SWOT

1

National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Pasadena, California

Surface Water and Ocean Topography (SWOT) Mission

River  Data  Products  and  Func2onal  Flow  Michael  Durand  

Ohio  State  University    

Sylvain  Biancamaria  LEGOS  

 14  January  2015  

SWOT

2

Status

•  Discussed in some depth at the first Algorithm Definition Team meeting in New York (October 2014)

•  What is being defined is not the L2 point cloud, but (largely) vector products derived therefrom

•  Based on these discussions, produced a 10-page proposal / draft description of products, which was circulated to the ADT

•  This draft was discussed via telecon

•  Goal today is to solicit feedback from the SDT on proposed river products

•  Product definitions are currently flexible and can be discussed!

•  Future version of the simulator will include many of these attributes as part of the River Vectorizer

SWOT

3

Guiding Philosophy

SWOT

4

Rivers & Co. ~ A taxonomy

1.  Rivers

1.  Single-channel planforms

2.  Simple multi-channel planforms

3.  Braided and anastamosing planforms

4.  Floodplain-river systems

2.  Reservoirs

3.  Spillways, dams and waterfalls

4.  Tidal reaches

5.  Low spatial resolution product Case  1.1  will  represent  many  rivers.  Special  cases  are  more  challenging.  

SWOT

5

Products for single-channel planform

1.  Polygon product showing river inundated area 2.  Centerline products 3.  Attributes of the center-line/polygon products

1.  Reach ID 2.  River name 3.  Reach length 4.  Reach-averaged height & uncertainty 5.  Reach-averaged slope & uncertainty 6.  Reach-averaged inundated area & uncertainty 7.  Reach-averaged discharge & uncertainty 8.  Time-invariant parameters used in discharge calculation

Descrip8on  currently  applies  to  pass-­‐based  products,  only.  Cycle-­‐based  or  monthly  products  are  currently  being  discussed  

SWOT

6

Products for single-channel planform

3.  Attributes of the center-line/polygon products (cont.) 9.  Island detection flag 10.  River planform classification 11.  Quality and other flags (ice/snow/high precipitation rate, etc.) 12.  Connectivity: upstream and downstream reaches

Descrip8on  currently  applies  to  pass-­‐based  products,  only.  Cycle-­‐based  or  monthly  products  are  currently  being  discussed  

A  revision  to  this  has  been  proposed  by  Ernesto  et  al.  in  which  products  would  be  evaluated  at  nodes  con8nuous  along  the  river  centerline.  The  first  draB  of  the  “river  vectorizer”  has  been  released  to  the  ADT  and  includes  addi8onal  products  such  as  minimum  &  maximum  longitude  &  la8tude,  pass  number,  etc.  

SWOT

7

Example courtesy Ernesto

1.  Reach  ID:  3  2.  River  Name:  Ohio  3.  Reach  length:  8391.3  m  4.  Height:  161.67  m  5.  Slope:  14.73  cm/km  6.  Area:  1568429.9  m2  

7.  etc.  

SWOT

8

Rivers & Co. ~ A taxonomy

1.  Rivers

1.  Single-channel planforms

2.  Simple multi-channel planforms

3.  Braided and anastamosing planforms

4.  Floodplain-river systems

2.  Reservoirs

3.  Spillways, dams and waterfalls

4.  Tidal reaches

5.  Low spatial resolution product

SWOT

9

Case 1.2: Simple multi-channel planforms

•  Where possible, multiple channels will be considered separate objects, with their own attributes

•  Where not possible, their inundated area will be merged, average height calculated, and “multiple-channel” flag set

0  

50  

100  

150  

200  

250  

300  

650   660   670   680   690   700  

Chan

nel  w

idth  [m

]  River  flow  distance  [km]  

Channel  1  (Main)   Channel  2   Channel  3  

Seine  River  model:  courtesy  Nicolas  Flipo  

SWOT

10

Case 1.3: Braided and Anastamosing planforms

•  Where possible, individual channels will have separate products. A nomenclature for reach connectivity will be developed

•  Where multiple channels cannot be resolved, aggregate products will have to be developed, starting with the RivWidth-style approach

•  To be explored using instrument simulator runs

Tanana  River  model,  courtesy  Elizabeth  Humphries,  UNC  

SWOT

11

Case 1.4: River-Floodplain systems

•  In the floodplain for 2-D flow, 2-D gridded products are needed: rasters from L2 pixel cloud. Options: –  NASA/CNES pre-stages products over select areas –  NASA/CNES provides online web tools where users select areas and

products are served up –  Tools are provided so users can resample the pixel cloud as they wish

Logone  River  floodplain,  Cameroon   Amazon  floodplain.  Alsdorf  et  al.,  2007  

SWOT

12

Case 2: Reservoirs

•  Reservoirs will be treated as lakes in terms of their products. Will be included in the river databases for along-stream continuity

•  Will use a priori databases of reservoir locations. This will be refined using the first year of SWOT data

Priest  Rapids  Lake,  along  the  Columbia  River  

SWOT

13

Case 3: Spillways, dams, and waterfalls

•  In some cases, drops occur over very short distances. Usual products cannot be calculated

•  Instead, an “elevation drop” product will be calculated •  Similar to case 2, an a priori database will be refined after

one year of SWOT data

Newburg  Lock  and  Dam  on  the  Ohio  River.  Eleva8ons  via  the  Community  HEC-­‐RAS  model.    

SWOT

14

Case 3: Spillways, dams, and waterfalls

•  In some cases, despite drops occurring over short distances, the drops are small (decimeter) and distance between drops is small (e.g. <10 km).

