5:15 PM - 7:15 PM
[U11-P01] Incision after the 2024 Noto Peninsula Earthquake around the Hakka River mouth in the northwestern Noto Peninsula, central Japan
Keywords:2024 Noto Peninsula Earthquake, 2024 September Noto Peninsula Heavy Rain, Coastal uplifting, River incision, Knickpoint, Terrace
Interaction between crustal deformation and fluvial systems is one of the most significant processes for terrestrial landform development. Base-level lowering or local deformation on longitudinal profile by the surface rupture develops knickpoints which will migrate to the upstream after earthquake resulting in the formation of river terraces. Huge earthquake events with sudden uplifting and surface rupture can be the chance for revealing the fluvial response to the seismic crustal deformation and also landscape development in the long-term timescales. Following that the knickpoints were formed by the surface rupture of the recent earthquake events, e.g. 1999 Chi-chi (Mw 7.6), 2008 Wenchuan (Mw 7.9), researchers observed and investigated the processes of their mitigation and incision after earthquakes. But the processes of the base-level lowering and fluvial terrace formation in short-term (timescales of 10-1-100 yr) have been limitedly understood because of few studies observing knickpoint migration induced by coastal uplifting.
2024 Noto Peninsula Earthquake (Mw 7.6) caused the seismic uplifting with ~4.4 m at maximum along their northern coast, resulting in the drastic changes in river landforms around the mouths in this region. Continuously measuring these landform changes in high-resolution is expected to enable revealing the processes of the river profile changes and fluvial terrace formation according to the seismic crustal deformation, which is a fundamental issue in geomorphology. We continue to achieve UAV-measurements for the landform changes in the rivers and coasts which were affected by the 2024 Noto Peninsula Earthquake and subsequent heavy rains in high-resolution, and report the landform changes in one year after the earthquake around the mouth of the Hakka River, northwestern Noto Peninsula, based on the results of the observation and measuring carried out on the February, May, September and November 2024 to discuss their hydrology.
The knickpoint formed by the uplifting on January 1st on the Hakka River channel migrated to ~700 m upstream from the mouth after the earthquake in 10 days at latest. Incision with had occurred downstream of the knickpoint resulting in the formation of the river terrace at the riverside until early September. We guess that the flood of heavy rain on July 24 accelerated the incision. Subsequent flood triggered by the heavy rain on September 21-23 eroded the terrace and made the knickpoint move toward the check dam at more 300-m upstream.
We observed that the knickpoint formed by the 2024 Noto Peninsula Earthquake migrated toward ~1 km upstream from the mouth only one year after earthquake, and that migrations intermittently and rapidly occurred just after the uplifting event and during the floods. Incising riverbed transformed from the gentle alluvial river into the steep gravel bed river as the result of sorting according to incising. Although the incision in the lower part of the knickpoint seems to being temporarily constrained by the coarse gravel on today’s riverbed, the riverbed lowering in one year has surely affected the artificial structures around the river channel. In the future, the effects for infrastructures will become apparent in the long-term as the result of the knickpoint migration and incision will get worse around the river moths in the northern Noto Peninsula.
2024 Noto Peninsula Earthquake (Mw 7.6) caused the seismic uplifting with ~4.4 m at maximum along their northern coast, resulting in the drastic changes in river landforms around the mouths in this region. Continuously measuring these landform changes in high-resolution is expected to enable revealing the processes of the river profile changes and fluvial terrace formation according to the seismic crustal deformation, which is a fundamental issue in geomorphology. We continue to achieve UAV-measurements for the landform changes in the rivers and coasts which were affected by the 2024 Noto Peninsula Earthquake and subsequent heavy rains in high-resolution, and report the landform changes in one year after the earthquake around the mouth of the Hakka River, northwestern Noto Peninsula, based on the results of the observation and measuring carried out on the February, May, September and November 2024 to discuss their hydrology.
The knickpoint formed by the uplifting on January 1st on the Hakka River channel migrated to ~700 m upstream from the mouth after the earthquake in 10 days at latest. Incision with had occurred downstream of the knickpoint resulting in the formation of the river terrace at the riverside until early September. We guess that the flood of heavy rain on July 24 accelerated the incision. Subsequent flood triggered by the heavy rain on September 21-23 eroded the terrace and made the knickpoint move toward the check dam at more 300-m upstream.
We observed that the knickpoint formed by the 2024 Noto Peninsula Earthquake migrated toward ~1 km upstream from the mouth only one year after earthquake, and that migrations intermittently and rapidly occurred just after the uplifting event and during the floods. Incising riverbed transformed from the gentle alluvial river into the steep gravel bed river as the result of sorting according to incising. Although the incision in the lower part of the knickpoint seems to being temporarily constrained by the coarse gravel on today’s riverbed, the riverbed lowering in one year has surely affected the artificial structures around the river channel. In the future, the effects for infrastructures will become apparent in the long-term as the result of the knickpoint migration and incision will get worse around the river moths in the northern Noto Peninsula.