Table 7. Summary of morphology-based sediment-transport-volume estimates, Chetco River, Oregon.
[Abbreviations: m2, square meter; m3, cubic meter; m3/yr, cubic meter per year; –, no data]
|
Analysis period |
|
1939–43 |
1962–65 |
1995–2000 |
2000–2005 |
2005–08 |
| Number of years |
4 |
3 |
5 |
5 |
3 |
| Area of eroded bar (m2) |
67,000 |
157,000 |
152,000 |
204,000 |
102,000 |
| New bar area (m2) |
187,000 |
211,000 |
337,000 |
74,000 |
257,000 |
| Net measured change in bar area (m2) |
120,000 |
54,000 |
185,000 |
-130,000 |
155,000 |
| Flow-adjusted change in bar area (m2) |
19,000 |
115,000 |
44,000 |
-57,000 |
144,000 |
Scenario 1: Erosion and deposition,
where bar thickness in each reach is average of all bars |
| Volume of erosion (m3) |
183,000 |
443,000 |
421,000 |
560,000 |
283,000 |
| Volume of deposition (m3) |
538,000 |
598,000 |
942,000 |
214,000 |
723,000 |
| Net change in bed-material (m3) |
355,000 |
155,000 |
521,000 |
-346,000 |
440,000 |
| Flow-adjusted net change in bed-material (m3) |
42,000 |
333,000 |
100,000 |
-150,000 |
411,000 |
| Annual net balance3 (m3/yr) |
89,000 |
52,000 |
104,000 |
-69,000 |
147,000 |
| Flow-adjusted annual net balance3 (m3/yr) |
11,000 |
111,000 |
25,000 |
-30,000 |
137,000 |
Scenario 2: Erosion and deposition,
where bar thickness in each reach is average of all low bars |
| Volume of erosion (m3) |
116,000 |
282,000 |
268,000 |
338,000 |
171,000 |
| Volume of deposition (m3) |
361,000 |
375,000 |
581,000 |
133,000 |
462,000 |
| Net change in bed-material (m3) |
245,000 |
93,000 |
313,000 |
-205,000 |
291,000 |
| Flow-adjusted net change in bed-material (m3) |
56,000 |
204,000 |
75,000 |
-85,000 |
273,000 |
| Annual net balance3 (m3/yr) |
61,000 |
31,000 |
63,000 |
-41,000 |
97,000 |
| Flow-adjusted annual net balance3 (m3/yr) |
14,000 |
68,000 |
15,000 |
-17,000 |
91,000 |
Scenario 3: Erosion calculated using reach average thickness of all bars;
deposition calculated using reach average thickness of low bars |
| Volume erosion |
183,000 |
443,000 |
421,000 |
560,000 |
283,000 |
| Volume of deposition |
361,000 |
375,000 |
581,000 |
133,000 |
462,000 |
| Net change in bed-material (m3) |
178,000 |
-68,000 |
160,000 |
-427,000 |
179,000 |
| Flow-adjusted net change in bed-material (m3) |
-48,000 |
81,000 |
-145,000 |
-245,000 |
153,000 |
| Annual net balance3 (m3/yr) |
44,000 |
-22,000 |
32,000 |
-85,000 |
59,000 |
| Flow-adjusted annual net balance3 (m3/yr) |
-12,000 |
27,000 |
-29,000 |
-49,000 |
51,000 |
| Summary Ranges: Flow-adjusted annual net
balances (m3) |
-12,000 to 14,000 |
-27,000 to 111,000 |
-29,000 to 25,000 |
-49,000 to -17,000 |
51,000 to 137,000 |
| Summary comparisons |
| Total volume (m3) removed due to gravel mining1 |
– |
– |
160,000 |
310,000 |
185,000 |
| Total bed-material (m3) influx as calculated by transport equations2 |
– |
– |
390,000 to 530,000 |
190,000 to 270,000 |
200,000 to 270,000 |
| Total bed-material (m3) influx as calculated by morphologic approach (flow-adjusted) and accounting for gravel extraction volumes3 |
– |
– |
15,000 to 260,000 |
65,000 to 225,000 |
338,000 to 596,000 |
| Average annual lower Chetco River influx from bedload transport equations4 (m3/yr) |
– |
– |
78,000 to 106,000 |
38,000 to
54,000 |
67,000 to 90,000 |
| Annual lower Chetco River bed-material influx as calculated from range of flow-adjusted morphologic estimates, accounting for gravel extraction volumes, and assuming no bed-material transport out the lower river (m3/yr) |
5-12,000 to 14,000 |
5-27,000 to 111,000 |
3,000 to
52,000 |
13,000 to
45,000 |
113,000 to 197,000 |
|
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U.S. Department of the Interior | U.S. Geological Survey