Sediment samples were collected from Los Padres reservoir in the Carmel River watershed, central California coast, between July 11 and 17, 2017, using a CME-45 barge-mounted drill rig, to characterize sedimentary properties in the reservoir deposits following the Soberanes Fire of 2016 and high river flows in winter 2017. Borehole samples were recovered using direct push coring with an Osterberg piston sampler operated by Taber Drilling Company of Sacramento, California, and overseen by AECOM, Inc. Sediment was recovered using a split-barrel sampler and a rotary drill bit was added to the sampler where needed to penetrate coarse sediment. Samples from three boreholes are described in this data release: two sampled at multiple sediment depths (B2 and B7) and a third (B4) from which only the topmost sample is included. Each borehole was drilled to the depth of apparent pre-dam alluvium or bedrock. Alternate sections were described and sampled; every second section was discarded without examination. Geochemical data are reported for sediment cores. Data include short-lived cosmogenic and natural radionuclide activities for Lead-210; Radium-226, Cesium-137, Thorium-234, and excess Lead-210. The USGS gratefully acknowledges collaboration with B. Kozlowicz of AECOM, Inc., in the collection of these data. Purpose: Laboratory measurements of natural lead, radium, cesium, and thorium isotope concentrations in Los Padres reservoir, Carmel River watershed, California, to characterize post-fire sedimentation history.