Presentation on theme: "Floodplain Mapping Models. Discussion & Objectives Floodplains can be difficult and frustrating to map in “traditional” soil survey. – Why? – Do you agree?"— Presentation transcript:
Floodplain Mapping Models
Discussion & Objectives Floodplains can be difficult and frustrating to map in “traditional” soil survey. – Why? – Do you agree? Without an underlying geomorphic model, floodplain mapping may be dependent on the mapper. – What does this mean? – Do you agree? Objectives – Discuss some fluvial mapping models in the lower Missouri river valley SSURGO LiDAR (detailed mapping)
Consider a mapping project in a river valley…. or a benchmark soil update project…. How do you start to organize your mental models? What will you use to establish testable mapping hypotheses? What tools/techniques will you use? Considerations/questions about the system? Etc. Discussion….
Fred’s response (let’s see how well I did) What is the nature of the fluvial system? – Sediment sources Loess-covered uplands vs glacial uplands vs cherty limestone residuum vs soft cacareous cretaceous sediments…. or mixtures. – River system Braided vs meandering; bedrock controls; faulting; etc. Post-settlement modifications (levees, drainage, leveling, channelization) Possible tools to discern geomorphic surfaces – LiDAR (NED DEMs probably inadequate) – Aerial photography/imagery – Go out and look (clean windshield) Hole mapping? – Last resort
Case Study: Examine the mapping model in the Missouri R valley of NW MO
What were the characteristics of the pre-settlement lower Missouri River?
Missouri River Examine mapping model in the Missouri R valley of NW Missouri (and SE NE)
SSURGO soils in the Mo R valley
Consider a “classic” model of floodplains: - Sand, silts, clay - Similar to mid-20 th century mapping in the Mo R bottoms How well does the mapping fit the meander belt model of the lower Mississippi?
Consider the early 19 th century location of the Missouri River. How closely is the alluvial stratigraphy related to the current riverbed?
Many soils are “two-tiered”, split families. Complex depositional history.
“Prominent” scarp noted in Atchison county mapping - 1 to 3 meters high - windshield technique (Low) floodplain soils - carbonates to surface (High) floodplain step soils - carbs below about 50cm How well does this model work?
County boundaries added to the floodplain surfaces model. How can this model be used in update activities for MLRA 107B?
Early 19 th century River superimposed on the floodplain surfaces SSURGO model. Pretty good match! (except in NE)
Low floodplain; calcareous to surface High floodplain; calcareous at >24” Natural levee co-si calcareous backswamp Wet, clayey Footslope; cumulic Hapludoll, co-si Note: existing soil lines only partially follow landforms shown here Missouri River floodplain, NW MO N
Consider the confluence of the Chariton R and the Missouri R.
Missouri –Chariton confluence, with LiDAR backdrop Chariton R 1m LiDAR, resampled to 5m Missouri R Is this the source of the pre-settlement Chariton R sediments?
Soils of the Chariton R floodplain (& other local upland sources) Mo R
High floodplain of the Missouri R (as defined by soil survey)
Low floodplain of the Missouri R (as defined by soil survey) Mo R
Surfaces as derived from soil survey MO River floodplain MO River Floodplain-step Chariton R floodplain
Can elevation (absolute) be used to separate surfaces? 190m class break Works well here Natural levee (high) Sloughs (low)
High, loess-covered terrace at Malta Bend on the Missouri River, central Missouri 10m DEM Some of Missouri’s most productive agricultural soils are on this surface Joy series: fi-si Aquic Hapludolls Missouri R. N
Location of Cora Island mapping area Missouri River floodplain, St. Charles county (near St. Louis) Detailed (Order 1) floodplain mapping
Low-relief terrain; difficult to see the soil-landscape relationships
10m NED DEM – not much help
LiDAR – wow! Testable hypotheses about soil variability are now apparent.