Most of what happens on this coast happens inside a cut. The bays sit behind the barrier islands, wide and shallow, and the water that carries a working draft is water somebody dredged and keeps dredging. Where that water ends is a matter of marks and the chart rather than a change in color you can read from the helm. Ship traffic uses the same lines you do, so the places with the least room to maneuver are the places most likely to have something large coming the other way.
The Texas pack is built from 213 official NOAA ENC cells and holds 74,056 individual soundings, 14,635 charted depth areas and 14,167 depth contours, covering the coast from Sabine Lake down past Corpus Christi. Inside it are 1,794 dredged areas, 6,930 charted obstructions, 1,103 wrecks, 3,231 lights and 79 NOAA tide prediction stations. All of that is 26 MB on the phone, downloaded once.
Of the eighteen US regions Helm builds packs for, only one carries more dredged area than Texas. There are 1,794 of them here. That one figure describes the coast better than any account of the scenery, because the usable water is maintained water and it is maintained in lines.
The charted depths inside those areas run from 0.1 m to 17.9 m, which is about four inches at one end and close to fifty nine feet at the other. The median is 3.8 m, roughly twelve and a half feet. So the fill pattern that says dredged tells you nothing on its own about whether your boat fits. A small working cut and the deep water an ocean ship uses look the same at low zoom, and the difference between them is the depth figure the chart carries for each one, which is what Helm measures your draft against.
Helm calls water clear when there are three feet under your keel. A boat drawing five feet therefore wants eight, and against a median maintained depth near twelve and a half feet that is a comfortable margin down the middle and a thin one close to the edge. Routing is computed at datum, MLLW, so a line that only worked because the tide cooperated never gets drawn in the first place.
Where a Corps channel survey has been ingested for an area, the depth comes from the survey rather than the chart, and the route explanation tells you which one it used. That distinction carries more weight here than in most regions. With 1,794 dredged areas, a great deal of the depth on this coast is a maintenance schedule rather than a fact of geology.
| In the chart pack | Count |
|---|---|
| NOAA ENC cells | 213 |
| Charted soundings | 74,056 |
| Depth areas | 14,635 |
| Depth contours | 14,167 |
| Lateral buoys | 911 |
| Lateral beacons | 2,813 |
| Charted lights | 3,231 |
| Anchorage areas | 79 |
| Bridges | 612 |
| Overhead cables | 645 |
| Dredged areas | 1,794 |
| Charted wrecks | 1,103 |
| Charted obstructions | 6,930 |
| Underwater rocks | 656 |
| Restricted areas | 115 |
| NOAA tide prediction stations | 79 |
Counted from the Helm chart pack for Texas Coast, built from official NOAA electronic navigational charts. The pack downloads at about 26 MB.
The pack carries 6,930 charted obstructions and 1,103 wrecks, third and fifth among the eighteen regions. It carries 656 underwater rocks, which puts Texas twelfth. Read those together and the bottom takes on a shape: what you have to miss was built, sunk or left behind, and it lies where work happened, which means near the channels, the harbor approaches and the lanes offshore.
Two of the region's tide stations sit on platforms, COX WC-53 and Fieldwood WC-289. That is a fair description of what the chart looks like once you are past the jetties, and it is the reason a wreck symbol out there is worth reading rather than scrolling past.
In practice this changes two habits. The first is anchoring. There are 79 charted anchorage areas in the pack, and with an obstruction count this high the time to look at what surrounds one is before the hook goes down. The second is cutting a corner. Water you cannot cross is shaded, and the measure tool reports the shallowest point along any line you draw rather than the average, which is the honest way to check a shortcut across a bay that looks empty until you zoom in.
There are 79 NOAA tide prediction stations inside the Texas box, dense enough that the gauge Helm reads is usually in the water you are in rather than a bay over. Eagle Point and the Galveston Railroad Bridge cover the upper bay. Buffalo Bayou sits in the Houston Ship Channel, Clear Lake and Christmas Bay have their own, and Alligator Point covers West Bay. Down the coast there is Freeport Entrance Jetty at the jetties, Bayside in Copano Bay, Conn Brown Harbor at Aransas Pass, and Bob Hall Pier at Corpus Christi. East Sabine Lake and East Matagorda cover the ends.
Helm labels where a tide height came from. The strongest version is the NOAA prediction corrected by the residual from the nearest live gauge, so water sitting below prediction reads as less water instead of as the figure the table promised. With no signal the curve is computed on the device from the station's harmonic constants. The sentence on screen says which of those you are looking at.
None of those numbers decide whether a leg is passable. The tide height is there to tell you how much easier than datum the water will be at the hour you expect to be in that spot.
Texas ranks third of the eighteen regions for charted lights. The more telling pair is 2,813 lateral beacons against 911 lateral buoys, which puts about three quarters of the lateral marking on this coast on fixed structure standing in the bottom. A beacon does not drag, swing on its chain or disappear after a blow, so the mark positions on the chart here are mostly the real ones, and a mark that is missing is worth slowing down for rather than shrugging at.
Fourteen safe water marks is a modest number for a coast this size, which follows from how the water is arranged. Almost everything is an entrance or a lined fairway, so the mark that means deep water all around is something you pass at the jetties rather than something you steer between for an hour.
There are more overhead cables charted in this region than bridges, 645 against 612, and the cable count puts Texas sixth of eighteen. The wire is at least as common a crossing here as the span, which makes air draft a working number on this coast rather than a sailboat concern.
Helm reads charted vertical clearance, measured above mean high water, against the air draft you entered, and it reads the down position of an opening bridge as well as fixed spans. Where the chart carries no clearance figure for a crossing, Helm reports it as unknown instead of printing a zero, since a zero in that field is the absence of data and would send you the long way around something you could have cleared. In a region with 1,257 charted things over your head, that difference comes up often.
One of the 79 tide stations sits at the Galveston Railroad Bridge. That is useful, because clearance is charted above mean high water, and the number you want at a low crossing is the one that tells you how much of it the tide has taken.
These counts describe what the chart pack carries, not the state of the water today. Charted data ages, channels shoal and marks move. Keep a lookout and verify locally.
Yes. The pack is built from 213 NOAA ENC cells covering the coast from Sabine Lake down past Corpus Christi, and the ship channel is in it along with the bay around it. Buffalo Bayou, Eagle Point and the Galveston Railroad Bridge are three of the 79 tide stations inside the region, and the channel is part of the 1,794 charted dredged areas the pack carries.
The nearest one, and it names it. With 79 NOAA prediction stations inside the region the gauge is usually in the same water you are: Bayside in Copano Bay, Clear Lake, Christmas Bay, East Matagorda, Alligator Point in West Bay, Bob Hall Pier at Corpus Christi. Where a live gauge is reporting, the prediction is corrected by its residual, and the screen tells you which of the two you are reading.
The pack carries 1,794 dredged areas with charted depths from 0.1 m to 17.9 m and a median of 3.8 m, about twelve and a half feet. Where a Corps channel survey has been ingested for an area, Helm uses the surveyed depth and shows the date it was measured. Where the chart is the only source, the route explanation says so in a sentence, so you know whether you are reading a survey of the channel as it is now or a sounding off the chart.
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