow equations for both pipe flow

and flow over a weir to determine daily discharge

Determined dimensions of pipe and ponds

Calculated sediment reduction

Questions?