CRMS monitoring: 390-site network shows higher baseline water levels since 2011; CPRA to continue annual measurements

Leanne Sharp (CRMS program, CPRA Lafayette office) briefed the board on the Coastwide Reference Monitoring System (CRMS), a network of roughly 390 monitoring sites distributed across coastal Louisiana to measure vegetation, surface elevation, accretion, water level and salinity. Sharp said the network is a standardized, randomized reference design intended to let scientists and planners make coastwide inferences about marsh condition and long‑term change.

Sharp summarized recent CRMS data analysis and the network’s role in planning and adaptive management. Key points:

- CRMS is a randomized network of about 390 sites, designed to represent basin and marsh‑type distributions so analysts can draw inferences about marsh types and basins rather than only project sites. Sharp said, "we didn't put it there. We used randomization to distribute them across the coast proportional to the marsh types and basins."

- Measured variables include hourly water level and salinity, annual vegetation composition, surface elevation table (SET) measurements and accretion plates to track sediment accumulation and soil formation. The data are publicly available and used by agencies, academics and consultants.

- CRMS analyses detect a change in baseline coastal water levels beginning around 2011. Sharp and CPRA staff reported an accelerated period of higher water that produced elevated inundation and flooding stress on marshes, with a 2019 peak in water levels and a later low‑water interval in 2023 that nevertheless remained higher than pre‑2011 low water in many locations.

- Spatial patterns were heterogeneous: some deltaic and fringe marsh sites were relatively high; other areas — particularly parts of Calcasieu‑Sabine and the Atchafalaya reach — showed episodic and severe land‑loss patterns. A recent coastwide synthesis that grouped change trajectories identified seven distinct coastwide land‑change groupings, including continuous land loss in some lower delta and saline marshes, localized episodic loss elsewhere, and stability in many inland swamp sites.

- Monitoring season is active: CRMS field crews are collecting surface elevation and accretion data through April and vegetation data in summer and fall; a coastwide aerial flight completed in 2024 will feed updated spatial analyses later in the year.

Sharp said CRMS data have guided project design decisions — for example, identifying where hydrologic control structures or marsh creation would be most effective — and noted that the network’s randomized design was recommended by national science bodies as a model for long‑term monitoring.

Board members asked about real‑time water‑level monitoring, possible expansion of real‑time gauges, how the 20‑year high/low water cycle is understood, and whether CRMS data could be packaged for landowners and parishes. Sharp said USGS maintains a subset of about 10 CRMS stations in real time and that converting more sites to real‑time service is technically feasible but requires funding and agreements. She also agreed that CPRA staff would explore opportunities to present regional CRMS results for landowners and parish officials in concise formats.

Sharp said CRMS will continue to publish data and results and that the dataset supports master planning, project evaluation and adaptive management for coastal restoration.