Application of Hydrology Enhanced Flow Direction Grids Within Arc Hydro Frank Kenny and Bryce Matthews Ontario Ministry of Natural Resources Peterborough, Ontario, CANADA Frank.kenny@mnr.gov.on.ca and Bryce.Matthews@mnr.gov.on.ca - We are told we can not have a LOGO - so this here is our “Visual Identity” - for those of you unfamiliar, with us, we a project with the Ontario government. We are a “cluster piece” expected to work across the MOE, MNR, OMAF and MNDM. - we are not a program - and our sunset us this changes is just over a year from now. Remote Sensing Across the Great Lakes: Observations, Monitoring and Action April 4-6th, 2006

ONTARIO, CANADA Peterborough

Presentation Overview Provincial Watershed Project – where we are in Ontario/where we are going Commonly encountered problems in raster hydrology Strategies for optimizing the Raster environment for hydrology Developing “Enhanced” flow direction grids Application Example – Accommodating Tile Drain fields with “Enhanced” flow direction grids.

Where we are in Ontario Seamless Covers Hydrology Network - The Arc Hydro “Backbone” Provincial Digital Elevation Model Over 10,000, 1:10/20 K scale Photogrammetrically derived topographic maps have been seamlessly merged. Network Geometry has been developed for the province (to approx.. 52 deg) Every Ontario stream QA/QC by local Conservation Authorities and MNR district. Version I completed (2000) – Utilizing ANUDEM Version II just completed (2006) – Includes the integration of lake elevation and DTM data.

Removing Systematic Artefacts from the Digital Elevation Model OBM with Stripe Artefact DTM Filtering

Where we are at (part II) Arc Hydro Provincial Flow Direction Grid 3 major rounds of Training Completed – Dr. Dean Djokic Implementation in seven major northern Ontario Watersheds. Being adopted across 30 southern Ontario Watershed Based Conservation Authorities Methodology refined and finished Developed and loaded into the Land Information Ontario Warehouse

Commonly Encountered Problems in Raster Hydrology Application of a uniform “cutoff” value to accurately reflect known hydrology. Limitations of the DEM source data to accurately depict hydrology patterns.

100 Pixel Flow Accumulation Overlain the 1:50K Hydrology Notice alignment is generally good - although one major watershed error is evident (denoted )

STREAMLINE FUNCTION AT VARIOUS FLOW ACCUMULATION CUT-OFFS 1:50K NTS HYDROLOGY 200 PIXEL DRAINAGE 100 PIXEL DRAINAGE 50 PIXEL DRAINAGE

Strategies for Optimizing the Raster Environment for Hydrology Inclusion of a flow directed hydrology network as a boundary condition during DEM interpolation. To encode known flow directions in decreasing elevations. (e.g. ANUDEM, TOPOGRID). DEM modifications, post creation using a drainage network to ensure focused flow along and down known water courses. (eg. Stream Burning, AGREE) 3. Redeveloping the Flow Direction Grid to include the Topological information Content of the hydrology network and water bodies. (The proposed method – this Presentation)

Steps to Developing an “Enhanced” Flow Direction Grid Three Primary Inputs 1. Standard Approach to deriving flow directions (eg. FLOWDIRECTION) A hybridized raster/vector topological analysis to assigning D8 flow directions to cells that intersect the network. An iterative raster single cell dilation and D8 assignment from within water bodies to focus flow towards the virtual segments. 4. A merging of results from steps 1, 2 and 3 to produce a final “enhanced flow direction grid”.

Catchment, DrainagePoint and DrainageLine The Catchment, DrainagePoint and DrainageLine feature classes in Arc Hydro store the vector products resulting from terrain analysis using a Digital Elevation Model.

Automated Catchment, DrainageLine and DrainagePoint Generation in Arc Hydro

Scales of representation of Drainage Systems Basins – drainage areas for water resources management Watersheds – subdivision of Basin for a particular hydrologic purpose Catchments – subdivision of Basin into elementary drainage areas by physical rules Digital Elevation Model – land surface terrain grid cells

Arc Hydro Drainage (raster) and Arc Hydro Hydrography (vector) (continued) This is actually two separate problems appearing as one… 1) Gross alignment errors between the raster flow direction grid and the vector photogrammetrically interpreted hydrography 2) A DrainageLine density issue associated with applying a uniform flow accumulation cut-off value. Within WRIP we believe we have in a very efficient manner solved both.

Example of a Junction within a Wetland TIN to Grid ANUDEM Stream Burning Enhanced Flow Direction A) B) 100 m. C) D)

Example of On-Network Lakes and Stream Junctions within a Wetland TIN to Grid ANUDEM Stream Burning Enhanced Flow Direction A) B) 100 m. C) D)

A Single Meandering Stream TIN to Grid ANUDEM Steam Burning Enhanced Flow Direction A) B) 100 m. C) D) 2 1

Full Arc Hydro partitioned catchments using the photo-interpreted stream network, and an Enhanced, Flow Direction grid. Note, each hydrographic reach has one and only one catchment.

Accommodating Tile Drain Fields with “Enhanced” Flow Direction Grids. Natural Drainage Stream Network Anthropogenic Boundary Anthropogenic “Pipes” Relative Time of Travel 0 - 600 600 - 1,200 1,200 - 1,800 1,800 - 12,483 Minutes to Water Features

Hydro Networks “The hydro network is the backbone of Arc Hydro, created from edges and junctions. The topological connection of its HydroEdges and HydroJunctions in a geometric network enables tracing of water movements upstream and through streams, rivers, and water bodies” “ Relationships built from the HydroJunctions connect drainage areas and point features such as stream gage stations to the hydro network. Locations on the hydro network are defined by a river-addressing scheme that defines where points are located on lines within drainage areas, allowing measurements of flow distance between any two points on a flow path.”

Scales of representation of Drainage Systems Basins – drainage areas for water resources management Watersheds – subdivision of Basin for a particular hydrologic purpose Catchments – subdivision of Basin into elementary drainage areas by physical rules Digital Elevation Model – land surface terrain grid cells