Drain office uses for LiDAR MACDC Summer Drain Conference August 17, 2016 Steve

INTRODUCTIONS Eric Deibel Eaton County Deputy Drain Commissioner Marya Colpaert, P.E., LEED AP Saginaw County Deputy Public Works Commissioner Steve Roznowski, P.E. Project Manager, Spicer Group, Inc. Steve

WHAT IS LiDAR? Light Detection and Ranging (LiDAR) Various types Aerial LiDAR - Collected by survey aircraft Used by the USGS Has replaced contour maps Mobile LiDAR – Collected by truck, boat, etc. Static LiDAR Steve

WHAT IS LiDAR? LiDAR USGS Quadrangle Steve – discuss contours vs. LiDAR (same data) LiDAR USGS Quadrangle

WHAT IS LiDAR? Marya Describe map – Colors – (highest to lowest) = white, brown, red, yellow, green cream, light blue/aqua (lowest); parcel lines, district splitting parcels based on high points, other drainage flow paths

USES OF LiDAR Day of Review of Drainage District Boundaries Watershed delineation Culvert Sizing Concept Design Plan Reviews Resolving Landowner Disputes Hydraulic modeling Flood mapping Marya

DAY OF REVIEW Drainage district boundaries Partial acreage Flow paths Meeting with landowners Marya Landowners now expect higher accuracy If flooding not related to drain, helps identify problem areas Picture showing high points and parcels split by district line

DAY OF REVIEW Marya Large 60-inch screen in front of the office to use when talking with landowners. We zoom right in on their property. If they question the district line on their property, we turn on LiDAR layer and are able to show them the contours. Usually when we start asking about hills/high points on their property matching up with the district line, they agree with us. Plus – generally everyone is amazed with the program and love seeing the aerial and contours on their property. They think it’s pretty cool! Dazzle them with technology.

WATERSHED DELINEATION Marya - Updating old/outdated district boundaries. Blue = Old, White = New – based much on LiDAR. Fixing districts so we don’t have gaps and overlaps - for more proper assessing. Want to make sure we are properly assessing people to the best of our ability. If they are not in district, we do not want to charge them. Conversely, if they are in the district, they should help pay for the work on the drain. Also, we don’t want to charge a landowner for multiple drains on one piece of property when it’s obvious the property all flows to one drain. LiDAR allows us to quickly see if the old district map is incorrect, and to draft a revised district, for checking in the future.

CULVERT SIZING Determine culvert size for installation or replacement Calculate upstream area Estimate cover over crossing Marya – Use LiDAR to create subdistricts - estimate upstream area to size culverts. Point out the ridges, other drains, and Hemlock Road as high point.

PLAN REVIEWS Verify elevations Review offsite drainage Reduce future problems Minimize disputes with neighbors Compare to other GIS information Drains, roads, parcels, etc. Phased development Eric - Site developed highlighted in blue. Flow arrows shown to add clarity.

CONCEPT DESIGN Supplement survey information Identify feasible alternatives Do I have enough grade? Existing overland flow patterns Estimate earthwork quantities Eric – General project planning

LANDOWNER DISPUTES Earth change causes flooding Review drainage patterns Identify historical conditions LiDAR Aerial photography Compare to current conditions Eric - Earth changes Historical drainage patterns – coupled with site review

HYDRAULIC MODELING Supplement survey data Estimate extent of flooding Allows for detailed flood mapping Calculate/verify upstream drainage area Steve – HEC-RAS or Geo-RAS. Highlight low-flow surveyed cross section (still needed). Very dense points in overbank. Cuts down on survey cost.

FLOOD MAPPING Great tool for public presentations Can also get depth information Depths approximate Only as good as the model Anecdotal information helpful Steve - Public presentations. Show limits of flooding. Depths are approximate. Calibration helpful.

LIMITATIONS OF LiDAR Aerial LiDAR is a valuable tool Understanding limitations is necessary Limited accuracy in some instances: Under water Abrupt changes in grade and steep slopes Very detailed or subtle changes in grade Snapshot in time Steve

RECAP Aerial LiDAR has many uses Saves money Asset available at your finger tips Great for understanding drainage Supplement to survey work Important to understand limitations Steve

DISCUSSION AND QUESTIONS Does your office use LiDAR? What do you use it for? Do you have suggestions? What has been your experience? What use do you find most beneficial?