Geomatics Tools for Mapping Headwater Streams Adam Hogg Inventory Monitoring & Assessment, Ministry of Natural Resources Headwaters Workshop May 20, 2009
Outline The Challenge What is a headwater stream? Mapping history Map scale Suggested Methods & Data Know your data Data available in Southern Ontario Two ways to map headwater streams Accuracy assessment Case Example North Carolina
Outline Current related efforts in Ontario Ongoing projects involving geomatics Example of how geomatics can help Summary
The Challenge
What is a Headwater Stream? The furthest point from the watershed outlet from which flowing water is: measurable year round OR measurable at sometime in the year First and second-order streams streams that have no upstream tributaries or only first-order tributaries (Gomi et al. 2002, Meyer and Wallace 2001) Wetlands? Represent the transition zone Where water is channelized Constructed drainage?
Mapping History Over the last few decades many agencies and researchers have attempted Medium scale topographic mapping (~1:10000 1:24000) Sources like OBM, USGS Past maps: greatly underestimate # and length misrepresent flow duration Unsuitable for identifying streams Variable scale a problem Seeing through the coniferous trees Sources: Morisawa 1957; Hansen 2001; Firman and Jacobs 2002; Heine et al. 2004; Paybins 2002; Colson 2006
Map Scale A need for large scale (detailed) Water Resource Information Program (WRIP) & Conservation Ontario large scale hydrology mapping standards 1 1 1 1 2 3 1 1 2 1 1:10 1:2 000 Stream Note: 1:2 000 stream mapping courtesy of Niagara Peninsula CA
Methods & Data
Know Your Data All spatial data is a model with inherent error Data search: Province (LIO), CA, engineering firms, your network Data dictionary, a table including information on: source, accuracy, scale/resolution, intended use stream mapping, orthophoto s, DEM s.
Data Available in Southern Ontario Orthophotos Streams Surficial Soils & Geology DEM s
Interpretive Spring photo s ideal Existing stream data Look for hydrologic indicators Understand the topography
Stream Prediction Model DEM upslope contributing area D-Infinity (Tarboton, 1997) Topographic Index (Beven & Kirkby, 1978) flow accumulation local slope soil conductivity? Calibrate model Interpretively with orthophoto Other comparative and verified stream data *In the field
Strengths & Weaknesses Interpretive & the human element : + Intelligent selection and accurate (time permitted) A snapshot in time, expensive and time consuming, random error Prediction & the computer element + Efficient and more cost effective, can be altered easily, easy to standardize for large nonjurisdictional areas Less intelligence and accuracy, difficult to employ intelligent selection
Accuracy Assessment Purpose of accuracy assessment Crucial to understanding quality and use Rules of thumb: 1/3 the total mapping effort Independently evaluated Statistically sound (>50 validation samples) Validation source should be at least 3 times more precise Report overall accuracy, omission, commission and absolute and/or relative spatial error Sources: Assessing the accuracy of remotely sensed data: principles and practices (Congalton and Green, 1998) USGS NPS Vegetation Mapping Program (USGS Center for Biological Informatics, 1994)
Case Example: North Carolina Mapping Headwater Streams: Intermittent and Perennial Headwater Stream Model Development and Spatial Application (Russell, 2008) Use high precision DEM for first and second order stream prediction Survey grade GPS mapping for calibration and accuracy assessment
Case Example: North Carolina Successes: Spatially accurate, presence absence, length of permanent streams Challenges: Commission error, stream length of non-perennial streams, labeling of permanence Other interesting findings: Sedimentary areas similar to Southern Ontario 70% of headwater streams were intermittent or ephemeral Bedrock dominated areas similar to Ontario Shield majority are ephemeral or perennial
Current Related Efforts In Ontario Using Geomatics
Existing Projects Large Scale Mapping Standards Conservation Ontario and OMNR Ontario Headwater Restoration Initiative (OHRI) OMNR led Identify and map all roadside potential headwater stream and wetland restoration opportunities Restore a few headwater systems Oak Ridges Moraine, Lake Simcoe Wetland loss Ducks Unlimited Canada led Estimate wetland loss using current land cover (SOLRIS) and soils Losses > 10ha Southern Ontario CA s? Toronto, Niagara,Grand River, Credit Valley
How Geomatics Could Help OHRI field data comparison with stream prediction Standardized mapping Screening tool
Summary It is possible to map headwater streams Mapping and characterization will be challenging and potentially expensive depending project objectives Know all data available and use a multi-layered approach Rigorous accuracy assessment is crucial A few related projects
Questions? Source: GOES Project, NASA - http://goes.gsfc.nasa.gov
A Possible Decision Support Tool Restoration Mitigation Protection Note: source SOLRIS wetlands
A Possible Decision Support Tool Restoration Mitigation Protection Note: Source topographic index
A Possible Decision Support Tool Restoration Mitigation Protection Note: source SOLRIS frequently tilled agriculture
A Possible Decision Support Tool Restoration Mitigation Protection Note: Source untilled SOLRIS agriculture
A Possible Decision Support Tool Prevent development Cyan Ellipse: Development Mitigation Magenta Ellipse: Protection Blue Ellipse: Restoration
Case Example: North Carolina Results: Overall accuracy 83% Commission 17% Omission 3% Length Over predicted stream length by 24% Most error in intermittent and ephemeral Permanency Low accuracy ~30% Spatial 70% were within 2.5 meters of actual centerline