Presentation on theme: "Sinkholes Modeling, and Soil Survey. Objectives Examine a few techniques and efforts to model karst features for map unit and/or component delineation."— Presentation transcript:
Objectives Examine a few techniques and efforts to model karst features for map unit and/or component delineation. Consider some case studies of mapping and updating karst areas: – Lawrence co, Indiana – Springfield plateau, Missouri
Karst: Dade county, MO GIS techniques to enhance identification of karst
Same area: 10m DEM, hillshade relief, hypso lines
Flowaccumulation (multi-path): karst area Didn’t work that well…
Karst: wetness index (multi-path) Works fairly well for some sinkholes. However, not all upland wet areas are sinkholes.
Can we model these sinkholes? Moderately high elevation Avg about 325m; range about 315 to 335m High Flow accumulation Above about 200 High Wetness Index Above about 9 Not on the stream network Not so easy to model
Fuzzy Membership Model for Sinks Higher-elevation valleys confounded w sinks What about using streams in the model? USGS streams layer is incomplete (missing tributaries) Modeled stream network runs into sinks
Fuzzy Membership Model w more restrictive lower elevation criteria (lost the lowest elevation sinkhole)
Simple Fuzzy Membership model for Pierpont sinkhole areas: High elevation (full membership above 225m) High wetness index (full membership above 5) Does an OK job of identifying areas where the sinkholes occur
Mapping karst in SSURGO How can we identify karst features in… – Spatial data – Attribute data How might this affect interpretations? Case studies: karst in soil survey – Lawrence county, IN – Springfield Plateau (MLRA 116B), MO
Karst mapping: Lawrence county, IN Acknowledgements: Dena Marshall (now Lexington KY) Genny Helt (Indianapolis IN)
Physiographic Features of southern Indiana (Schneider, 1966)
A closer look at features of the Crawford Upland & Mitchell Plain
Highland Rim & Pennyroyal KY & IN Sandstone & Shale Hills & Valleys Lawrence county - 30m DEM - MLRAs How do the lines look? Where’s the karst?
Mitchell Plain Norman Upland Crawford Upland Physiographic Regions Mitchell Plain: middle Mississippian- aged limestones
Karst map units in Lawrence county, IN Note: no sinkhole spot symbols
The karst soils in Lawrence county “Terra rossa” Loess over “residuum” (in situ?) Crider – Fi-si Typic Paleudalfs – 10R w depth Knobcreek (Frederick correlated to this in IN) – Fi-si / clayey Typic Paleudalfs – Not as red
Mapping patterns & rules Limestone underlain w siltstone: little/no karst. Limestone thickens westerly; sinkholes appear. IN Geomorphology Tour “some years ago”: – Karst map unit: Areas w sinkhole density of > 1 per 5 acres – Spot symbol: Sinkhole density < 1 per 5 acres Ref: Pers. Comm., Dena Marshall, SS, currently Lexington KY
Attributes (NASIS soil properties) Bedrock in a karst component within 80” – Higher Ksat than corresponding non-karst unit Entry for Ksat in R layer – E.g., Navilleton components, Floyd co IN: Karst component: R Ksat 1.42 – 141.14 Non-karst component: R ksat 0.43 – 42.34 Bedrock below 80” – No known differences in soil properties between karst and non-karst map units If we could populate soil property data below 80”, there would be differences.
MLRA Soil Survey Project: Updating Karst Areas on the Springfield Plateau (MLRA 116B) Ignored in some, Spot symbols in some, Karst map units in some. Inconsistent use of all of the above, both within and among counties. County-based soil surveys (over 40+ years) handled karst in various ways. Springfield Plateau
Karst Project: Methodology Primarily a GIS office project Utilize: – Elevation data DEMs, Hypsography lines – Existing SSURGO – Orthophotos – Sinkholes layer (statewide; USGS) On-screen digitizing/editing of SSURGO Establish new map units – “Karst” in name, or – Soil series that occur only in sinkhole basins.
Results: 20 new map units in 7 counties “Karst” map units; e.g., – Goss grsil, karst, 8-15% Sinkhole basin map units; e.g., – Lowassie sil, 0-3%, freq. ponded Zoom in to this area (next slide)
Sinkholes point layer over 10m DEM, with SSURGO polygons
Map units added in this area Blue = sinkhole basin units; Red = “Karst” in MU Name
Karst discussion “answers” Spatial identification of karst: – Map unit phases (i.e., “karst” in muname). – Spot symbols. – Map units named by components that only occur in karst (i.e., no need for “karst” in muname). e.g., in Missouri: Lowassie, Grandgulf series only occur in sinkholes. Attribute interpretation – Muname contains “karst” – Component geomorphic description table: landform = “sinkhole” – Differences in soil properties? Interpretations – Possibility for groundwater contamination – Onsite wastewater disposal; lagoons; others? – Not keyed in standard National Interps (?) – Custom, state-created interps (e.g., MO onsite wastewater interp) Keys on “karst” in the muname, and “sinkhole” landform