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

2. 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

3. 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

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

5. 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

6. 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

7. 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

8. 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.

9. 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Marya - Updating old/outdated district boundaries.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.

10. 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.

11. 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.

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

13. 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

14. 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.

15. 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.

16. 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

17. 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

18. 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?