•  In these cases, average height and slope will be calculated

In  situ  GPS  measurements  along  the  Olentangy  River.  Summer,  2014.    

SWOT

15

Case 4: Tidal Reaches

•  Nominally we will produce the same products used for case 1.1

•  Need to determine where each river ends. How will this be determined?

•  Many of these reaches will be very low slope: At what point do we say slope cannot be accurately produced? E.g. would we really want to say slope is 0.1 cm/km ± 1 cm/km?

•  These need to be assessed in the context of instrument simulation of tidal reaches

SWOT

16

Case 5: Low-resolution product

•  It’s not clear in what cases this product would have value (under investigation by the ADT)

•  The product might have value over floodplains with significant inundation extent, or over large reservoirs in line with the river network

SWOT

17

The polygon product

•  Due to classification and geolocation issues, it is not clear that a reliable 2-D polygon mask can be produced

•  Science requirements stress total inundated area, which can be produced

•  Current philosophy:

–  If we can produce the polygon reliably, then we should do so

–  If we cannot, we should re-evaluate whether to produce

SWOT

18

Floods

•  What data product should be produced for floods?

•  Perhaps we could produce a gridded product similar to the floodplain product, when that is defined?

Water  depth.  Simula2on  courtesy  Jeremiah  Lant.  

SWOT

19

Dra=  of  River  Processor  flow  chart  for  single-­‐channel  planform  rivers.      FuncEonal  flow  will  be  refined  a=er  data  products  are  beHer  specified.  

SWOT

20

River Simulation Priorities

•  Sacramento River: 100 m wide. In progress. •  Upstream Garonne: 100 m wide. Complete. •  Platte River: 50-100 m wide. Braided. Complex

dynamics. Complete. •  Tanana: 400-600 m wide. Braided. Complex dynamics. •  St Lawrence: Includes lakes, multiple channels. •  Seine Estuary: Tidal area. Includes some 2-D flow. In

progress. •  Connecticut: Tidal, relatively wider. Some floodplain

interaction. •  Downstream Garonne: Less steep and wider than

upstream reach. Almost complete.

SWOT

21

Summary

•  Initial product definitions taxonomy, and product differentiation has been proposed

•  New river products from Ernesto are excellent. The upcoming new version the simulator that includes these is critical

•  Decisions on polygons, products in complex environments are upcoming

•  Need to determine who is going to define estuarine data products

SWOT

22

Questions for Discussion

•  Is the hierarchy correct?

•  What difficult and special cases are missing?

•  What are the right priorities for simulation and further study?

•  What other data products should be produced?

•  What products should be produced in complex environments?

SWOT

23

Extra Slides

SWOT

24

Basic  Func2onal  Flow  Details  

SWOT

25

Snap water pixels to reaches

•  Inputs: –  SWOT pixel cloud

•  classification •  height •  associated accuracy

–  Static database of reach boundaries •  Defined a priori •  Perhaps refined after a period of SWOT data available

•  Purpose: –  Determine which pixels are associated with which reaches –  Currently we will assume a one-to-one mapping (in theory,

the same pixel could be used to inform reach-properties of multiple reaches)

•  Output: –  A database linking pixels on each pass to reaches

SWOT

26

Centerline calculation & multi-channel handling

•  Inputs: –  SWOT pixel cloud & map to reaches –  Static database of reach boundaries

•  Purpose: –  Determine river centerline (needed for slope calculations), which

can be dynamic from pass-to-pass –  Determine flow distance along centerline –  For now, assume the RivWidth approach to centerline calculation

for braided rivres •  Output (on a per pass basis)

–  River centerline –  Reach length

•  Issues –  What do the products look like for massively braided rivers?

Need example instrument simulator runs for these cases

SWOT

27

Centerline reach-averaged height & slope

•  Inputs –  River centerline and flow length along the centerline for

each reach –  SWOT pixel cloud and map to each reach

•  Purpose –  For 1D rivers: Snap pixels to centerline to associate them

with a 1-D flow distance (less trivial than it sounds) –  Reach average slope should be in the 1-D direction.

Heritage: fit first-order polynomial to each reach –  Reach average height should be straightforward.

•  Issues –  How to handle 2-D flow environments? –  How to handle lakes along river network? –  How is uncertainty calculated?

•  Output: reach average height, slope, and uncertainty

SWOT

28

Inundated extent and reach average width

•  Inputs –  SWOT pixel cloud and map to each reach –  Flow distance for each reach

•  Purpose –  Calculate total inundated extent: probabilistic algorithm

being explored –  Reach average width would be inundated extent divided by

reach length •  Issues

–  How to handle 2-D flow environments? –  How to handle lakes along river network? –  How is uncertainty calculated? –  Is a polygon being considered?

•  Output: inundated extent, reach average width

SWOT

29

Inversion of hydraulic parameters for discharge calculation

•  Inputs –  Reach average height, width, and slope –  Prior first guess of reach average hydraulic parameters

(e.g. bathymetry & roughness coefficient) •  Purpose

–  Calculate optimal hydraulic parameters for each reach, probably after receiving several seasons or one year of SWOT data

–  This would be done as a one-time or special-case step: not iteratively with each new pass or cycle

•  Issues –  How to handle 2-D flow environments? –  How to handle lakes along river network?

•  Output: database of hydraulic parameters

SWOT

30

Operational discharge production

•  Inputs –  Reach average height, width, and slope –  Optimal hydraulic parameters

•  Purpose –  Calculate discharge on a per-pass basis, probably using

Manning’s equation •  Issues

–  How to handle 2-D flow environments? –  How to handle lakes along river network? –  Should we apply some operational flow constraints to

ensure continuity? •  Output: database of reach-averaged river discharge